Question

我试图在幻灯片中添加基于2个不同键的2种幻灯片，只是元查询非常慢。我正在使用的wordpress查询是：

$args = array(
    'meta_query' => array(
        'relation' => 'OR',
        array(
            'key' => 'sgt_slide',
            'value' => 'on',
            'compare' => '='
        ),
        array(
            'key' => 'sgt_slide_home',
            'value' => 'on',
            'compare' => '='
        )
    ),
    'no_found_rows' => true, //exclude unnecessary paging calculations
    'numberposts' => -1,
    'post_status' => array( 'publish', 'inherit' ),
    'post_type' => array( 'post', 'attachment' )
    );
$slides = get_posts($args);

和结果的SQL匹配查询

SELECT   nd_posts.* FROM nd_posts  INNER JOIN nd_postmeta ON (nd_posts.ID = nd_postmeta.post_id)
INNER JOIN nd_postmeta AS mt1 ON (nd_posts.ID = mt1.post_id) WHERE 1=1  AND nd_posts.post_type IN ('post', 'attachment') AND ((nd_posts.post_status = 'publish' OR nd_posts.post_status = 'inherit')) AND ( (nd_postmeta.meta_key = 'sgt_slide' AND CAST(nd_postmeta.meta_value AS CHAR) = 'on')
OR  (mt1.meta_key = 'sgt_slide_home' AND CAST(mt1.meta_value AS CHAR) = 'on') ) GROUP BY nd_posts.ID ORDER BY nd_posts.post_date DESC

此sql导致查询在7秒内加载，在phpmyadmin中测试。我怎么能克服这个。

EXPLAIN SQL

explain sql

Answer 1

尝试添加 'cache_results' => false, 到你的循环

Answer 2

WordPress强制转换为char（），它会停止使用的索引。以下代码使用过滤器删除强制转换：

/**
 * Remove casting a meta_query to a char as this stops it using the index!
 */

function my_filter_meta_query( $pieces ) {
 if ( !empty( $pieces['where'] ) ) {
     // remove casting to CHAR as this is already a string
     $pieces['where'] = preg_replace("@CAST\(([^.]*.meta_value) AS CHAR\)@", "$1",$pieces['where']);
 }
return $pieces;
}

add_filter( 'get_meta_sql', 'my_filter_meta_query' );

更多详情http://www.topsemtips.com/2015/01/wordpress-meta-query-slow-wp_query/

Answer 3

很高兴基于此解决方法：https://wordpress.stackexchange.com/questions/158898/meta-query-terribly-slow

function wpse158898_posts_clauses( $pieces, $query ) {
    global $wpdb;
    $relation = isset( $query->meta_query->relation ) ? $query->meta_query->relation : 'AND';
    if ( $relation != 'OR' ) return $pieces; // Only makes sense if OR.
    $prepare_args = array();
    $key_value_compares = array();
    foreach ( $query->meta_query->queries as $meta_query ) {
        // Doesn't work for IN, NOT IN, BETWEEN, NOT BETWEEN, NOT EXISTS.
        if ( ! isset( $meta_query['value'] ) || is_array( $meta_query['value'] ) ) return $pieces; // Bail if no value or is array.
        $key_value_compares[] = '(pm.meta_key = %s AND pm.meta_value ' . $meta_query['compare'] . ' %s)';
        $prepare_args[] = $meta_query['key'];
        $prepare_args[] = $meta_query['value'];
    }
    $sql = ' JOIN ' . $wpdb->postmeta . ' pm on pm.post_id = ' . $wpdb->posts . '.ID'
        . ' AND (' . implode( ' ' . $relation . ' ', $key_value_compares ) . ')';
    array_unshift( $prepare_args, $sql );
    $pieces['join'] = call_user_func_array( array( $wpdb, 'prepare' ), $prepare_args );
    $pieces['where'] = preg_replace( '/ AND[^' . $wpdb->postmeta[0] . ']+' . $wpdb->postmeta . '.*$/s', '', $pieces['where'] ); // Zap postmeta clauses.
    return $pieces;
}
add_filter( 'posts_clauses', 'wpse158898_posts_clauses', 10, 2 );
$slidess = new WP_Query($args);
$slides = $slidess->get_posts();
remove_filter( 'posts_clauses', 'wpse158898_posts_clauses', 10 );

并设法使用新的get_posts和WP_query函数模仿get_posts()的相同模式。

由元查询引起的对wordpress的查询非常慢

3 个答案: