chore: import upstream snapshot with attribution

server/functions/generate_subscripts.go

@@ -0,0 +1,62 @@
+// Copyright 2025 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 (
+	"io"
+
+	"github.com/dolthub/go-mysql-server/sql"
+
+	"github.com/dolthub/doltgresql/server/functions/framework"
+	pgtypes "github.com/dolthub/doltgresql/server/types"
+)
+
+// initGenerateSeries registers the functions to the catalog.
+func initGenerateSubscripts() {
+	framework.RegisterFunction(generate_subscripts)
+}
+
+// generate_series_int32_int32 represents the PostgreSQL function of the same name, taking the same parameters.
+var generate_subscripts = framework.Function2{
+	Name:       "generate_subscripts",
+	Return:     pgtypes.RowTypeWithReturnType(pgtypes.Int32),
+	Parameters: [2]*pgtypes.DoltgresType{pgtypes.AnyArray, pgtypes.Int32},
+	Strict:     true,
+	SRF:        true,
+	Callable: func(ctx *sql.Context, t [3]*pgtypes.DoltgresType, val1, val2 any) (any, error) {
+		arr := val1.([]any)
+		dimension := val2.(int32)
+		if dimension != 1 {
+			return nil, sql.ErrUnsupportedFeature.New("generate_subscripts only supports 1-dimensional arrays")
+		}
+
+		// Int2vector (int16vector in doltgresql) and Oidvector are old postgres types that are primarily found in pg_catalog tables.
+		// Unlike other array types, they are zero-indexed.
+		start := 1
+		if t[0] == pgtypes.Int16vector || t[0] == pgtypes.Oidvector {
+			start = 0
+		}
+
+		var i = start
+		return pgtypes.NewSetReturningFunctionRowIter(func(ctx *sql.Context) (sql.Row, error) {
+			if i >= len(arr)+start {
+				return nil, io.EOF
+			}
+			idx := i
+			i++
+			return sql.Row{int32(idx)}, nil
+		}), nil
+	},
+}