Start improvements to db API

Allowing for querying of scalars with db.Query, and a choice of prefix
in $columns to remove the need for single-field structs in many queries.

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
@@ -32,9 +27,43 @@ require (
 	github.com/yuin/goldmark v1.4.1
 	github.com/yuin/goldmark-highlighting v0.0.0-20210516132338-9216f9c5aa01
 	golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2
+	golang.org/x/exp v0.0.0-20220314205449-43aec2f8a4e7
 	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 v0.0.0-20211019181941-9d821ace8654 // 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=
@@ -372,6 +370,8 @@ golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL
 golang.org/x/exp v0.0.0-20190510132918-efd6b22b2522/go.mod h1:ZjyILWgesfNpC6sMxTJOJm9Kp84zZh5NQWvqDGG3Qr8=
 golang.org/x/exp v0.0.0-20190829153037-c13cbed26979/go.mod h1:86+5VVa7VpoJ4kLfm080zCjGlMRFzhUhsZKEZO7MGek=
 golang.org/x/exp v0.0.0-20191030013958-a1ab85dbe136/go.mod h1:JXzH8nQsPlswgeRAPE3MuO9GYsAcnJvJ4vnMwN/5qkY=
+golang.org/x/exp v0.0.0-20220314205449-43aec2f8a4e7 h1:jynE66seADJbyWMUdeOyVTvPtBZt7L6LJHupGwxPZRM=
+golang.org/x/exp v0.0.0-20220314205449-43aec2f8a4e7/go.mod h1:lgLbSvA5ygNOMpwM/9anMpWVlVJ7Z+cHWq/eFuinpGE=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/image v0.0.0-20210628002857-a66eb6448b8d h1:RNPAfi2nHY7C2srAV8A49jpsYr0ADedCk1wq6fTMTvs=
@@ -439,8 +439,9 @@ golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200413165638-669c56c373c4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20211019181941-9d821ace8654 h1:id054HUawV2/6IGm2IV8KZQjqtwAOo2CYlOToYqa0d0=
+golang.org/x/sys v0.0.0-20211019181941-9d821ace8654/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

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"
@@ -95,14 +96,20 @@ func NewConnPool(minConns, maxConns int32) *pgxpool.Pool {
 	return conn
 }
 
-type StructQueryIterator struct {
+type columnName []string
-	fieldPaths [][]int
+
+// 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 StructQueryIterator[T any] struct {
+	fieldPaths []fieldPath
 	rows       pgx.Rows
 	destType   reflect.Type
 	closed     chan struct{}
 }
 
-func (it *StructQueryIterator) Next() (interface{}, bool) {
+func (it *StructQueryIterator[T]) Next() (*T, bool) {
 	hasNext := it.rows.Next()
 	if !hasNext {
 		it.Close()
@@ -172,10 +179,10 @@ func (it *StructQueryIterator) Next() (interface{}, bool) {
 		currentValue = reflect.Value{}
 	}
 
-	return result.Interface(), true
+	return result.Interface().(*T), true
 }
 
-func (it *StructQueryIterator) Close() {
+func (it *StructQueryIterator[any]) Close() {
 	it.rows.Close()
 	select {
 	case it.closed <- struct{}{}:
@@ -183,9 +190,9 @@ func (it *StructQueryIterator) Close() {
 	}
 }
 
-func (it *StructQueryIterator) ToSlice() []interface{} {
+func (it *StructQueryIterator[T]) ToSlice() []*T {
 	defer it.Close()
-	var result []interface{}
+	var result []*T
 	for {
 		row, ok := it.Next()
 		if !ok {
@@ -231,8 +238,8 @@ func followPathThroughStructs(structPtrVal reflect.Value, path []int) (reflect.V
 	return val, field
 }
 
