PHP Unconference Europe 2015

Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

SQL hint related

The query cache is controled by SQL hints. SQL hints are used to enable and disable caching. SQL hints can be used to set the TTL of a query.

The SQL hints recognized by the query cache can be manually changed at compile time. This makes it possible to use mysqlnd_qc in environments in which the default SQL hints are already taken and interpreted by other systems. Therefore it is recommended to use the SQL hint string constants instead of manually adding the default SQL hints to the query string.

<?php
/* Use constants for maximum portability */
$query "/*" MYSQLND_QC_ENABLE_SWITCH "*/SELECT id FROM test";

/* Valid but less portable: default TTL */
$query "/*qc=on*/SELECT id FROM test";

/* Valid but less portable: per statement TTL */
$query "/*qc=on*//*qc_ttl=5*/SELECT id FROM test";

printf("MYSQLND_QC_ENABLE_SWITCH: %s\n"MYSQLND_QC_ENABLE_SWITCH);
printf("MYSQLND_QC_DISABLE_SWITCH: %s\n"MYSQLND_QC_DISABLE_SWITCH);
printf("MYSQLND_QC_TTL_SWITCH: %s\n"MYSQLND_QC_TTL_SWITCH);
?>

The above examples will output:

MYSQLND_QC_ENABLE_SWITCH: qc=on
MYSQLND_QC_DISABLE_SWITCH: qc=off
MYSQLND_QC_TTL_SWITCH: qc_ttl=

MYSQLND_QC_ENABLE_SWITCH ( string)
SQL hint used to enable caching of a query.
MYSQLND_QC_DISABLE_SWITCH ( string)
SQL hint used to disable caching of a query if mysqlnd_qc.cache_by_default = 1.
MYSQLND_QC_TTL_SWITCH ( string)
SQL hint used to set the TTL of a result set.

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