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Bug#37075: offset of limit clause might be truncated on 32-bits server w/o big tables

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The problem is that the offset argument of the limit clause
might be truncated on a 32-bits server built without big
tables support. The truncation was happening because the
original 64-bits long argument was being cast to a 32-bits
(ha_rows) offset counter.

The solution is to check if the conversing resulted in value
truncation and if so, the offset is set to the maximum possible
value that can fit on the type.
This commit is contained in:
Davi Arnaut 2008-10-15 18:34:51 -03:00
parent d4c75b7d0f
commit 4ab10baace
3 changed files with 29 additions and 4 deletions
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3
mysql-test/r/limit.result
View File

@ -111,3 +111,6 @@ set @a=-14632475938453979136;
execute s using @a, @a;
ERROR HY000: Incorrect arguments to EXECUTE
End of 5.0 tests
select 1 as a limit 4294967296,10;
a
End of 5.1 tests

8
mysql-test/t/limit.test
View File

@ -95,3 +95,11 @@ set @a=-14632475938453979136;
execute s using @a, @a;
--echo End of 5.0 tests
#
# Bug#37075: offset of limit clause might be truncated to 0 on 32-bits server w/o big tables
#
select 1 as a limit 4294967296,10;
--echo End of 5.1 tests

22
sql/sql_lex.cc
View File

@ -2041,12 +2041,26 @@ st_lex::copy_db_to(char **p_db, uint *p_db_length) const
void st_select_lex_unit::set_limit(SELECT_LEX *sl)
{
ha_rows select_limit_val;
ulonglong val;
DBUG_ASSERT(! thd->stmt_arena->is_stmt_prepare());
select_limit_val= (ha_rows)(sl->select_limit ? sl->select_limit->val_uint() :
HA_POS_ERROR);
offset_limit_cnt= (ha_rows)(sl->offset_limit ? sl->offset_limit->val_uint() :
ULL(0));
val= sl->select_limit ? sl->select_limit->val_uint() : HA_POS_ERROR;
select_limit_val= (ha_rows)val;
#ifndef BIG_TABLES
/*
Check for overflow : ha_rows can be smaller then ulonglong if
BIG_TABLES is off.
*/
if (val != (ulonglong)select_limit_val)
select_limit_val= HA_POS_ERROR;
#endif
val= sl->offset_limit ? sl->offset_limit->val_uint() : ULL(0);
offset_limit_cnt= (ha_rows)val;
#ifndef BIG_TABLES
/* Check for truncation. */
if (val != (ulonglong)offset_limit_cnt)
offset_limit_cnt= HA_POS_ERROR;
#endif
select_limit_cnt= select_limit_val + offset_limit_cnt;
if (select_limit_cnt < select_limit_val)
select_limit_cnt= HA_POS_ERROR; // no limit