Rework DB API

This takes advantage of generics, and generally clears up a lot of
inconsistencies and quality-of-life issues.

Start of db rework: clean up, start generics, improve tests

Write some nice aspirational package docs

Rework and document the db API

Tests still pass, at least...now for everything else

Update all callsites of db functions

Finish converting all callsites

Not too bad actually! Centralizing access into the helpers makes a big
difference.

wtf it works

go.mod

@@ -1,10 +1,8 @@
 module git.handmade.network/hmn/hmn
 
-go 1.16
+go 1.18
 
 require (
-	github.com/Masterminds/goutils v1.1.1 // indirect
-	github.com/Masterminds/semver v1.5.0 // indirect
 	github.com/Masterminds/sprig v2.22.0+incompatible
 	github.com/alecthomas/chroma v0.9.2
 	github.com/aws/aws-sdk-go-v2 v1.8.1
@@ -16,13 +14,10 @@ require (
 	github.com/go-stack/stack v1.8.0
 	github.com/google/uuid v1.2.0
 	github.com/gorilla/websocket v1.4.2
-	github.com/huandu/xstrings v1.3.2 // indirect
-	github.com/imdario/mergo v0.3.12 // indirect
 	github.com/jackc/pgconn v1.8.0
 	github.com/jackc/pgtype v1.6.2
 	github.com/jackc/pgx/v4 v4.10.1
 	github.com/jpillora/backoff v1.0.0
-	github.com/mitchellh/copystructure v1.1.1 // indirect
 	github.com/rs/zerolog v1.21.0
 	github.com/spf13/cobra v1.1.3
 	github.com/stretchr/testify v1.7.0
@@ -35,6 +30,39 @@ require (
 	golang.org/x/image v0.0.0-20210628002857-a66eb6448b8d
 )
 
+require (
+	github.com/Masterminds/goutils v1.1.1 // indirect
+	github.com/Masterminds/semver v1.5.0 // indirect
+	github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.4.1 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/ini v1.2.1 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/accept-encoding v1.2.2 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.2.3 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/s3shared v1.5.3 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sso v1.3.3 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sts v1.6.2 // indirect
+	github.com/danwakefield/fnmatch v0.0.0-20160403171240-cbb64ac3d964 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/dlclark/regexp2 v1.4.0 // indirect
+	github.com/huandu/xstrings v1.3.2 // indirect
+	github.com/imdario/mergo v0.3.12 // indirect
+	github.com/inconshreveable/mousetrap v1.0.0 // indirect
+	github.com/jackc/chunkreader/v2 v2.0.1 // indirect
+	github.com/jackc/pgio v1.0.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgproto3/v2 v2.0.6 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20200714003250-2b9c44734f2b // indirect
+	github.com/jackc/puddle v1.1.3 // indirect
+	github.com/mitchellh/copystructure v1.1.1 // indirect
+	github.com/mitchellh/reflectwalk v1.0.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 // indirect
+	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 // indirect
+	golang.org/x/text v0.3.6 // indirect
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)
+
 replace (
 	github.com/frustra/bbcode v0.0.0-20201127003707-6ef347fbe1c8 => github.com/HandmadeNetwork/bbcode v0.0.0-20210623031351-ec0e2e2e39d9
 	github.com/yuin/goldmark v1.4.1 => github.com/HandmadeNetwork/goldmark v1.4.1-0.20210707024600-f7e596e26b5e

go.sum

@@ -159,7 +159,6 @@ github.com/imdario/mergo v0.3.12 h1:b6R2BslTbIEToALKP7LxUvijTsNI9TAe80pLWN2g/HU=
 github.com/imdario/mergo v0.3.12/go.mod h1:jmQim1M+e3UYxmgPu/WyfjB3N3VflVyUjjjwH0dnCYA=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
-github.com/jackc/chunkreader v1.0.0 h1:4s39bBR8ByfqH+DKm8rQA3E1LHZWB9XWcrz8fqaZbe0=
 github.com/jackc/chunkreader v1.0.0/go.mod h1:RT6O25fNZIuasFJRyZ4R/Y2BbhasbmZXF9QQ7T3kePo=
 github.com/jackc/chunkreader/v2 v2.0.0/go.mod h1:odVSm741yZoC3dpHEUXIqA9tQRhFrgOHwnPIn9lDKlk=
 github.com/jackc/chunkreader/v2 v2.0.1 h1:i+RDz65UE+mmpjTfyz0MoVTnzeYxroil2G82ki7MGG8=
@@ -178,7 +177,6 @@ github.com/jackc/pgmock v0.0.0-20190831213851-13a1b77aafa2 h1:JVX6jT/XfzNqIjye47
 github.com/jackc/pgmock v0.0.0-20190831213851-13a1b77aafa2/go.mod h1:fGZlG77KXmcq05nJLRkk0+p82V8B8Dw8KN2/V9c/OAE=
 github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
-github.com/jackc/pgproto3 v1.1.0 h1:FYYE4yRw+AgI8wXIinMlNjBbp/UitDJwfj5LqqewP1A=
 github.com/jackc/pgproto3 v1.1.0/go.mod h1:eR5FA3leWg7p9aeAqi37XOTgTIbkABlvcPB3E5rlc78=
 github.com/jackc/pgproto3/v2 v2.0.0-alpha1.0.20190420180111-c116219b62db/go.mod h1:bhq50y+xrl9n5mRYyCBFKkpRVTLYJVWeCc+mEAI3yXA=
 github.com/jackc/pgproto3/v2 v2.0.0-alpha1.0.20190609003834-432c2951c711/go.mod h1:uH0AWtUmuShn0bcesswc4aBTWGvw0cAxIJp+6OB//Wg=

src/admintools/adminproject.go

@@ -55,7 +55,7 @@ func addCreateProjectCommand(projectCommand *cobra.Command) {
 			}
 			hmn := p.Project
 
-			newProjectID, err := db.QueryInt(ctx, tx,
+			newProjectID, err := db.QueryOneScalar[int](ctx, tx,
 				`
 				INSERT INTO handmade_project (
 					slug,

src/admintools/admintools.go

@@ -210,7 +210,7 @@ func init() {
 			}
 			defer tx.Rollback(ctx)
 
-			projectId, err := db.QueryInt(ctx, tx, `SELECT id FROM handmade_project WHERE slug = $1`, projectSlug)
+			projectId, err := db.QueryOneScalar[int](ctx, tx, `SELECT id FROM handmade_project WHERE slug = $1`, projectSlug)
 			if err != nil {
 				panic(err)
 			}
@@ -218,7 +218,7 @@ func init() {
 			var parentId *int
 			if parentSlug == "" {
 				// Select the root subforum
-				id, err := db.QueryInt(ctx, tx,
+				id, err := db.QueryOneScalar[int](ctx, tx,
 					`SELECT id FROM handmade_subforum WHERE parent_id IS NULL AND project_id = $1`,
 					projectId,
 				)
@@ -228,7 +228,7 @@ func init() {
 				parentId = &id
 			} else {
 				// Select the parent
-				id, err := db.QueryInt(ctx, tx,
+				id, err := db.QueryOneScalar[int](ctx, tx,
 					`SELECT id FROM handmade_subforum WHERE slug = $1 AND project_id = $2`,
 					parentSlug, projectId,
 				)
@@ -238,7 +238,7 @@ func init() {
 				parentId = &id
 			}
 
-			newId, err := db.QueryInt(ctx, tx,
+			newId, err := db.QueryOneScalar[int](ctx, tx,
 				`
 				INSERT INTO handmade_subforum (name, slug, blurb, parent_id, project_id)
 				VALUES ($1, $2, $3, $4, $5)
@@ -289,12 +289,12 @@ func init() {
 			}
 			defer tx.Rollback(ctx)
 
-			projectId, err := db.QueryInt(ctx, tx, `SELECT id FROM handmade_project WHERE slug = $1`, projectSlug)
+			projectId, err := db.QueryOneScalar[int](ctx, tx, `SELECT id FROM handmade_project WHERE slug = $1`, projectSlug)
 			if err != nil {
 				panic(err)
 			}
 
-			subforumId, err := db.QueryInt(ctx, tx,
+			subforumId, err := db.QueryOneScalar[int](ctx, tx,
 				`SELECT id FROM handmade_subforum WHERE slug = $1 AND project_id = $2`,
 				subforumSlug, projectId,
 			)

src/assets/assets.go

@@ -140,7 +140,7 @@ func Create(ctx context.Context, dbConn db.ConnOrTx, in CreateInput) (*models.As
 	}
 
 	// Fetch and return the new record
-	iasset, err := db.QueryOne(ctx, dbConn, models.Asset{},
+	asset, err := db.QueryOne[models.Asset](ctx, dbConn,
 		`
 		SELECT $columns
 		FROM handmade_asset
@@ -152,5 +152,5 @@ func Create(ctx context.Context, dbConn db.ConnOrTx, in CreateInput) (*models.As
 		return nil, oops.New(err, "failed to fetch newly-created asset")
 	}
 
-	return iasset.(*models.Asset), nil
+	return asset, nil
 }

src/auth/session.go

@@ -45,7 +45,7 @@ func makeCSRFToken() string {
 var ErrNoSession = errors.New("no session found")
 
 func GetSession(ctx context.Context, conn *pgxpool.Pool, id string) (*models.Session, error) {
-	row, err := db.QueryOne(ctx, conn, models.Session{}, "SELECT $columns FROM sessions WHERE id = $1", id)
+	sess, err := db.QueryOne[models.Session](ctx, conn, "SELECT $columns FROM sessions WHERE id = $1", id)
 	if err != nil {
 		if errors.Is(err, db.NotFound) {
 			return nil, ErrNoSession
@@ -53,7 +53,6 @@ func GetSession(ctx context.Context, conn *pgxpool.Pool, id string) (*models.Ses
 			return nil, oops.New(err, "failed to get session")
 		}
 	}
-	sess := row.(*models.Session)
 
 	return sess, nil
 }

src/db/db.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"regexp"
 	"strings"
 
 	"git.handmade.network/hmn/hmn/src/config"
@@ -20,46 +21,17 @@ import (
 )
 
 /*
-Values of these kinds are ok to query even if they are not directly understood by pgtype.
-This is common for custom types like:
-
-	type ThreadType int
+A general error to be used when no results are found. This is the error returned
+by QueryOne, and can generally be used by other database helpers that fetch a single
+result but find nothing.
 */
-var queryableKinds = []reflect.Kind{
-	reflect.Int,
-}
-
-/*
-Checks if we are able to handle a particular type in a database query. This applies only to
-primitive types and not structs, since the database only returns individual primitive types
-and it is our job to stitch them back together into structs later.
-*/
-func typeIsQueryable(t reflect.Type) bool {
-	_, isRecognizedByPgtype := connInfo.DataTypeForValue(reflect.New(t).Elem().Interface()) // if pgtype recognizes it, we don't need to dig in further for more `db` tags
-	// NOTE: boy it would be nice if we didn't have to do reflect.New here, considering that pgtype is just doing reflection on the value anyway
-
-	if isRecognizedByPgtype {
-		return true
-	} else if t == reflect.TypeOf(uuid.UUID{}) {
-		return true
-	}
-
-	// pgtype doesn't recognize it, but maybe it's a primitive type we can deal with
-	k := t.Kind()
-	for _, qk := range queryableKinds {
-		if k == qk {
-			return true
-		}
-	}
-
-	return false
-}
+var NotFound = errors.New("not found")
 
 // This interface should match both a direct pgx connection or a pgx transaction.
 type ConnOrTx interface {
-	Query(ctx context.Context, sql string, args ...interface{}) (pgx.Rows, error)
-	QueryRow(ctx context.Context, sql string, args ...interface{}) pgx.Row
-	Exec(ctx context.Context, sql string, args ...interface{}) (pgconn.CommandTag, error)
+	Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)
+	QueryRow(ctx context.Context, sql string, args ...any) pgx.Row
+	Exec(ctx context.Context, sql string, args ...any) (pgconn.CommandTag, error)
 
 	// Both raw database connections and transactions in pgx can begin/commit
 	// transactions. For database connections it does the obvious thing; for
@@ -70,6 +42,8 @@ type ConnOrTx interface {
 
 var connInfo = pgtype.NewConnInfo()
 
+// Creates a new connection to the HMN database.
+// This connection is not safe for concurrent use.
 func NewConn() *pgx.Conn {
 	conn, err := pgx.Connect(context.Background(), config.Config.Postgres.DSN())
 	if err != nil {
@@ -79,6 +53,8 @@ func NewConn() *pgx.Conn {
 	return conn
 }
 
+// Creates a connection pool for the HMN database.
+// The resulting pool is safe for concurrent use.
 func NewConnPool(minConns, maxConns int32) *pgxpool.Pool {
 	cfg, err := pgxpool.ParseConfig(config.Config.Postgres.DSN())
 
@@ -95,144 +71,20 @@ func NewConnPool(minConns, maxConns int32) *pgxpool.Pool {
 	return conn
 }
 
-type StructQueryIterator struct {
-	fieldPaths [][]int
-	rows       pgx.Rows
-	destType   reflect.Type
-	closed     chan struct{}
-}
+/*
+Performs a SQL query and returns a slice of all the result rows. The query is just plain SQL, but make sure to read the package documentation for details. You must explicitly provide the type argument - this is how it knows what Go type to map the results to, and it cannot be inferred.
 
-func (it *StructQueryIterator) Next() (interface{}, bool) {
-	hasNext := it.rows.Next()
-	if !hasNext {
-		it.Close()
-		return nil, false
-	}
+Any SQL query may be performed, including INSERT and UPDATE - as long as it returns a result set, you can use this. If the query does not return a result set, or you simply do not care about the result set, call Exec directly on your pgx connection.
 
