pg_connection_busy()

(PHP 4 >= 4.2.0, PHP 5, PHP 7)

获知连接是否为忙

说明

pg_connection_busy(resource $connection): bool

pg_connection_busy()在此连接状态为忙的时候返回TRUE。如果连接状态为忙，说明前一个查询仍然在执行。如果调用pg_get_result()函数的话，则会被锁死。

Example #1 pg_connection_busy()例子

<?php
    $dbconn = pg_connect("dbname=publisher") or die("Could not connect");
    $bs = pg_connection_busy($dbconn);
    if ($bs) {
        echo 'connection is busy';
    }
    else {
       echo 'connection is not busy';
    }
?>

参见pg_connection_status()和pg_get_result()。

pg_connection_busy() returning true does not necessarily mean that there are results waiting for pg_get_result(); it also stays true for some time after a query that causes any sort of postgres error. (See http://bugs.php.net/bug.php?id=36469)

There doesn't seem to be any documented way of using this function here, and I'm sore most people trying this are going to default to using a busy loop if there is nothing else to do while waiting (in which case pg_get_result would be better, since it just blocks until a result is ready) or a sleep loop if trying to cancel the query after a certain time.
The C documentation for libPq reccomends using PQisBusy (the C equivalent of pg_connection_busy) by waiting on a socket instead, which lets you timeout if the state doesn't change after a certain period but immediately react if it changes. If you want to cancel after a timeout, you would have something like this :
<?php
class SomeKindOfTimeoutException extends Exception { }
class SomeKindOfSQLErrorException extends Exception { }
function query_with_timeout($conn, $query, $timeout_seconds) {
  assert(pg_get_result($conn) === false); // Ensure that nothing is running
  $socket = [pg_socket($conn)];
  $null = [];
  $dispatch_ok = pg_send_query($conn, $query);
  $still_running = pg_connection_busy($conn);
  while($still_running) {
    // https://www.postgresql.org/docs/current/libpq-async.html
    // "A typical application using these functions will have a main loop that uses select() or poll() to wait for all the conditions that it must respond to."
    // "One of the conditions will be input available from the server, which in terms of select() means readable data on the file descriptor identified by PQsocket."
    // PQisBusy is mapped to pg_connection_busy
    stream_select($socket, $null, $null, $timeout_seconds); // Will wait on that socket until that happens or the timeout is reached
    $still_running = pg_connection_busy($conn); // False on timeout, true if complete
    // You could keep polling like that, this just breaks and throws immediately on first loop
    if ($still_running) {
      $cancel_ok = pg_cancel_query($conn);
      throw new SomeKindOfTimeoutException("TIMEOUT");
    }
  }
  $res = pg_get_result($conn);
  try {
    $error_msg = pg_result_error($res);
    if ($error_msg) throw new SomeKindOfSQLErrorException($error_msg);
    return pg_fetch_all($res);
  } finally {
    pg_free_result($res);
  }
}
$conn_string = "host=localhost port=5433 dbname=postgres";
$db = pg_connect($conn_string);
query_with_timeout($db, "SELECT pg_sleep(10)", 3); // Will throw
?>