- In print_explain_row(), do not forget to print r_rows.
- Switch Explain_update from using its own counters to re-using
Table_access_tracker.
- Make ANALYZE UPDATE code structure uniform with ANALYZE DELETE.
- "ANALYZE $stmt" should discard select's output, but it should still
evaluate the output columns (otherwise, subqueries in select list
are not executed)
- SHOW EXPLAIN's code practice of calling JOIN::save_explain_data()
after JOIN::exec() is disastrous for ANALYZE, because it resets
all counters after the first execution. It is stopped
= "Late" test_if_skip_sort_order() calls explicitly update their part
of the query plan.
= Also, I had to rewrite I_S optimization to actually have optimization
and execution stages.
MDEV-406: ANALYZE $stmt
- Ported the old patch to new explain code
- New SQL syntax (ANALYZE $stmt)
- ANALYZE UPDATE/DELETE is now supported (because EXPLAIN UPDATE/DELETE is supported)
- Basic counters are calculated for basic kinds of queries
(still need to see what happens with join buffer, ORDER BY...LIMIT queries, etc)
Update the SHOW EXPLAIN code to work with the
new architecture (part#1):
Before, SHOW EXPLAIN operated on real query plan structures,
which meant it had to check when SELECTs are created/deleted.
SELECTs would call apc_target->enable() when they got a query
plan and disable() when their query plan was deleted.
Now, Explain data structure becomes available at once (and we
call apc_target->enable()) and then it stays until it is deleted
(when that happens, we call apc_target->disable()).
- Generate correct contents of `Extra` column for UPDATEs/DELETEs that use quick selects
- UPDATEs with used_key_is_modified=true will show "Using buffer"
