mysqlnd_qc_get_cache_info

Returns information on the current handler, the number of cache entries and cache entries, if available

&reftitle.description; `array` `mysqlnd_qc_get_cache_info`

&reftitle.parameters; &no.function.parameters;
&reftitle.returnvalues;

Returns information on the current handler, the number of cache entries and cache entries, if available. If and what data will be returned for the cache entries is subject to the active storage handler. Storage handler are free to return any data. Storage handler are recommended to return at least the data provided by the default handler, if technically possible.

The scope of the information is the PHP process. Depending on the PHP deployment model a process may serve one or more web requests.

Values are aggregated for all cache activities on a per storage handler basis. It is not possible to tell how much queries originating from `mysqli`, `PDO_MySQL` or `mysql`.API calls have contributed to the aggregated data values. Use `mysqlnd_qc_get_core_stats` to get timing data aggregated for all storage handlers.

Array of cache information

`handler` `string`

- The active storage handler.

  All storage handler. Since 1.0.0.

`handler_version` `string`

- The version of the active storage handler.

  All storage handler. Since 1.0.0.

`num_entries` `int`

- The number of cache entries. The value depends on the storage handler in use.

  The default, APC and SQLite storage handler provide the actual number of cache entries.

  The MEMCACHE storage handler always returns `0`. MEMCACHE does not support counting the number of cache entries.

  If a user defined handler is used, the number of entries of the `data` property is reported.

  Since 1.0.0.

`data` `array`

- The version of the active storage handler.

  Additional storage handler dependent data on the cache entries. Storage handler are requested to provide similar and comparable information. A user defined storage handler is free to return any data.

  Since 1.0.0.

  The following information is provided by the default storage handler for the `data` property.

  The `data` property holds a hash. The hash is indexed by the internal cache entry identifier of the storage handler. The cache entry identifier is human-readable and contains the query string leading to the cache entry. Please, see also the example below. The following data is given for every cache entry.

  `statistics` `array`

- Statistics of the cache entry.

  Since 1.0.0.

  Property | Description | Version
  `rows` | Number of rows of the cached result set. | Since 1.0.0.
  `stored_size` | The size of the cached result set in bytes. This is the size of the payload. The value is not suited for calculating the total memory consumption of all cache entries including the administrative overhead of the cache entries. | Since 1.0.0.
  `cache_hits` | How often the cached entry has been returned. | Since 1.0.0.
  `run_time` | Run time of the statement to which the cache entry belongs. This is the run time of the uncached statement. It is the time between sending the statement to MySQL receiving a reply from MySQL. Run time saved by using the query cache plugin can be calculated like this: `cache_hits * ((run_time - avg_run_time) + (store_time - avg_store_time))`. | Since 1.0.0.
  `store_time` | Store time of the statements result set to which the cache entry belongs. This is the time it took to fetch and store the results of the uncached statement. | Since 1.0.0.
  `min_run_time` | Minimum run time of the cached statement. How long it took to find the statement in the cache. | Since 1.0.0.
  `min_store_time` | Minimum store time of the cached statement. The time taken for fetching the cached result set from the storage medium and decoding | Since 1.0.0.
  `avg_run_time` | Average run time of the cached statement. | Since 1.0.0.
  `avg_store_time` | Average store time of the cached statement. | Since 1.0.0.
  `max_run_time` | Average run time of the cached statement. | Since 1.0.0.
  `max_store_time` | Average store time of the cached statement. | Since 1.0.0.
  `valid_until` | Timestamp when the cache entry expires. | Since 1.1.0.

`metadata` `array`

- Metadata of the cache entry. This is the metadata provided by MySQL together with the result set of the statement in question. Different versions of the MySQL server may return different metadata. Unlike with some of the PHP MySQL extensions no attempt is made to hide MySQL server version dependencies and version details from the caller. Please, refer to the MySQL C API documentation that belongs to the MySQL server in use for further details.

  The metadata list contains one entry for every column.

  Since 1.0.0.

  Property | Description | Version
  `name` | The field name. Depending on the MySQL version this may be the fields alias name. | Since 1.0.0.
  `org_name` | The field name. | Since 1.0.0.
  `table` | The table name. If an alias name was used for the table, this usually holds the alias name. | Since 1.0.0.
  `org_table` | The table name. | Since 1.0.0.
  `db` | The database/schema name. | Since 1.0.0.
  `max_length` | The maximum width of the field. Details may vary by MySQL server version. | Since 1.0.0.
  `length` | The width of the field. Details may vary by MySQL server version. | Since 1.0.0.
  `type` | The data type of the field. Details may vary by the MySQL server in use. This is the MySQL C API type constants value. It is recommended to use type constants provided by the `mysqli` extension to test for its meaning. You should not test for certain type values by comparing with certain numbers. | Since 1.0.0.

The APC storage handler returns the same information for the `data` property but no `metadata`. The `metadata` of a cache entry is set to `NULL`.

The MEMCACHE storage handler does not fill the `data` property. Statistics are not available on a per cache entry basis with the MEMCACHE storage handler.

A user defined storage handler is free to provide any data.

&reftitle.examples;

### `mysqlnd_qc_get_cache_info` example

The example shows the output from the built-in default storage handler. Other storage handler may report different data.

    <?php
    /* Populate the cache, e.g. using mysqli */
    $mysqli = new mysqli("host", "user", "password", "schema");
    $mysqli->query("/*" . MYSQLND_QC_ENABLE_SWITCH . "*/SELECT id FROM test");

    /* Display cache information */
    var_dump(mysqlnd_qc_get_cache_info());
    ?>

&examples.outputs;

    array(4) {
     ["num_entries"]=>
     int(1)
     ["handler"]=>
     string(7) "default"
     ["handler_version"]=>
     string(5) "1.0.0"
     ["data"]=>
     array(1) {
       ["Localhost via UNIX socket 3306 user schema|/*qc=on*/SELECT id FROM test"]=>
       array(2) {
         ["statistics"]=>
         array(11) {
           ["rows"]=>
           int(6)
           ["stored_size"]=>
           int(101)
           ["cache_hits"]=>
           int(0)
           ["run_time"]=>
           int(471)
           ["store_time"]=>
           int(27)
           ["min_run_time"]=>
           int(0)
           ["max_run_time"]=>
           int(0)
           ["min_store_time"]=>
           int(0)
           ["max_store_time"]=>
           int(0)
           ["avg_run_time"]=>
           int(0)
           ["avg_store_time"]=>
           int(0)
         }
         ["metadata"]=>
         array(1) {
           [0]=>
           array(8) {
             ["name"]=>
             string(2) "id"
             ["orig_name"]=>
             string(2) "id"
             ["table"]=>
             string(4) "test"
             ["orig_table"]=>
             string(4) "test"
             ["db"]=>
             string(4) "schema"
             ["max_length"]=>
             int(1)
             ["length"]=>
             int(11)
             ["type"]=>
             int(3)
           }
         }
       }
     }
    }

&reftitle.seealso;

- `mysqlnd_qc_get_core_stats`