-func Query(ctx context.Context, conn ConnOrTx, destExample interface{}, query string, args ...interface{}) ([]interface{}, error) {
+func Query[T any](ctx context.Context, conn ConnOrTx, query string, args ...interface{}) ([]*T, error) {
-	it, err := QueryIterator(ctx, conn, destExample, query, args...)
+	it, err := QueryIterator[T](ctx, conn, query, args...)
 	if err != nil {
 		return nil, err
 	} else {
@@ -240,27 +247,13 @@ 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) {
+func QueryIterator[T any](ctx context.Context, conn ConnOrTx, query string, args ...interface{}) (*StructQueryIterator[T], error) {
+	var destExample T
 	destType := reflect.TypeOf(destExample)
-	columnNames, fieldPaths, err := getColumnNamesAndPaths(destType, nil, nil)
-	if err != nil {
-		return nil, oops.New(err, "failed to generate column names")
-	}
 
-	columns := make([]string, 0, len(columnNames))
+	compiled := compileQuery(query, destType)
-	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, ", ")
+	rows, err := conn.Query(ctx, compiled.query, args...)
-	query = strings.Replace(query, "$columns", columnNamesString, -1)
-
-	rows, err := conn.Query(ctx, query, args...)
 	if err != nil {
 		if errors.Is(err, context.DeadlineExceeded) {
 			panic("query exceeded its deadline")
@@ -268,10 +261,10 @@ func QueryIterator(ctx context.Context, conn ConnOrTx, destExample interface{},
 		return nil, err
 	}
 
-	it := &StructQueryIterator{
+	it := &StructQueryIterator[T]{
-		fieldPaths: fieldPaths,
+		fieldPaths: compiled.fieldPaths,
 		rows:       rows,
-		destType:   destType,
+		destType:   compiled.destType,
 		closed:     make(chan struct{}, 1),
 	}
 
@@ -292,16 +285,70 @@ 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) {
+type compiledQuery struct {
-	var columnNames [][]string
+	query      string
-	var fieldPaths [][]int
+	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 some kind of 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 {
@@ -348,19 +395,16 @@ 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)
+				subCols, subPaths := getColumnNamesAndPaths(fieldType, path, fieldColumnNames)
-				if err != nil {
-					return nil, nil, err
-				}
 				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
 }
 
 /*
@@ -370,8 +414,8 @@ result but find nothing.
 */
 var NotFound = errors.New("not found")
 
-func QueryOne(ctx context.Context, conn ConnOrTx, destExample interface{}, query string, args ...interface{}) (interface{}, error) {
+func QueryOne[T any](ctx context.Context, conn ConnOrTx, query string, args ...interface{}) (*T, error) {
-	rows, err := QueryIterator(ctx, conn, destExample, query, args...)
+	rows, err := QueryIterator[T](ctx, conn, query, args...)
 	if err != nil {
 		return nil, err
 	}

src/db/db_test.go

@@ -10,13 +10,90 @@ import (
 
 func TestPaths(t *testing.T) {
 	type CustomInt int
+	type S2 struct {
+		B  bool  `db:"B"`  // field 0
+		PB *bool `db:"PB"` // field 1
+
+		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"`  // field 0
+		PS *S `db:"PS"` // field 1
+
+		NoTag S // field 2
+	}
+	type Embedded struct {
+		NoTag  S // field 0
+		Nested   // field 1
+	}
+
+	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][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"`
-		B   bool       `db:"B"`
+			S2  `db:"S2"`  // embedded!
-		PB  *bool      `db:"PB"`
+			PS2 *S2        `db:"PS2"`
 
 			NoTag int
 		}
@@ -26,34 +103,48 @@ func TestPaths(t *testing.T) {
 
 			NoTag S
 		}
-	type Embedded struct {
+		type Dest struct {
 			NoTag S
 			Nested
 		}
 