-	result := reflect.New(it.destType)
-
-	vals, err := it.rows.Values()
-	if err != nil {
-		panic(err)
-	}
-
-	// Better logging of panics in this confusing reflection process
-	var currentField reflect.StructField
-	var currentValue reflect.Value
-	var currentIdx int
-	defer func() {
-		if r := recover(); r != nil {
-			if currentValue.IsValid() {
-				logging.Error().
-					Int("index", currentIdx).
-					Str("field name", currentField.Name).
-					Stringer("field type", currentField.Type).
-					Interface("value", currentValue.Interface()).
-					Stringer("value type", currentValue.Type()).
-					Msg("panic in iterator")
-			}
-
-			if currentField.Name != "" {
-				panic(fmt.Errorf("panic while processing field '%s': %v", currentField.Name, r))
-			} else {
-				panic(r)
-			}
-		}
-	}()
-
-	for i, val := range vals {
-		currentIdx = i
-		if val == nil {
-			continue
-		}
-
-		var field reflect.Value
-		field, currentField = followPathThroughStructs(result, it.fieldPaths[i])
-		if field.Kind() == reflect.Ptr {
-			field.Set(reflect.New(field.Type().Elem()))
-			field = field.Elem()
-		}
-
-		// Some actual values still come through as pointers (like net.IPNet). Dunno why.
-		// Regardless, we know it's not nil, so we can get at the contents.
-		valReflected := reflect.ValueOf(val)
-		if valReflected.Kind() == reflect.Ptr {
-			valReflected = valReflected.Elem()
-		}
-		currentValue = valReflected
-
-		switch field.Kind() {
-		case reflect.Int:
-			field.SetInt(valReflected.Int())
-		default:
-			field.Set(valReflected)
-		}
-
-		currentField = reflect.StructField{}
-		currentValue = reflect.Value{}
-	}
-
-	return result.Interface(), true
-}
-
-func (it *StructQueryIterator) Close() {
-	it.rows.Close()
-	select {
-	case it.closed <- struct{}{}:
-	default:
-	}
-}
-
-func (it *StructQueryIterator) ToSlice() []interface{} {
-	defer it.Close()
-	var result []interface{}
-	for {
-		row, ok := it.Next()
-		if !ok {
-			err := it.rows.Err()
-			if err != nil {
-				panic(oops.New(err, "error while iterating through db results"))
-			}
-			break
-		}
-		result = append(result, row)
-	}
-	return result
-}
-
-func followPathThroughStructs(structPtrVal reflect.Value, path []int) (reflect.Value, reflect.StructField) {
-	if len(path) < 1 {
-		panic(oops.New(nil, "can't follow an empty path"))
-	}
-
-	if structPtrVal.Kind() != reflect.Ptr || structPtrVal.Elem().Kind() != reflect.Struct {
-		panic(oops.New(nil, "structPtrVal must be a pointer to a struct; got value of type %s", structPtrVal.Type()))
-	}
-
-	// more informative panic recovery
-	var field reflect.StructField
-	defer func() {
-		if r := recover(); r != nil {
-			panic(oops.New(nil, "panic at field '%s': %v", field.Name, r))
-		}
-	}()
-
-	val := structPtrVal
-	for _, i := range path {
-		if val.Kind() == reflect.Ptr && val.Type().Elem().Kind() == reflect.Struct {
-			if val.IsNil() {
-				val.Set(reflect.New(val.Type().Elem()))
-			}
-			val = val.Elem()
-		}
-		field = val.Type().Field(i)
-		val = val.Field(i)
-	}
-	return val, field
-}
-
-func Query(ctx context.Context, conn ConnOrTx, destExample interface{}, query string, args ...interface{}) ([]interface{}, error) {
-	it, err := QueryIterator(ctx, conn, destExample, query, args...)
+This function always returns pointers to the values. This is convenient for structs, but for other types, you may wish to use QueryScalar.
+*/
+func Query[T any](
+	ctx context.Context,
+	conn ConnOrTx,
+	query string,
+	args ...any,
+) ([]*T, error) {
+	it, err := QueryIterator[T](ctx, conn, query, args...)
 	if err != nil {
 		return nil, err
 	} else {
@@ -240,27 +92,99 @@ func Query(ctx context.Context, conn ConnOrTx, destExample interface{}, query st
 	}
 }
 
-func QueryIterator(ctx context.Context, conn ConnOrTx, destExample interface{}, query string, args ...interface{}) (*StructQueryIterator, error) {
-	destType := reflect.TypeOf(destExample)
-	columnNames, fieldPaths, err := getColumnNamesAndPaths(destType, nil, nil)
+/*
+Identical to Query, but returns only the first result row. If there are no
+rows in the result set, returns NotFound.
+*/
+func QueryOne[T any](
+	ctx context.Context,
+	conn ConnOrTx,
+	query string,
+	args ...any,
+) (*T, error) {
+	rows, err := QueryIterator[T](ctx, conn, query, args...)
 	if err != nil {
-		return nil, oops.New(err, "failed to generate column names")
+		return nil, err
+	}
+	defer rows.Close()
+
+	result, hasRow := rows.Next()
+	if !hasRow {
+		return nil, NotFound
 	}
 
-	columns := make([]string, 0, len(columnNames))
-	for _, strSlice := range columnNames {
-		tableName := strings.Join(strSlice[0:len(strSlice)-1], "_")
-		fullName := strSlice[len(strSlice)-1]
-		if tableName != "" {
-			fullName = tableName + "." + fullName
+	return result, nil
+}
+
+/*
+Identical to Query, but returns concrete values instead of pointers. More convenient
+for primitive types.
+*/
+func QueryScalar[T any](
+	ctx context.Context,
+	conn ConnOrTx,
+	query string,
+	args ...any,
+) ([]T, error) {
+	rows, err := QueryIterator[T](ctx, conn, query, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []T
+	for {
+		val, hasRow := rows.Next()
+		if !hasRow {
+			break
 		}
-		columns = append(columns, fullName)
+		result = append(result, *val)
 	}
 
-	columnNamesString := strings.Join(columns, ", ")
-	query = strings.Replace(query, "$columns", columnNamesString, -1)
+	return result, nil
+}
 
-	rows, err := conn.Query(ctx, query, args...)
+/*
+Identical to QueryScalar, but returns only the first result value. If there are
+no rows in the result set, returns NotFound.
+*/
+func QueryOneScalar[T any](
+	ctx context.Context,
+	conn ConnOrTx,
+	query string,
+	args ...any,
+) (T, error) {
+	rows, err := QueryIterator[T](ctx, conn, query, args...)
+	if err != nil {
+		var zero T
+		return zero, err
+	}
+	defer rows.Close()
+
+	result, hasRow := rows.Next()
+	if !hasRow {
+		var zero T
+		return zero, NotFound
+	}
+
+	return *result, nil
+}
+
+/*
+Identical to Query, but returns the ResultIterator instead of automatically converting the results to a slice. The iterator must be closed after use.
+*/
+func QueryIterator[T any](
+	ctx context.Context,
+	conn ConnOrTx,
+	query string,
+	args ...any,
+) (*Iterator[T], error) {
+	var destExample T
+	destType := reflect.TypeOf(destExample)
+
+	compiled := compileQuery(query, destType)
+
+	rows, err := conn.Query(ctx, compiled.query, args...)
 	if err != nil {
 		if errors.Is(err, context.DeadlineExceeded) {
 			panic("query exceeded its deadline")
@@ -268,11 +192,12 @@ func QueryIterator(ctx context.Context, conn ConnOrTx, destExample interface{},
 		return nil, err
 	}
 
-	it := &StructQueryIterator{
-		fieldPaths: fieldPaths,
-		rows:       rows,
-		destType:   destType,
-		closed:     make(chan struct{}, 1),
+	it := &Iterator[T]{
+		fieldPaths:       compiled.fieldPaths,
+		rows:             rows,
+		destType:         compiled.destType,
+		destTypeIsScalar: typeIsQueryable(compiled.destType),
+		closed:           make(chan struct{}, 1),
 	}
 
 	// Ensure that iterators are closed if context is cancelled. Otherwise, iterators can hold
@@ -292,16 +217,72 @@ func QueryIterator(ctx context.Context, conn ConnOrTx, destExample interface{},
 	return it, nil
 }
 
-func getColumnNamesAndPaths(destType reflect.Type, pathSoFar []int, prefix []string) (names [][]string, paths [][]int, err error) {
-	var columnNames [][]string
-	var fieldPaths [][]int
+// TODO: QueryFunc?
+
+type compiledQuery struct {
+	query      string
+	destType   reflect.Type
+	fieldPaths []fieldPath
+}
+
+var reColumnsPlaceholder = regexp.MustCompile(`\$columns({(.*?)})?`)
+
+func compileQuery(query string, destType reflect.Type) compiledQuery {
+	columnsMatch := reColumnsPlaceholder.FindStringSubmatch(query)
+	hasColumnsPlaceholder := columnsMatch != nil
+
+	if hasColumnsPlaceholder {
+		// The presence of the $columns placeholder means that the destination type
+		// must be a struct, and we will plonk that struct's fields into the query.
+
+		if destType.Kind() != reflect.Struct {
+			panic("$columns can only be used when querying into a struct")
+		}
+
+		var prefix []string
+		prefixText := columnsMatch[2]
+		if prefixText != "" {
+			prefix = []string{prefixText}
+		}
+
+		columnNames, fieldPaths := getColumnNamesAndPaths(destType, nil, prefix)
+
+		columns := make([]string, 0, len(columnNames))
+		for _, strSlice := range columnNames {
+			tableName := strings.Join(strSlice[0:len(strSlice)-1], "_")
+			fullName := strSlice[len(strSlice)-1]
+			if tableName != "" {
+				fullName = tableName + "." + fullName
+			}
+			columns = append(columns, fullName)
+		}
+
+		columnNamesString := strings.Join(columns, ", ")
+		query = reColumnsPlaceholder.ReplaceAllString(query, columnNamesString)
+
+		return compiledQuery{
+			query:      query,
+			destType:   destType,
+			fieldPaths: fieldPaths,
+		}
+	} else {
+		return compiledQuery{
+			query:    query,
+			destType: destType,
+		}
+	}
+}
+
+func getColumnNamesAndPaths(destType reflect.Type, pathSoFar []int, prefix []string) (names []columnName, paths []fieldPath) {
+	var columnNames []columnName
+	var fieldPaths []fieldPath
 
 	if destType.Kind() == reflect.Ptr {
 		destType = destType.Elem()
 	}
 
 	if destType.Kind() != reflect.Struct {
-		return nil, nil, oops.New(nil, "can only get column names and paths from a struct, got type '%v' (at prefix '%v')", destType.Name(), prefix)
+		panic(fmt.Errorf("can only get column names and paths from a struct, got type '%v' (at prefix '%v')", destType.Name(), prefix))
 	}
 
 	type AnonPrefix struct {
@@ -348,108 +329,214 @@ func getColumnNamesAndPaths(destType reflect.Type, pathSoFar []int, prefix []str
 				columnNames = append(columnNames, fieldColumnNames)
 				fieldPaths = append(fieldPaths, path)
 			} else if fieldType.Kind() == reflect.Struct {
-				subCols, subPaths, err := getColumnNamesAndPaths(fieldType, path, fieldColumnNames)
-				if err != nil {
-					return nil, nil, err
-				}
+				subCols, subPaths := getColumnNamesAndPaths(fieldType, path, fieldColumnNames)
 				columnNames = append(columnNames, subCols...)
 				fieldPaths = append(fieldPaths, subPaths...)
 			} else {
-				return nil, nil, oops.New(nil, "field '%s' in type %s has invalid type '%s'", field.Name, destType, field.Type)
+				panic(fmt.Errorf("field '%s' in type %s has invalid type '%s'", field.Name, destType, field.Type))
 			}
 		}
 	}
 
-	return columnNames, fieldPaths, nil
+	return columnNames, fieldPaths
 }
 
 /*
-A general error to be used when no results are found. This is the error returned
-by QueryOne, and can generally be used by other database helpers that fetch a single
-result but find nothing.
+Values of these kinds are ok to query even if they are not directly understood by pgtype.
+This is common for custom types like:
+
+	type ThreadType int
 */
-var NotFound = errors.New("not found")
-
-func QueryOne(ctx context.Context, conn ConnOrTx, destExample interface{}, query string, args ...interface{}) (interface{}, error) {
-	rows, err := QueryIterator(ctx, conn, destExample, query, args...)
-	if err != nil {
-		return nil, err
-	}
-	defer rows.Close()
-
-	result, hasRow := rows.Next()
-	if !hasRow {
-		return nil, NotFound
-	}
-
-	return result, nil
+var queryableKinds = []reflect.Kind{
+	reflect.Int,
 }
 
-func QueryScalar(ctx context.Context, conn ConnOrTx, query string, args ...interface{}) (interface{}, error) {
-	rows, err := conn.Query(ctx, query, args...)
-	if err != nil {
-		return nil, err
+/*
+Checks if we are able to handle a particular type in a database query. This applies only to
+primitive types and not structs, since the database only returns individual primitive types
+and it is our job to stitch them back together into structs later.
+*/
+func typeIsQueryable(t reflect.Type) bool {
+	_, isRecognizedByPgtype := connInfo.DataTypeForValue(reflect.New(t).Elem().Interface()) // if pgtype recognizes it, we don't need to dig in further for more `db` tags
+	// NOTE: boy it would be nice if we didn't have to do reflect.New here, considering that pgtype is just doing reflection on the value anyway
+
+	if isRecognizedByPgtype {
+		return true
+	} else if t == reflect.TypeOf(uuid.UUID{}) {
+		return true
 	}
-	defer rows.Close()
 
-	if rows.Next() {
-		vals, err := rows.Values()
-		if err != nil {
-			panic(err)
+	// pgtype doesn't recognize it, but maybe it's a primitive type we can deal with
+	k := t.Kind()
+	for _, qk := range queryableKinds {
+		if k == qk {
+			return true
 		}
+	}
 
