data": remove the fix for another bug (8807) that
added OUTER_REF_TABLE_BIT to all subqueries that used a placeholder
to prevent their evaluation at prepare. As this bit hanged in
Item_subselect::used_tables_cache for ever, a constant subquery with
a placeholder was never evaluated as such, which caused wrong
choice of the execution plan for the statement.
- to fix Bug#8807 backport a better fix from 5.0
- post-review fixes.
- Add function Item_param::fix_fields which will update any subselect they are part of and indicate that the subsleect is not const during prepare phase, and thus should not be executed during prepare.
improved mechanisn of detection posibility to be NULL for single row queries
switched off substitution optimisation for single row subqueries in PS due to problem in resolving substituted expressions
(changes to make subselects test working with PS protocol)
a second time". The bug was caused by incompatibility of
negations elimination algorithm and PS: during first statement
execute a subtree with negation was replaced with equivalent
subtree without NOTs.
The problem was that although this transformation was permanent,
items of the new subtree were created in execute-local memory.
The patch adds means to check if it is the first execute of a
prepared statement, and if this is the case, to allocate items
in memory of the prepared statement.
The implementation:
- backports Item_arena from 5.0
- adds Item_arena::is_stmt_prepare(),
Item_arena::is_first_stmt_execute().
- deletes THD::allocate_temporary_pool_for_ps_preparing(),
THD::free_temporary_pool_for_ps_preparing(); they
were redundant.
and adds a few invariants:
- thd->free_list never contains junk (= freed items)
- thd->current_arena is never null. If there is no
prepared statement, it points at the thd.
The rest of the patch contains mainly mechanical changes and
cleanups.
This bug happens when a query, having subselects in the fields list,
needs temporary table.
Item_subselect::get_tmp_table_item isn't implemented and just returns
*this. So the tmp_table_item takes value not from temporary but
from original table.
Fixed compiler warnings (a lot of hidden variables detected by the Forte compiler)
Added a lot of 'version_xxx' strings to 'show variables'
Prevent copying of TMP_TABLE_PARAM (This caused core dump bug on Solaris)
Fixed problem with printing sub selects to debug log
fixed number of rows of external field reported to optimizer
added check of choosen key (checked left expression tag)
(SCRUM fix for simple IN optimisation)