-	names, paths, err := getColumnNamesAndPaths(reflect.TypeOf(Embedded{}), nil, "")
+		compiled := compileQuery("SELECT $columns FROM greeblies", reflect.TypeOf(Dest{}))
-	if assert.Nil(t, err) {
+		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)
-		assert.Equal(t, []string{
+	})
-			"S.I", "S.PI",
+	t.Run("int", func(t *testing.T) {
-			"S.CI", "S.PCI",
+		type Dest int
-			"S.B", "S.PB",
+
-			"PS.I", "PS.PI",
+		// There should be no error here because we do not need to extract columns from
-			"PS.CI", "PS.PCI",
+		// the destination type. There may be errors down the line in value iteration, but
-			"PS.B", "PS.PB",
+		// that is always the case if the Go types don't match the query.
-		}, names)
+		compiled := compileQuery("SELECT id FROM greeblies", reflect.TypeOf(Dest(0)))
-		assert.Equal(t, [][]int{
+		assert.Equal(t, "SELECT id FROM greeblies", compiled.query)
-			{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},
+	t.Run("just one table", func(t *testing.T) {
-		}, paths)
+		type Dest struct {
-		assert.True(t, len(names) == len(paths))
+			Foo  int    `db:"foo"`
+			Bar  bool   `db:"bar"`
+			Nope string // no tag
 		}
 
-	testStruct := Embedded{}
+		// The prefix is necessary because otherwise we would have to provide a struct with
-	for i, path := range paths {
+		// a db tag in order to provide the query with the `greeblies.` prefix in the
-		val, field := followPathThroughStructs(reflect.ValueOf(&testStruct), path)
+		// final query. This comes up a lot when we do a JOIN to help with a condition, but
-		assert.True(t, val.IsValid())
+		// don't actually care about any of the data we joined to.
-		assert.True(t, strings.Contains(names[i], field.Name))
+		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) {

src/discord/commands.go

@@ -93,7 +93,7 @@ func (bot *botInstance) handleProfileCommand(ctx context.Context, i *Interaction
 	type profileResult struct {
 		HMNUser models.User `db:"auth_user"`
 	}
-	ires, err := db.QueryOne(ctx, bot.dbConn, profileResult{},
+	res, err := db.QueryOne[profileResult](ctx, bot.dbConn,
 		`
 		SELECT $columns
 		FROM
@@ -122,7 +122,6 @@ 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},

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{
@@ -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 {
+				for _, msg := range msgs {
-					msg := imsg.(*models.DiscordOutgoingMessage)
 					if time.Now().After(msg.ExpiresAt) {
 						continue
 					}

src/discord/history.go

@@ -76,7 +76,7 @@ func fetchMissingContent(ctx context.Context, dbConn *pgxpool.Pool) {
 	type query struct {
 		Message models.DiscordMessage `db:"msg"`
 	}
-	imessagesWithoutContent, err := db.Query(ctx, dbConn, query{},
+	messagesWithoutContent, err := db.Query[query](ctx, dbConn,
 		`
 		SELECT $columns
 		FROM
@@ -95,10 +95,10 @@ func fetchMissingContent(ctx context.Context, dbConn *pgxpool.Pool) {
 		return
 	}
 
-	if len(imessagesWithoutContent) > 0 {
+	if len(messagesWithoutContent) > 0 {
-		log.Info().Msgf("There are %d Discord messages without content, fetching their content now...", len(imessagesWithoutContent))
+		log.Info().Msgf("There are %d Discord messages without content, fetching their content now...", len(messagesWithoutContent))
 	msgloop:
-		for _, imsg := range imessagesWithoutContent {
+		for _, msgRow := range messagesWithoutContent {
 			select {
 			case <-ctx.Done():
 				log.Info().Msg("Scrape was canceled")
@@ -106,7 +106,7 @@ func fetchMissingContent(ctx context.Context, dbConn *pgxpool.Pool) {
 			default:
 			}
 
-			msg := imsg.(*query).Message
+			msg := msgRow.Message
 
 			discordMsg, err := GetChannelMessage(ctx, msg.ChannelID, msg.ID)
 			if errors.Is(err, NotFound) {

