mysqli::poll

mysqli_poll

(PHP 5 >= 5.3.0)

mysqli::poll -- mysqli_pollPoll connections

Description

Object oriented style

public static int mysqli::poll ( array &$read , array &$error , array &$reject , int $sec [, int $usec ] )

Procedural style

int mysqli_poll ( array &$read , array &$error , array &$reject , int $sec [, int $usec ] )

Poll connections. Available only with mysqlnd. The method can be used as static.

Parameters

read

List of connections to check for outstanding results that can be read.

error

List of connections on which an error occured, for example, query failure or lost connection.

reject

List of connections rejected because no asynchronous query has been run on for which the function could poll results.

sec

Number of seconds to wait, must be non-negative.

usec

Number of microseconds to wait, must be non-negative.

Return Values

Returns number of ready connections upon success, FALSE otherwise.

Examples

Example #1 A mysqli_poll() example

<?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$errors$reject1)) {
        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));
?>

The above example will output:

Array
(
    [0] => test
)

See Also

Коментарии

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.
2014-07-21 22:56:26
http://php5.kiev.ua/manual/ru/mysqli.poll.html
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 ?
2016-01-21 02:24:15
http://php5.kiev.ua/manual/ru/mysqli.poll.html
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($SelectSqlMYSQLI_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$errors$reject0500000);
         
// 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);
?>
2017-10-04 00:54:00
http://php5.kiev.ua/manual/ru/mysqli.poll.html
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($SelectSqlMYSQLI_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$errors$reject0500000);
         
// 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);
?>
2017-10-04 22:07:57
http://php5.kiev.ua/manual/ru/mysqli.poll.html
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.
2022-12-14 16:23:55
http://php5.kiev.ua/manual/ru/mysqli.poll.html

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