Fix bug #11864 non unique names are allowed in subquery

Column names weren't checked for uniqueness for subqueries.

Code for names uniqueness checking used for view creation moved into 
separate function named check_duplicate_names(). It's called on 
preparation of subqueries to check uniqueness of names. If duplicate names 
are found then error is raised.

1 files changed, 67 insertions, 29 deletions

diff --git a/sql/sql_view.cc b/sql/sql_view.cc
index aedff648e5c..ecaab9db0cd 100644
--- a/sql/sql_view.cc
+++ b/sql/sql_view.cc
@@ -94,6 +94,71 @@ static void make_unique_view_field_name(Item *target,
   target->set_name(buff, name_len, system_charset_info);
 }
 
+
+/*
+  Check if items with same names are present in list and possibly
+  generate unique names for them.
+
+  SYNOPSIS
+    item_list             list of Items which should be checked for duplicates
+    gen_unique_view_name  flag: generate unique name or return with error when
+                          duplicate names are found.
+
+  DESCRIPTION
+    This function is used on view creation and preparation of derived tables.
+    It checks item_list for items with duplicate names. If it founds two
+    items with same name and conversion to unique names isn't allowed, or
+    names for both items are set by user - function fails.
+    Otherwise it generates unique name for one item with autogenerated name
+    using make_unique_view_field_name()
+
+  RETURN VALUE
+    FALSE no duplicate names found, or they are converted to unique ones
+    TRUE  duplicate names are found and they can't be converted or conversion
+          isn't allowed
+*/
+
+bool check_duplicate_names(List<Item> &item_list, bool gen_unique_view_name)
+{
+  DBUG_ENTER("check_duplicate_names");
+  /* Test absence of duplicates names */
+  {
+    Item *item;
+    List_iterator_fast<Item> it(item_list);
+    List_iterator_fast<Item> itc(item_list);
+    while ((item= it++))
+    {
+      Item *check;
+      /* treat underlying fields like set by user names */
+      if (item->real_item()->type() == Item::FIELD_ITEM)
+        item->is_autogenerated_name= FALSE;
+      itc.rewind();
+      while ((check= itc++) && check != item)
+      {
+        if (my_strcasecmp(system_charset_info, item->name, check->name) == 0)
+        {
+          if (!gen_unique_view_name)
+          {
+            my_error(ER_DUP_FIELDNAME, MYF(0), item->name);
+            DBUG_RETURN(TRUE);
+          }
+          else if (item->is_autogenerated_name)
+            make_unique_view_field_name(item, item_list, item);
+          else if (check->is_autogenerated_name)
+            make_unique_view_field_name(check, item_list, item);
+          else
+          {
+            my_error(ER_DUP_FIELDNAME, MYF(0), item->name);
+            DBUG_RETURN(TRUE);
+          }
+        }
+      }
+    }
+  }
+  DBUG_RETURN(FALSE);
+}
+
+
 /*
   Creating/altering VIEW procedure
 
@@ -308,35 +373,8 @@ bool mysql_create_view(THD *thd,
     }
   }
 
-  /* Test absence of duplicates names */
-  {
-    Item *item;
-    List_iterator_fast<Item> it(select_lex->item_list);
-    List_iterator_fast<Item> itc(select_lex->item_list);
-    while ((item= it++))
-    {
-      Item *check;
-      /* treat underlying fields like set by user names */
-      if (item->real_item()->type() == Item::FIELD_ITEM)
-        item->is_autogenerated_name= FALSE;
-      itc.rewind();
-      while ((check= itc++) && check != item)
-      {
-        if (my_strcasecmp(system_charset_info, item->name, check->name) == 0)
-        {
-          if (item->is_autogenerated_name)
-            make_unique_view_field_name(item, select_lex->item_list, item);
-          else if (check->is_autogenerated_name)
-            make_unique_view_field_name(check, select_lex->item_list, item);
-          else
-          {
-            my_error(ER_DUP_FIELDNAME, MYF(0), item->name);
-            DBUG_RETURN(TRUE);
-          }
-        }
-      }
-    }
-  }
+  if (check_duplicate_names(select_lex->item_list, 1))
+    DBUG_RETURN(TRUE);
 
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   /*