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
@@ -236,7 +236,6 @@ func FetchInternedMessage(ctx context.Context, dbConn db.ConnOrTx, msgId string)
 		return nil, err
 	}
 
-	interned := result.(*InternedMessage)
 	return interned, nil
 }
 
@@ -283,7 +282,7 @@ 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 +293,6 @@ 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 +362,7 @@ 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 +375,7 @@ func SaveMessageContents(
 			if err != nil {
 				return oops.New(err, "failed to fetch message contents")
 			}
-			interned.MessageContent = icontent.(*models.DiscordMessageContent)
+			interned.MessageContent = content
 		}
 
 		// Save attachments
@@ -472,7 +467,7 @@ 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 +476,7 @@ 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 +529,7 @@ 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 +541,7 @@ 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 +631,7 @@ 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 +643,11 @@ 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 +664,7 @@ func FetchSnippetForMessage(ctx context.Context, dbConn db.ConnOrTx, msgID strin
 		}
 	}
 
-	return iresult.(*models.Snippet), nil
+	return snippet, nil
 }
 
 /*
@@ -808,7 +803,7 @@ func HandleSnippetForInternedMessage(ctx context.Context, dbConn db.ConnOrTx, in
 		type tagsRow struct {
 			Tag models.Tag `db:"tags"`
 		}
-		iUserTags, err := db.Query(ctx, tx, tagsRow{},
+		userTags, err := db.Query[tagsRow](ctx, tx,
 			`
 			SELECT $columns
 			FROM
@@ -823,8 +818,8 @@ func HandleSnippetForInternedMessage(ctx context.Context, dbConn db.ConnOrTx, in
 			return oops.New(err, "failed to fetch tags for user projects")
 		}
 
-		for _, itag := range iUserTags {
+		for _, userTag := range userTags {
-			tag := itag.(*tagsRow).Tag
+			tag := userTag.Tag
 			allTags = append(allTags, tag.ID)
 			for _, messageTag := range messageTags {
 				if strings.EqualFold(tag.Text, messageTag) {
@@ -890,7 +885,7 @@ 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 +896,12 @@ 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 {
+	for _, attachment := range attachments {
-		attachment := iattachment.(*models.DiscordMessageAttachment)
 		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 +912,7 @@ 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 {
+	for _, embed := range embeds {
-		embed := iembed.(*models.DiscordMessageEmbed)
 		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()...)
+	projects, 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))
+	projectIds := make([]int, len(projects))
-	for i, iproject := range iprojects {
+	for i, projectRow := range projects {
-		projectIds[i] = iproject.(*projectRow).Project.ID
+		projectIds[i] = projectRow.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 {
+	for i, row := range projects {
-		row := iproject.(*projectRow)
 		owners := projectOwners[i].Owners
 
 		/*
@@ -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 {
+	for _, userProject := range userProjects {
-		userProject := iuserproject.(*userProject)
-
 		addUserId := true
 		for _, uid := range userIds {
 			if uid == userProject.UserID {
@@ -364,7 +361,7 @@ func FetchMultipleProjectsOwners(
 	type userQuery struct {
 		User models.User `db:"auth_user"`
 	}
-	iusers, err := db.Query(ctx, tx, userQuery{},
+	projectUsers, err := db.Query[userQuery](ctx, tx,
 		`
 		SELECT $columns
 		FROM auth_user
@@ -383,9 +380,7 @@ func FetchMultipleProjectsOwners(
 	for i, pid := range projectIds {
 		res[i] = ProjectOwners{ProjectID: pid}
 	}
-	for _, iuserproject := range iuserprojects {
+	for _, userProject := range userProjects {
-		userProject := iuserproject.(*userProject)
-
 		// Get a pointer to the existing record in the result
 		var projectOwners *ProjectOwners
 		for i := range res {
@@ -396,8 +391,8 @@ func FetchMultipleProjectsOwners(
 
