allow using function as table function

enginetest/join_stats_tests.go

@@ -360,12 +360,12 @@ func (t TestProvider) Function(ctx *sql.Context, name string) (sql.Function, boo
 	return nil, false
 }
 
-func (t TestProvider) TableFunction(_ *sql.Context, name string) (sql.TableFunction, error) {
+func (t TestProvider) TableFunction(_ *sql.Context, name string) (sql.TableFunction, bool) {
 	if tf, ok := t.tableFunctions[strings.ToLower(name)]; ok {
-		return tf, nil
+		return tf, true
 	}
 
-	return nil, sql.ErrTableFunctionNotFound.New(name)
+	return nil, false
 }
 
 func (t TestProvider) WithTableFunctions(fns ...sql.TableFunction) (sql.TableFunctionProvider, error) {

memory/provider.go

@@ -194,10 +194,10 @@ func (pro *DbProvider) ExternalStoredProcedures(_ *sql.Context, name string) ([]
 }
 
 // TableFunction implements sql.TableFunctionProvider
-func (pro *DbProvider) TableFunction(_ *sql.Context, name string) (sql.TableFunction, error) {
+func (pro *DbProvider) TableFunction(_ *sql.Context, name string) (sql.TableFunction, bool) {
 	if tableFunction, ok := pro.tableFunctions[name]; ok {
-		return tableFunction, nil
+		return tableFunction, true
 	}
 
-	return nil, sql.ErrTableFunctionNotFound.New(name)
+	return nil, false
 }

sql/analyzer/catalog.go

@@ -384,17 +384,14 @@ func (c *Catalog) ExternalStoredProcedures(ctx *sql.Context, name string) ([]sql
 }
 
 // TableFunction implements the TableFunctionProvider interface
-func (c *Catalog) TableFunction(ctx *sql.Context, name string) (sql.TableFunction, error) {
+func (c *Catalog) TableFunction(ctx *sql.Context, name string) (sql.TableFunction, bool) {
 	if fp, ok := c.DbProvider.(sql.TableFunctionProvider); ok {
-		tf, err := fp.TableFunction(ctx, name)
-		if err != nil {
-			return nil, err
-		} else if tf != nil {
-			return tf, nil
+		tf, found := fp.TableFunction(ctx, name)
+		if found && tf != nil {
+			return tf, true
 		}
 	}
-
-	return nil, sql.ErrTableFunctionNotFound.New(name)
+	return nil, false
 }
 
 func (c *Catalog) RefreshTableStats(ctx *sql.Context, table sql.Table, db string) error {

sql/catalog_map.go

@@ -25,11 +25,11 @@ func (t MapCatalog) Function(ctx *Context, name string) (Function, bool) {
 	return nil, false
 }
 
-func (t MapCatalog) TableFunction(ctx *Context, name string) (TableFunction, error) {
+func (t MapCatalog) TableFunction(ctx *Context, name string) (TableFunction, bool) {
 	if f, ok := t.tabFuncs[name]; ok {
-		return f, nil
+		return f, true
 	}
-	return nil, fmt.Errorf("table func not found")
+	return nil, false
 }
 
 func (t MapCatalog) ExternalStoredProcedure(ctx *Context, name string, numOfParams int) (*ExternalStoredProcedureDetails, error) {

sql/databases.go

@@ -57,8 +57,9 @@ type CollatedDatabaseProvider interface {
 // TableFunctionProvider is an interface that allows custom table functions to be provided. It's usually (but not
 // always) implemented by a DatabaseProvider.
 type TableFunctionProvider interface {
-	// TableFunction returns the table function with the name provided, case-insensitive
-	TableFunction(ctx *Context, name string) (TableFunction, error)
+	// TableFunction returns the table function with the name provided, case-insensitive.
+	// It also returns boolean param for whether the table function was found.
+	TableFunction(ctx *Context, name string) (TableFunction, bool)
 	// WithTableFunctions returns a new provider with (only) the list of table functions arguments
 	WithTableFunctions(fns ...TableFunction) (TableFunctionProvider, error)
 }

