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.

src/db/db.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"regexp"
 	"strings"
 
 	"git.handmade.network/hmn/hmn/src/config"
@@ -95,8 +96,14 @@ func NewConnPool(minConns, maxConns int32) *pgxpool.Pool {
 	return conn
 }
 
+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 StructQueryIterator[T any] struct {
-	fieldPaths [][]int
+	fieldPaths []fieldPath
 	rows       pgx.Rows
 	destType   reflect.Type
 	closed     chan struct{}
@@ -243,25 +250,10 @@ func Query[T any](ctx context.Context, conn ConnOrTx, query string, args ...inte
 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")
@@ -270,9 +262,9 @@ func QueryIterator[T any](ctx context.Context, conn ConnOrTx, query string, args
 	}
 
 	it := &StructQueryIterator[T]{
-		fieldPaths: fieldPaths,
+		fieldPaths: compiled.fieldPaths,
 		rows:       rows,
-		destType:   destType,
+		destType:   compiled.destType,
 		closed:     make(chan struct{}, 1),
 	}
 
@@ -293,16 +285,70 @@ func QueryIterator[T any](ctx context.Context, conn ConnOrTx, query string, args
 	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 {
@@ -349,19 +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
 }
 
 /*

src/db/db_test.go

@@ -10,52 +10,143 @@ import (
 
 func TestPaths(t *testing.T) {
 	type CustomInt int
-	type S struct {
+	type S2 struct {
-		I   int        `db:"I"`
+		B  bool  `db:"B"`  // field 0
-		PI  *int       `db:"PI"`
+		PB *bool `db:"PB"` // field 1
-		CI  CustomInt  `db:"CI"`
-		PCI *CustomInt `db:"PCI"`
-		B   bool       `db:"B"`
-		PB  *bool      `db:"PB"`
 
-		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"`
+		S  S  `db:"S"`  // field 0
-		PS *S `db:"PS"`
+		PS *S `db:"PS"` // field 1
 
-		NoTag S
+		NoTag S // field 2
 	}
 	type Embedded struct {
-		NoTag S
+		NoTag  S // field 0
-		Nested
+		Nested   // field 1
 	}
 
-	names, paths, err := getColumnNamesAndPaths(reflect.TypeOf(Embedded{}), nil, "")
+	names, paths := getColumnNamesAndPaths(reflect.TypeOf(Embedded{}), nil, nil)
-	if assert.Nil(t, err) {
+	assert.Equal(t, []columnName{
-		assert.Equal(t, []string{
+		{"S", "I"}, {"S", "PI"},
-			"S.I", "S.PI",
+		{"S", "CI"}, {"S", "PCI"},
-			"S.CI", "S.PCI",
+		{"S", "S2", "B"}, {"S", "S2", "PB"},
-			"S.B", "S.PB",
+		{"S", "PS2", "B"}, {"S", "PS2", "PB"},
-			"PS.I", "PS.PI",
+		{"PS", "I"}, {"PS", "PI"},
-			"PS.CI", "PS.PCI",
+		{"PS", "CI"}, {"PS", "PCI"},
-			"PS.B", "PS.PB",
+		{"PS", "S2", "B"}, {"PS", "S2", "PB"},
-		}, names)
+		{"PS", "PS2", "B"}, {"PS", "PS2", "PB"},
-		assert.Equal(t, [][]int{
+	}, names)
-			{1, 0, 0}, {1, 0, 1}, {1, 0, 2}, {1, 0, 3}, {1, 0, 4}, {1, 0, 5},
+	assert.Equal(t, []fieldPath{
-			{1, 1, 0}, {1, 1, 1}, {1, 1, 2}, {1, 1, 3}, {1, 1, 4}, {1, 1, 5},
+		{1, 0, 0}, {1, 0, 1}, // Nested.S.I, Nested.S.PI
-		}, paths)
+		{1, 0, 2}, {1, 0, 3}, // Nested.S.CI, Nested.S.PCI
-		assert.True(t, len(names) == len(paths))
+		{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/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 {