Fix user var bug in plsql.

src/gausskernel/process/tcop/postgres.cpp

@@ -1266,6 +1266,11 @@ static List* pg_rewrite_query(Query* query)
             PrepareStmt *stmt = (PrepareStmt *)query->utilityStmt;
             if (IsA(stmt->query, UserVar)) {
                 querytree_list = QueryRewritePrepareStmt(query);
+            } else if (IsA(stmt->query, Const)) {
+                if (((Const *)stmt->query)->constisnull) {
+                    ereport(ERROR, (errcode(ERRCODE_UNRECOGNIZED_NODE_TYPE),
+                            errmsg("userdefined variable in prepare statement must be text type.")));
+                }
             } else {
                 querytree_list = list_make1(query);
             }

src/gausskernel/runtime/executor/execQual.cpp

@@ -1096,6 +1096,7 @@ static Datum ExecEvalConst(ExprState* exprstate, ExprContext* econtext, bool* is
         if (found) {
             if (entry->isParse) {
                 con = (Const *)uservar->value;
+                entry->isParse = false;
             } else {
                 Node *node = coerce_type(NULL, (Node *)entry->value, entry->value->consttype, ((Const *)uservar->value)->consttype,
                     -1, COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);

src/test/regress/expected/mysql_compatibility.out

@@ -1648,6 +1648,33 @@ select @a_1131028:=cast(2 as number);
         2
 (1 row)
 
+DROP PROCEDURE IF EXISTS load_tbtest_WITH_REPLACE;
+NOTICE:  function load_tbtest_with_replace() does not exist, skipping
+CREATE PROCEDURE load_tbtest_WITH_REPLACE(id_count IN INT) AS
+BEGIN
+    SET @id = 1;
+    WHILE @id <= id_count LOOP
+        raise info 'id is %',@id;
+        IF @id % 10 = 0 THEN
+            SET @lsql = '';
+        END IF;
+        SET @id = @id + 1;
+        raise info 'id+ is %',@id;
+    END LOOP;
+END;
+/
+call load_tbtest_WITH_REPLACE(3);
+INFO:  id is 1
+INFO:  id+ is 2
+INFO:  id is 2
+INFO:  id+ is 3
+INFO:  id is 3
+INFO:  id+ is 4
+ load_tbtest_with_replace 
+--------------------------
+ 
+(1 row)
+
 set enable_set_variable_b_format = 0;
 select @var_t_1 := 2;
 ERROR:  syntax error at or near ":="

src/test/regress/sql/mysql_compatibility.sql

@@ -539,7 +539,21 @@ select @a_1131028:=cast('x' as text);
 select @a_1131028:=cast(2 as int);
 select @a_1131028:=cast(2 as number);
 
-
+DROP PROCEDURE IF EXISTS load_tbtest_WITH_REPLACE;
+CREATE PROCEDURE load_tbtest_WITH_REPLACE(id_count IN INT) AS
+BEGIN
+    SET @id = 1;
+    WHILE @id <= id_count LOOP
+        raise info 'id is %',@id;
+        IF @id % 10 = 0 THEN
+            SET @lsql = '';
+        END IF;
+        SET @id = @id + 1;
+        raise info 'id+ is %',@id;
+    END LOOP;
+END;
+/
+call load_tbtest_WITH_REPLACE(3);
 
 set enable_set_variable_b_format = 0;
 select @var_t_1 := 2;