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Comments: Improve caching for hierarchical queries. 

Hierarchical comment queries work by first fetching the IDs of top-level
comments, and then filling the descendant tree one level at a time based on the
top-level results. When top-level comment IDs are found in the cache,
`WP_Comment_Query` does not generate the SQL used to fetch these comments. In
this case, the `fill_descendants()` query does not have enough information
to fill children. As a result, descendant comments were failing to be filled
in cases where the top-level comments were found in the cache.

This was a minor bug previously, because comment caches were not maintained
between pageloads. Since comment caches are now persistent [37613], the problem
becomes evident anywhere that a persistent object cache is in use.

The solution is to cache parent-child relationships, so that when top-level
comments are found in the cache, descendant comments should be found there as
well.

Fixes #36487.

git-svn-id: https://develop.svn.wordpress.org/trunk@37625 602fd350-edb4-49c9-b593-d223f7449a82
This commit is contained in:
Boone Gorges 2016-06-02 18:27:43 +00:00
parent 230f2986fb
commit 1f5147bf83
2 changed files with 86 additions and 11 deletions
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52
src/wp-includes/class-wp-comment-query.php
View File

@ -742,12 +742,13 @@ class WP_Comment_Query {
}
}
if ( $this->query_vars['hierarchical'] && ! $this->query_vars['parent'] ) {
$this->query_vars['parent'] = 0;
$parent = $this->query_vars['parent'];
if ( $this->query_vars['hierarchical'] && ! $parent ) {
$parent = 0;
}
if ( '' !== $this->query_vars['parent'] ) {
$this->sql_clauses['where']['parent'] = $wpdb->prepare( 'comment_parent = %d', $this->query_vars['parent'] );
if ( '' !== $parent ) {
$this->sql_clauses['where']['parent'] = $wpdb->prepare( 'comment_parent = %d', $parent );
}
if ( is_array( $this->query_vars['user_id'] ) ) {
@ -941,20 +942,49 @@ class WP_Comment_Query {
}
}
$key = md5( serialize( wp_array_slice_assoc( $this->query_vars, array_keys( $this->query_var_defaults ) ) ) );
$last_changed = wp_cache_get( 'last_changed', 'comment' );
if ( ! $last_changed ) {
$last_changed = microtime();
wp_cache_set( 'last_changed', $last_changed, 'comment' );
}
// Fetch an entire level of the descendant tree at a time.
$level = 0;
do {
$parent_ids = $levels[ $level ];
if ( ! $parent_ids ) {
break;
// Parent-child relationships may be cached. Only query for those that are not.
$child_ids = $uncached_parent_ids = array();
$_parent_ids = $levels[ $level ];
foreach ( $_parent_ids as $parent_id ) {
$cache_key = "get_comment_child_ids:$parent_id:$key:$last_changed";
$parent_child_ids = wp_cache_get( $cache_key, 'comment' );
if ( false !== $parent_child_ids ) {
$child_ids = array_merge( $child_ids, $parent_child_ids );
} else {
$uncached_parent_ids[] = $parent_id;
}
}
$where = 'WHERE ' . $_where . ' AND comment_parent IN (' . implode( ',', array_map( 'intval', $parent_ids ) ) . ')';
$comment_ids = $wpdb->get_col( "{$this->sql_clauses['select']} {$this->sql_clauses['from']} {$where} {$this->sql_clauses['groupby']} ORDER BY comment_date_gmt ASC, comment_ID ASC" );
if ( $uncached_parent_ids ) {
$where = 'WHERE ' . $_where . ' AND comment_parent IN (' . implode( ',', array_map( 'intval', $uncached_parent_ids ) ) . ')';
$level_comments = $wpdb->get_results( "SELECT $wpdb->comments.comment_ID, $wpdb->comments.comment_parent {$this->sql_clauses['from']} {$where} {$this->sql_clauses['groupby']} ORDER BY comment_date_gmt ASC, comment_ID ASC" );
// Cache parent-child relationships.
$parent_map = array_fill_keys( $uncached_parent_ids, array() );
foreach ( $level_comments as $level_comment ) {
$parent_map[ $level_comment->comment_parent ][] = $level_comment->comment_ID;
$child_ids[] = $level_comment->comment_ID;
}
foreach ( $parent_map as $parent_id => $children ) {
$cache_key = "get_comment_child_ids:$parent_id:$key:$last_changed";
wp_cache_set( $cache_key, $children, 'comment' );
}
}
$level++;
$levels[ $level ] = $comment_ids;
} while ( $comment_ids );
$levels[ $level ] = $child_ids;
} while ( $child_ids );
// Prime comment caches for non-top-level comments.
$descendant_ids = array();

45
tests/phpunit/tests/comment/query.php
View File

@ -2430,6 +2430,51 @@ class Tests_Comment_Query extends WP_UnitTestCase {
$clauses['where'] .= $wpdb->prepare( ' AND comment_ID != %d AND comment_ID != %d', $this->to_exclude[0], $this->to_exclude[1] );
return $clauses;
}
/**
* @ticket 36487
*/
public function test_cache_should_be_hit_when_querying_descendants() {
global $wpdb;
$p = self::factory()->post->create();
$comment_1 = self::factory()->comment->create( array(
'comment_post_ID' => $p,
'comment_approved' => '1',
) );
$comment_2 = self::factory()->comment->create( array(
'comment_post_ID' => $p,
'comment_approved' => '1',
'comment_parent' => $comment_1,
) );
$comment_3 = self::factory()->comment->create( array(
'comment_post_ID' => $p,
'comment_approved' => '1',
'comment_parent' => $comment_1,
) );
$comment_4 = self::factory()->comment->create( array(
'comment_post_ID' => $p,
'comment_approved' => '1',
'comment_parent' => $comment_2,
) );
$q1 = new WP_Comment_Query( array(
'post_id' => $p,
'hierarchical' => true,
) );
$q1_ids = wp_list_pluck( $q1->comments, 'comment_ID' );
$num_queries = $wpdb->num_queries;
$q2 = new WP_Comment_Query( array(
'post_id' => $p,
'hierarchical' => true,
) );
$q2_ids = wp_list_pluck( $q2->comments, 'comment_ID' );
$this->assertEqualSets( $q1_ids, $q2_ids );
$this->assertSame( $num_queries, $wpdb->num_queries );
}
/**
* @ticket 27571
*/