chore: import upstream snapshot with attribution

server/functions/current_setting.go

@@ -0,0 +1,86 @@
+// 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"
+
+	"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"
+)
+
+// initCurrentSetting registers the functions to the catalog.
+func initCurrentSetting() {
+	framework.RegisterFunction(current_setting_text)
+	framework.RegisterFunction(current_setting_text_bool)
+}
+
+// current_setting_text represents the PostgreSQL function of the same name, taking the same parameters.
+var current_setting_text = framework.Function1{
+	Name:       "current_setting",
+	Return:     pgtypes.Text, // TODO: it would be nice to support non-text values as well, but this is all postgres supports
+	Parameters: [1]*pgtypes.DoltgresType{pgtypes.Text},
+	Strict:     true,
+	Callable: func(ctx *sql.Context, _ [2]*pgtypes.DoltgresType, val1 any) (any, error) {
+		return getCurSetting(ctx, val1.(string), false)
+	},
+}
+
+// current_setting_text_bool represents the PostgreSQL function of the same name, taking the same parameters.
+var current_setting_text_bool = framework.Function2{
+	Name:       "current_setting",
+	Return:     pgtypes.Text, // TODO: it would be nice to support non-text values as well, but this is all postgres supports
+	Parameters: [2]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Bool},
+	Strict:     true,
+	Callable: func(ctx *sql.Context, _ [3]*pgtypes.DoltgresType, val1, val2 any) (any, error) {
+		return getCurSetting(ctx, val1.(string), val2.(bool))
+	},
+}
+
+// getCurSetting returns value set for given user variable. It returns nil instead of an error
+// if it doesn't exist and missingOk is set to true.
+func getCurSetting(ctx *sql.Context, s string, missingOk bool) (any, error) {
+	_, variable, err := ctx.GetUserVariable(ctx, s)
+	if err != nil {
+		if missingOk {
+			return nil, nil
+		}
+		return nil, err
+	}
+
+	if variable != nil {
+		return fmt.Sprintf("%v", variable), nil
+	}
+
+	variable, err = ctx.GetSessionVariable(ctx, s)
+	if err != nil {
+		if missingOk {
+			return nil, nil
+		}
+		return nil, errors.Errorf(`unrecognized configuration parameter "%s"`, s)
+	}
+
+	if variable != nil {
+		return fmt.Sprintf("%v", variable), nil
+	}
+
+	if missingOk {
+		return nil, nil
+	}
+	return nil, errors.Errorf(`unrecognized configuration parameter "%s"`, s)
+}