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| author | Igor Babaev <igor@askmonty.org> | 2011-12-24 08:55:10 -0800 |
|---|---|---|
| committer | Igor Babaev <igor@askmonty.org> | 2011-12-24 08:55:10 -0800 |
| commit | 2b1f0b875775b65496e959db7f54f6eb4220400e (patch) | |
| tree | 13c9bd8ec3780974596279996d8215caf21c5225 /mysql-test/r/status.result | |
| parent | 5d9fbc617724ce0bb7f90090596772dbb792139d (diff) | |
| download | mariadb-git-2b1f0b875775b65496e959db7f54f6eb4220400e.tar.gz | |
Back-ported the patch of the mysql-5.6 code line that
fixed several defects in the greedy optimization:
1) The greedy optimizer calculated the 'compare-cost' (CPU-cost)
for iterating over the partial plan result at each level in
the query plan as 'record_count / (double) TIME_FOR_COMPARE'
This cost was only used locally for 'best' calculation at each
level, and *not* accumulated into the total cost for the query plan.
This fix added the 'CPU-cost' of processing 'current_record_count'
records at each level to 'current_read_time' *before* it is used as
'accumulated cost' argument to recursive
best_extension_by_limited_search() calls. This ensured that the
cost of a huge join-fanout early in the QEP was correctly
reflected in the cost of the final QEP.
To get identical cost for a 'best' optimized query and a
straight_join with the same join order, the same change was also
applied to optimize_straight_join() and get_partial_join_cost()
2) Furthermore to get equal cost for 'best' optimized query and a
straight_join the new code substrcated the same '0.001' in
optimize_straight_join() as it had been already done in
best_extension_by_limited_search()
3) When best_extension_by_limited_search() aggregated the 'best' plan a
plan was 'best' by the check :
'if ((search_depth == 1) || (current_read_time < join->best_read))'
The term '(search_depth == 1' incorrectly caused a new best plan to be
collected whenever the specified 'search_depth' was reached - even if
this partial query plan was more expensive than what we had already
found.
Diffstat (limited to 'mysql-test/r/status.result')
| -rw-r--r-- | mysql-test/r/status.result | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mysql-test/r/status.result b/mysql-test/r/status.result index 2c88345646c..5579728e0b2 100644 --- a/mysql-test/r/status.result +++ b/mysql-test/r/status.result @@ -149,7 +149,7 @@ a a 1 1 SHOW SESSION STATUS LIKE 'Last_query_cost'; Variable_name Value -Last_query_cost 4.805836 +Last_query_cost 5.205836 DROP TABLE t1; show status like 'com_show_status'; Variable_name Value |