Question

以下查询使用索引进行了优化。在PHP中执行查询之前和之后准确测量时间，有时需要10或20秒。我似乎并不依赖于行数，因为有时行数小于10，即使这样查询运行缓慢。除了如下所示的查询执行之外，PHP不会执行任何其他操作。

SELECT * FROM (
  SELECT o.op AS orid,
  (3959 * acos(cos(radians(59.4369583424862))
  * cos(radians(d.latitude)) * cos( radians( d.longitude) -
  radians(24.7535276412964)) + sin(radians(59.4369583424862))
  * sin( radians( d.latitude ) ) ) ) AS distance
  FROM (
  SELECT * FROM d WHERE
    d.type='rdw' AND d.longitude > 24.4837311595 AND
    d.longitude < 25.0233241231 AND d.latitude > 59.1671618607 AND
    d.latitude < 59.7067548243
  ) AS d
  LEFT JOIN o ON d.destinid = o.destinid
  LEFT JOIN op ON o.operatorid = op.operatorid
  having distance < 30
  ORDER BY distance
) AS t
GROUP BY trajectoperatorid
LIMIT 0, 30

这是查询的执行方式：

$stmt = $pdo->prepare($sql1);
$stmt->execute();
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC); //foreach($rows as $row){

在首次测量之前已经存在与数据的连接。

当使用SQL_NO_CACHE在phpmyadmin中运行相同的查询时，它始终只需0.06秒。为什么在PHP脚本中运行时查询完全相同？

下面是php scrip：

write_log_file('Start query'.date('l jS \of F Y h:i:s') . substr((string)microtime(), 1, 8));

$sql1 = "
SELECT * FROM (
  SELECT o.op AS orid,
  (3959 * acos(cos(radians(59.4369583424862))
  * cos(radians(d.latitude)) * cos( radians( d.longitude) -
  radians(24.7535276412964)) + sin(radians(59.4369583424862))
  * sin( radians( d.latitude ) ) ) ) AS distance
  FROM (
  SELECT * FROM d WHERE
    d.type='rdw' AND d.longitude > 24.4837311595 AND
    d.longitude < 25.0233241231 AND d.latitude > 59.1671618607 AND
    d.latitude < 59.7067548243
  ) AS d
  LEFT JOIN o ON d.destinid = o.destinid
  LEFT JOIN op ON o.operatorid = op.operatorid
  having distance < 30
  ORDER BY distance
) AS t
GROUP BY trajectoperatorid
LIMIT 0, 30";

$stmt = $pdo->prepare($sql1);
$stmt->execute();
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

Answer 1

这是要阅读的大量SQL！我建议进入MySQL中的EXPLAIN命令来追踪问题，而不是试图从PHP中进行分析。

另请查看Optimizing Queries with EXPLAIN。

一旦了解了数据库内部的情况，如果需要，可能更容易调整PDO用法。

Answer 2

你在MySQL中放了“skip_name_resolve”吗？ 10-20秒对我来说听起来像DNS。你是PHPMyAdmin在同一台机器上 - 连接到localhost？你使用IP连接PHP吗？

为什么我的查询在PHP中慢，在PHPMYadmin中快？

2 个答案: