pg_send_query
(PHP 4 >= 4.2.0, PHP 5)
pg_send_query — Sends asynchronous query
Описание
pg_send_query() sends a query or queries asynchronously to the connection . Unlike pg_query(), it can send multiple queries at once to PostgreSQL and get the results one by one using pg_get_result().
Script execution is not blocked while the queries are executing. Use pg_connection_busy() to check if the connection is busy (i.e. the query is executing). Queries may be cancelled using pg_cancel_query().
Although the user can send multiple queries at once, multiple queries cannot be sent over a busy connection. If a query is sent while the connection is busy, it waits until the last query is finished and discards all its results.
Список параметров
- connection
-
PostgreSQL database connection resource.
- query
-
The SQL statement or statements to be executed.
Возвращаемые значения
Возвращает TRUE в случае успешного завершения или FALSE в случае возникновения ошибки.
Use pg_get_result() to determine the query result.
Примеры
Пример #1 pg_send_query() example
<?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 $rows2 records\n";
?>
Результат выполнения данного примера:
First call to pg_get_result(): Resource id #3 Resource id #3 has 3 records Second call to pg_get_result(): Resource id #4 Resource id #4 has 1 records
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Коментарии
If there is an error in one of your queries, the queries following it will not get executed, and there will *not* be an error message displayed. The only way I can think of to determine if an SQL error happened is to use pg_trace.
Example:
pg_send_query($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.
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
<?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();
?>
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($conn) ? 1 : 0);
}
?>
You will have to write a higher level of abstraction if you want a "send all queries now, receive them later" behaviour.
Regarding the failure to process them all now, then retrieve the results later, I found that all queries would return successfully if I added a further condition to your while loop in the "stack_query()" method.
By adding:
&& (pg_transaction_status($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);
}
?>
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.