+	return false
+}
+
+type columnName []string
+
+// A path to a particular field in query's destination type. Each index in the slice
+// corresponds to a field index for use with Field on a reflect.Type or reflect.Value.
+type fieldPath []int
+
+type Iterator[T any] struct {
+	fieldPaths       []fieldPath
+	rows             pgx.Rows
+	destType         reflect.Type
+	destTypeIsScalar bool // NOTE(ben): Make sure this gets set every time destType gets set, based on typeIsQueryable(destType). This is kinda fragile...but also contained to this file, so doesn't seem worth a lazy evaluation or a constructor function.
+	closed           chan struct{}
+}
+
+func (it *Iterator[T]) Next() (*T, bool) {
+	// TODO(ben): What happens if this panics? Does it leak resources? Do we need
+	// to put a recover() here and close the rows?
+
+	hasNext := it.rows.Next()
+	if !hasNext {
+		it.Close()
+		return nil, false
+	}
+
+	result := reflect.New(it.destType)
+
+	vals, err := it.rows.Values()
+	if err != nil {
+		panic(err)
+	}
+
+	if it.destTypeIsScalar {
+		// This type can be directly queried, meaning pgx recognizes it, it's
+		// a simple scalar thing, and we can just take the easy way out.
 		if len(vals) != 1 {
-			return nil, oops.New(nil, "you must query exactly one field with QueryScalar, not %v", len(vals))
+			panic(fmt.Errorf("tried to query a scalar value, but got %v values in the row", len(vals)))
+		}
+		setValueFromDB(result.Elem(), reflect.ValueOf(vals[0]))
+		return result.Interface().(*T), true
+	} else {
+		var currentField reflect.StructField
+		var currentValue reflect.Value
+		var currentIdx int
+
+		// Better logging of panics in this confusing reflection process
+		defer func() {
+			if r := recover(); r != nil {
+				if currentValue.IsValid() {
+					logging.Error().
+						Int("index", currentIdx).
+						Str("field name", currentField.Name).
+						Stringer("field type", currentField.Type).
+						Interface("value", currentValue.Interface()).
+						Stringer("value type", currentValue.Type()).
+						Msg("panic in iterator")
+				}
+
+				if currentField.Name != "" {
+					panic(fmt.Errorf("panic while processing field '%s': %v", currentField.Name, r))
+				} else {
+					panic(r)
+				}
+			}
+		}()
+
+		for i, val := range vals {
+			currentIdx = i
+			if val == nil {
+				continue
+			}
+
+			var field reflect.Value
+			field, currentField = followPathThroughStructs(result, it.fieldPaths[i])
+			if field.Kind() == reflect.Ptr {
+				field.Set(reflect.New(field.Type().Elem()))
+				field = field.Elem()
+			}
+
+			// Some actual values still come through as pointers (like net.IPNet). Dunno why.
+			// Regardless, we know it's not nil, so we can get at the contents.
+			valReflected := reflect.ValueOf(val)
+			if valReflected.Kind() == reflect.Ptr {
+				valReflected = valReflected.Elem()
+			}
+			currentValue = valReflected
+
+			setValueFromDB(field, valReflected)
+
+			currentField = reflect.StructField{}
+			currentValue = reflect.Value{}
 		}
 
-		return vals[0], nil
+		return result.Interface().(*T), true
 	}
-
-	return nil, NotFound
 }
 
-func QueryString(ctx context.Context, conn ConnOrTx, query string, args ...interface{}) (string, error) {
-	result, err := QueryScalar(ctx, conn, query, args...)
-	if err != nil {
-		return "", err
-	}
-
-	switch r := result.(type) {
-	case string:
-		return r, nil
+func setValueFromDB(dest reflect.Value, value reflect.Value) {
+	switch dest.Kind() {
+	case reflect.Int:
+		dest.SetInt(value.Int())
 	default:
-		return "", oops.New(nil, "QueryString got a non-string result: %v", result)
+		dest.Set(value)
 	}
 }
 
-func QueryInt(ctx context.Context, conn ConnOrTx, query string, args ...interface{}) (int, error) {
-	result, err := QueryScalar(ctx, conn, query, args...)
-	if err != nil {
-		return 0, err
-	}
-
-	switch r := result.(type) {
-	case int:
-		return r, nil
-	case int32:
-		return int(r), nil
-	case int64:
-		return int(r), nil
+func (it *Iterator[any]) Close() {
+	it.rows.Close()
+	select {
+	case it.closed <- struct{}{}:
 	default:
-		return 0, oops.New(nil, "QueryInt got a non-int result: %v", result)
 	}
 }
 
-func QueryBool(ctx context.Context, conn ConnOrTx, query string, args ...interface{}) (bool, error) {
-	result, err := QueryScalar(ctx, conn, query, args...)
-	if err != nil {
-		return false, err
+/*
+Pulls all the remaining values into a slice, and closes the iterator.
+*/
+func (it *Iterator[T]) ToSlice() []*T {
+	defer it.Close()
+	var result []*T
+	for {
+		row, ok := it.Next()
+		if !ok {
+			err := it.rows.Err()
+			if err != nil {
+				panic(oops.New(err, "error while iterating through db results"))
+			}
+			break
+		}
+		result = append(result, row)
+	}
+	return result
+}
+
+func followPathThroughStructs(structPtrVal reflect.Value, path []int) (reflect.Value, reflect.StructField) {
+	if len(path) < 1 {
+		panic(oops.New(nil, "can't follow an empty path"))
 	}
 
-	switch r := result.(type) {
-	case bool:
-		return r, nil
-	default:
-		return false, oops.New(nil, "QueryBool got a non-bool result: %v", result)
+	if structPtrVal.Kind() != reflect.Ptr || structPtrVal.Elem().Kind() != reflect.Struct {
+		panic(oops.New(nil, "structPtrVal must be a pointer to a struct; got value of type %s", structPtrVal.Type()))
 	}
+
+	// more informative panic recovery
+	var field reflect.StructField
+	defer func() {
+		if r := recover(); r != nil {
+			panic(oops.New(nil, "panic at field '%s': %v", field.Name, r))
+		}
+	}()
+
+	val := structPtrVal
+	for _, i := range path {
+		if val.Kind() == reflect.Ptr && val.Type().Elem().Kind() == reflect.Struct {
+			if val.IsNil() {
+				val.Set(reflect.New(val.Type().Elem()))
+			}
+			val = val.Elem()
+		}
+		field = val.Type().Field(i)
+		val = val.Field(i)
+	}
+	return val, field
 }

src/db/db_test.go

@@ -10,52 +10,143 @@ import (
 
 func TestPaths(t *testing.T) {
 	type CustomInt int
-	type S struct {
-		I   int        `db:"I"`
-		PI  *int       `db:"PI"`
-		CI  CustomInt  `db:"CI"`
-		PCI *CustomInt `db:"PCI"`
-		B   bool       `db:"B"`
-		PB  *bool      `db:"PB"`
+	type S2 struct {
+		B  bool  `db:"B"`  // field 0
+		PB *bool `db:"PB"` // field 1
 
-		NoTag int
+		NoTag string // field 2
+	}
+	type S struct {
+		I   int        `db:"I"`   // field 0
+		PI  *int       `db:"PI"`  // field 1
+		CI  CustomInt  `db:"CI"`  // field 2
+		PCI *CustomInt `db:"PCI"` // field 3
+		S2  `db:"S2"`  // field 4 (embedded!)
+		PS2 *S2        `db:"PS2"` // field 5
+
+		NoTag int // field 6
 	}
 	type Nested struct {
-		S  S  `db:"S"`
-		PS *S `db:"PS"`
+		S  S  `db:"S"`  // field 0
+		PS *S `db:"PS"` // field 1
 
-		NoTag S
+		NoTag S // field 2
 	}
 	type Embedded struct {
-		NoTag S
-		Nested
+		NoTag  S // field 0
+		Nested   // field 1
 	}
 
-	names, paths, err := getColumnNamesAndPaths(reflect.TypeOf(Embedded{}), nil, "")
-	if assert.Nil(t, err) {
-		assert.Equal(t, []string{
-			"S.I", "S.PI",
-			"S.CI", "S.PCI",
-			"S.B", "S.PB",
-			"PS.I", "PS.PI",
-			"PS.CI", "PS.PCI",
-			"PS.B", "PS.PB",
-		}, names)
-		assert.Equal(t, [][]int{
-			{1, 0, 0}, {1, 0, 1}, {1, 0, 2}, {1, 0, 3}, {1, 0, 4}, {1, 0, 5},
-			{1, 1, 0}, {1, 1, 1}, {1, 1, 2}, {1, 1, 3}, {1, 1, 4}, {1, 1, 5},
-		}, paths)
-		assert.True(t, len(names) == len(paths))
-	}
+	names, paths := getColumnNamesAndPaths(reflect.TypeOf(Embedded{}), nil, nil)
+	assert.Equal(t, []columnName{
+		{"S", "I"}, {"S", "PI"},
+		{"S", "CI"}, {"S", "PCI"},
+		{"S", "S2", "B"}, {"S", "S2", "PB"},
+		{"S", "PS2", "B"}, {"S", "PS2", "PB"},
+		{"PS", "I"}, {"PS", "PI"},
+		{"PS", "CI"}, {"PS", "PCI"},
+		{"PS", "S2", "B"}, {"PS", "S2", "PB"},
+		{"PS", "PS2", "B"}, {"PS", "PS2", "PB"},
+	}, names)
+	assert.Equal(t, []fieldPath{
+		{1, 0, 0}, {1, 0, 1}, // Nested.S.I, Nested.S.PI
+		{1, 0, 2}, {1, 0, 3}, // Nested.S.CI, Nested.S.PCI
+		{1, 0, 4, 0}, {1, 0, 4, 1}, // Nested.S.S2.B, Nested.S.S2.PB
+		{1, 0, 5, 0}, {1, 0, 5, 1}, // Nested.S.PS2.B, Nested.S.PS2.PB
+		{1, 1, 0}, {1, 1, 1}, // Nested.PS.I, Nested.PS.PI
+		{1, 1, 2}, {1, 1, 3}, // Nested.PS.CI, Nested.PS.PCI
+		{1, 1, 4, 0}, {1, 1, 4, 1}, // Nested.PS.S2.B, Nested.PS.S2.PB
+		{1, 1, 5, 0}, {1, 1, 5, 1}, // Nested.PS.PS2.B, Nested.PS.PS2.PB
+	}, paths)
+	assert.True(t, len(names) == len(paths))
 
 	testStruct := Embedded{}
 	for i, path := range paths {
 		val, field := followPathThroughStructs(reflect.ValueOf(&testStruct), path)
 		assert.True(t, val.IsValid())
-		assert.True(t, strings.Contains(names[i], field.Name))
+		assert.True(t, strings.Contains(names[i][len(names[i])-1], field.Name))
 	}
 }
 
+func TestCompileQuery(t *testing.T) {
+	t.Run("simple struct", func(t *testing.T) {
+		type Dest struct {
+			Foo  int    `db:"foo"`
+			Bar  bool   `db:"bar"`
+			Nope string // no tag
+		}
+
+		compiled := compileQuery("SELECT $columns FROM greeblies", reflect.TypeOf(Dest{}))
+		assert.Equal(t, "SELECT foo, bar FROM greeblies", compiled.query)
+	})
+	t.Run("complex structs", func(t *testing.T) {
+		type CustomInt int
+		type S2 struct {
+			B  bool  `db:"B"`
+			PB *bool `db:"PB"`
+
+			NoTag string
+		}
+		type S struct {
+			I   int        `db:"I"`
+			PI  *int       `db:"PI"`
+			CI  CustomInt  `db:"CI"`
+			PCI *CustomInt `db:"PCI"`
+			S2  `db:"S2"`  // embedded!
+			PS2 *S2        `db:"PS2"`
+
+			NoTag int
+		}
+		type Nested struct {
+			S  S  `db:"S"`
+			PS *S `db:"PS"`
+
+			NoTag S
+		}
+		type Dest struct {
+			NoTag S
+			Nested
+		}
+
+		compiled := compileQuery("SELECT $columns FROM greeblies", reflect.TypeOf(Dest{}))
+		assert.Equal(t, "SELECT S.I, S.PI, S.CI, S.PCI, S_S2.B, S_S2.PB, S_PS2.B, S_PS2.PB, PS.I, PS.PI, PS.CI, PS.PCI, PS_S2.B, PS_S2.PB, PS_PS2.B, PS_PS2.PB FROM greeblies", compiled.query)
+	})
+	t.Run("int", func(t *testing.T) {
+		type Dest int
+
+		// There should be no error here because we do not need to extract columns from
+		// the destination type. There may be errors down the line in value iteration, but
+		// that is always the case if the Go types don't match the query.
+		compiled := compileQuery("SELECT id FROM greeblies", reflect.TypeOf(Dest(0)))
+		assert.Equal(t, "SELECT id FROM greeblies", compiled.query)
+	})
+	t.Run("just one table", func(t *testing.T) {
+		type Dest struct {
+			Foo  int    `db:"foo"`
+			Bar  bool   `db:"bar"`
+			Nope string // no tag
+		}
+
+		// The prefix is necessary because otherwise we would have to provide a struct with
+		// a db tag in order to provide the query with the `greeblies.` prefix in the
+		// final query. This comes up a lot when we do a JOIN to help with a condition, but
+		// don't actually care about any of the data we joined to.
+		compiled := compileQuery(
+			"SELECT $columns{greeblies} FROM greeblies NATURAL JOIN props",
+			reflect.TypeOf(Dest{}),
+		)
+		assert.Equal(t, "SELECT greeblies.foo, greeblies.bar FROM greeblies NATURAL JOIN props", compiled.query)
+	})
+
+	t.Run("using $columns without a struct is not allowed", func(t *testing.T) {
+		type Dest int
+
+		assert.Panics(t, func() {
+			compileQuery("SELECT $columns FROM greeblies", reflect.TypeOf(Dest(0)))
+		})
+	})
+}
+
 func TestQueryBuilder(t *testing.T) {
 	t.Run("happy time", func(t *testing.T) {
 		var qb QueryBuilder

