PHP 5.5.16 is released

mysql_unbuffered_query

(PHP 4 >= 4.0.6, PHP 5)

mysql_unbuffered_querySend an SQL query to MySQL without fetching and buffering the result rows.

Avertizare

Această extensie este dezaprobată începând cu PHP 5.5.0 și va fi eliminată în viitor. În locul ei trebuie utilizate extensiile MySQLi sau PDO_MySQL. Vedeți de asemenea ghidul MySQL: selectarea unei API și FAQ asociat pentru mai multe informații. Alternative ale acestei funcții includ:

Descrierea

resource mysql_unbuffered_query ( string $query [, resource $link_identifier = NULL ] )

mysql_unbuffered_query() sends the SQL query query to MySQL without automatically fetching and buffering the result rows as mysql_query() does. This saves a considerable amount of memory with SQL queries that produce large result sets, and you can start working on the result set immediately after the first row has been retrieved as you don't have to wait until the complete SQL query has been performed. To use mysql_unbuffered_query() while multiple database connections are open, you must specify the optional parameter link_identifier to identify which connection you want to use.

Parametri

query

The SQL query to execute.

Data inside the query should be properly escaped.

link_identifier

Conexiunea MySQL. Dacă identificatorul legăturii nu este specificat, se presupune că este ultima legătură deschisă cu ajutorul mysql_connect(). Dacă nu este găsită nici o astfel de legătură, se va încerca crearea uneia prin apelul mysql_connect () fără argumente. În caz că nici o conexiune nu este găsită sau stabilită, se va genera o eroare de nivelul E_WARNING.

Valorile întoarse

For SELECT, SHOW, DESCRIBE or EXPLAIN statements, mysql_unbuffered_query() returns a resource on success, or FALSE on error.

For other type of SQL statements, UPDATE, DELETE, DROP, etc, mysql_unbuffered_query() returns TRUE on success or FALSE on error.

Note

Notă:

The benefits of mysql_unbuffered_query() come at a cost: you cannot use mysql_num_rows() and mysql_data_seek() on a result set returned from mysql_unbuffered_query(), until all rows are fetched. You also have to fetch all result rows from an unbuffered SQL query before you can send a new SQL query to MySQL, using the same link_identifier.

Vedeți de asemenea

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User Contributed Notes 5 notes

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2
crazyone at crazycoders dot net
6 years ago
You are NOT required to read all rows from the resultset when using unbuffered query, you may opt out at any time and use mysql_free_result. Imagine looking at 1 million row when the first 50 suffice? Just free the result and you are good to go again.
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0
post at jfl dot dk
10 years ago
If using optimized MyISAM tables I guess there is a big advantage with this function as it is possible to do selects and inserts on the same time as long as no rows in the table gets updated.
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0
frappyjohn at dos2linux dot org
11 years ago
Don't let the two hands confuse you, these are both advantages (they should really be on the same hand):

On the one hand, this saves a considerable amount of memory with SQL queries that produce large result sets.

On the other hand, you can start working on the result set immediately ...
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0
david at php dot net
12 years ago
You are absolutely required to retrieve all rows in the result set (option 'a' in the first comment). If you fail to do so, PHP will do so for you, and will emit a NOTICE warning you of the fact. From the MySQL API, "Furthermore, you must retrieve all the rows even if you determine in mid-retrieval that you've found the information you were looking for. ".

Also note that if you are using this function, you should be quick about processing the result set, or you will tie up the MySQL server (other threads will be unable to write to the tables you are reading from).

If you want to be able to 'abort' mid result-set or if you want to do lengthy processing on the results, you are misunderstanding the purpose of this function.

Also note that UPDATE queries etc return no result set, so this function is only useful for SELECT etc.
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-3
shaner at accretivetg dot com
11 years ago
Regarding bailing on a really large result, while doing an unbuffered query, there _is_ a way to do this: kill the thread and exit your processing loop.  This, of course, requires having a separate database link.  Something like below does the trick:

<?php
// a db link for queries
$lh  = mysql_connect( 'server', 'uname', 'pword' );
// and a controller link
$clh = mysql_connect( 'server', 'uname', 'pword', true );

if (
mysql_select_db ( 'big_database', $lh ) )
{
 
$began  time();
 
$tout   = 60 * 5; // five minute limit
 
$qry    = "SELECT * FROM my_bigass_table";
 
$rh     = mysql_unbuffered_query( $qry, $lh );
 
$thread = mysql_thread_id ( $lh );
  while (
$res = mysql_fetch_row( $rh ) )
  {
   
/* do what you need to do
     * ...
     * ...
     */
   
if ( ( time() - $began ) > $tout )
    {
     
// this is taking too long
     
mysql_query( "KILL $thread", $clh );
      break;
    }
  }
}
?>
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