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A fix and test case for Bug#6088 "FOUND_ROWS returns wrong values for

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prepared statements when LIMIT is used" and post-review comments.
The fix changes the approach we calculate the need for ORDER BY 
in UNION: the previous was not PS friendly, as it damaged SELECT_LEX 
options in case of single select.


mysql-test/r/ps.result:
  Test results fixed: the test case for Bug#6088
mysql-test/r/subselect.result:
  Test results fixed: now we don't perform ORDER BY for parts of UNION
  if there is no LIMIT clause.
mysql-test/t/ps.test:
  A test case for Bug#6088 "FOUND_ROWS returns wrong values for
   prepared statements when LIMIT is used".
sql/sql_union.cc:
  The actual fix for Bug#6088:
  - don't modify SELECT_LEX'es
  - use boolean variable can_skip_order_by to check if we can skip
    ORDER BY in UNION
This commit is contained in:
unknown
2004-10-22 22:51:16 +04:00
parent 1cd249e0ed
commit 9b5cf9464c
4 changed files with 54 additions and 18 deletions
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28
sql/sql_union.cc
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@@ -147,6 +147,7 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
SELECT_LEX *lex_select_save= thd_arg->lex->current_select;
SELECT_LEX *sl, *first_select;
select_result *tmp_result;
bool is_union;
DBUG_ENTER("st_select_lex_unit::prepare");
describe= test(additional_options & SELECT_DESCRIBE);
@@ -183,10 +184,11 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
thd_arg->lex->current_select= sl= first_select= first_select_in_union();
found_rows_for_union= first_select->options & OPTION_FOUND_ROWS;
is_union= test(first_select->next_select());
/* Global option */
if (first_select->next_select())
if (is_union)
{
if (!(tmp_result= union_result= new select_union(0)))
goto err;
@@ -195,14 +197,11 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
tmp_result= sel_result;
}
else
{
tmp_result= sel_result;
// single select should be processed like select in p[arantses
first_select->braces= 1;
}
for (;sl; sl= sl->next_select())
{
bool can_skip_order_by;
sl->options|= SELECT_NO_UNLOCK;
JOIN *join= new JOIN(thd_arg, sl->item_list,
sl->options | thd_arg->options | additional_options,
@@ -217,14 +216,17 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
select_limit_cnt= HA_POS_ERROR; // no limit
if (select_limit_cnt == HA_POS_ERROR || sl->braces)
sl->options&= ~OPTION_FOUND_ROWS;
can_skip_order_by= is_union &&
(!sl->braces || select_limit_cnt == HA_POS_ERROR);
res= join->prepare(&sl->ref_pointer_array,
(TABLE_LIST*) sl->table_list.first, sl->with_wild,
sl->where,
((sl->braces) ? sl->order_list.elements : 0) +
sl->group_list.elements,
(sl->braces) ?
(ORDER *)sl->order_list.first : (ORDER *) 0,
(can_skip_order_by ? 0 : sl->order_list.elements) +
sl->group_list.elements,
can_skip_order_by ?
(ORDER*) 0 : (ORDER *)sl->order_list.first,
(ORDER*) sl->group_list.first,
sl->having,
(ORDER*) NULL,
@@ -264,10 +266,8 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
}
}
if (first_select->next_select())
if (is_union)
{
/* This is not a single select */
/*
Check that it was possible to aggregate
all collations together for UNION.
@@ -364,8 +364,6 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
}
}
}
else
first_select->braces= 0; // remove our changes
thd_arg->lex->current_select= lex_select_save;