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MWL#89: Cost-based choice between Materialization and IN->EXISTS transformation

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Added/corrected/improved comments.
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unknown
2010-10-05 16:00:31 +03:00
parent 77c03bcf45
commit 4a3f135a2e
5 changed files with 243 additions and 150 deletions
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49
sql/sql_select.cc
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@@ -19264,8 +19264,18 @@ bool JOIN::change_result(select_result *res)
/**
Save the original query execution plan so that the caller can revert to it
if needed.
Save a query execution plan so that the caller can revert to it if needed,
and reset the current query plan so that it can be reoptimized.
@param save_keyuse[out] a KEYUSE array to save JOIN::keyuse
@param save_best_positions[out] array to save JOIN::best_positions
@param save_join_tab_keyuse[out] array of KEYUSE pointers to save each
JOIN_TAB::keyuse pointer
@param save_join_tab_checked_keys[out] an array of bitmaps to save
each JOIN_TAB::checked_keys
@retval 0 OK
@retval 1 memory allocation error
*/
int JOIN::save_query_plan(DYNAMIC_ARRAY *save_keyuse,
POSITION *save_best_positions,
@@ -19298,8 +19308,14 @@ int JOIN::save_query_plan(DYNAMIC_ARRAY *save_keyuse,
/**
Restore the query plan saved before reoptimization with additional
conditions.
Restore a query plan previously saved by the caller.
@param save_keyuse a KEYUSE array to restore into JOIN::keyuse
@param save_best_positions array to restore into JOIN::best_positions
@param save_join_tab_keyuse array of KEYUSE pointers to restore each
JOIN_TAB::keyuse pointer
@param save_join_tab_checked_keys an array of bitmaps to restore
each JOIN_TAB::checked_keys
*/
void JOIN::restore_query_plan(DYNAMIC_ARRAY *save_keyuse,
@@ -19328,8 +19344,29 @@ void JOIN::restore_query_plan(DYNAMIC_ARRAY *save_keyuse,
/**
Reoptimize a query plan taking into account an additional conjunct to the
WHERE clause.
Reoptimize a query plan taking into account an additional conjunct to the
WHERE clause.
@param added_where An extra conjunct to the WHERE clause to reoptimize with
@param join_tables The set of tables to reoptimize
@param save_best_positions The join order of the original plan to restore to
if needed.
@notes
Given a query plan that already optimized taking into account some WHERE clause
'C', reoptimize this plan with a new WHERE clause 'C AND added_where'. The
reoptimization works as follows:
1. Call update_ref_and_keys *only* for the new conditions 'added_where'
that are about to be injected into the query.
2. Expand if necessary the original KEYUSE array JOIN::keyuse to
accommodate the new REF accesses computed for the 'added_where' condition.
3. Add the new KEYUSEs into JOIN::keyuse.
4. Re-sort and re-filter the JOIN::keyuse array with the newly added
KEYUSE elements.
@retval 0 OK
@retval 1 memory allocation error
*/
int JOIN::reoptimize(Item *added_where, table_map join_tables,