MDEV-14689 Server crashes in find_field_in_tables on 2nd execution of PS with versioned table and view

SQL: wrong usage of Item::transform()

Author: kevgs

mysql-test/suite/versioning/r/view.result

@@ -107,5 +107,14 @@ create or replace view vt1 as select * from t1 union select * from t2;
 select * from vt1;
 a
 1
+# MDEV-14689 crash on second PS execute
+create or replace table t1 (a int);
+create or replace view v1 as select * from t1;
+create or replace table t2 (b int) with system versioning;
+prepare stmt from 'select a from v1 inner join t2 group by a order by a';
+execute stmt;
+a
+execute stmt;
+a
 drop database test;
 create database test;

mysql-test/suite/versioning/t/view.test

@@ -89,5 +89,14 @@ create or replace table t2 (a int);
 create or replace view vt1 as select * from t1 union select * from t2;
 select * from vt1;
 
+--echo # MDEV-14689 crash on second PS execute
+create or replace table t1 (a int);
+create or replace view v1 as select * from t1;
+create or replace table t2 (b int) with system versioning;
+prepare stmt from 'select a from v1 inner join t2 group by a order by a';
+execute stmt;
+execute stmt;
+
+
 drop database test;
 create database test;

sql/sql_select.cc

@@ -700,24 +700,36 @@ void JOIN::vers_check_items()
 
   if (conds)
   {
-    conds= conds->transform(thd, transformer, NULL);
+    Item *tmp = conds->transform(thd, transformer, NULL);
+    if (conds != tmp)
+      conds= tmp;
   }
 
   for (ORDER *ord= order; ord; ord= ord->next)
   {
-    ord->item_ptr= (*ord->item)->transform(thd, transformer, NULL);
-    *ord->item= ord->item_ptr;
+    Item *tmp= (*ord->item)->transform(thd, transformer, NULL);
+    if (*ord->item != tmp)
+    {
+      ord->item_ptr= tmp;
+      *ord->item= ord->item_ptr;
+    }
   }
 
   for (ORDER *ord= group_list; ord; ord= ord->next)
   {
-    ord->item_ptr= (*ord->item)->transform(thd, transformer, NULL);
-    *ord->item= ord->item_ptr;
+    Item *tmp= (*ord->item)->transform(thd, transformer, NULL);
+    if (*ord->item != tmp)
+    {
+      ord->item_ptr= tmp;
+      *ord->item= ord->item_ptr;
+    }
   }
 
   if (having)
   {
-    having= having->transform(thd, transformer, NULL);
+    Item *tmp= having->transform(thd, transformer, NULL);
+    if (having != tmp)
+      having= tmp;
   }
 }