src/db/doc.go

@@ -0,0 +1,59 @@
+/*
+This package contains lowish-level APIs for making database queries to our Postgres database. It streamlines the process of mapping query results to Go types, while allowing you to write arbitrary SQL queries.
+
+The primary functions are Query and QueryIterator. See the package and function examples for detailed usage.
+
+Query syntax
+
+This package allows a few small extensions to SQL syntax to streamline the interaction between Go and Postgres.
+
+Arguments can be provided using placeholders like $1, $2, etc. All arguments will be safely escaped and mapped from their Go type to the correct Postgres type. (This is a direct proxy to pgx.)
+
+	projectIDs, err := db.Query[int](ctx, conn,
+		`
+		SELECT id
+		FROM handmade_project
+		WHERE
+			slug = ANY($1)
+			AND hidden = $2
+		`,
+		[]string{"4coder", "metadesk"},
+		false,
+	)
+
+(This also demonstrates a useful tip: if you want to use a slice in your query, use Postgres arrays instead of IN.)
+
+When querying individual fields, you can simply select the field like so:
+
+	ids, err := db.Query[int](ctx, conn, `SELECT id FROM handmade_project`)
+
+To query multiple columns at once, you may use a struct type with `db:"column_name"` tags, and the special $columns placeholder:
+
+	type Project struct {
+		ID          int       `db:"id"`
+		Slug        string    `db:"slug"`
+		DateCreated time.Time `db:"date_created"`
+	}
+	projects, err := db.Query[Project](ctx, conn, `SELECT $columns FROM ...`)
+	// Resulting query:
+	// SELECT id, slug, date_created FROM ...
+
+Sometimes a table name prefix is required on each column to disambiguate between column names, especially when performing a JOIN. In those situations, you can include the prefix in the $columns placeholder like $columns{prefix}:
+
+	type Project struct {
+		ID          int       `db:"id"`
+		Slug        string    `db:"slug"`
+		DateCreated time.Time `db:"date_created"`
+	}
+	orphanedProjects, err := db.Query[Project](ctx, conn, `
+		SELECT $columns{projects}
+		FROM
+			handmade_project AS projects
+			LEFT JOIN handmade_user_projects AS uproj
+		WHERE
+			uproj.user_id IS NULL
+	`)
+	// Resulting query:
+	// SELECT projects.id, projects.slug, projects.date_created FROM ...
+*/
+package db

src/db/query_builder.go

@@ -7,7 +7,7 @@ import (
 
 type QueryBuilder struct {
 	sql  strings.Builder
-	args []interface{}
+	args []any
 }
 
 /*
@@ -18,7 +18,7 @@ of `$?` will be replaced with the correct argument number.
 	foo ARG1 bar ARG2 baz $?
 	foo ARG1 bar ARG2 baz ARG3
 */
-func (qb *QueryBuilder) Add(sql string, args ...interface{}) {
+func (qb *QueryBuilder) Add(sql string, args ...any) {
 	numPlaceholders := strings.Count(sql, "$?")
 	if numPlaceholders != len(args) {
 		panic(fmt.Errorf("cannot add chunk to query; expected %d arguments but got %d", numPlaceholders, len(args)))
@@ -37,6 +37,6 @@ func (qb *QueryBuilder) String() string {
 	return qb.sql.String()
 }
 
-func (qb *QueryBuilder) Args() []interface{} {
+func (qb *QueryBuilder) Args() []any {
 	return qb.args
 }

src/discord/commands.go

@@ -90,12 +90,9 @@ func (bot *botInstance) handleProfileCommand(ctx context.Context, i *Interaction
 		return
 	}
 
-	type profileResult struct {
-		HMNUser models.User `db:"auth_user"`
-	}
-	ires, err := db.QueryOne(ctx, bot.dbConn, profileResult{},
+	hmnUser, err := db.QueryOne[models.User](ctx, bot.dbConn,
 		`
-		SELECT $columns
+		SELECT $columns{auth_user}
 		FROM
 			handmade_discorduser AS duser
 			JOIN auth_user ON duser.hmn_user_id = auth_user.id
@@ -122,16 +119,15 @@ func (bot *botInstance) handleProfileCommand(ctx context.Context, i *Interaction
 		}
 		return
 	}
-	res := ires.(*profileResult)
 
 	projectsAndStuff, err := hmndata.FetchProjects(ctx, bot.dbConn, nil, hmndata.ProjectsQuery{
-		OwnerIDs: []int{res.HMNUser.ID},
+		OwnerIDs: []int{hmnUser.ID},
 	})
 	if err != nil {
 		logging.ExtractLogger(ctx).Error().Err(err).Msg("failed to fetch user projects")
 	}
 
-	url := hmnurl.BuildUserProfile(res.HMNUser.Username)
+	url := hmnurl.BuildUserProfile(hmnUser.Username)
 	msg := fmt.Sprintf("<@%s>'s profile can be viewed at %s.", member.User.ID, url)
 	if len(projectsAndStuff) > 0 {
 		projectNoun := "projects"

src/discord/gateway.go

@@ -250,7 +250,7 @@ func (bot *botInstance) connect(ctx context.Context) error {
 	// an old one or starting a new one.
 
 	shouldResume := true
-	isession, err := db.QueryOne(ctx, bot.dbConn, models.DiscordSession{}, `SELECT $columns FROM discord_session`)
+	session, err := db.QueryOne[models.DiscordSession](ctx, bot.dbConn, `SELECT $columns FROM discord_session`)
 	if err != nil {
 		if errors.Is(err, db.NotFound) {
 			// No session yet! Just identify and get on with it
@@ -262,8 +262,6 @@ func (bot *botInstance) connect(ctx context.Context) error {
 
 	if shouldResume {
 		// Reconnect to the previous session
-		session := isession.(*models.DiscordSession)
-
 		err := bot.sendGatewayMessage(ctx, GatewayMessage{
 			Opcode: OpcodeResume,
 			Data: Resume{
@@ -356,7 +354,7 @@ func (bot *botInstance) doSender(ctx context.Context) {
 		}
 		bot.didAckHeartbeat = false
 
-		latestSequenceNumber, err := db.QueryInt(ctx, bot.dbConn, `SELECT sequence_number FROM discord_session`)
+		latestSequenceNumber, err := db.QueryOneScalar[int](ctx, bot.dbConn, `SELECT sequence_number FROM discord_session`)
 		if err != nil {
 			log.Error().Err(err).Msg("failed to fetch latest sequence number from the db")
 			return false
@@ -408,7 +406,7 @@ func (bot *botInstance) doSender(ctx context.Context) {
 				}
 				defer tx.Rollback(ctx)
 
-				msgs, err := db.Query(ctx, tx, models.DiscordOutgoingMessage{}, `
+				msgs, err := db.Query[models.DiscordOutgoingMessage](ctx, tx, `
 					SELECT $columns
 					FROM discord_outgoingmessages
 					ORDER BY id ASC
@@ -418,8 +416,7 @@ func (bot *botInstance) doSender(ctx context.Context) {
 					return
 				}
 
-				for _, imsg := range msgs {
-					msg := imsg.(*models.DiscordOutgoingMessage)
+				for _, msg := range msgs {
 					if time.Now().After(msg.ExpiresAt) {
 						continue
 					}

src/discord/history.go

@@ -73,12 +73,9 @@ func RunHistoryWatcher(ctx context.Context, dbConn *pgxpool.Pool) <-chan struct{
 func fetchMissingContent(ctx context.Context, dbConn *pgxpool.Pool) {
 	log := logging.ExtractLogger(ctx)
 
-	type query struct {
-		Message models.DiscordMessage `db:"msg"`
-	}
-	imessagesWithoutContent, err := db.Query(ctx, dbConn, query{},
+	messagesWithoutContent, err := db.Query[models.DiscordMessage](ctx, dbConn,
 		`
-		SELECT $columns
+		SELECT $columns{msg}
 		FROM
 			handmade_discordmessage AS msg
 			JOIN handmade_discorduser AS duser ON msg.user_id = duser.userid -- only fetch messages for linked discord users
@@ -95,10 +92,10 @@ func fetchMissingContent(ctx context.Context, dbConn *pgxpool.Pool) {
 		return
 	}
 
-	if len(imessagesWithoutContent) > 0 {
-		log.Info().Msgf("There are %d Discord messages without content, fetching their content now...", len(imessagesWithoutContent))
+	if len(messagesWithoutContent) > 0 {
+		log.Info().Msgf("There are %d Discord messages without content, fetching their content now...", len(messagesWithoutContent))
 	msgloop:
-		for _, imsg := range imessagesWithoutContent {
+		for _, msg := range messagesWithoutContent {
 			select {
 			case <-ctx.Done():
 				log.Info().Msg("Scrape was canceled")
@@ -106,8 +103,6 @@ func fetchMissingContent(ctx context.Context, dbConn *pgxpool.Pool) {
 			default:
 			}
 
-			msg := imsg.(*query).Message
-
 			discordMsg, err := GetChannelMessage(ctx, msg.ChannelID, msg.ID)
 			if errors.Is(err, NotFound) {
 				// This message has apparently been deleted; delete it from our database

src/discord/message_handling.go

@@ -165,7 +165,7 @@ func InternMessage(
 	dbConn db.ConnOrTx,
 	msg *Message,
 ) error {
-	_, err := db.QueryOne(ctx, dbConn, models.DiscordMessage{},
+	_, err := db.QueryOne[models.DiscordMessage](ctx, dbConn,
 		`
 		SELECT $columns
 		FROM handmade_discordmessage
@@ -219,7 +219,7 @@ type InternedMessage struct {
 }
 
 func FetchInternedMessage(ctx context.Context, dbConn db.ConnOrTx, msgId string) (*InternedMessage, error) {
-	result, err := db.QueryOne(ctx, dbConn, InternedMessage{},
+	interned, err := db.QueryOne[InternedMessage](ctx, dbConn,
 		`
 		SELECT $columns
 		FROM
@@ -235,8 +235,6 @@ func FetchInternedMessage(ctx context.Context, dbConn db.ConnOrTx, msgId string)
 	if err != nil {
 		return nil, err
 	}
-
-	interned := result.(*InternedMessage)
 	return interned, nil
 }
 
@@ -283,7 +281,7 @@ func HandleInternedMessage(ctx context.Context, dbConn db.ConnOrTx, msg *Message
 }
 
 func DeleteInternedMessage(ctx context.Context, dbConn db.ConnOrTx, interned *InternedMessage) error {
-	isnippet, err := db.QueryOne(ctx, dbConn, models.Snippet{},
+	snippet, err := db.QueryOne[models.Snippet](ctx, dbConn,
 		`
 		SELECT $columns
 		FROM handmade_snippet
@@ -294,10 +292,6 @@ func DeleteInternedMessage(ctx context.Context, dbConn db.ConnOrTx, interned *In
 	if err != nil && !errors.Is(err, db.NotFound) {
 		return oops.New(err, "failed to fetch snippet for discord message")
 	}
-	var snippet *models.Snippet
-	if !errors.Is(err, db.NotFound) {
-		snippet = isnippet.(*models.Snippet)
-	}
 
 	// NOTE(asaf): Also deletes the following through a db cascade:
 	//			   * handmade_discordmessageattachment
@@ -367,7 +361,7 @@ func SaveMessageContents(
 				return oops.New(err, "failed to create or update message contents")
 			}
 
-			icontent, err := db.QueryOne(ctx, dbConn, models.DiscordMessageContent{},
+			content, err := db.QueryOne[models.DiscordMessageContent](ctx, dbConn,
 				`
 				SELECT $columns
 				FROM
@@ -380,7 +374,7 @@ func SaveMessageContents(
 			if err != nil {
 				return oops.New(err, "failed to fetch message contents")
 			}
-			interned.MessageContent = icontent.(*models.DiscordMessageContent)
+			interned.MessageContent = content
 		}
 
 		// Save attachments
@@ -395,12 +389,12 @@ func SaveMessageContents(
 
 		// Save / delete embeds
 		if msg.OriginalHasFields("embeds") {
-			numSavedEmbeds, err := db.QueryInt(ctx, dbConn,
+			numSavedEmbeds, err := db.QueryOneScalar[int](ctx, dbConn,
 				`
-			SELECT COUNT(*)
-			FROM handmade_discordmessageembed
-			WHERE message_id = $1
-			`,
+				SELECT COUNT(*)
+				FROM handmade_discordmessageembed
+				WHERE message_id = $1
+				`,
 				msg.ID,
 			)
 			if err != nil {
@@ -472,7 +466,7 @@ func saveAttachment(
 	hmnUserID int,
 	discordMessageID string,
 ) (*models.DiscordMessageAttachment, error) {
-	iexisting, err := db.QueryOne(ctx, tx, models.DiscordMessageAttachment{},
+	existing, err := db.QueryOne[models.DiscordMessageAttachment](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_discordmessageattachment
@@ -481,7 +475,7 @@ func saveAttachment(
 		attachment.ID,
 	)
 	if err == nil {
-		return iexisting.(*models.DiscordMessageAttachment), nil
+		return existing, nil
 	} else if errors.Is(err, db.NotFound) {
 		// this is fine, just create it
 	} else {
@@ -534,7 +528,7 @@ func saveAttachment(
 		return nil, oops.New(err, "failed to save Discord attachment data")
 	}
 
-	iDiscordAttachment, err := db.QueryOne(ctx, tx, models.DiscordMessageAttachment{},
+	discordAttachment, err := db.QueryOne[models.DiscordMessageAttachment](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_discordmessageattachment
@@ -546,7 +540,7 @@ func saveAttachment(
 		return nil, oops.New(err, "failed to fetch new Discord attachment data")
 	}
 
-	return iDiscordAttachment.(*models.DiscordMessageAttachment), nil
+	return discordAttachment, nil
 }
 
