mysqli::poll

mysqli_poll

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

mysqli::poll -- mysqli_poll — 轮询连接

说明

面向对象风格

public static mysqli::poll(
    ?array &$read,
    ?array &$error,
    array &$reject,
    int $seconds,
    int $microseconds = 0
): int|false

过程化风格

mysqli_poll(
    ?array &$read,
    ?array &$error,
    array &$reject,
    int $seconds,
    int $microseconds = 0
): int|false

轮询连接。此方法是 static 的。

注意:
仅可用于 mysqlnd。

参数

read: 要检测是否存在可以读取的结果集的连接的数组。
error: 发生错误的，例如：SQL 语句执行失败或者已经断开的连接的数组。
reject: 没有可以读取的结果集的连接的数组。
seconds: 秒为单位的最大等待时间，不可以为负数。
microseconds: 微秒为单位的最大等待时间，不可以为负数。

返回值

成功执行则返回存在可以读取结果集的连接数量，否则 false。

错误／异常

当没有传递 read 和 error 参数时抛出 ValueError 异常。

更新日志

版本	说明
8.3.0	现在，当没有传递 `read` 和 `error` 参数时抛出 ValueError 异常。

示例

示例 #1 mysqli_poll() 示例

<?php
$link1 = mysqli_connect();
$link1->query("SELECT 'test'", MYSQLI_ASYNC);
$all_links = array($link1);
$processed = 0;
do {
    $links = $errors = $reject = array();
    foreach ($all_links as $link) {
        $links[] = $errors[] = $reject[] = $link;
    }
    if (!mysqli_poll($links, $errors, $reject, 1)) {
        continue;
    }
    foreach ($links as $link) {
        if ($result = $link->reap_async_query()) {
            print_r($result->fetch_row());
            if (is_object($result))
                mysqli_free_result($result);
        } else die(sprintf("MySQLi Error: %s", mysqli_error($link)));
        $processed++;
    }
} while ($processed < count($all_links));
?>

以上示例会输出：

Array
(
    [0] => test
)

参见

mysqli_query() - 对数据库执行查询
mysqli_reap_async_query() - 获取异步查询的结果

改进此页面

了解如何改进此页面 • 提交拉取请求 • 报告一个错误

＋添加备注

用户贡献的备注 5 notes

down

l_sanczyk at hotmail dot com ¶

10 years ago

You can use the following code to execute, for example, 10 simultaneous queries:

$query = "SELECT `field1`, `field2` FROM `table` WHERE `field1`='something'";

$all_links = array();
for($i=0; $i<10; $i++) {
    $link = mysqli_connect("your.mysql.server.here","your@user","pa$$w0rd",DataBase_Name");
    $link->query($query, MYSQLI_ASYNC);
    $all_links[] = $link;
}

$processed = 0;
do {
    $links = $errors = $reject = array();
    foreach ($all_links as $link) {
        $links[] = $errors[] = $reject[] = $link;
    }
    if (!mysqli_poll($links, $errors, $reject, 1)) {
        continue;
    }
    foreach ($links as $link) {
        if ($result = $link->reap_async_query()) {
            print_r($result->fetch_row());
            if (is_object($result))
                mysqli_free_result($result);
        } else die(sprintf("MySQLi Error: %s", mysqli_error($link)));
        $processed++;
    }
} while ($processed < count($all_links));

NOTE: If you get a "Warning: mysqli::query() expects parameter 2 to be long, string given" you have a mysqlnd installation or configuration issue.

down

shestero at meta dot ua ¶

8 years ago

Sometime it's not clear what does it mean as connection is "ready" . Does it mean the query completed or just some records ready to read?
Is it possible to use asynchronous (unblocking) and unbuffered SELECT-query? I.e. with both MYSQLI_ASYNC|MYSQLI_USE_RESULT

I want some poll-like code inside my loop that has four case-options:
1. Poll wait time-out is over but no records of result set is ready.
2. One or more records are ready to read (but the query still running).
3. Query is successfully over (completed; no more records).
4. Error.

Is it possible?

As I understood the operation of reading a record from unbuffered query is blocking if there are no ready records at the moment, and there is no functions to get out how much records are ready ?

down

marcin dot wanat at gmail dot com ¶

1 year ago

It is worth to note that example from this docs will results in waiting for all queries to be executed before you can reap your results.

