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[ticket/15941] Replace MAX to speed up query in update_post_information

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Replace MAX SQL function with faster query using order by and limit.
The ajacent query could also be optimized to eliminate the usage of MAX.
Note that adding a compound key as suggested by EXPLAIN SQL yields an
improvement, but not nearly as fast as ORDER + LIMIT.

PHPBB3-15941
This commit is contained in:
jasonmarlin
2019-01-15 11:31:38 -05:00
parent 5e302c7e15
commit cffdc8efff
1 changed files with 5 additions and 3 deletions
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8
phpBB/includes/functions_posting.php
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@@ -202,11 +202,13 @@ function update_post_information($type, $ids, $return_update_sql = false)
if (count($ids) == 1)
{
$sql = 'SELECT MAX(p.post_id) as last_post_id
$sql = 'SELECT p.post_id as last_post_id
FROM ' . POSTS_TABLE . " p $topic_join
WHERE " . $db->sql_in_set('p.' . $type . '_id', $ids) . "
$topic_condition
AND p.post_visibility = " . ITEM_APPROVED;
AND p.post_visibility = " . ITEM_APPROVED . "
ORDER BY p.post_id DESC";
$result = $db->sql_query_limit($sql, 1);
}
else
{
@@ -216,8 +218,8 @@ function update_post_information($type, $ids, $return_update_sql = false)
$topic_condition
AND p.post_visibility = " . ITEM_APPROVED . "
GROUP BY p.{$type}_id";
}
$result = $db->sql_query($sql);
}
$last_post_ids = array();
while ($row = $db->sql_fetchrow($result))