 // Saves an embed from Discord. NOTE: This is _not_ idempotent, so only call it
@@ -636,7 +630,7 @@ func saveEmbed(
 		return nil, oops.New(err, "failed to insert new embed")
 	}
 
-	iDiscordEmbed, err := db.QueryOne(ctx, tx, models.DiscordMessageEmbed{},
+	discordEmbed, err := db.QueryOne[models.DiscordMessageEmbed](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_discordmessageembed
@@ -648,11 +642,11 @@ func saveEmbed(
 		return nil, oops.New(err, "failed to fetch new Discord embed data")
 	}
 
-	return iDiscordEmbed.(*models.DiscordMessageEmbed), nil
+	return discordEmbed, nil
 }
 
 func FetchSnippetForMessage(ctx context.Context, dbConn db.ConnOrTx, msgID string) (*models.Snippet, error) {
-	iresult, err := db.QueryOne(ctx, dbConn, models.Snippet{},
+	snippet, err := db.QueryOne[models.Snippet](ctx, dbConn,
 		`
 		SELECT $columns
 		FROM handmade_snippet
@@ -669,7 +663,7 @@ func FetchSnippetForMessage(ctx context.Context, dbConn db.ConnOrTx, msgID strin
 		}
 	}
 
-	return iresult.(*models.Snippet), nil
+	return snippet, nil
 }
 
 /*
@@ -805,12 +799,9 @@ func HandleSnippetForInternedMessage(ctx context.Context, dbConn db.ConnOrTx, in
 			projectIDs[i] = p.Project.ID
 		}
 
-		type tagsRow struct {
-			Tag models.Tag `db:"tags"`
-		}
-		iUserTags, err := db.Query(ctx, tx, tagsRow{},
+		userTags, err := db.Query[models.Tag](ctx, tx,
 			`
-			SELECT $columns
+			SELECT $columns{tags}
 			FROM
 				tags
 				JOIN handmade_project AS project ON project.tag = tags.id
@@ -823,8 +814,7 @@ func HandleSnippetForInternedMessage(ctx context.Context, dbConn db.ConnOrTx, in
 			return oops.New(err, "failed to fetch tags for user projects")
 		}
 
-		for _, itag := range iUserTags {
-			tag := itag.(*tagsRow).Tag
+		for _, tag := range userTags {
 			allTags = append(allTags, tag.ID)
 			for _, messageTag := range messageTags {
 				if strings.EqualFold(tag.Text, messageTag) {
@@ -890,7 +880,7 @@ var RESnippetableUrl = regexp.MustCompile(`^https?://(youtu\.be|(www\.)?youtube\
 
 func getSnippetAssetOrUrl(ctx context.Context, tx db.ConnOrTx, msg *models.DiscordMessage) (*uuid.UUID, *string, error) {
 	// Check attachments
-	attachments, err := db.Query(ctx, tx, models.DiscordMessageAttachment{},
+	attachments, err := db.Query[models.DiscordMessageAttachment](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_discordmessageattachment
@@ -901,13 +891,12 @@ func getSnippetAssetOrUrl(ctx context.Context, tx db.ConnOrTx, msg *models.Disco
 	if err != nil {
 		return nil, nil, oops.New(err, "failed to fetch message attachments")
 	}
-	for _, iattachment := range attachments {
-		attachment := iattachment.(*models.DiscordMessageAttachment)
+	for _, attachment := range attachments {
 		return &attachment.AssetID, nil, nil
 	}
 
 	// Check embeds
-	embeds, err := db.Query(ctx, tx, models.DiscordMessageEmbed{},
+	embeds, err := db.Query[models.DiscordMessageEmbed](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_discordmessageembed
@@ -918,8 +907,7 @@ func getSnippetAssetOrUrl(ctx context.Context, tx db.ConnOrTx, msg *models.Disco
 	if err != nil {
 		return nil, nil, oops.New(err, "failed to fetch discord embeds")
 	}
-	for _, iembed := range embeds {
-		embed := iembed.(*models.DiscordMessageEmbed)
+	for _, embed := range embeds {
 		if embed.VideoID != nil {
 			return embed.VideoID, nil, nil
 		} else if embed.ImageID != nil {

src/hmndata/project_helper.go

@@ -140,15 +140,15 @@ func FetchProjects(
 	}
 
 	// Do the query
-	iprojects, err := db.Query(ctx, dbConn, projectRow{}, qb.String(), qb.Args()...)
+	projectRows, err := db.Query[projectRow](ctx, dbConn, qb.String(), qb.Args()...)
 	if err != nil {
 		return nil, oops.New(err, "failed to fetch projects")
 	}
 
 	// Fetch project owners to do permission checks
-	projectIds := make([]int, len(iprojects))
-	for i, iproject := range iprojects {
-		projectIds[i] = iproject.(*projectRow).Project.ID
+	projectIds := make([]int, len(projectRows))
+	for i, p := range projectRows {
+		projectIds[i] = p.Project.ID
 	}
 	projectOwners, err := FetchMultipleProjectsOwners(ctx, tx, projectIds)
 	if err != nil {
@@ -156,8 +156,7 @@ func FetchProjects(
 	}
 
 	var res []ProjectAndStuff
-	for i, iproject := range iprojects {
-		row := iproject.(*projectRow)
+	for i, p := range projectRows {
 		owners := projectOwners[i].Owners
 
 		/*
@@ -191,10 +190,10 @@ func FetchProjects(
 		}
 
 		projectGenerallyVisible := true &&
-			row.Project.Lifecycle.In(models.VisibleProjectLifecycles) &&
-			!row.Project.Hidden &&
-			(!row.Project.Personal || allOwnersApproved || row.Project.IsHMN())
-		if row.Project.IsHMN() {
+			p.Project.Lifecycle.In(models.VisibleProjectLifecycles) &&
+			!p.Project.Hidden &&
+			(!p.Project.Personal || allOwnersApproved || p.Project.IsHMN())
+		if p.Project.IsHMN() {
 			projectGenerallyVisible = true // hard override
 		}
 
@@ -205,11 +204,11 @@ func FetchProjects(
 
 		if projectVisible {
 			res = append(res, ProjectAndStuff{
-				Project:        row.Project,
-				LogoLightAsset: row.LogoLightAsset,
-				LogoDarkAsset:  row.LogoDarkAsset,
+				Project:        p.Project,
+				LogoLightAsset: p.LogoLightAsset,
+				LogoDarkAsset:  p.LogoDarkAsset,
 				Owners:         owners,
-				Tag:            row.Tag,
+				Tag:            p.Tag,
 			})
 		}
 	}
@@ -334,7 +333,7 @@ func FetchMultipleProjectsOwners(
 		UserID    int `db:"user_id"`
 		ProjectID int `db:"project_id"`
 	}
-	iuserprojects, err := db.Query(ctx, tx, userProject{},
+	userProjects, err := db.Query[userProject](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_user_projects
@@ -348,9 +347,7 @@ func FetchMultipleProjectsOwners(
 
 	// Get the unique user IDs from this set and fetch the users from the db
 	var userIds []int
-	for _, iuserproject := range iuserprojects {
-		userProject := iuserproject.(*userProject)
-
+	for _, userProject := range userProjects {
 		addUserId := true
 		for _, uid := range userIds {
 			if uid == userProject.UserID {
@@ -361,14 +358,12 @@ func FetchMultipleProjectsOwners(
 			userIds = append(userIds, userProject.UserID)
 		}
 	}
-	type userQuery struct {
-		User models.User `db:"auth_user"`
-	}
-	iusers, err := db.Query(ctx, tx, userQuery{},
+	users, err := db.Query[models.User](ctx, tx,
 		`
-		SELECT $columns
-		FROM auth_user
-		LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
+		SELECT $columns{auth_user}
+		FROM
+			auth_user
+			LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
 		WHERE
 			auth_user.id = ANY($1)
 		`,
@@ -383,9 +378,7 @@ func FetchMultipleProjectsOwners(
 	for i, pid := range projectIds {
 		res[i] = ProjectOwners{ProjectID: pid}
 	}
-	for _, iuserproject := range iuserprojects {
-		userProject := iuserproject.(*userProject)
-
+	for _, userProject := range userProjects {
 		// Get a pointer to the existing record in the result
 		var projectOwners *ProjectOwners
 		for i := range res {
@@ -396,10 +389,9 @@ func FetchMultipleProjectsOwners(
 
 		// Get the full user record we fetched
 		var user *models.User
-		for _, iuser := range iusers {
-			u := iuser.(*userQuery).User
+		for _, u := range users {
 			if u.ID == userProject.UserID {
-				user = &u
+				user = u
 			}
 		}
 		if user == nil {
@@ -473,7 +465,7 @@ func SetProjectTag(
 		resultTag = p.Tag
 	} else if p.Project.TagID == nil {
 		// Create a tag
-		itag, err := db.QueryOne(ctx, tx, models.Tag{},
+		tag, err := db.QueryOne[models.Tag](ctx, tx,
 			`
 			INSERT INTO tags (text) VALUES ($1)
 			RETURNING $columns
@@ -483,7 +475,7 @@ func SetProjectTag(
 		if err != nil {
 			return nil, oops.New(err, "failed to create new tag for project")
 		}
-		resultTag = itag.(*models.Tag)
+		resultTag = tag
 
 		// Attach it to the project
 		_, err = tx.Exec(ctx,
@@ -499,7 +491,7 @@ func SetProjectTag(
 		}
 	} else {
 		// Update the text of an existing one
-		itag, err := db.QueryOne(ctx, tx, models.Tag{},
+		tag, err := db.QueryOne[models.Tag](ctx, tx,
 			`
 			UPDATE tags
 			SET text = $1
@@ -511,7 +503,7 @@ func SetProjectTag(
 		if err != nil {
 			return nil, oops.New(err, "failed to update existing tag")
 		}
-		resultTag = itag.(*models.Tag)
+		resultTag = tag
 	}
 
 	err = tx.Commit(ctx)

src/hmndata/snippet_helper.go

@@ -44,10 +44,7 @@ func FetchSnippets(
 
 	if len(q.Tags) > 0 {
 		// Get snippet IDs with this tag, then use that in the main query
-		type snippetIDRow struct {
-			SnippetID int `db:"snippet_id"`
-		}
-		iSnippetIDs, err := db.Query(ctx, tx, snippetIDRow{},
+		snippetIDs, err := db.QueryScalar[int](ctx, tx,
 			`
 			SELECT DISTINCT snippet_id
 			FROM
@@ -63,14 +60,11 @@ func FetchSnippets(
 		}
 
 		// special early-out: no snippets found for these tags at all
-		if len(iSnippetIDs) == 0 {
+		if len(snippetIDs) == 0 {
 			return nil, nil
 		}
 
-		q.IDs = make([]int, len(iSnippetIDs))
-		for i := range iSnippetIDs {
-			q.IDs[i] = iSnippetIDs[i].(*snippetIDRow).SnippetID
-		}
+		q.IDs = snippetIDs
 	}
 
 	var qb db.QueryBuilder
@@ -125,16 +119,14 @@ func FetchSnippets(
 		DiscordMessage *models.DiscordMessage `db:"discord_message"`
 	}
 
-	iresults, err := db.Query(ctx, tx, resultRow{}, qb.String(), qb.Args()...)
+	results, err := db.Query[resultRow](ctx, tx, qb.String(), qb.Args()...)
 	if err != nil {
 		return nil, oops.New(err, "failed to fetch threads")
 	}
 
-	result := make([]SnippetAndStuff, len(iresults)) // allocate extra space because why not
-	snippetIDs := make([]int, len(iresults))
-	for i, iresult := range iresults {
-		row := *iresult.(*resultRow)
-
+	result := make([]SnippetAndStuff, len(results)) // allocate extra space because why not
+	snippetIDs := make([]int, len(results))
+	for i, row := range results {
 		result[i] = SnippetAndStuff{
 			Snippet:        row.Snippet,
 			Owner:          row.Owner,
@@ -150,7 +142,7 @@ func FetchSnippets(
 		SnippetID int         `db:"snippet_tags.snippet_id"`
 		Tag       *models.Tag `db:"tags"`
 	}
-	iSnippetTags, err := db.Query(ctx, tx, snippetTagRow{},
+	snippetTags, err := db.Query[snippetTagRow](ctx, tx,
 		`
 		SELECT $columns
 		FROM
@@ -170,8 +162,7 @@ func FetchSnippets(
 	for i := range result {
 		resultBySnippetId[result[i].Snippet.ID] = &result[i]
 	}
-	for _, iSnippetTag := range iSnippetTags {
-		snippetTag := iSnippetTag.(*snippetTagRow)
+	for _, snippetTag := range snippetTags {
 		item := resultBySnippetId[snippetTag.SnippetID]
 		item.Tags = append(item.Tags, snippetTag.Tag)
 	}

src/hmndata/tag_helper.go

@@ -40,18 +40,11 @@ func FetchTags(ctx context.Context, dbConn db.ConnOrTx, q TagQuery) ([]*models.T
 		qb.Add(`LIMIT $? OFFSET $?`, q.Limit, q.Offset)
 	}
 
-	itags, err := db.Query(ctx, dbConn, models.Tag{}, qb.String(), qb.Args()...)
+	tags, err := db.Query[models.Tag](ctx, dbConn, qb.String(), qb.Args()...)
 	if err != nil {
 		return nil, oops.New(err, "failed to fetch tags")
 	}
-
-	res := make([]*models.Tag, len(itags))
-	for i, itag := range itags {
-		tag := itag.(*models.Tag)
-		res[i] = tag
-	}
-
-	return res, nil
+	return tags, nil
 }
 
 func FetchTag(ctx context.Context, dbConn db.ConnOrTx, q TagQuery) (*models.Tag, error) {

src/hmndata/threads_and_posts_helper.go

@@ -145,15 +145,13 @@ func FetchThreads(
 		ForumLastReadTime  *time.Time `db:"slri.lastread"`
 	}
 
