pg_send_query()

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

发送异步查询

说明

pg_send_query(resource $connection,string $query): bool

pg_send_query(string $query): bool

pg_send_query()向$connection连接发送异步查询。和pg_query()不同，它可以向 PostgreSQL 发送多个查询并用pg_get_result()依次得到结果。当执行查询时脚本的执行不会被锁定。用pg_connection_busy()来检查连接连接是否为忙（即查询正在执行中）。调用pg_cancel_query()则有可能取消查询。

尽管用户可以一次发送多个查询，但用户不能通过正忙的连接发送多个查询。如果向正忙的连接发送了查询，则会等待上一条查询结束并丢弃所有结果。

Example #1 异步查询

<?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";
?>

上例输出如下：

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()，pg_cancel_query()，pg_get_result()和pg_connection_busy()。

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.

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);
}
?>

<?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();
?>

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

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.

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.