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Change default value for PDO_Mysql driver ATTR_EMULATE_PREPARES to off #108

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4 participants

Anthony Ferrara Stanislav Malyshev Josh Duff Juan Manuel Palacios
Anthony Ferrara

This pull request changes the default value for PDO_Mysql to disable prepared statement emulation. It can still be turned on with $pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, true).

This fixes issue


The PDO_MySQL driver defaults emulate_prepare to 1, which forces all prepared
queries to be emulated by the driver. This means that even though the client
library (mysqlnd or libmysql) may support prepared statements, PDO will never
really use them.

You can set the attribute PDO::ATTR_EMULATE_PREPARES to 0, and it prepares and
executes the prepared statements just fine using the native mode (rather than
emulation). However this is not documented at all on PHP.NET.

Since PDO_MYSQL will fallback to emulation automatically if the client library or
server are too old for prepared statements, I would suggest that the default
value for emulate_prepare should be set to 0 to allow for true prepared

Stanislav Malyshev

This would need some comments from PDO_mysql maintainers, I have no idea if this is the right thing to do.

Josh Duff

It does seem pretty messed up that a prepared statement interface would not actually use prepared statements by default.

Anthony Ferrara

@smalyshev it was discussed on the list and agreed that it was the right thing to do:

The only reason that I have not finished and resolved this request is that getting the tests to pass was turning out to be a nightmare due to their fragility.

Juan Manuel Palacios

If a non-PHP-developer (but heavy PHP/PDO/MySQL user) may chime in, I'd like to add a little weight in favor of this change since, if I'm not mistaken, not emulating prepared statements is a requirement to get INOUT/OUT MySQL variables in stored procedures working directly from PHP/PDO.

There are several bugs about the failure to use MySQL INOUT/OUT variables directly from PHP reported in both MySQL's & PHP's databases, but I'd like to draw your attention to the one I reported in the former because, as far as I know, it's the only one that's been verified as such by the MySQL team: Incidentally, PHP's failure to use server-side prepared statements was assessed in that bug report, and that's why I think my comment is relevant to this discussion. Hope I'm not mistaken.

PS: I also made a related comment here: a047ece#commitcomment-3884212

Stanislav Malyshev

@ircmaxell I've run it through Travis and there are a number of tests failing: compared to pre-patch one:
Looks like some queries that worked previously don't work anymore. So I'm not sure what to do about it.

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3  NEWS
@@ -50,6 +50,9 @@ PHP                                                                        NEWS
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   . Deprecated the /e modifier
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     ( (Nikita Popov)
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+  . Changed default value for ATTR_EMULATE_PREPARES to 0. (Anthony Ferrara)
53 56
 - pgsql
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   . Added pg_escape_literal() and pg_escape_identifier() (Yasuo)
55 58
3  ext/pdo_mysql/mysql_driver.c
@@ -587,7 +587,8 @@ static int pdo_mysql_handle_factory(pdo_dbh_t *dbh, zval *driver_options TSRMLS_
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 	H->max_buffer_size = 1024*1024;
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-	H->buffered = H->emulate_prepare = 1;
+	H->buffered = 1;
+	H->emulate_prepare = 0;
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 	/* handle MySQL options */
593 594
 	if (driver_options) {

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