 		// Get the full user record we fetched
 		var user *models.User
-		for _, iuser := range iusers {
+		for _, projectUser := range projectUsers {
-			u := iuser.(*userQuery).User
+			u := projectUser.User
 			if u.ID == userProject.UserID {
 				user = &u
 			}
@@ -473,7 +468,7 @@ 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 +478,7 @@ 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 +494,7 @@ 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 +506,7 @@ 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

@@ -47,7 +47,7 @@ func FetchSnippets(
 		type snippetIDRow struct {
 			SnippetID int `db:"snippet_id"`
 		}
-		iSnippetIDs, err := db.Query(ctx, tx, snippetIDRow{},
+		snippetIDs, err := db.Query[snippetIDRow](ctx, tx,
 			`
 			SELECT DISTINCT snippet_id
 			FROM
@@ -63,13 +63,13 @@ 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))
+		q.IDs = make([]int, len(snippetIDs))
-		for i := range iSnippetIDs {
+		for i := range snippetIDs {
-			q.IDs[i] = iSnippetIDs[i].(*snippetIDRow).SnippetID
+			q.IDs[i] = snippetIDs[i].SnippetID
 		}
 	}
 
@@ -125,16 +125,14 @@ func FetchSnippets(
 		DiscordMessage *models.DiscordMessage `db:"discord_message"`
 	}
 
-	iresults, err := db.Query(ctx, tx, resultRow{}, qb.String(), qb.Args()...)
+	rows, 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
+	result := make([]SnippetAndStuff, len(rows)) // allocate extra space because why not
-	snippetIDs := make([]int, len(iresults))
+	snippetIDs := make([]int, len(rows))
-	for i, iresult := range iresults {
+	for i, row := range rows {
-		row := *iresult.(*resultRow)
-
 		result[i] = SnippetAndStuff{
 			Snippet:        row.Snippet,
 			Owner:          row.Owner,
@@ -150,7 +148,7 @@ 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 +168,7 @@ func FetchSnippets(
 	for i := range result {
 		resultBySnippetId[result[i].Snippet.ID] = &result[i]
 	}
-	for _, iSnippetTag := range iSnippetTags {
+	for _, snippetTag := range snippetTags {
-		snippetTag := iSnippetTag.(*snippetTagRow)
 		item := resultBySnippetId[snippetTag.SnippetID]
 		item.Tags = append(item.Tags, snippetTag.Tag)
 	}

src/hmndata/tag_helper.go

@@ -40,18 +40,12 @@ 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))
+	return tags, nil
-	for i, itag := range itags {
-		tag := itag.(*models.Tag)
-		res[i] = tag
-	}
-
-	return res, 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()...)
+	results, 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))
+	result := make([]ThreadAndStuff, len(results))
-	for i, iresult := range iresults {
+	for i, row := range results {
-		row := *iresult.(*resultRow)
-
 		hasRead := false
 		if currentUser != nil && currentUser.MarkedAllReadAt.After(row.LastPost.PostDate) {
 			hasRead = true
@@ -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()...)
+	results, 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))
+	result := make([]PostAndStuff, len(results))
-	for i, iresult := range iresults {
+	for i, row := range results {
-		row := *iresult.(*resultRow)
-
 		hasRead := false
 		if currentUser != nil && currentUser.MarkedAllReadAt.After(row.Post.PostDate) {
 			hasRead = true
@@ -611,7 +607,7 @@ func UserCanEditPost(ctx context.Context, connOrTx db.ConnOrTx, user models.User
 	type postResult struct {
 		AuthorID *int `db:"post.author_id"`
 	}
-	iresult, err := db.QueryOne(ctx, connOrTx, postResult{},
+	result, err := db.QueryOne[postResult](ctx, connOrTx,
 		`
 		SELECT $columns
 		FROM
@@ -629,7 +625,6 @@ 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
 }
@@ -709,7 +704,7 @@ 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 +717,6 @@ func DeletePost(
 	if err != nil {
 		panic(oops.New(err, "failed to fetch thread info"))
 	}
-	info := ti.(*threadInfo)
 	if info.Deleted {
 		return true
 	}
@@ -851,7 +845,7 @@ func CreatePostVersion(ctx context.Context, tx pgx.Tx, postId int, unparsedConte
 	type assetId struct {
 		AssetID uuid.UUID `db:"id"`
 	}
-	assetResult, err := db.Query(ctx, tx, assetId{},
+	assets, err := db.Query[assetId](ctx, tx,
 		`
 		SELECT $columns
 		FROM handmade_asset
@@ -865,8 +859,8 @@ func CreatePostVersion(ctx context.Context, tx pgx.Tx, postId int, unparsedConte
 
