Предопределённые константы
Перечисленные ниже константы определены данным расширением и могут быть доступны только в том случае, если PHP был собран с поддержкой этого расширения или же в том случае, если данное расширение было подгружено во время выполнения.
SQL hint related
Пример #1 Using SQL hint constants
The query cache is controlled 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);
?>
Результат выполнения данных примеров:
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.
-
MYSQLND_QC_SERVER_ID_SWITCH(string) - This SQL hint should not be used in general. It is needed by PECL/mysqlnd_ms to group cache entries for one statement but originating from different physical connections. If the hint is used connection settings such as user, hostname and charset are not considered for generating a cache key of a query. Instead the given value and the query string are used as input to the hashing function that generates the key. PECL/mysqlnd_ms may, if instructed, cache results from MySQL Replication slaves. Because it can hold many connections to the slave the cache key shall not be formed from the user, hostname or other settings that may vary for the various slave connections. Instead, PECL/mysqlnd_ms provides an identifier which refers to the group of slave connections that shall be enabled to share cache entries no matter which physical slave connection was to generate the cache entry. Use of this feature outside of PECL/mysqlnd_ms is not recommended.
mysqlnd_qc_set_cache_condition() related
Пример #2 Example mysqlnd_qc_set_cache_condition() usage
The function mysqlnd_qc_set_cache_condition() allows setting conditions for automatic caching of statements which don't begin with the SQL hints necessary to manually enable caching.
<?php
/* Cache all accesses to tables with the name "new%" in schema/database "db_example" for 1 second */
if (!mysqlnd_qc_set_cache_condition(MYSQLND_QC_CONDITION_META_SCHEMA_PATTERN, "db_example.new%", 1)) {
die("Failed to set cache condition!");
}
$mysqli = new mysqli("host", "user", "password", "db_example", "port");
/* cached although no SQL hint given */
$mysqli->query("SELECT id, title FROM news");
$pdo_mysql = new PDO("mysql:host=host;dbname=db_example;port=port", "user", "password");
/* not cached: no SQL hint, no pattern match */
$pdo_mysql->query("SELECT id, title FROM latest_news");
/* cached: TTL 1 second, pattern match */
$pdo_mysql->query("SELECT id, title FROM news");
?>
-
MYSQLND_QC_CONDITION_META_SCHEMA_PATTERN(int) - Used as a parameter of mysqlnd_qc_set_cache_condition() to set conditions for schema based automatic caching.
Other
The plugin version number can be obtained using either
MYSQLND_QC_VERSION, which is the string representation
of the numerical version number, or MYSQLND_QC_VERSION_ID,
which is an integer such as 10000. Developers can calculate the version number
as follows.
| Version (part) | Example |
|---|---|
| Major*10000 | 1*10000 = 10000 |
| Minor*100 | 0*100 = 0 |
| Patch | 0 = 0 |
| MYSQLND_QC_VERSION_ID | 10000 |
-
MYSQLND_QC_VERSION(string) -
Plugin version string, for example,
1.0.0-prototype
.
-
MYSQLND_QC_VERSION_ID(int) - Plugin version number, for example, 10000.
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