Add support for pg_get_serial_sequence(text,text)

server/functions/init.go

@@ -133,6 +133,7 @@ func Init() {
 	initPgIsInRecovery()
 	initPgPostmasterStartTime()
 	initPgRelationSize()
+	initPgGetSerialSequence()
 	initPgStatGetNumscans()
 	initPgTableIsVisible()
 	initPgTableSize()

server/functions/pg_get_serial_sequence.go

@@ -0,0 +1,117 @@
+// 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 functions
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/dolthub/dolt/go/libraries/doltcore/doltdb"
+	"github.com/dolthub/dolt/go/libraries/doltcore/sqle/dsess"
+	"github.com/dolthub/dolt/go/libraries/doltcore/sqle/resolve"
+	"github.com/dolthub/go-mysql-server/sql"
+
+	"github.com/dolthub/doltgresql/core"
+	"github.com/dolthub/doltgresql/server/functions/framework"
+	pgtypes "github.com/dolthub/doltgresql/server/types"
+)
+
+// initPgGetSerialSequence registers the functions to the catalog.
+func initPgGetSerialSequence() {
+	framework.RegisterFunction(pg_get_serial_sequence_text_text)
+}
+
+// pg_get_serial_sequence_text_text represents the PostgreSQL function of the same name, taking the same parameters.
+var pg_get_serial_sequence_text_text = framework.Function2{
+	Name:               "pg_get_serial_sequence",
+	Return:             pgtypes.Text,
+	Parameters:         [2]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Text},
+	Variadic:           false,
+	IsNonDeterministic: false,
+	Strict:             true,
+	Callable: func(ctx *sql.Context, paramsAndReturn [3]*pgtypes.DoltgresType, val1 any, val2 any) (any, error) {
+		tableName := val1.(string)
+		columnName := val2.(string)
+
+		// Parse out the schema if one was supplied
+		var err error
+		schemaName := ""
+		if strings.Contains(tableName, ".") {
+			// TODO: parseRelationName() will return the first schema from the search_path if one is not included
+			//       in the relation name, but that doesn't mean it's the correct schema. It should be updated to
+			//       not return any schema name if one wasn't explicitly specified, then we should search for the
+			//       table on the search_path and find the first schema that contains a table with that name.
+			schemaName, tableName, err = parseRelationName(ctx, tableName)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		// Resolve the table's schema if it wasn't specified
+		if schemaName == "" {
+			doltSession := dsess.DSessFromSess(ctx.Session)
+			roots, ok := doltSession.GetRoots(ctx, ctx.GetCurrentDatabase())
+			if !ok {
+				return nil, fmt.Errorf("unable to get roots")
+			}
+			foundTableName, _, ok, err := resolve.TableWithSearchPath(ctx, roots.Working, tableName)
+			if err != nil {
+				return nil, err
+			}
+			if !ok {
+				return nil, fmt.Errorf(`relation "%s" does not exist`, tableName)
+			}
+			schemaName = foundTableName.Schema
+		}
+
+		// Validate the full schema + table name and grab the columns
+		table, err := core.GetSqlTableFromContext(ctx, "", doltdb.TableName{
+			Schema: schemaName,
+			Name:   tableName,
+		})
+		if err != nil {
+			return nil, err
+		}
+		if table == nil {
+			return nil, fmt.Errorf(`relation "%s" does not exist`, tableName)
+		}
+		tableSchema := table.Schema()
+
+		// Find the column in the table's schema
+		columnIndex := tableSchema.IndexOfColName(columnName)
+		if columnIndex < 0 {
+			return nil, fmt.Errorf(`column "%s" of relation "%s" does not exist`, columnName, tableName)
+		}
+		column := tableSchema[columnIndex]
+
+		// Find any sequence associated with the column
+		sequenceCollection, err := core.GetSequencesCollectionFromContext(ctx)
+		if err != nil {
+			return nil, err
+		}
+		sequences := sequenceCollection.GetSequencesWithTable(doltdb.TableName{
+			Name:   tableName,
+			Schema: schemaName,
+		})
+		for _, sequence := range sequences {
+			if sequence.OwnerColumn == column.Name {
+				// pg_get_serial_sequence() always includes the schema name in its output
+				return schemaName + "." + sequence.Name, nil
+			}
+		}
+
+		return nil, nil
+	},
+}

testing/go/functions_test.go

@@ -907,6 +907,58 @@ func TestSystemInformationFunctions(t *testing.T) {
 				},
 			},
 		},
+		{
+			Name: "pg_get_serial_sequence",
+			SetUpScript: []string{
+				`create table t0 (id INTEGER NOT NULL PRIMARY KEY);`,
+				`create table t1 (id SERIAL PRIMARY KEY);`,
+				`create sequence t2_id_seq START 1 INCREMENT 3;`,
+				`create table t2 (id INTEGER NOT NULL DEFAULT nextval('t2_id_seq'));`,
+				// TODO: ALTER SEQUENCE OWNED BY is not supported yet. When the sequence is created
+				//       explicitly, separate from the column, the owner must be udpated before
+				//       pg_get_serial_sequence() will identify it.
+				//`ALTER SEQUENCE t2_id_seq OWNED BY t2.id;`,
+			},
+			Assertions: []ScriptTestAssertion{
+				{
+					Query:       `SELECT pg_get_serial_sequence('doesnotexist.t1', 'id');`,
+					ExpectedErr: "does not exist",
+				},
+				{
+					Query:       `SELECT pg_get_serial_sequence('doesnotexist', 'id');`,
+					ExpectedErr: "does not exist",
+				},
+				{
+					Query:       `SELECT pg_get_serial_sequence('t0', 'doesnotexist');`,
+					ExpectedErr: "does not exist",
+				},
+				{
+					// No sequence for column returns null
+					Query:    `SELECT pg_get_serial_sequence('t0', 'id');`,
+					Cols:     []string{"pg_get_serial_sequence"},
+					Expected: []sql.Row{{nil}},
+				},
+				{
+					Query:    `SELECT pg_get_serial_sequence('public.t1', 'id');`,
+					Cols:     []string{"pg_get_serial_sequence"},
+					Expected: []sql.Row{{"public.t1_id_seq"}},
+				},
+				{
+					// Test with no schema specified
+					Query:    `SELECT pg_get_serial_sequence('t1', 'id');`,
+					Cols:     []string{"pg_get_serial_sequence"},
+					Expected: []sql.Row{{"public.t1_id_seq"}},
+				},
+				{
+					// TODO: This test shouldn't pass until we're able to use
+					//       ALTER SEQUENCE OWNED BY to set the owning column.
+					Skip:     true,
+					Query:    `SELECT pg_get_serial_sequence('t2', 'id');`,
+					Cols:     []string{"pg_get_serial_sequence"},
+					Expected: []sql.Row{{"public.t2_id_seq"}},
+				},
+			},
+		},
 	})
 }