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pg_send_query

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

pg_send_query — 发送异步查询

说明

pg_send_query(PgSql\Connection $connection, string $query): int|bool

pg_send_query() 向 connection 发送异步查询。跟 pg_query() 不同，它可以一次性向 PostgreSQL 发送多个查询并用 pg_get_result() 依次得到结果。

当执行查询时不会阻塞脚本执行。用 pg_connection_busy() 来检查连接是否繁忙（即查询正在执行中）。可以使用 pg_cancel_query() 取消查询。

尽管用户可以同时发送多个查询，但连接繁忙的情况下无法发送多个查询。如果连接繁忙时发送了查询，则会等待上一个查询结束，并且丢弃上个查询的所有结果。

参数

connection

PgSql\Connection 实例。

query

要执行的 SQL 语句或者语句集合。

应该正确转义查询中的数据。

返回值

成功时返回 true，失败时返回 false 或 0。使用 pg_get_result() 来确定查询结果。

更新日志

版本	说明
8.1.0	现在 `connection` 参数接受 PgSql\Connection 实例，之前接受 resource。

示例

示例 #1 pg_send_query() 示例

<?php
  $dbconn = pg_connect("dbname=publisher") or die("Could not connect");

  if (!pg_connection_busy($dbconn)) {
      pg_send_query($dbconn, "select * from authors; select count(*) from authors;");
  }
  
  $res1 = pg_get_result($dbconn);
  echo "First call to pg_get_result(): $res1\n";
  $rows1 = pg_num_rows($res1);
  echo "$res1 has $rows1 records\n\n";
  
  $res2 = pg_get_result($dbconn);
  echo "Second call to pg_get_result(): $res2\n";
  $rows2 = pg_num_rows($res2);
  echo "$res2 has $rows2 records\n";
?>

以上示例会输出：

 
First call to pg_get_result(): Resource id #3
Resource id #3 has 3 records

Second call to pg_get_result(): Resource id #4
Resource id #4 has 1 records

参见

pg_query() - 执行查询
pg_cancel_query() - 取消异步查询
pg_get_result() - 取得异步查询结果
pg_connection_busy() - 获取连接是否繁忙

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User Contributed Notes 6 notes

down

rw burgholzer is name at deq dot virginia dot gov ¶

14 years ago

Regarding the failure to process them all now, then retrieve the results later, I found that all queries would return successfully if I added a further condition to your while loop in the "stack_query()" method.

By adding:
&& (pg_transaction_status($conn) === PGSQL_TRANSACTION_IDLE ) )

Every query executed with no errors.

<?php
$conn = pg_connect("dbname=dbname host=localhost user=psql ");
if ($conn === FALSE)
  exit("Can't connect to db");

$q = array();
// send some queries
foreach (range(0, 50) as $i)
  stack_query($q, $conn, "SELECT 'query $i' AS str;");
// receive them
while (true)
  {
    $left = stack_query($q, $conn);
    echo "$left left... ";
    $result = pg_get_result($conn);
    if ($left == 0 && $result === FALSE)
      break;
    $row = pg_fetch_assoc($result);
    // depending on race conditions, you wont get all your original queries here.
    echo "got $row[str]\n";
  }

function stack_query(&$queries, $conn, $sql = FALSE)
{
  if ($sql !== FALSE)
    $queries[] = $sql;
  while (count($queries) && !pg_connection_busy($conn)  && (pg_transaction_status($conn) === PGSQL_TRANSACTION_IDLE ) )
    pg_send_query($conn, array_shift($queries));
  return count($queries) + (pg_connection_busy($conn) ? 1 : 0);
}
?>

down

Mikewithme at yahoo dot com ¶

20 years ago

Due to a bug, OLD API does not available with PHP 4.2.0 and 4.2.1.

PHP 4.2.2 will support OLD API again and will be kept long enough.

New API will be available PHP 4.2.0 to later versions. 
yohgaki at php dot net
19-Jun-2002 04:00 
Due to a bug, PHP 4.2.0 and 4.2.1 does not support pg_lo_import() old API. It's fixed in PHP 4.2.2.

