chore: import upstream snapshot with attribution

server/functions/set_config.go

@@ -0,0 +1,67 @@
+// 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 (
+	"strings"
+
+	"github.com/cockroachdb/errors"
+	"github.com/dolthub/go-mysql-server/sql"
+
+	"github.com/dolthub/doltgresql/server/functions/framework"
+	pgtypes "github.com/dolthub/doltgresql/server/types"
+)
+
+func initSetConfig() {
+	framework.RegisterFunction(set_config_text_text_boolean)
+}
+
+// set_config_text_text_boolean implements the set_config() function
+// https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-ADMIN-SET
+var set_config_text_text_boolean = framework.Function3{
+	Name:       "set_config",
+	Return:     pgtypes.Text,
+	Parameters: [3]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Text, pgtypes.Bool},
+	Callable: func(ctx *sql.Context, _ [4]*pgtypes.DoltgresType, settingName any, newValue any, isLocal any) (any, error) {
+		if settingName == nil {
+			return nil, errors.Errorf("NULL value not allowed for configuration setting name")
+		}
+
+		// NULL is not supported for configuration values, and gets turned into the empty string
+		if newValue == nil {
+			newValue = ""
+		}
+
+		if isLocal == true {
+			// TODO: If isLocal is true, then the config setting should only persist for the current transaction
+			return nil, errors.Errorf("setting configuration values for the current transaction is not supported yet")
+		}
+
+		// set_config can set system configuration or user configuration. System configuration settings are in top
+		// level settings, while user configuration settings are namespaced.
+		isUserConfig := strings.Contains(settingName.(string), ".")
+		if isUserConfig {
+			if err := ctx.SetUserVariable(ctx, settingName.(string), newValue.(string), pgtypes.Text); err != nil {
+				return nil, err
+			}
+		} else {
+			if err := ctx.SetSessionVariable(ctx, settingName.(string), newValue.(string)); err != nil {
+				return nil, err
+			}
+		}
+
+		return newValue.(string), nil
+	},
+}