-	iresults, err := db.Query(ctx, dbConn, resultRow{}, qb.String(), qb.Args()...)
+	rows, err := db.Query[resultRow](ctx, dbConn, qb.String(), qb.Args()...)
 	if err != nil {
 		return nil, oops.New(err, "failed to fetch threads")
 	}
 
-	result := make([]ThreadAndStuff, len(iresults))
-	for i, iresult := range iresults {
-		row := *iresult.(*resultRow)
-
+	result := make([]ThreadAndStuff, len(rows))
+	for i, row := range rows {
 		hasRead := false
 		if currentUser != nil && currentUser.MarkedAllReadAt.After(row.LastPost.PostDate) {
 			hasRead = true
@@ -263,7 +261,7 @@ func CountThreads(
 		)
 	}
 
-	count, err := db.QueryInt(ctx, dbConn, qb.String(), qb.Args()...)
+	count, err := db.QueryOneScalar[int](ctx, dbConn, qb.String(), qb.Args()...)
 	if err != nil {
 		return 0, oops.New(err, "failed to fetch count of threads")
 	}
@@ -405,15 +403,13 @@ func FetchPosts(
 		qb.Add(`LIMIT $? OFFSET $?`, q.Limit, q.Offset)
 	}
 
-	iresults, err := db.Query(ctx, dbConn, resultRow{}, qb.String(), qb.Args()...)
+	rows, err := db.Query[resultRow](ctx, dbConn, qb.String(), qb.Args()...)
 	if err != nil {
 		return nil, oops.New(err, "failed to fetch posts")
 	}
 
-	result := make([]PostAndStuff, len(iresults))
-	for i, iresult := range iresults {
-		row := *iresult.(*resultRow)
-
+	result := make([]PostAndStuff, len(rows))
+	for i, row := range rows {
 		hasRead := false
 		if currentUser != nil && currentUser.MarkedAllReadAt.After(row.Post.PostDate) {
 			hasRead = true
@@ -595,7 +591,7 @@ func CountPosts(
 		)
 	}
 
-	count, err := db.QueryInt(ctx, dbConn, qb.String(), qb.Args()...)
+	count, err := db.QueryOneScalar[int](ctx, dbConn, qb.String(), qb.Args()...)
 	if err != nil {
 		return 0, oops.New(err, "failed to count posts")
 	}
@@ -608,12 +604,9 @@ func UserCanEditPost(ctx context.Context, connOrTx db.ConnOrTx, user models.User
 		return true
 	}
 
-	type postResult struct {
-		AuthorID *int `db:"post.author_id"`
-	}
-	iresult, err := db.QueryOne(ctx, connOrTx, postResult{},
+	authorID, err := db.QueryOneScalar[*int](ctx, connOrTx,
 		`
-		SELECT $columns
+		SELECT post.author_id
 		FROM
 			handmade_post AS post
 		WHERE
@@ -629,9 +622,8 @@ func UserCanEditPost(ctx context.Context, connOrTx db.ConnOrTx, user models.User
 			panic(oops.New(err, "failed to get author of post when checking permissions"))
 		}
 	}
-	result := iresult.(*postResult)
 
-	return result.AuthorID != nil && *result.AuthorID == user.ID
+	return authorID != nil && *authorID == user.ID
 }
 
 func CreateNewPost(
@@ -709,7 +701,7 @@ func DeletePost(
 		FirstPostID int  `db:"first_id"`
 		Deleted     bool `db:"deleted"`
 	}
-	ti, err := db.QueryOne(ctx, tx, threadInfo{},
+	info, err := db.QueryOne[threadInfo](ctx, tx,
 		`
 		SELECT $columns
 		FROM
@@ -722,7 +714,6 @@ func DeletePost(
 	if err != nil {
 		panic(oops.New(err, "failed to fetch thread info"))
 	}
-	info := ti.(*threadInfo)
 	if info.Deleted {
 		return true
 	}
@@ -848,12 +839,9 @@ func CreatePostVersion(ctx context.Context, tx pgx.Tx, postId int, unparsedConte
 		keys = append(keys, key)
 	}
 
-	type assetId struct {
-		AssetID uuid.UUID `db:"id"`
-	}
-	assetResult, err := db.Query(ctx, tx, assetId{},
+	assetIDs, err := db.QueryScalar[uuid.UUID](ctx, tx,
 		`
-		SELECT $columns
+		SELECT id
 		FROM handmade_asset
 		WHERE s3_key = ANY($1)
 		`,
@@ -865,8 +853,8 @@ func CreatePostVersion(ctx context.Context, tx pgx.Tx, postId int, unparsedConte
 
 	var values [][]interface{}
 
-	for _, asset := range assetResult {
-		values = append(values, []interface{}{postId, asset.(*assetId).AssetID})
+	for _, assetID := range assetIDs {
+		values = append(values, []interface{}{postId, assetID})
 	}
 
 	_, err = tx.CopyFrom(ctx, pgx.Identifier{"handmade_post_asset_usage"}, []string{"post_id", "asset_id"}, pgx.CopyFromRows(values))
@@ -886,7 +874,7 @@ Returns errThreadEmpty if the thread contains no visible posts any more.
 You should probably mark the thread as deleted in this case.
 */
 func FixThreadPostIds(ctx context.Context, tx pgx.Tx, threadId int) error {
-	postsIter, err := db.Query(ctx, tx, models.Post{},
+	posts, err := db.Query[models.Post](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_post
@@ -901,9 +889,7 @@ func FixThreadPostIds(ctx context.Context, tx pgx.Tx, threadId int) error {
 	}
 
 	var firstPost, lastPost *models.Post
-	for _, ipost := range postsIter {
-		post := ipost.(*models.Post)
-
+	for _, post := range posts {
 		if firstPost == nil || post.PostDate.Before(firstPost.PostDate) {
 			firstPost = post
 		}

src/hmndata/twitch.go

@@ -22,12 +22,9 @@ type TwitchStreamer struct {
 var twitchRegex = regexp.MustCompile(`twitch\.tv/(?P<login>[^/]+)$`)
 
 func FetchTwitchStreamers(ctx context.Context, dbConn db.ConnOrTx) ([]TwitchStreamer, error) {
-	type linkResult struct {
-		Link models.Link `db:"link"`
-	}
-	streamers, err := db.Query(ctx, dbConn, linkResult{},
+	dbStreamers, err := db.Query[models.Link](ctx, dbConn,
 		`
-		SELECT $columns
+		SELECT $columns{link}
 		FROM
 			handmade_links AS link
 			LEFT JOIN auth_user AS link_owner ON link_owner.id = link.user_id
@@ -49,10 +46,8 @@ func FetchTwitchStreamers(ctx context.Context, dbConn db.ConnOrTx) ([]TwitchStre
 		return nil, oops.New(err, "failed to fetch twitch links")
 	}
 
-	result := make([]TwitchStreamer, 0, len(streamers))
-	for _, s := range streamers {
-		dbStreamer := s.(*linkResult).Link
-
+	result := make([]TwitchStreamer, 0, len(dbStreamers))
+	for _, dbStreamer := range dbStreamers {
 		streamer := TwitchStreamer{
 			UserID:    dbStreamer.UserID,
 			ProjectID: dbStreamer.ProjectID,
@@ -81,7 +76,7 @@ func FetchTwitchStreamers(ctx context.Context, dbConn db.ConnOrTx) ([]TwitchStre
 }
 
 func FetchTwitchLoginsForUserOrProject(ctx context.Context, dbConn db.ConnOrTx, userId *int, projectId *int) ([]string, error) {
-	links, err := db.Query(ctx, dbConn, models.Link{},
+	links, err := db.Query[models.Link](ctx, dbConn,
 		`
 		SELECT $columns
 		FROM
@@ -100,8 +95,7 @@ func FetchTwitchLoginsForUserOrProject(ctx context.Context, dbConn db.ConnOrTx,
 	result := make([]string, 0, len(links))
 
 	for _, l := range links {
-		url := l.(*models.Link).URL
-		match := twitchRegex.FindStringSubmatch(url)
+		match := twitchRegex.FindStringSubmatch(l.URL)
 		if match != nil {
 			login := strings.ToLower(match[twitchRegex.SubexpIndex("login")])
 			result = append(result, login)

src/migration/migrations/2021-11-06T033930Z_PersonalProjects.go

@@ -110,7 +110,7 @@ func (m PersonalProjects) Up(ctx context.Context, tx pgx.Tx) error {
 	// Port "jam snippets" to use a tag
 	//
 
-	jamTagId, err := db.QueryInt(ctx, tx, `INSERT INTO tags (text) VALUES ('wheeljam') RETURNING id`)
+	jamTagId, err := db.QueryOneScalar[int](ctx, tx, `INSERT INTO tags (text) VALUES ('wheeljam') RETURNING id`)
 	if err != nil {
 		return oops.New(err, "failed to create jam tag")
 	}

src/models/subforum.go

@@ -44,14 +44,10 @@ func (node *SubforumTreeNode) GetLineage() []*Subforum {
 }
 
 func GetFullSubforumTree(ctx context.Context, conn *pgxpool.Pool) SubforumTree {
-	type subforumRow struct {
-		Subforum Subforum `db:"sf"`
-	}
-	rowsSlice, err := db.Query(ctx, conn, subforumRow{},
+	subforums, err := db.Query[Subforum](ctx, conn,
 		`
 		SELECT $columns
-		FROM
-			handmade_subforum as sf
+		FROM handmade_subforum
 		ORDER BY sort, id ASC
 		`,
 	)
@@ -59,10 +55,9 @@ func GetFullSubforumTree(ctx context.Context, conn *pgxpool.Pool) SubforumTree {
 		panic(oops.New(err, "failed to fetch subforum tree"))
 	}
 
-	sfTreeMap := make(map[int]*SubforumTreeNode, len(rowsSlice))
-	for _, row := range rowsSlice {
-		sf := row.(*subforumRow).Subforum
-		sfTreeMap[sf.ID] = &SubforumTreeNode{Subforum: sf}
+	sfTreeMap := make(map[int]*SubforumTreeNode, len(subforums))
+	for _, sf := range subforums {
+		sfTreeMap[sf.ID] = &SubforumTreeNode{Subforum: *sf}
 	}
 
 	for _, node := range sfTreeMap {
@@ -71,9 +66,8 @@ func GetFullSubforumTree(ctx context.Context, conn *pgxpool.Pool) SubforumTree {
 		}
 	}
 
-	for _, row := range rowsSlice {
+	for _, cat := range subforums {
 		// NOTE(asaf): Doing this in a separate loop over rowsSlice to ensure that Children are in db order.
-		cat := row.(*subforumRow).Subforum
 		node := sfTreeMap[cat.ID]
 		if node.Parent != nil {
 			node.Parent.Children = append(node.Parent.Children, node)

src/twitch/twitch.go

@@ -440,7 +440,7 @@ func updateStreamStatusInDB(ctx context.Context, conn db.ConnOrTx, status *strea
 	inserted := false
 	if isStatusRelevant(status) {
 		log.Debug().Msg("Status relevant")
-		_, err := db.QueryOne(ctx, conn, models.TwitchStream{},
+		_, err := db.QueryOne[models.TwitchStream](ctx, conn,
 			`
 			SELECT $columns
 			FROM twitch_streams

src/website/admin.go

@@ -207,7 +207,7 @@ func AdminApprovalQueue(c *RequestContext) ResponseData {
 		userIds = append(userIds, u.User.ID)
 	}
 
-	userLinks, err := db.Query(c.Context(), c.Conn, models.Link{},
+	userLinks, err := db.Query[models.Link](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -222,8 +222,7 @@ func AdminApprovalQueue(c *RequestContext) ResponseData {
 		return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch user links"))
 	}
 
-	for _, ul := range userLinks {
-		link := ul.(*models.Link)
+	for _, link := range userLinks {
 		userData := unapprovedUsers[userIDToDataIdx[*link.UserID]]
 		userData.UserLinks = append(userData.UserLinks, templates.LinkToTemplate(link))
 	}
@@ -257,12 +256,9 @@ func AdminApprovalQueueSubmit(c *RequestContext) ResponseData {
 		return RejectRequest(c, "User id can't be parsed")
 	}
 
-	type userQuery struct {
-		User models.User `db:"auth_user"`
-	}
-	u, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+	user, err := db.QueryOne[models.User](c.Context(), c.Conn,
 		`
-		SELECT $columns
+		SELECT $columns{auth_user}
 			FROM auth_user
 			LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
 		WHERE auth_user.id = $1
@@ -276,7 +272,6 @@ func AdminApprovalQueueSubmit(c *RequestContext) ResponseData {
 			return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch user"))
 		}
 	}
-	user := u.(*userQuery).User
 
 	whatHappened := ""
 	if action == ApprovalQueueActionApprove {
@@ -337,7 +332,7 @@ type UnapprovedPost struct {
 }
 
 func fetchUnapprovedPosts(c *RequestContext) ([]*UnapprovedPost, error) {
-	it, err := db.Query(c.Context(), c.Conn, UnapprovedPost{},
+	posts, err := db.Query[UnapprovedPost](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -358,11 +353,7 @@ func fetchUnapprovedPosts(c *RequestContext) ([]*UnapprovedPost, error) {
 	if err != nil {
 		return nil, oops.New(err, "failed to fetch unapproved posts")
 	}
-	var res []*UnapprovedPost
-	for _, iresult := range it {
-		res = append(res, iresult.(*UnapprovedPost))
-	}
-	return res, nil
+	return posts, nil
 }
 
 type UnapprovedProject struct {
@@ -372,12 +363,9 @@ type UnapprovedProject struct {
 }
 
 func fetchUnapprovedProjects(c *RequestContext) ([]UnapprovedProject, error) {
-	type unapprovedUser struct {
-		ID int `db:"id"`
-	}
-	it, err := db.Query(c.Context(), c.Conn, unapprovedUser{},
+	ownerIDs, err := db.QueryScalar[int](c.Context(), c.Conn,
 		`
-		SELECT $columns
+		SELECT id
 		FROM
 			auth_user AS u
 		WHERE
@@ -388,10 +376,6 @@ func fetchUnapprovedProjects(c *RequestContext) ([]UnapprovedProject, error) {
 	if err != nil {
 		return nil, oops.New(err, "failed to fetch unapproved users")
 	}
-	ownerIDs := make([]int, 0, len(it))
-	for _, uid := range it {
-		ownerIDs = append(ownerIDs, uid.(*unapprovedUser).ID)
-	}
 
 	projects, err := hmndata.FetchProjects(c.Context(), c.Conn, c.CurrentUser, hmndata.ProjectsQuery{
 		OwnerIDs:      ownerIDs,
@@ -406,7 +390,7 @@ func fetchUnapprovedProjects(c *RequestContext) ([]UnapprovedProject, error) {
 		projectIDs = append(projectIDs, p.Project.ID)
 	}
 