sql/expression/tablefunction/table_function.go

@@ -0,0 +1,139 @@
+// Copyright 2024 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package dtablefunctions
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/dolthub/go-mysql-server/sql"
+)
+
+var _ sql.TableFunction = &TableFunctionWrapper{}
+var _ sql.ExecSourceRel = &TableFunctionWrapper{}
+
+// TableFunctionWrapper represents a table function with underlying
+// regular function. It allows using regular function as table function.
+type TableFunctionWrapper struct {
+	underlyingFunc sql.Function
+
+	args     []sql.Expression
+	database sql.Database
+	funcExpr sql.Expression
+}
+
+// NewTableFunctionWrapper creates new TableFunction
+// with given Function as underlying function.
+func NewTableFunctionWrapper(f sql.Function) sql.TableFunction {
+	return &TableFunctionWrapper{
+		underlyingFunc: f,
+	}
+}
+
+func (t *TableFunctionWrapper) NewInstance(ctx *sql.Context, db sql.Database, args []sql.Expression) (sql.Node, error) {
+	nt := *t
+	nt.database = db
+	nt.args = args
+	f, err := nt.underlyingFunc.NewInstance(args)
+	if err != nil {
+		return nil, err
+	}
+	nt.funcExpr = f
+	return &nt, nil
+}
+
+func (t *TableFunctionWrapper) Children() []sql.Node {
+	return nil
+}
+
+func (t *TableFunctionWrapper) Database() sql.Database {
+	return t.database
+}
+
+func (t *TableFunctionWrapper) Expressions() []sql.Expression {
+	if t.funcExpr == nil {
+		return nil
+	}
+	return t.funcExpr.Children()
+}
+
+func (t *TableFunctionWrapper) IsReadOnly() bool {
+	return true
+}
+
+func (t *TableFunctionWrapper) Name() string {
+	return t.underlyingFunc.FunctionName()
+}
+
+func (t *TableFunctionWrapper) RowIter(ctx *sql.Context, r sql.Row) (sql.RowIter, error) {
+	v, err := t.funcExpr.Eval(ctx, r)
+	if err != nil {
+		return nil, err
+	}
+	return sql.RowsToRowIter(sql.Row{v}), nil
+}
+
+func (t *TableFunctionWrapper) Resolved() bool {
+	for _, expr := range t.args {
+		if !expr.Resolved() {
+			return false
+		}
+	}
+	return true
+}
+
+func (t *TableFunctionWrapper) Schema() sql.Schema {
+	return sql.Schema{&sql.Column{Name: t.underlyingFunc.FunctionName(), Type: t.funcExpr.Type()}}
+}
+
+func (t *TableFunctionWrapper) String() string {
+	var args []string
+	for _, expr := range t.args {
+		args = append(args, expr.String())
+	}
+	return fmt.Sprintf("%s(%s)", t.underlyingFunc.FunctionName(), strings.Join(args, ", "))
+}
+
+func (t *TableFunctionWrapper) WithChildren(children ...sql.Node) (sql.Node, error) {
+	if len(children) != 0 {
+		return nil, sql.ErrInvalidChildrenNumber.New(t, len(children), 0)
+	}
+	return t, nil
+}
+
+func (t *TableFunctionWrapper) WithDatabase(database sql.Database) (sql.Node, error) {
+	nt := *t
+	nt.database = database
+	return &nt, nil
+}
+
+func (t *TableFunctionWrapper) WithExpressions(exprs ...sql.Expression) (sql.Node, error) {
+	if t.funcExpr == nil {
+		if len(exprs) != 0 {
+			return nil, sql.ErrInvalidChildrenNumber.New(t, len(exprs), 0)
+		}
+	}
+	l := len(t.funcExpr.Children())
+	if len(exprs) != l {
+		return nil, sql.ErrInvalidChildrenNumber.New(t, len(exprs), l)
+	}
+	nt := *t
+	nf, err := nt.funcExpr.WithChildren(exprs...)
+	if err != nil {
+		return nil, err
+	}
+	nt.funcExpr = nf
+	return &nt, nil
+}

sql/planbuilder/from.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/dolthub/go-mysql-server/sql"
 	"github.com/dolthub/go-mysql-server/sql/expression"
+	dtablefunctions "github.com/dolthub/go-mysql-server/sql/expression/tablefunction"
 	"github.com/dolthub/go-mysql-server/sql/mysql_db"
 	"github.com/dolthub/go-mysql-server/sql/plan"
 	"github.com/dolthub/go-mysql-server/sql/transform"
@@ -447,30 +448,26 @@ func (b *Builder) resolveTable(tab, db string, asOf interface{}) *plan.ResolvedT
 func (b *Builder) buildTableFunc(inScope *scope, t *ast.TableFuncExpr) (outScope *scope) {
 	//TODO what are valid mysql table arguments
 	args := make([]sql.Expression, 0, len(t.Exprs))
-	for _, e := range t.Exprs {
-		switch e := e.(type) {
+	for _, expr := range t.Exprs {
+		switch e := expr.(type) {
 		case *ast.AliasedExpr:
-			expr := b.buildScalar(inScope, e.Expr)
-
-			if !e.As.IsEmpty() {
-				b.handleErr(sql.ErrUnsupportedSyntax.New(ast.String(e)))
-			}
-
-			if selectExprNeedsAlias(e, expr) {
-				b.handleErr(sql.ErrUnsupportedSyntax.New(ast.String(e)))
-			}
-
-			args = append(args, expr)
+			scalarExpr := b.buildScalar(inScope, e.Expr)
+			args = append(args, scalarExpr)
 		default:
 			b.handleErr(sql.ErrUnsupportedSyntax.New(ast.String(e)))
 		}
 	}
 
 	utf := expression.NewUnresolvedTableFunction(t.Name, args)
 
-	tableFunction, err := b.cat.TableFunction(b.ctx, utf.Name())
-	if err != nil {
-		b.handleErr(err)
+	tableFunction, found := b.cat.TableFunction(b.ctx, utf.Name())
+	if !found {
+		// try getting regular function
+		f, funcFound := b.cat.Function(b.ctx, utf.Name())
+		if !funcFound {
+			b.handleErr(sql.ErrTableFunctionNotFound.New(utf.Name()))
+		}
+		tableFunction = dtablefunctions.NewTableFunctionWrapper(f)
 	}
 
 	database := b.currentDb()

test/test_catalog.go

@@ -159,7 +159,7 @@ func (c *Catalog) UnlockTables(ctx *sql.Context, id uint32) error {
 	return nil
 }
 
-func (c *Catalog) TableFunction(ctx *sql.Context, name string) (sql.TableFunction, error) {
+func (c *Catalog) TableFunction(ctx *sql.Context, name string) (sql.TableFunction, bool) {
 	//TODO implement me
 	panic("implement me")
 }