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BUG#58456 - Assertion 0 in QUICK_INDEX_MERGE_SELECT::need_sorted_output

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in opt_range.h

In this bug, there are two alternative access plans: 
 * Index merge range access
 * Const ref access

best_access_path() decided that the ref access was preferrable, 
but make_join_select() still decided to point 
SQL_SELECT::quick to the index merge because the table had 
type==JT_CONST which was not handled. 

At the same time the table's ref.key still referred to the 
index the ref access would use indicating that ref access 
should be used. In this state, different parts of the 
optimizer code have different perceptions of which access path
is in use (ref or range).

test_if_skip_sort_order() was called to check if the ref access
needed ordering, but test_if_skip_sort_order() got confused and
requested the index merge to return records in sorted order. 
Index merge cannot do this, and fired an ASSERT.

The fix is to take join_tab->type==JT_CONST into concideration
when make_join_select() decides whether or not to use the 
range access method.
This commit is contained in:
Jorgen Loland
2010-12-16 12:25:02 +01:00
parent 28a5059a92
commit 664f06de7c
3 changed files with 81 additions and 7 deletions
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16
sql/sql_select.cc
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@ -6499,10 +6499,12 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
{
/* Use quick key read if it's a constant and it's not used
with key reading */
if (tab->needed_reg.is_clear_all() && tab->type != JT_EQ_REF
&& tab->type != JT_FT && (tab->type != JT_REF ||
(uint) tab->ref.key == tab->quick->index))
{
if (tab->needed_reg.is_clear_all() && tab->type != JT_EQ_REF &&
tab->type != JT_FT &&
((tab->type != JT_CONST && tab->type != JT_REF) ||
(uint)tab->ref.key == tab->quick->index))
{
DBUG_ASSERT(tab->quick->index != MAX_KEY);
sel->quick=tab->quick; // Use value from get_quick_...
sel->quick_keys.clear_all();
sel->needed_reg.clear_all();
@ -13857,7 +13859,7 @@ check_reverse_order:
SYNOPSIS
create_sort_index()
thd Thread handler
tab Table to sort (in join structure)
join Join with table to sort
order How table should be sorted
filesort_limit Max number of rows that needs to be sorted
select_limit Max number of rows in final output
@ -13867,8 +13869,8 @@ check_reverse_order:
IMPLEMENTATION
- If there is an index that can be used, 'tab' is modified to use
this index.
- If there is an index that can be used, the first non-const join_tab in
'join' is modified to use this index.
- If no index, create with filesort() an index file that can be used to
retrieve rows in order (should be done with 'read_record').
The sorted data is stored in tab->table and will be freed when calling