MDEV-11848 Automatic statement repreparation changes query semantics

mysql-test/r/set_statement.result

@@ -652,7 +652,9 @@ v1	v2
 3	4
 ALTER TABLE t1 ADD COLUMN v3 int;
 execute stmt;
-ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '.* FROM t1' at line 1
+v1	v2	v3
+1	2	NULL
+3	4	NULL
 ALTER TABLE t1 drop COLUMN v3;
 deallocate prepare stmt;
 ''
@@ -670,7 +672,9 @@ v1	v2
 3	4
 ALTER TABLE t1 ADD COLUMN v3 int;
 execute stmt;
-ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '.* FROM t1' at line 1
+v1	v2	v3
+1	2	NULL
+3	4	NULL
 ALTER TABLE t1 drop COLUMN v3;
 deallocate prepare stmt;
 SELECT @@sql_mode;

mysql-test/r/sql_mode.result

@@ -742,3 +742,20 @@ DROP FUNCTION test_function;
 SET @@sql_mode= @org_mode;
 
 #End of Test for Bug#12601974 
+#
+# MDEV-11848 Automatic statement repreparation changes query semantics
+#
+SET sql_mode=DEFAULT;
+CREATE OR REPLACE TABLE t1 (a TEXT);
+PREPARE stmt FROM 'INSERT INTO t1 (a) VALUES (2||3)';
+EXECUTE stmt;
+SET sql_mode=ORACLE;
+EXECUTE stmt;
+ALTER TABLE t1 ADD b INT;
+EXECUTE stmt;
+SELECT * FROM t1;
+a	b
+1	NULL
+1	NULL
+1	NULL
+DROP TABLE t1;

mysql-test/t/set_statement.test

@@ -618,8 +618,7 @@ SELECT @@sql_mode;
 SET STATEMENT sql_mode='ansi' FOR PREPARE stmt FROM 'SELECT "t1".* FROM t1';
 execute stmt;
 ALTER TABLE t1 ADD COLUMN v3 int;
-# repreparation with other mode cause an error
---error ER_PARSE_ERROR
+# repreparation with other mode does not cause an error
 execute stmt;
 ALTER TABLE t1 drop COLUMN v3;
 deallocate prepare stmt;
@@ -632,8 +631,7 @@ PREPARE stmt FROM 'SELECT "t1".* FROM t1';
 SET sql_mode=default;
 execute stmt;
 ALTER TABLE t1 ADD COLUMN v3 int;
-# repreparation with other mode cause an error
---error ER_PARSE_ERROR
+# repreparation with other mode does not cause an error
 execute stmt;
 ALTER TABLE t1 drop COLUMN v3;
 deallocate prepare stmt;

mysql-test/t/sql_mode.test

@@ -513,3 +513,17 @@ SET @@sql_mode= @org_mode;
 
 --echo 
 --echo #End of Test for Bug#12601974 
+
+--echo #
+--echo # MDEV-11848 Automatic statement repreparation changes query semantics
+--echo #
+SET sql_mode=DEFAULT;
+CREATE OR REPLACE TABLE t1 (a TEXT);
+PREPARE stmt FROM 'INSERT INTO t1 (a) VALUES (2||3)';
+EXECUTE stmt;
+SET sql_mode=ORACLE;
+EXECUTE stmt;
+ALTER TABLE t1 ADD b INT;
+EXECUTE stmt;
+SELECT * FROM t1;
+DROP TABLE t1;

sql/sql_prepare.cc

@@ -227,6 +227,7 @@ class Prepared_statement: public Statement
     SELECT_LEX and other classes).
   */
   MEM_ROOT main_mem_root;
+  sql_mode_t m_sql_mode;
 private:
   bool set_db(const char *db, uint db_length);
   bool set_parameters(String *expanded_query,
@@ -3603,7 +3604,8 @@ Prepared_statement::Prepared_statement(THD *thd_arg)
   param_count(0),
   last_errno(0),
   flags((uint) IS_IN_USE),
-  start_param(0)
+  start_param(0),
+  m_sql_mode(thd->variables.sql_mode)
 {
   init_sql_alloc(&main_mem_root, thd_arg->variables.query_alloc_block_size,
                  thd_arg->variables.query_prealloc_size, MYF(MY_THREAD_SPECIFIC));
@@ -3777,6 +3779,7 @@ bool Prepared_statement::prepare(const char *packet, uint packet_len)
   Statement stmt_backup;
   Query_arena *old_stmt_arena;
   DBUG_ENTER("Prepared_statement::prepare");
+  DBUG_ASSERT(m_sql_mode == thd->variables.sql_mode);
   /*
     If this is an SQLCOM_PREPARE, we also increase Com_prepare_sql.
     However, it seems handy if com_stmt_prepare is increased always,
@@ -4365,6 +4368,7 @@ Prepared_statement::reprepare()
   bool error;
 
   Prepared_statement copy(thd);
+  copy.m_sql_mode= m_sql_mode;
 
   copy.set_sql_prepare(); /* To suppress sending metadata to the client. */
 
@@ -4374,9 +4378,12 @@ Prepared_statement::reprepare()
                           &cur_db_changed))
     return TRUE;
 
+  sql_mode_t save_sql_mode= thd->variables.sql_mode;
+  thd->variables.sql_mode= m_sql_mode;
   error= ((name.str && copy.set_name(&name)) ||
           copy.prepare(query(), query_length()) ||
           validate_metadata(&copy));
+  thd->variables.sql_mode= save_sql_mode;
 
   if (cur_db_changed)
     mysql_change_db(thd, &saved_cur_db_name, TRUE);