From de5029a4586176b9fed06ab96fb3a6e0bbcd8c54 Mon Sep 17 00:00:00 2001 From: Georgi Kodinov Date: Fri, 30 Jul 2010 16:35:06 +0300 Subject: Bug #55188: GROUP BY, GROUP_CONCAT and TEXT - inconsistent results In order to be able to check if the set of the grouping fields in a GROUP BY has changed (and thus to start a new group) the optimizer caches the current values of these fields in a set of Cached_item derived objects. The Cached_item_str, used for caching varchar and TEXT columns, is limited in length by the max_sort_length variable. A String buffer to store the value with an alloced length of either the max length of the string or the value of max_sort_length (whichever is smaller) in Cached_item_str's constructor. Then, at compare time the value of the string to compare to was truncated to the alloced length of the string buffer inside Cached_item_str. This is all fine and valid, but only if you're not assigning values near or equal to the alloced length of this buffer. Because when assigning values like this the alloced length is rounded up and as a result the next set of data will not match the group buffer, thus leading to wrong results because of the changed alloced_length. Fixed by preserving the original maximum length in the Cached_item_str's constructor and using this instead of the alloced_length to limit the string to compare to. Test case added. --- sql/item_buff.cc | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'sql/item_buff.cc') diff --git a/sql/item_buff.cc b/sql/item_buff.cc index 2f45d0a17c2..0ac4edb3656 100644 --- a/sql/item_buff.cc +++ b/sql/item_buff.cc @@ -58,7 +58,9 @@ Cached_item::~Cached_item() {} */ Cached_item_str::Cached_item_str(THD *thd, Item *arg) - :item(arg), value(min(arg->max_length, thd->variables.max_sort_length)) + :item(arg), + value_max_length(min(arg->max_length, thd->variables.max_sort_length)), + value(value_max_length) {} bool Cached_item_str::cmp(void) @@ -67,7 +69,7 @@ bool Cached_item_str::cmp(void) bool tmp; if ((res=item->val_str(&tmp_value))) - res->length(min(res->length(), value.alloced_length())); + res->length(min(res->length(), value_max_length)); if (null_value != item->null_value) { if ((null_value= item->null_value)) -- cgit v1.2.1