 	var values [][]interface{}
 
-	for _, asset := range assetResult {
+	for _, asset := range assets {
-		values = append(values, []interface{}{postId, asset.(*assetId).AssetID})
+		values = append(values, []interface{}{postId, asset.AssetID})
 	}
 
 	_, err = tx.CopyFrom(ctx, pgx.Identifier{"handmade_post_asset_usage"}, []string{"post_id", "asset_id"}, pgx.CopyFromRows(values))
@@ -886,7 +880,7 @@ 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 +895,7 @@ func FixThreadPostIds(ctx context.Context, tx pgx.Tx, threadId int) error {
 	}
 
 	var firstPost, lastPost *models.Post
-	for _, ipost := range postsIter {
+	for _, post := range posts {
-		post := ipost.(*models.Post)
-
 		if firstPost == nil || post.PostDate.Before(firstPost.PostDate) {
 			firstPost = post
 		}

src/models/subforum.go

@@ -47,7 +47,7 @@ func GetFullSubforumTree(ctx context.Context, conn *pgxpool.Pool) SubforumTree {
 	type subforumRow struct {
 		Subforum Subforum `db:"sf"`
 	}
-	rowsSlice, err := db.Query(ctx, conn, subforumRow{},
+	rowsSlice, err := db.Query[subforumRow](ctx, conn,
 		`
 		SELECT $columns
 		FROM
@@ -61,7 +61,7 @@ func GetFullSubforumTree(ctx context.Context, conn *pgxpool.Pool) SubforumTree {
 
 	sfTreeMap := make(map[int]*SubforumTreeNode, len(rowsSlice))
 	for _, row := range rowsSlice {
-		sf := row.(*subforumRow).Subforum
+		sf := row.Subforum
 		sfTreeMap[sf.ID] = &SubforumTreeNode{Subforum: sf}
 	}
 
@@ -73,7 +73,7 @@ func GetFullSubforumTree(ctx context.Context, conn *pgxpool.Pool) SubforumTree {
 
 	for _, row := range rowsSlice {
 		// NOTE(asaf): Doing this in a separate loop over rowsSlice to ensure that Children are in db order.
-		cat := row.(*subforumRow).Subforum
+		cat := row.Subforum
 		node := sfTreeMap[cat.ID]
 		if node.Parent != nil {
 			node.Parent.Children = append(node.Parent.Children, node)

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 {
+	for _, link := range userLinks {
-		link := ul.(*models.Link)
 		userData := unapprovedUsers[userIDToDataIdx[*link.UserID]]
 		userData.UserLinks = append(userData.UserLinks, templates.LinkToTemplate(link))
 	}
@@ -260,10 +259,11 @@ func AdminApprovalQueueSubmit(c *RequestContext) ResponseData {
 	type userQuery struct {
 		User models.User `db:"auth_user"`
 	}
-	u, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+	u, err := db.QueryOne[userQuery](c.Context(), c.Conn,
 		`
 		SELECT $columns
-			FROM 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 +276,7 @@ func AdminApprovalQueueSubmit(c *RequestContext) ResponseData {
 			return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fetch user"))
 		}
 	}
-	user := u.(*userQuery).User
+	user := u.User
 
