Changed default for database/sql driver from TABLE service to QUERY service

CHANGELOG.md

@@ -1,3 +1,5 @@
+* Changed default for `database/sql` driver from TABLE service to QUERY service
+
 ## v3.121.0
 * Changed internal pprof label to pyroscope supported format
 * Added `query.ImplicitTxControl()` transaction control (the same as `query.NoTx()` and `query.EmptyTxControl()`). See more about implicit transactions on [ydb.tech](https://ydb.tech/docs/en/concepts/transactions?version=v25.2#implicit)

internal/xsql/connector.go

@@ -212,11 +212,13 @@ func Open(
 		balancer:    balancer,
 		queryConfig: queryConfig,
 		processor: func() Engine {
-			if overQueryService, _ := strconv.ParseBool(os.Getenv("YDB_DATABASE_SQL_OVER_QUERY_SERVICE")); overQueryService {
-				return QUERY
+			overQueryService, err := strconv.ParseBool(os.Getenv("YDB_DATABASE_SQL_OVER_QUERY_SERVICE"))
+			if err == nil && !overQueryService {
+				return TABLE
 			}
 
-			return TABLE
+			// default is Query Engine
+			return QUERY
 		}(),
 		clock:          clockwork.NewRealClock(),
 		done:           make(chan struct{}),

tests/integration/database_sql_defaults_test.go

@@ -0,0 +1,22 @@
+//go:build integration
+// +build integration
+
+package integration
+
+import (
+	"database/sql"
+	"testing"
+
+	_ "github.com/ydb-platform/ydb-go-sdk/v3"
+)
+
+func TestDatabaseSQLDefaultProcessor(st *testing.T) {
+	t := newScope(st)
+
+	db, err := sql.Open("ydb", t.ConnectionString())
+	t.Require.NoError(err)
+	defer db.Close()
+
+	_, err = db.Exec("DISCARD SELECT 1")
+	t.Require.Error(err, "DISCARD is supported in TABLE service but not in QUERY service")
+}