-	projectLinks, err := db.Query(c.Context(), c.Conn, models.Link{},
+	projectLinks, err := db.Query[models.Link](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -425,8 +409,7 @@ func fetchUnapprovedProjects(c *RequestContext) ([]UnapprovedProject, error) {
 
 	for idx, proj := range projects {
 		links := make([]*models.Link, 0, 10) // NOTE(asaf): 10 should be enough for most projects.
-		for _, l := range projectLinks {
-			link := l.(*models.Link)
+		for _, link := range projectLinks {
 			if *link.ProjectID == proj.Project.ID {
 				links = append(links, link)
 			}
@@ -455,7 +438,7 @@ func deleteAllPostsForUser(ctx context.Context, conn *pgxpool.Pool, userId int)
 		ThreadID int `db:"thread.id"`
 		PostID   int `db:"post.id"`
 	}
-	it, err := db.Query(ctx, tx, toDelete{},
+	rows, err := db.Query[toDelete](ctx, tx,
 		`
 		SELECT $columns
 		FROM
@@ -471,8 +454,7 @@ func deleteAllPostsForUser(ctx context.Context, conn *pgxpool.Pool, userId int)
 		return oops.New(err, "failed to fetch posts to delete for user")
 	}
 
-	for _, iResult := range it {
-		row := iResult.(*toDelete)
+	for _, row := range rows {
 		hmndata.DeletePost(ctx, tx, row.ThreadID, row.PostID)
 	}
 	err = tx.Commit(ctx)
@@ -489,9 +471,9 @@ func deleteAllProjectsForUser(ctx context.Context, conn *pgxpool.Pool, userId in
 	}
 	defer tx.Rollback(ctx)
 
-	toDelete, err := db.Query(ctx, tx, models.Project{},
+	projectIDsToDelete, err := db.QueryScalar[int](ctx, tx,
 		`
-		SELECT $columns
+		SELECT project.id
 		FROM
 			handmade_project AS project
 			JOIN handmade_user_projects AS up ON up.project_id = project.id
@@ -504,17 +486,12 @@ func deleteAllProjectsForUser(ctx context.Context, conn *pgxpool.Pool, userId in
 		return oops.New(err, "failed to fetch user's projects")
 	}
 
-	var projectIds []int
-	for _, p := range toDelete {
-		projectIds = append(projectIds, p.(*models.Project).ID)
-	}
-
-	if len(projectIds) > 0 {
+	if len(projectIDsToDelete) > 0 {
 		_, err = tx.Exec(ctx,
 			`
 			DELETE FROM handmade_project WHERE id = ANY($1)
 			`,
-			projectIds,
+			projectIDsToDelete,
 		)
 		if err != nil {
 			return oops.New(err, "failed to delete user's projects")

src/website/api.go

@@ -19,12 +19,9 @@ func APICheckUsername(c *RequestContext) ResponseData {
 		requestedUsername := usernameArgs[0]
 		found = true
 		c.Perf.StartBlock("SQL", "Fetch user")
-		type userQuery struct {
-			User models.User `db:"auth_user"`
-		}
-		userResult, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+		user, err := db.QueryOne[models.User](c.Context(), c.Conn,
 			`
-			SELECT $columns
+			SELECT $columns{auth_user}
 			FROM
 				auth_user
 				LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
@@ -43,7 +40,7 @@ func APICheckUsername(c *RequestContext) ResponseData {
 				return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch user: %s", requestedUsername))
 			}
 		} else {
-			canonicalUsername = userResult.(*userQuery).User.Username
+			canonicalUsername = user.Username
 		}
 	}
 

src/website/auth.go

@@ -75,13 +75,11 @@ func Login(c *RequestContext) ResponseData {
 		return res
 	}
 
-	type userQuery struct {
-		User models.User `db:"auth_user"`
-	}
-	userRow, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+	user, err := db.QueryOne[models.User](c.Context(), c.Conn,
 		`
-		SELECT $columns
-			FROM auth_user
+		SELECT $columns{auth_user}
+		FROM
+			auth_user
 			LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
 		WHERE LOWER(username) = LOWER($1)
 		`,
@@ -94,7 +92,6 @@ func Login(c *RequestContext) ResponseData {
 			return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to look up user by username"))
 		}
 	}
-	user := &userRow.(*userQuery).User
 
 	success, err := tryLogin(c, user, password)
 
@@ -174,7 +171,7 @@ func RegisterNewUserSubmit(c *RequestContext) ResponseData {
 
 	c.Perf.StartBlock("SQL", "Check for existing usernames and emails")
 	userAlreadyExists := true
-	_, err := db.QueryInt(c.Context(), c.Conn,
+	_, err := db.QueryOneScalar[int](c.Context(), c.Conn,
 		`
 		SELECT id
 		FROM auth_user
@@ -195,7 +192,7 @@ func RegisterNewUserSubmit(c *RequestContext) ResponseData {
 	}
 
 	emailAlreadyExists := true
-	_, err = db.QueryInt(c.Context(), c.Conn,
+	_, err = db.QueryOneScalar[int](c.Context(), c.Conn,
 		`
 		SELECT id
 		FROM auth_user
@@ -454,17 +451,16 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 		return RejectRequest(c, "You must provide a username and an email address.")
 	}
 
-	var user *models.User
-
 	c.Perf.StartBlock("SQL", "Fetching user")
 	type userQuery struct {
 		User models.User `db:"auth_user"`
 	}
-	userRow, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+	user, err := db.QueryOne[models.User](c.Context(), c.Conn,
 		`
-		SELECT $columns
-		FROM auth_user
-		LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
+		SELECT $columns{auth_user}
+		FROM
+			auth_user
+			LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
 		WHERE
 			LOWER(username) = LOWER($1)
 			AND LOWER(email) = LOWER($2)
@@ -478,13 +474,10 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 			return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to look up user by username"))
 		}
 	}
-	if userRow != nil {
-		user = &userRow.(*userQuery).User
-	}
 
 	if user != nil {
 		c.Perf.StartBlock("SQL", "Fetching existing token")
-		tokenRow, err := db.QueryOne(c.Context(), c.Conn, models.OneTimeToken{},
+		resetToken, err := db.QueryOne[models.OneTimeToken](c.Context(), c.Conn,
 			`
 			SELECT $columns
 			FROM handmade_onetimetoken
@@ -501,10 +494,6 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 				return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch onetimetoken for user"))
 			}
 		}
-		var resetToken *models.OneTimeToken
-		if tokenRow != nil {
-			resetToken = tokenRow.(*models.OneTimeToken)
-		}
 		now := time.Now()
 
 		if resetToken != nil {
@@ -527,7 +516,7 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 
 		if resetToken == nil {
 			c.Perf.StartBlock("SQL", "Creating new token")
-			tokenRow, err := db.QueryOne(c.Context(), c.Conn, models.OneTimeToken{},
+			newToken, err := db.QueryOne[models.OneTimeToken](c.Context(), c.Conn,
 				`
 				INSERT INTO handmade_onetimetoken (token_type, created, expires, token_content, owner_id)
 				VALUES ($1, $2, $3, $4, $5)
@@ -543,7 +532,7 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 			if err != nil {
 				return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to create onetimetoken"))
 			}
-			resetToken = tokenRow.(*models.OneTimeToken)
+			resetToken = newToken
 
 			err = email.SendPasswordReset(user.Email, user.BestName(), user.Username, resetToken.Content, resetToken.Expires, c.Perf)
 			if err != nil {
@@ -787,7 +776,7 @@ func validateUsernameAndToken(c *RequestContext, username string, token string,
 		User         models.User          `db:"auth_user"`
 		OneTimeToken *models.OneTimeToken `db:"onetimetoken"`
 	}
-	row, err := db.QueryOne(c.Context(), c.Conn, userAndTokenQuery{},
+	data, err := db.QueryOne[userAndTokenQuery](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM auth_user
@@ -807,8 +796,7 @@ func validateUsernameAndToken(c *RequestContext, username string, token string,
 			return result
 		}
 	}
-	if row != nil {
-		data := row.(*userAndTokenQuery)
+	if data != nil {
 		result.User = &data.User
 		result.OneTimeToken = data.OneTimeToken
 		if result.OneTimeToken != nil {

src/website/blogs.go

@@ -558,7 +558,7 @@ func getCommonBlogData(c *RequestContext) (commonBlogData, bool) {
 		res.ThreadID = threadId
 
 		c.Perf.StartBlock("SQL", "Verify that the thread exists")
-		threadExists, err := db.QueryBool(c.Context(), c.Conn,
+		threadExists, err := db.QueryOneScalar[bool](c.Context(), c.Conn,
 			`
 			SELECT COUNT(*) > 0
 			FROM handmade_thread
@@ -586,7 +586,7 @@ func getCommonBlogData(c *RequestContext) (commonBlogData, bool) {
 		res.PostID = postId
 
 		c.Perf.StartBlock("SQL", "Verify that the post exists")
-		postExists, err := db.QueryBool(c.Context(), c.Conn,
+		postExists, err := db.QueryOneScalar[bool](c.Context(), c.Conn,
 			`
 			SELECT COUNT(*) > 0
 			FROM handmade_post

src/website/discord.go

@@ -104,7 +104,7 @@ func DiscordUnlink(c *RequestContext) ResponseData {
 	}
 	defer tx.Rollback(c.Context())
 
-	iDiscordUser, err := db.QueryOne(c.Context(), tx, models.DiscordUser{},
+	discordUser, err := db.QueryOne[models.DiscordUser](c.Context(), tx,
 		`
 		SELECT $columns
 		FROM handmade_discorduser
@@ -119,7 +119,6 @@ func DiscordUnlink(c *RequestContext) ResponseData {
 			return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to get Discord user for unlink"))
 		}
 	}
-	discordUser := iDiscordUser.(*models.DiscordUser)
 
 	_, err = tx.Exec(c.Context(),
 		`
@@ -146,7 +145,7 @@ func DiscordUnlink(c *RequestContext) ResponseData {
 }
 
 func DiscordShowcaseBacklog(c *RequestContext) ResponseData {
-	iduser, err := db.QueryOne(c.Context(), c.Conn, models.DiscordUser{},
+	duser, err := db.QueryOne[models.DiscordUser](c.Context(), c.Conn,
 		`SELECT $columns FROM handmade_discorduser WHERE hmn_user_id = $1`,
 		c.CurrentUser.ID,
 	)
@@ -157,14 +156,10 @@ func DiscordShowcaseBacklog(c *RequestContext) ResponseData {
 	} else if err != nil {
 		return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to get discord user"))
 	}
-	duser := iduser.(*models.DiscordUser)
 
-	type messageIdQuery struct {
-		MessageID string `db:"msg.id"`
-	}
-	iMsgIDs, err := db.Query(c.Context(), c.Conn, messageIdQuery{},
+	msgIDs, err := db.QueryScalar[string](c.Context(), c.Conn,
 		`
-		SELECT $columns
+		SELECT msg.id
 		FROM
 			handmade_discordmessage AS msg
 		WHERE
@@ -178,10 +173,6 @@ func DiscordShowcaseBacklog(c *RequestContext) ResponseData {
 		return c.ErrorResponse(http.StatusInternalServerError, err)
 	}
 
-	var msgIDs []string
-	for _, imsgId := range iMsgIDs {
-		msgIDs = append(msgIDs, imsgId.(*messageIdQuery).MessageID)
-	}
 	for _, msgID := range msgIDs {
 		interned, err := discord.FetchInternedMessage(c.Context(), c.Conn, msgID)
 		if err != nil && !errors.Is(err, db.NotFound) {

src/website/forums.go

@@ -936,7 +936,7 @@ func addForumUrlsToPost(urlContext *hmnurl.UrlContext, p *templates.Post, subfor
 // Takes a template post and adds information about how many posts the user has made
 // on the site.
 func addAuthorCountsToPost(ctx context.Context, conn db.ConnOrTx, p *templates.Post) {
-	numPosts, err := db.QueryInt(ctx, conn,
+	numPosts, err := db.QueryOneScalar[int](ctx, conn,
 		`
 		SELECT COUNT(*)
 		FROM
@@ -956,7 +956,7 @@ func addAuthorCountsToPost(ctx context.Context, conn db.ConnOrTx, p *templates.P
 		p.AuthorNumPosts = numPosts
 	}
 