 	whatHappened := ""
 	if action == ApprovalQueueActionApprove {
@@ -337,7 +337,7 @@ type UnapprovedPost struct {
 }
 
 func fetchUnapprovedPosts(c *RequestContext) ([]*UnapprovedPost, error) {
-	it, err := db.Query(c.Context(), c.Conn, UnapprovedPost{},
+	res, err := db.Query[UnapprovedPost](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -358,10 +358,6 @@ 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
 }
 
@@ -375,7 +371,7 @@ func fetchUnapprovedProjects(c *RequestContext) ([]UnapprovedProject, error) {
 	type unapprovedUser struct {
 		ID int `db:"id"`
 	}
-	it, err := db.Query(c.Context(), c.Conn, unapprovedUser{},
+	uids, err := db.Query[unapprovedUser](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM
@@ -388,9 +384,9 @@ 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))
+	ownerIDs := make([]int, 0, len(uids))
-	for _, uid := range it {
+	for _, uid := range uids {
-		ownerIDs = append(ownerIDs, uid.(*unapprovedUser).ID)
+		ownerIDs = append(ownerIDs, uid.ID)
 	}
 
 	projects, err := hmndata.FetchProjects(c.Context(), c.Conn, c.CurrentUser, hmndata.ProjectsQuery{

src/website/api.go

@@ -22,7 +22,7 @@ func APICheckUsername(c *RequestContext) ResponseData {
 		type userQuery struct {
 			User models.User `db:"auth_user"`
 		}
-		userResult, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+		userResult, err := db.QueryOne[userQuery](c.Context(), c.Conn,
 			`
 			SELECT $columns
 			FROM
@@ -43,7 +43,7 @@ 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 = userResult.User.Username
 		}
 	}
 

src/website/auth.go

@@ -78,10 +78,11 @@ func Login(c *RequestContext) ResponseData {
 	type userQuery struct {
 		User models.User `db:"auth_user"`
 	}
-	userRow, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+	userRow, err := db.QueryOne[userQuery](c.Context(), c.Conn,
 		`
 		SELECT $columns
-			FROM 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 +95,7 @@ func Login(c *RequestContext) ResponseData {
 			return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to look up user by username"))
 		}
 	}
-	user := &userRow.(*userQuery).User
+	user := &userRow.User
 
 	success, err := tryLogin(c, user, password)
 
@@ -460,7 +461,7 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 	type userQuery struct {
 		User models.User `db:"auth_user"`
 	}
-	userRow, err := db.QueryOne(c.Context(), c.Conn, userQuery{},
+	userRow, err := db.QueryOne[userQuery](c.Context(), c.Conn,
 		`
 		SELECT $columns
 		FROM auth_user
@@ -479,12 +480,12 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 		}
 	}
 	if userRow != nil {
-		user = &userRow.(*userQuery).User
+		user = &userRow.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 +502,6 @@ 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 +524,7 @@ 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{},
+			resetToken, 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 +540,6 @@ func RequestPasswordResetSubmit(c *RequestContext) ResponseData {
 			if err != nil {
 				return c.ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to create onetimetoken"))
 			}
-			resetToken = tokenRow.(*models.OneTimeToken)
 
 			err = email.SendPasswordReset(user.Email, user.BestName(), user.Username, resetToken.Content, resetToken.Expires, c.Perf)
 			if err != nil {
@@ -787,7 +783,7 @@ 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 +803,7 @@ func validateUsernameAndToken(c *RequestContext, username string, token string,
 			return result
 		}
 	}
-	if row != nil {
+	if data != nil {
-		data := row.(*userAndTokenQuery)
 		result.User = &data.User
 		result.OneTimeToken = data.OneTimeToken
 		if result.OneTimeToken != nil {