5 years ago bishop from php.net has posted solution that allow to fetch results of each query immediately after executed. For some reason this has never been merged to php manual.

https://bugs.php.net/bug.php?id=70505

The documentation for mysqli_poll suggests iterating through the links after running the poll:

    foreach ($links as $link) {
        if ($result = $link->reap_async_query()) {
            print_r($result->fetch_row());
            if (is_object($result))
                mysqli_free_result($result);
        } else die(sprintf("MySQLi Error: %s", mysqli_error($link)));
        $processed++;
    }

This is not a good way to go about it when you have queries of different run-times, because mysqli_reap_async_query() blocks until the query resolves, which is contrary to the nature of the async poll.

An approach that respects multiple queries of different run times is to run a reaping function over each of the modified arrays:

    $count = mysqli_poll($read, $error, $reject, 1);
    if (0 < $count) {
        array_walk($read,   'reap');
        array_walk($error,  'reap');
        array_walk($reject, 'reap');
    }

function reap($link) {
    $result = mysqli_reap_async_query($link);
    if (is_object($result)) {
        print_r($result->fetch_assoc()));
        mysqli_free_result($result);
    } else if (false !== $result) {
        print_r($link);
    } else {
        die(mysqli_error($link));
    }
}

This also handles the case where the query is a CRUD and the result of reap_async_query isn't a result object.

down

ekalashnikov at gmail dot com ¶

7 years ago

Improved version of using polling to check for slow query,
"KILL #ID" does not work if id of the myqsli link is the same as the one that kills it,
so you have to disconnect from mysqli and connect again with new link to 
kill the #ID.
<?php
// Slow SQL Query
      $SelectSql = 'SELECT * FROM SLOW_QUERY';
      $link = mysqli_connect('localhost','user','pass','database');
      mysqli_query($SelectSql, MYSQLI_ASYNC);
      $thread_id = mysqli_thread_id($link);
      // Ignore user abort so we can kill the query
      ignore_user_abort(true);
      $MaxTime = 5; // seconds
      $Overtime = false;
      $StartTime = time();
      do
      {
          // Poll MySQL
        $links = $errors = $reject = array($link);
        $poll = mysqli_poll($links, $errors, $reject, 0, 500000);
         // Check if the connection is aborted and the query was killed
        if (connection_aborted()) {
          $link_new = mysqli_connect('localhost','user','pass','database');
          mysqli_kill($link_new, $thread_id);
          $kill = mysqli_kill($link_new, $thread_id);
          if ($kill)
          {
            die();
          }
        }
        $EndTime = time();
        // Check overtime, kill if detected overtime
        if ($EndTime - $StartTime > $MaxTime)
        {
          $link_new = mysqli_connect('localhost','user','pass','database');
          mysqli_kill($link_new, $thread_id);
          $Overtime = true;
          echo 'Error: Query took over '.$Overtime.'.';
        }
      } while (!$poll && $Overtime == false);
?>

down

ekalashnikov at gmail dot com ¶

7 years ago

This is how you can test and terminate slow query with polling.

<?php
// Slow SQL Query
      $SelectSql = 'SELECT * FROM SLOW_QUERY';
      $link = mysqli_connect('localhost','user','pass','database');
      mysqli_query($SelectSql, MYSQLI_ASYNC);
      $thread_id = mysqli_thread_id($link);
      // Ignore user abort so we can kill the query
      ignore_user_abort(true);
      $MaxTime = 5; // seconds
      $Overtime = false;
      $StartTime = time();
      do
      {
          // Poll MySQL
        $links = $errors = $reject = array($link);
        $poll = mysqli_poll($links, $errors, $reject, 0, 500000);
         // Check if the connection is aborted and the query was killed
        if (connection_aborted() && mysqli_kill($link, $thread_id)) {
            die();
        }
        $EndTime = time();
        // Check overtime, kill if detected overtime
        if ($EndTime - $StartTime > $MaxTime)
        {
          mysqli_kill($link, $thread_id);
          $Overtime = true;
          echo 'Error: Query took over '.$Overtime.'.';
        }
      } while (!$poll && $Overtime == false);
?>