-	numProjects, err := db.QueryInt(ctx, conn,
+	numProjects, err := db.QueryOneScalar[int](ctx, conn,
 		`
 		SELECT COUNT(*)
 		FROM

src/website/imagefile_helper.go

@@ -89,8 +89,7 @@ func SaveImageFile(c *RequestContext, dbConn db.ConnOrTx, fileFieldName string,
 		img.Seek(0, io.SeekStart)
 		io.Copy(hasher, img) // NOTE(asaf): Writing to hash.Hash never returns an error according to the docs
 		sha1sum := hasher.Sum(nil)
-		// TODO(db): Should use insert helper
-		imageFile, err := db.QueryOne(c.Context(), dbConn, models.ImageFile{},
+		imageFile, err := db.QueryOne[models.ImageFile](c.Context(), dbConn,
 			`
 			INSERT INTO handmade_imagefile (file, size, sha1sum, protected, width, height)
 			VALUES ($1, $2, $3, $4, $5, $6)
@@ -105,7 +104,7 @@ func SaveImageFile(c *RequestContext, dbConn db.ConnOrTx, fileFieldName string,
 		}
 
 		return SaveImageFileResult{
-			ImageFile: imageFile.(*models.ImageFile),
+			ImageFile: imageFile,
 		}
 	}
 

src/website/links_helper.go

@@ -30,10 +30,9 @@ func ParseLinks(text string) []ParsedLink {
 	return res
 }
 
-func LinksToText(links []interface{}) string {
+func LinksToText(links []*models.Link) string {
 	linksText := ""
-	for _, l := range links {
-		link := l.(*models.Link)
+	for _, link := range links {
 		linksText += fmt.Sprintf("%s %s\n", link.URL, link.Name)
 	}
 	return linksText

src/website/podcast.go

@@ -532,11 +532,12 @@ func FetchPodcast(c *RequestContext, projectId int, fetchEpisodes bool, episodeG
 		Podcast       models.Podcast `db:"podcast"`
 		ImageFilename string         `db:"imagefile.file"`
 	}
-	podcastQueryResult, err := db.QueryOne(c.Context(), c.Conn, podcastQuery{},
+	podcastQueryResult, err := db.QueryOne[podcastQuery](c.Context(), c.Conn,
 		`
 		SELECT $columns
-		FROM handmade_podcast AS podcast
-		LEFT JOIN handmade_imagefile AS imagefile ON imagefile.id = podcast.image_id
+		FROM
+			handmade_podcast AS podcast
+			LEFT JOIN handmade_imagefile AS imagefile ON imagefile.id = podcast.image_id
 		WHERE podcast.project_id = $1
 		`,
 		projectId,
@@ -549,18 +550,15 @@ func FetchPodcast(c *RequestContext, projectId int, fetchEpisodes bool, episodeG
 			return result, oops.New(err, "failed to fetch podcast")
 		}
 	}
-	podcast := podcastQueryResult.(*podcastQuery).Podcast
-	podcastImageFilename := podcastQueryResult.(*podcastQuery).ImageFilename
+	podcast := podcastQueryResult.Podcast
+	podcastImageFilename := podcastQueryResult.ImageFilename
 	result.Podcast = &podcast
 	result.ImageFile = podcastImageFilename
 
 	if fetchEpisodes {
-		type podcastEpisodeQuery struct {
-			Episode models.PodcastEpisode `db:"episode"`
-		}
 		if episodeGUID == "" {
 			c.Perf.StartBlock("SQL", "Fetch podcast episodes")
-			podcastEpisodeQueryResult, err := db.Query(c.Context(), c.Conn, podcastEpisodeQuery{},
+			episodes, err := db.Query[models.PodcastEpisode](c.Context(), c.Conn,
 				`
 				SELECT $columns
 				FROM handmade_podcastepisode AS episode
@@ -573,16 +571,14 @@ func FetchPodcast(c *RequestContext, projectId int, fetchEpisodes bool, episodeG
 			if err != nil {
 				return result, oops.New(err, "failed to fetch podcast episodes")
 			}
-			for _, episodeRow := range podcastEpisodeQueryResult {
-				result.Episodes = append(result.Episodes, &episodeRow.(*podcastEpisodeQuery).Episode)
-			}
+			result.Episodes = episodes
 		} else {
 			guid, err := uuid.Parse(episodeGUID)
 			if err != nil {
 				return result, err
 			}
 			c.Perf.StartBlock("SQL", "Fetch podcast episode")
-			podcastEpisodeQueryResult, err := db.QueryOne(c.Context(), c.Conn, podcastEpisodeQuery{},
+			episode, err := db.QueryOne[models.PodcastEpisode](c.Context(), c.Conn,
 				`
 				SELECT $columns
 				FROM handmade_podcastepisode AS episode
@@ -599,8 +595,7 @@ func FetchPodcast(c *RequestContext, projectId int, fetchEpisodes bool, episodeG
 					return result, oops.New(err, "failed to fetch podcast episode")
 				}
 			}
-			episode := podcastEpisodeQueryResult.(*podcastEpisodeQuery).Episode
-			result.Episodes = append(result.Episodes, &episode)
+			result.Episodes = append(result.Episodes, episode)
 		}
 	}
 

src/website/projects.go

@@ -187,12 +187,9 @@ func ProjectHomepage(c *RequestContext) ResponseData {
 	}
 
 	c.Perf.StartBlock("SQL", "Fetching screenshots")
-	type screenshotQuery struct {
-		Filename string `db:"screenshot.file"`
-	}
-	screenshotQueryResult, err := db.Query(c.Context(), c.Conn, screenshotQuery{},
+	screenshotFilenames, err := db.QueryScalar[string](c.Context(), c.Conn,
 		`
-		SELECT $columns
+		SELECT screenshot.file
 		FROM
 			handmade_imagefile AS screenshot
 			INNER JOIN handmade_project_screenshots ON screenshot.id = handmade_project_screenshots.imagefile_id
@@ -207,10 +204,7 @@ func ProjectHomepage(c *RequestContext) ResponseData {
 	c.Perf.EndBlock()
 
 	c.Perf.StartBlock("SQL", "Fetching project links")
-	type projectLinkQuery struct {
-		Link models.Link `db:"link"`
-	}
-	projectLinkResult, err := db.Query(c.Context(), c.Conn, projectLinkQuery{},
+	projectLinks, err := db.Query[models.Link](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -237,7 +231,7 @@ func ProjectHomepage(c *RequestContext) ResponseData {
 		Thread models.Thread `db:"thread"`
 		Author models.User   `db:"author"`
 	}
-	postQueryResult, err := db.Query(c.Context(), c.Conn, postQuery{},
+	posts, err := db.Query[postQuery](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -318,21 +312,21 @@ func ProjectHomepage(c *RequestContext) ResponseData {
 		}
 	}
 
-	for _, screenshot := range screenshotQueryResult {
-		templateData.Screenshots = append(templateData.Screenshots, hmnurl.BuildUserFile(screenshot.(*screenshotQuery).Filename))
+	for _, screenshotFilename := range screenshotFilenames {
+		templateData.Screenshots = append(templateData.Screenshots, hmnurl.BuildUserFile(screenshotFilename))
 	}
 
-	for _, link := range projectLinkResult {
-		templateData.ProjectLinks = append(templateData.ProjectLinks, templates.LinkToTemplate(&link.(*projectLinkQuery).Link))
+	for _, link := range projectLinks {
+		templateData.ProjectLinks = append(templateData.ProjectLinks, templates.LinkToTemplate(link))
 	}
 
-	for _, post := range postQueryResult {
+	for _, post := range posts {
 		templateData.RecentActivity = append(templateData.RecentActivity, PostToTimelineItem(
 			c.UrlContext,
 			lineageBuilder,
-			&post.(*postQuery).Post,
-			&post.(*postQuery).Thread,
-			&post.(*postQuery).Author,
+			&post.Post,
+			&post.Thread,
+			&post.Author,
 			c.Theme,
 		))
 	}
@@ -498,7 +492,7 @@ func ProjectEdit(c *RequestContext) ResponseData {
 	}
 
 	c.Perf.StartBlock("SQL", "Fetching project links")
-	projectLinkResult, err := db.Query(c.Context(), c.Conn, models.Link{},
+	projectLinks, err := db.Query[models.Link](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -525,7 +519,7 @@ func ProjectEdit(c *RequestContext) ResponseData {
 		c.Theme,
 	)
 
-	projectSettings.LinksText = LinksToText(projectLinkResult)
+	projectSettings.LinksText = LinksToText(projectLinks)
 
 	var res ResponseData
 	res.MustWriteTemplate("project_edit.html", ProjectEditData{
@@ -822,14 +816,12 @@ func updateProject(ctx context.Context, tx pgx.Tx, user *models.User, payload *P
 		}
 	}
 
-	type userQuery struct {
-		User models.User `db:"auth_user"`
-	}
-	ownerRows, err := db.Query(ctx, tx, userQuery{},
+	owners, err := db.Query[models.User](ctx, tx,
 		`
-		SELECT $columns
-		FROM auth_user
-		LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
+		SELECT $columns{auth_user}
+		FROM
+			auth_user
+			LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
 		WHERE LOWER(username) = ANY ($1)
 		`,
 		payload.OwnerUsernames,
@@ -849,7 +841,7 @@ func updateProject(ctx context.Context, tx pgx.Tx, user *models.User, payload *P
 		return oops.New(err, "Failed to delete project owners")
 	}
 
-	for _, ownerRow := range ownerRows {
+	for _, owner := range owners {
 		_, err = tx.Exec(ctx,
 			`
 			INSERT INTO handmade_user_projects
@@ -857,7 +849,7 @@ func updateProject(ctx context.Context, tx pgx.Tx, user *models.User, payload *P
 			VALUES
 				($1,      $2)
 			`,
-			ownerRow.(*userQuery).User.ID,
+			owner.ID,
 			payload.ProjectID,
 		)
 		if err != nil {

src/website/routes.go

@@ -548,13 +548,11 @@ func getCurrentUserAndSession(c *RequestContext, sessionId string) (*models.User
 		}
 	}
 
-	type userQuery struct {
-		User models.User `db:"auth_user"`
-	}
-	userRow, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+	user, err := db.QueryOne[models.User](c.Context(), c.Conn,
 		`
-		SELECT $columns
-			FROM auth_user
+		SELECT $columns{auth_user}
+		FROM
+			auth_user
 			LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
 		WHERE username = $1
 		`,
@@ -568,7 +566,6 @@ func getCurrentUserAndSession(c *RequestContext, sessionId string) (*models.User
 			return nil, nil, oops.New(err, "failed to get user for session")
 		}
 	}
-	user := &userRow.(*userQuery).User
 
 	return user, session, nil
 }

src/website/twitch.go

@@ -70,7 +70,7 @@ func TwitchEventSubCallback(c *RequestContext) ResponseData {
 }
 
 func TwitchDebugPage(c *RequestContext) ResponseData {
-	streams, err := db.Query(c.Context(), c.Conn, models.TwitchStream{},
+	streams, err := db.Query[models.TwitchStream](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -83,8 +83,7 @@ func TwitchDebugPage(c *RequestContext) ResponseData {
 	}
 
 	html := ""
-	for _, stream := range streams {
-		s := stream.(*models.TwitchStream)
+	for _, s := range streams {
 		html += fmt.Sprintf(`<a href="https://twitch.tv/%s">%s</a>%s<br />`, s.Login, s.Login, s.Title)
 	}
 	var res ResponseData

src/website/user.go

@@ -53,12 +53,9 @@ func UserProfile(c *RequestContext) ResponseData {
 		profileUser = c.CurrentUser
 	} else {
 		c.Perf.StartBlock("SQL", "Fetch user")
-		type userQuery struct {
-			User models.User `db:"auth_user"`
-		}
-		userResult, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+		user, err := db.QueryOne[models.User](c.Context(), c.Conn,
 			`
-			SELECT $columns
+			SELECT $columns{auth_user}
 			FROM
 				auth_user
 				LEFT JOIN handmade_asset AS auth_user_avatar ON auth_user_avatar.id = auth_user.avatar_asset_id
@@ -75,7 +72,7 @@ func UserProfile(c *RequestContext) ResponseData {
 				return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch user: %s", username))
 			}
 		}
-		profileUser = &userResult.(*userQuery).User
+		profileUser = user
 	}
 
 	{
@@ -87,10 +84,7 @@ func UserProfile(c *RequestContext) ResponseData {
 	}
 
 	c.Perf.StartBlock("SQL", "Fetch user links")
-	type userLinkQuery struct {
-		UserLink models.Link `db:"link"`
-	}
-	userLinksSlice, err := db.Query(c.Context(), c.Conn, userLinkQuery{},
+	userLinks, err := db.Query[models.Link](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -104,9 +98,9 @@ func UserProfile(c *RequestContext) ResponseData {
 	if err != nil {
 		return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch links for user: %s", username))
 	}
-	profileUserLinks := make([]templates.Link, 0, len(userLinksSlice))
-	for _, l := range userLinksSlice {
-		profileUserLinks = append(profileUserLinks, templates.LinkToTemplate(&l.(*userLinkQuery).UserLink))
+	profileUserLinks := make([]templates.Link, 0, len(userLinks))
+	for _, l := range userLinks {
+		profileUserLinks = append(profileUserLinks, templates.LinkToTemplate(l))
 	}
 	c.Perf.EndBlock()
 
@@ -231,7 +225,7 @@ func UserSettings(c *RequestContext) ResponseData {
 		DiscordShowcaseBacklogUrl string
 	}
 
-	links, err := db.Query(c.Context(), c.Conn, models.Link{},
+	links, err := db.Query[models.Link](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM handmade_links
@@ -248,7 +242,7 @@ func UserSettings(c *RequestContext) ResponseData {
 
 	var tduser *templates.DiscordUser
 	var numUnsavedMessages int
-	iduser, err := db.QueryOne(c.Context(), c.Conn, models.DiscordUser{},
+	duser, err := db.QueryOne[models.DiscordUser](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM handmade_discorduser
@@ -261,11 +255,10 @@ func UserSettings(c *RequestContext) ResponseData {
 	} else if err != nil {
 		return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch user's Discord account"))
 	} else {
-		duser := iduser.(*models.DiscordUser)
 		tmp := templates.DiscordUserToTemplate(duser)
 		tduser = &tmp
 
-		numUnsavedMessages, err = db.QueryInt(c.Context(), c.Conn,
+		numUnsavedMessages, err = db.QueryOneScalar[int](c.Context(), c.Conn,
 			`
 			SELECT COUNT(*)
 			FROM