Bug#52120 create view cause Assertion failed: 0, file .\item_subselect.cc, line 817

We should disable const subselect item evaluation because
subselect transformation does not happen in view_prepare_mode
and thus val_...() methods can not be called.

mysql-test/r/ctype_ucs.result

@@ -1230,4 +1230,12 @@ SELECT HEX(DAYNAME(19700101));
 HEX(DAYNAME(19700101))
 0427043504420432043504400433
 SET character_set_connection=latin1;
+#
+# Bug#52120 create view cause Assertion failed: 0, file .\item_subselect.cc, line 817
+#
+CREATE TABLE t1 (a CHAR(1) CHARSET ascii, b CHAR(1) CHARSET latin1);
+CREATE VIEW v1 AS SELECT 1 from t1
+WHERE t1.b <=> (SELECT a FROM t1 WHERE a < SOME(SELECT '1'));
+DROP VIEW v1;
+DROP TABLE t1;
 End of 5.0 tests

mysql-test/r/view.result

@@ -3874,6 +3874,14 @@ CREATE VIEW v1 AS SELECT 1 FROM t1 WHERE
 ROW(1,1) >= ROW(1, (SELECT 1 FROM t1 WHERE  f1 >= ANY ( SELECT '1' )));
 DROP VIEW v1;
 DROP TABLE t1;
+#
+# Bug#52120 create view cause Assertion failed: 0, file .\item_subselect.cc, line 817
+#
+CREATE TABLE t1 (a CHAR(1) CHARSET latin1, b CHAR(1) CHARSET utf8);
+CREATE VIEW v1 AS SELECT 1 from t1
+WHERE t1.b <=> (SELECT a FROM t1 WHERE a < SOME(SELECT '1'));
+DROP VIEW v1;
+DROP TABLE t1;
 # -----------------------------------------------------------------
 # -- End of 5.1 tests.
 # -----------------------------------------------------------------

mysql-test/t/ctype_ucs.test

@@ -732,4 +732,13 @@ SELECT HEX(MONTHNAME(19700101));
 SELECT HEX(DAYNAME(19700101));
 SET character_set_connection=latin1;
 
+--echo #
+--echo # Bug#52120 create view cause Assertion failed: 0, file .\item_subselect.cc, line 817
+--echo #
+CREATE TABLE t1 (a CHAR(1) CHARSET ascii, b CHAR(1) CHARSET latin1);
+CREATE VIEW v1 AS SELECT 1 from t1
+WHERE t1.b <=> (SELECT a FROM t1 WHERE a < SOME(SELECT '1'));
+DROP VIEW v1;
+DROP TABLE t1;
+
 --echo End of 5.0 tests

mysql-test/t/view.test

@@ -3916,6 +3916,15 @@ ROW(1,1) >= ROW(1, (SELECT 1 FROM t1 WHERE  f1 >= ANY ( SELECT '1' )));
 DROP VIEW v1;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#52120 create view cause Assertion failed: 0, file .\item_subselect.cc, line 817
+--echo #
+CREATE TABLE t1 (a CHAR(1) CHARSET latin1, b CHAR(1) CHARSET utf8);
+CREATE VIEW v1 AS SELECT 1 from t1
+WHERE t1.b <=> (SELECT a FROM t1 WHERE a < SOME(SELECT '1'));
+DROP VIEW v1;
+DROP TABLE t1;
+
 --echo # -----------------------------------------------------------------
 --echo # -- End of 5.1 tests.
 --echo # -----------------------------------------------------------------

sql/item.cc

@@ -1713,7 +1713,16 @@ bool agg_item_set_converter(DTCollation &coll, const char *fname,
 
     if (!(conv= (*arg)->safe_charset_converter(coll.collation)) &&
         ((*arg)->collation.repertoire == MY_REPERTOIRE_ASCII))
-      conv= new Item_func_conv_charset(*arg, coll.collation, 1);
+    {
+      /*
+        We should disable const subselect item evaluation because
+        subselect transformation does not happen in view_prepare_mode
+        and thus val_...() methods can not be called for const items.
+      */
+      bool resolve_const= ((*arg)->type() == Item::SUBSELECT_ITEM &&
+                           thd->lex->view_prepare_mode) ? FALSE : TRUE;
+      conv= new Item_func_conv_charset(*arg, coll.collation, resolve_const);
+    }
 
     if (!conv)
     {

sql/item_subselect.cc

@@ -122,6 +122,21 @@ void Item_subselect::cleanup()
   DBUG_VOID_RETURN;
 }
 
+
+/*
+   We cannot use generic Item::safe_charset_converter() because
+   Subselect transformation does not happen in view_prepare_mode
+   and thus we can not evaluate val_...() for const items.
+*/
+
+Item *Item_subselect::safe_charset_converter(CHARSET_INFO *tocs)
+{
+  Item_func_conv_charset *conv=
+    new Item_func_conv_charset(this, tocs, thd->lex->view_prepare_mode ? 0 : 1);
+  return conv->safe ? conv : NULL;
+}
+
+
 void Item_singlerow_subselect::cleanup()
 {
   DBUG_ENTER("Item_singlerow_subselect::cleanup");

sql/item_subselect.h

@@ -126,6 +126,7 @@ class Item_subselect :public Item_result_field
   virtual void reset_value_registration() {}
   enum_parsing_place place() { return parsing_place; }
   bool walk(Item_processor processor, bool walk_subquery, uchar *arg);
+  Item *safe_charset_converter(CHARSET_INFO *tocs);
 
   /**
     Get the SELECT_LEX structure associated with this Item.