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Fix for BUG#14920 Ordering aggregated result sets corrupts resultset.

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The cause of the bug was the use of end_write_group instead of end_write
in the case when ORDER BY required a temporary table, which didn't take
into account the fact that loose index scan already computes the result
of MIN/MAX aggregate functions (and performs grouping).

The solution is to call end_write instead of end_write_group and to add
the MIN/MAX functions to the list of regular functions so that their
values are inserted into the temporary table.
This commit is contained in:
timour@mysql.com
2005-11-30 12:52:12 +02:00
parent 519139b63a
commit 999a73ace5
6 changed files with 113 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

65
sql/sql_select.cc
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@ -1007,6 +1007,20 @@ JOIN::optimize()
}
having= 0;
/*
The loose index scan access method guarantees that all grouping or
duplicate row elimination (for distinct) is already performed
during data retrieval, and that all MIN/MAX functions are already
computed for each group. Thus all MIN/MAX functions should be
treated as regular functions, and there is no need to perform
grouping in the main execution loop.
Notice that currently loose index scan is applicable only for
single table queries, thus it is sufficient to test only the first
join_tab element of the plan for its access method.
*/
if (join_tab->is_using_loose_index_scan())
tmp_table_param.precomputed_group_by= TRUE;
/* Create a tmp table if distinct or if the sort is too complicated */
if (need_tmp)
{
@ -1410,6 +1424,15 @@ JOIN::exec()
else
{
/* group data to new table */
/*
If the access method is loose index scan then all MIN/MAX
functions are precomputed, and should be treated as regular
functions. See extended comment in JOIN::exec.
*/
if (curr_join->join_tab->is_using_loose_index_scan())
curr_join->tmp_table_param.precomputed_group_by= TRUE;
if (!(curr_tmp_table=
exec_tmp_table2= create_tmp_table(thd,
&curr_join->tmp_table_param,
@ -8279,6 +8302,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
MEM_ROOT *mem_root_save, own_root;
TABLE *table;
uint i,field_count,null_count,null_pack_length;
uint copy_func_count= param->func_count;
uint hidden_null_count, hidden_null_pack_length, hidden_field_count;
uint blob_count,group_null_items, string_count;
uint temp_pool_slot=MY_BIT_NONE;
@ -8342,6 +8366,16 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
field_count=param->field_count+param->func_count+param->sum_func_count;
hidden_field_count=param->hidden_field_count;
/*
When loose index scan is employed as access method, it already
computes all groups and the result of all aggregate functions. We
make space for the items of the aggregate function in the list of
functions TMP_TABLE_PARAM::items_to_copy, so that the values of
these items are stored in the temporary table.
*/
if (param->precomputed_group_by)
copy_func_count+= param->sum_func_count;
init_sql_alloc(&own_root, TABLE_ALLOC_BLOCK_SIZE, 0);
if (!multi_alloc_root(&own_root,
@ -8349,7 +8383,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
&reg_field, sizeof(Field*) * (field_count+1),
&blob_field, sizeof(uint)*(field_count+1),
&from_field, sizeof(Field*)*field_count,
&copy_func, sizeof(*copy_func)*(param->func_count+1),
&copy_func, sizeof(*copy_func)*(copy_func_count+1),
&param->keyinfo, sizeof(*param->keyinfo),
&key_part_info,
sizeof(*key_part_info)*(param->group_parts+1),
@ -9241,11 +9275,13 @@ bool create_myisam_from_heap(THD *thd, TABLE *table, TMP_TABLE_PARAM *param,
Next_select_func setup_end_select_func(JOIN *join)
{
TABLE *table= join->tmp_table;
TMP_TABLE_PARAM *tmp_tbl= &join->tmp_table_param;
Next_select_func end_select;
/* Set up select_end */
if (table)
{
if (table->group && join->tmp_table_param.sum_func_count)
if (table->group && tmp_tbl->sum_func_count)
{
if (table->s->keys)
{
@ -9258,7 +9294,7 @@ Next_select_func setup_end_select_func(JOIN *join)
end_select=end_unique_update;
}
}
else if (join->sort_and_group)
else if (join->sort_and_group && !tmp_tbl->precomputed_group_by)
{
DBUG_PRINT("info",("Using end_write_group"));
end_select=end_write_group;
@ -9267,19 +9303,27 @@ Next_select_func setup_end_select_func(JOIN *join)
{
DBUG_PRINT("info",("Using end_write"));
end_select=end_write;
if (tmp_tbl->precomputed_group_by)
{
/*
A preceding call to create_tmp_table in the case when loose
index scan is used guarantees that
TMP_TABLE_PARAM::items_to_copy has enough space for the group
by functions. It is OK here to use memcpy since we copy
Item_sum pointers into an array of Item pointers.
*/
memcpy(tmp_tbl->items_to_copy + tmp_tbl->func_count,
join->sum_funcs,
sizeof(Item*)*tmp_tbl->sum_func_count);
tmp_tbl->items_to_copy[tmp_tbl->func_count+tmp_tbl->sum_func_count]= 0;
}
}
}
else
{
/* Test if data is accessed via QUICK_GROUP_MIN_MAX_SELECT. */
bool is_using_quick_group_min_max_select=
(join->join_tab->select && join->join_tab->select->quick &&
(join->join_tab->select->quick->get_type() ==
QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX));
if ((join->sort_and_group ||
(join->procedure && join->procedure->flags & PROC_GROUP)) &&
!is_using_quick_group_min_max_select)
!tmp_tbl->precomputed_group_by)
end_select= end_send_group;
else
end_select= end_send;
@ -10553,7 +10597,6 @@ end_write(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
{
copy_fields(&join->tmp_table_param);
copy_funcs(join->tmp_table_param.items_to_copy);
#ifdef TO_BE_DELETED
if (!table->uniques) // If not unique handling
{