Faster Query for Differential Updates
Summary:
The old query was effectively
SELECT DISTINCT revision.* FROM differential_revision revision
JOIN `differential_relationship` relationship ON
(relationship.revisionID = revision.id
AND relationship.objectPHID in
('PHID-USER-a113b9ae4ee9524d0a20'))
OR revision.authorPHID = 'PHID-USER-a113b9ae4ee9524d0a20' LEFT JOIN `differential_viewtime` viewtime ON
viewtime.viewerPHID in ('PHID-USER-a113b9ae4ee9524d0a20')
AND viewtime.objectPHID = revision.phid AND GREATEST(1304022277, IFNULL(viewtime.viewTime, 0)) <
revision.dateModified
ORDER BY dateModified DESC;
I'm not a db performance expert but it looks like the problem is that we
have to scan all revisions
mysql> EXPLAIN SELECT DISTINCT revision.* FROM `differential_revision`
revision JOIN differential_relationship relationship ON
(relationship.revisionID = revision.id AND relationship.objectPHID
in ('PHID-USER-a113b9ae4ee9524d0a20')) OR revision.authorPHID =
'PHID-USER-a113b9ae4ee9524d0a20' LEFT JOIN differential_viewtime
viewtime ON viewtime.viewerPHID in ('PHID-USER-a113b9ae4ee9524d0a20')
AND viewtime.objectPHID = revision.phid AND GREATEST(1304022277,
IFNULL(viewtime.viewTime, 0)) < revision.dateModified ORDER BY
dateModified DESC;
+----+-------------+--------------+-------+--------------------+------------+---------+-------+--------+------------------------------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | Extra |
+----+-------------+--------------+-------+--------------------+------------+---------+-------+--------+------------------------------------+
| 1 | SIMPLE | revision | ALL | PRIMARY,authorPHID | NULL |
NULL | NULL | 254127 | Using temporary; Using filesort |
| 1 | SIMPLE | viewtime | ref | PRIMARY | PRIMARY |
66 | const | 17 | Distinct |
| 1 | SIMPLE | relationship | index | PRIMARY,objectPHID | objectPHID |
72 | NULL | 966900 | Using where; Using index; Distinct |
+----+-------------+--------------+-------+--------------------+------------+---------+-------+--------+------------------------------------+
The new query is a lot faster
mysql> EXPLAIN SELECT revs.* FROM ( (SELECT revision.* FROM
differential_revision revision WHERE revision.authorPHID in
('PHID-USER-a113b9ae4ee9524d0a20')) UNION (SELECT revision.* FROM
differential_revision revision JOIN differential_relationship rel WHERE
rel.revisionId = revision.Id AND rel.objectPHID =
'PHID-USER-a113b9ae4ee9524d0a20')) as revs LEFT JOIN differential_viewtime
viewtime ON viewtime.viewerPHID = 'PHID-USER-a113b9ae4ee9524d0a20' AND
viewtime.objectPHID = revs.phid WHERE GREATEST(1304022277,
IFNULL(viewtime.viewTime, 0)) < revs.dateModified ORDER BY revs.dateModified;
+----+--------------+------------+--------+--------------------+------------+---------+-----------------------------------------+------+--------------------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | Extra
|
+----+--------------+------------+--------+--------------------+------------+---------+-----------------------------------------+------+--------------------------+
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL |
NULL | NULL | 3021 | Using filesort
| | 1 | PRIMARY | viewtime | ref | PRIMARY | PRIMARY |
66 | const | 17 | Using where
| | 2 | DERIVED | revision | ref | authorPHID | authorPHID |
67 | | 1040 | Using where
| | 3 | UNION | rel | ref | PRIMARY,objectPHID | objectPHID |
66 | | 3822 | Using where; Using
index |
| 3 | UNION | revision | eq_ref | PRIMARY | PRIMARY |
4 | phabricator_differential.rel.revisionID | 1 |
| | NULL | UNION RESULT | <union2,3> | ALL | NULL | NULL
| NULL | NULL | NULL |
+----+--------------+------------+--------+--------------------+------------+---------+-----------------------------------------+------+--------------------------+
Test Plan:
Loaded differential updates with new query, made sure page loaded quickly. Ran
the query from the command-line, it took about .4 seconds.
Reviewed By: Girish
Reviewers: tuomaspelkonen, jungejason, Girish
Commenters: btrahan
CC: aran, btrahan, elynde, Girish
Differential Revision: 181