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Patch for Bug#13805127: Stored program cache produces wrong result in same THD.

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Background:

  - as described in MySQL Internals Prepared Stored
    (http://forge.mysql.com/wiki/MySQL_Internals_Prepared_Stored),
    the Optimizer sometimes does destructive changes to the parsed
    LEX-object (Item-tree), which makes it impossible to re-use
    that tree for PS/SP re-execution.

  - in order to be able to re-use the Item-tree, the destructive
    changes are remembered and rolled back after the statement execution.

The problem, discovered by this bug, was that the objects representing
GROUP-BY clause did not restored after query execution. So, the GROUP-BY
part of the statement could not be properly re-initialized for re-execution
after destructive changes.

Those objects do not take part in the Item-tree, so they can not be saved
using the approach for Item-tree.

The fix is as follows:

  - introduce a new array in st_select_lex to store the original
    ORDER pointers, representing the GROUP-BY clause;

  - Initialize this array in fix_prepare_information().

  - restore the list of GROUP-BY items in reinit_stmt_before_use().
This commit is contained in:
Tor Didriksen
2012-03-29 15:07:54 +02:00
parent 90436a096c
commit 71261282b1
8 changed files with 485 additions and 2 deletions
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8
sql/sql_prepare.cc
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@ -2422,6 +2422,14 @@ void reinit_stmt_before_use(THD *thd, LEX *lex)
DBUG_ASSERT(sl->join == 0);
ORDER *order;
/* Fix GROUP list */
if (sl->group_list_ptrs && sl->group_list_ptrs->size() > 0)
{
for (uint ix= 0; ix < sl->group_list_ptrs->size() - 1; ++ix)
{
order= sl->group_list_ptrs->at(ix);
order->next= sl->group_list_ptrs->at(ix+1);
}
}
for (order= sl->group_list.first; order; order= order->next)
order->item= &order->item_ptr;
/* Fix ORDER list */