BTW, new API will be always available from PHP 4.2.0 to later versions. Older API will be kept long enough, also. 
ceco at noxis dot net
15-May-2002 09:08 
it works for me (php-4.2.1)

not like this

int pg_lo_import ( string pathname [, resource connection])

but 
int pg_lo_import ( resource connection, string pathname )

don't know the reason

down

-1

moodsey211 at gmail dot com ¶

12 years ago

pg_send_query would not stop your script from executing but it would stop the script from exiting. 



Example:



<?php

$con = pg_connect('dbname=payroll');

pg_send_query('SELECT process_payroll()'); // Where process_payroll is a super long process

?>



You would still need to wait for the query to finish before the any display would be sent to the browser. And surprisingly, unlike pg_query this script would not generate the Maximum execution time error.

down

-1

Ron Howard ¶

20 years ago

If there is an error in one of your queries, the queries following it will not get executed, and there will *not* be an error message displayed. The only way I can think of to determine if an SQL error happened is to use pg_trace.

Example:

pg_send_query($connection,
    "SELECT id FROM users;
    SELECT * FROM customers;
     [INVALID-SQL-STATEMENT];
    SELECT name FROM countries;");

while ($result = pg_get_result($connection))
    $results[] = $result;

The $results array will only have two items in it.

down

-2

Likeyouover others at hotmail dot com ¶

20 years ago

<?php
// --------- OPEN CONN ---

   $conn = pg_connect("host='127.0.0.1' dbname='test' user='usertest' password='passtest'");

// --------- OPEN FILE ---

   $fp = fopen('logo.gif', "r");
   $buffer = fread($fp, filesize('logo.gif'));
   fclose($fp);

// --------- CREATE - INSERT OID ---

   pg_exec($conn, "begin");

   $oid = pg_locreate($conn);

   $rs = pg_exec($conn,"INSERT INTO test(tipo, images) VALUES('A1', $oid);");
   $handle = pg_loopen ($conn, $oid, "w");

   pg_lowrite ($handle, $buffer);
   pg_loclose ($handle);

   pg_exec($conn, "commit");

// --------- OPEN - INSERT OID ---

   $rs = pg_exec($conn, "SELECT images FROM test WHERE tipo = 'A1';");
   $row = pg_fetch_row($rs, 0);

   pg_exec($conn, "begin");
   $loid = pg_loopen($conn, $row[0], "r");

   header("Content-type: image/gif");

   pg_loreadall($loid);
   pg_loclose($loid);

   pg_exec ($conn, "commit");

// --------- UNLINK OID ---

   pg_exec($conn, "begin");

   $loid = $row[0];
   pg_lounlink($conn, $loid);

   pg_exec ($conn, "commit");

// --------- DELETE OID ---

   pg_exec($conn, "DELETE FROM test WHERE tipo = 'A1';");

// --------- CLOSE CONN ---

   pg_close();
?>

down

-5

vincentdephily ¶

17 years ago

Note that if you send a query without calling pg_get_result() for the previous one (supposing it has finished and the connection is not busy), the previous query will get discarded.

See for yourself (tested on php4.4.0, postgres8.0.4, Linux/FreeBSD) :
<?
$conn = pg_connect("dbname=template1 host=localhost user=pgsql");
if ($conn === FALSE)
  exit("Can't connect to db");

$q = array();
// send some queries
foreach (range(0, 500) as $i)
  stack_query($q, $conn, "SELECT 'query $i' AS str;");
// receive them
while (true)
  {
    $left = stack_query($q, $conn);
    echo "$left left... ";
    $result = pg_get_result($conn);
    if ($left == 0 && $result === FALSE)
      break;
    $row = pg_fetch_assoc($result);
    // depending on race conditions, you wont get all your original queries here.
    echo "got $row[str]\n";
  }

function stack_query(&$queries, $conn, $sql = FALSE)
{
  if ($sql !== FALSE)
    $queries[] = $sql;
  while (count($queries) && !pg_connection_busy($conn))
    pg_send_query($conn, array_shift($queries));
  return count($queries) + (pg_connection_busy($conn) ? 1 : 0);
}
?>

You will have to write a higher level of abstraction if you want a "send all queries now, receive them later" behaviour.

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