session: load variables before parsing SQL (#51466)

close #51387

Author: YangKeao

pkg/server/internal/testserverclient/server_client.go

@@ -16,6 +16,7 @@ package testserverclient
 
 import (
 	"bytes"
+	"context"
 	"database/sql"
 	"encoding/json"
 	"fmt"
@@ -2629,4 +2630,35 @@ func (cli *TestServerClient) RunTestInfoschemaClientErrors(t *testing.T) {
 	})
 }
 
+func (cli *TestServerClient) RunTestSQLModeIsLoadedBeforeQuery(t *testing.T) {
+	cli.RunTests(t, nil, func(dbt *testkit.DBTestKit) {
+		ctx := context.Background()
+
+		conn, err := dbt.GetDB().Conn(ctx)
+		require.NoError(t, err)
+		_, err = conn.ExecContext(ctx, "set global sql_mode='NO_BACKSLASH_ESCAPES';")
+		require.NoError(t, err)
+		_, err = conn.ExecContext(ctx, `
+		CREATE TABLE t1 (
+			id bigint(20) NOT NULL,
+			t text DEFAULT NULL,
+			PRIMARY KEY (id)
+		);`)
+		require.NoError(t, err)
+
+		// use another new connection
+		conn1, err := dbt.GetDB().Conn(ctx)
+		require.NoError(t, err)
+		_, err = conn1.ExecContext(ctx, "insert into t1 values (1, 'ab\\\\c');")
+		require.NoError(t, err)
+		result, err := conn1.QueryContext(ctx, "select t from t1 where id = 1;")
+		require.NoError(t, err)
+		require.True(t, result.Next())
+		var tStr string
+		require.NoError(t, result.Scan(&tStr))
+
+		require.Equal(t, "ab\\\\c", tStr)
+	})
+}
+
 //revive:enable:exported

pkg/server/tests/commontest/BUILD.bazel

@@ -8,7 +8,7 @@ go_test(
         "tidb_test.go",
     ],
     flaky = True,
-    shard_count = 47,
+    shard_count = 48,
     deps = [
         "//pkg/config",
         "//pkg/ddl/util",

pkg/server/tests/commontest/tidb_test.go

@@ -3067,3 +3067,8 @@ func TestPrepareCount(t *testing.T) {
 	require.Equal(t, prepareCnt, atomic.LoadInt64(&variable.PreparedStmtCount))
 	require.NoError(t, qctx.Close())
 }
+
+func TestSQLModeIsLoadedBeforeQuery(t *testing.T) {
+	ts := servertestkit.CreateTidbTestSuite(t)
+	ts.RunTestSQLModeIsLoadedBeforeQuery(t)
+}

pkg/session/session.go

@@ -1652,6 +1652,13 @@ func (s *session) Execute(ctx context.Context, sql string) (recordSets []sqlexec
 func (s *session) Parse(ctx context.Context, sql string) ([]ast.StmtNode, error) {
 	logutil.Logger(ctx).Debug("parse", zap.String("sql", sql))
 	parseStartTime := time.Now()
+
+	// Load the session variables to the context.
+	// This is necessary for the parser to get the current sql_mode.
+	if err := s.loadCommonGlobalVariablesIfNeeded(); err != nil {
+		return nil, err
+	}
+
 	stmts, warns, err := s.ParseSQL(ctx, sql, s.sessionVars.GetParseParams()...)
 	if err != nil {
 		s.rollbackOnError(ctx)