mysqlnd_qc_get_core_stats

(PECL mysqlnd_qc >= 1.0.0)

mysqlnd_qc_get_core_stats — Statistics collected by the core of the query cache

Description

array mysqlnd_qc_get_core_stats ( void )

Returns an array of statistics collected by the core of the cache plugin. The same data fields will be reported for any storage handler because the data is collected by the core.

The PHP configuration setting mysqlnd_qc.collect_statistics controls the collection of statistics. The collection of statistics is disabled by default for performance reasons. Disabling the collection of statistics will also disable the collection of time related statistics.

The PHP configuration setting mysqlnd_qc.collect_time_statistics controls the collection of time related statistics.

The scope of the core statistics is the PHP process. Depending on your deployment model a PHP process may handle one or multiple requests.

Statistics are aggregated for all cache entries and all storage handler. 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.

Parameters

This function has no parameters.

Return Values

Array of core statistics

Statistic Description Version
cache_hit Statement is considered cacheable and cached data has been reused. Statement is considered cacheable and a cache miss happened but the statement got cached by someone else while we process it and thus we can fetch the result from the refreshed cache. Since 1.0.0.
cache_miss Statement is considered cacheable...

  • ... and has been added to the cache

  • ... but the PHP configuration directive setting of mysqlnd_qc.cache_no_table = 1 has prevented caching.

  • ... but an unbuffered result set is requested.

  • ... but a buffered result set was empty.

Since 1.0.0.
cache_put Statement is considered cacheable and has been added to the cache. Take care when calculating derived statistics. Storage handler with a storage life time beyond process scope may report cache_put = 0 together with cache_hit > 0, if another process has filled the cache. You may want to use num_entries from mysqlnd_qc_get_cache_info() if the handler supports it ( default, APC). Since 1.0.0.
query_should_cache Statement is considered cacheable based on query string analysis. The statement may or may not be added to the cache. See also cache_put. Since 1.0.0.
query_should_not_cache Statement is considered not cacheable based on query string analysis. Since 1.0.0.
query_not_cached Statement is considered not cacheable or it is considered cachable but the storage handler has not returned a hash key for it. Since 1.0.0.
query_could_cache Statement is considered cacheable...

  • ... and statement has been run without errors

  • ... and meta data shows at least one column in the result set

The statement may or may not be in the cache already. It may or may not be added to the cache later on. 		Since 1.0.0.
query_found_in_cache Statement is considered cacheable and we have found it in the cache but we have not replayed the cached data yet and we have not send the result set to the client yet. This is not considered a cache hit because the client might not fetch the result or the cached data may be faulty. Since 1.0.0.
query_uncached_other Statement is considered cacheable and it may or may not be in the cache already but either replaying cached data has failed, no result set is available or some other error has happened.
query_uncached_no_table Statement has not been cached because the result set has at least one column which has no table name in its meta data. An example of such a query is SELECT SLEEP(1). To cache those statements you have to change default value of the PHP configuration directive mysqlnd_qc.cache_no_table and set mysqlnd_qc.cache_no_table = 1. Often, it is not desired to cache such statements. Since 1.0.0.
query_uncached_use_result Statement would have been cached if a buffered result set had been used. The situation is also consiered as a cache miss and cache_miss will be incremented as well. Since 1.0.0.
query_aggr_run_time_cache_hit Aggregated run time (ms) of all cached queries. Cached queries are those which have incremented cache_hit. Since 1.0.0.
query_aggr_run_time_cache_put Aggregated run time (ms) of all uncached queries that have been put into the cache. See also cache_put. Since 1.0.0.
query_aggr_run_time_total Aggregated run time (ms) of all uncached and cached queries that have been inspected and executed by the query cache. Since 1.0.0.
query_aggr_store_time_cache_hit Aggregated store time (ms) of all cached queries. Cached queries are those which have incremented cache_hit. Since 1.0.0.
query_aggr_store_time_cache_put Aggregated store time ( ms) of all uncached queries that have been put into the cache. See also cache_put. Since 1.0.0.
query_aggr_store_time_total Aggregated store time (ms) of all uncached and cached queries that have been inspected and executed by the query cache. Since 1.0.0.
receive_bytes_recorded Recorded incoming network traffic ( bytes) send from MySQL to PHP. The traffic may or may not have been added to the cache. The traffic is the total for all queries regardless if cached or not. Since 1.0.0.
receive_bytes_replayed Network traffic replayed during cache. This is the total amount of incoming traffic saved because of the usage of the query cache plugin. Since 1.0.0.
send_bytes_recorded Recorded outgoing network traffic ( bytes) send from MySQL to PHP. The traffic may or may not have been added to the cache. The traffic is the total for all queries regardless if cached or not. Since 1.0.0.
send_bytes_replayed Network traffic replayed during cache. This is the total amount of outgoing traffic saved because of the usage of the query cache plugin. Since 1.0.0.
slam_stale_refresh Number of cache misses which triggered serving stale data until the client causing the cache miss has refreshed the cache entry. Since 1.0.0.
slam_stale_hit Number of cache hits while a stale cache entry gets refreshed. Since 1.0.0.

Examples

Example #1 mysqlnd_qc_get_core_stats() example

<?php
/* Enable collection of statistics - default: disabled */
ini_set("mysqlnd_qc.collect_statistics", 1);

/* Enable collection of all timing related statistics -
default: enabled but overruled by mysqlnd_qc.collect_statistics = 0 */
ini_set("mysqlnd_qc.collect_time_statistics", 1);

/* Populate the cache, e.g. using mysqli */
$mysqli = new mysqli('host', 'user', 'password', 'schema');

/* Cache miss and cache put */
$mysqli->query("/*qc=on*/SELECT id FROM test");
/* Cache hit */
$mysqli->query("/*qc=on*/SELECT id FROM test");

/* Display core statstics */
var_dump(mysqlnd_qc_get_core_stats());
?>

The above examples will output:

array(26) {
  ["cache_hit"]=>
  string(1) "1"
  ["cache_miss"]=>
  string(1) "1"
  ["cache_put"]=>
  string(1) "1"
  ["query_should_cache"]=>
  string(1) "2"
  ["query_should_not_cache"]=>
  string(1) "0"
  ["query_not_cached"]=>
  string(1) "0"
  ["query_could_cache"]=>
  string(1) "2"
  ["query_found_in_cache"]=>
  string(1) "1"
  ["query_uncached_other"]=>
  string(1) "0"
  ["query_uncached_no_table"]=>
  string(1) "0"
  ["query_uncached_no_result"]=>
  string(1) "0"
  ["query_uncached_use_result"]=>
  string(1) "0"
  ["query_aggr_run_time_cache_hit"]=>
  string(1) "4"
  ["query_aggr_run_time_cache_put"]=>
  string(3) "395"
  ["query_aggr_run_time_total"]=>
  string(3) "399"
  ["query_aggr_store_time_cache_hit"]=>
  string(1) "2"
  ["query_aggr_store_time_cache_put"]=>
  string(1) "8"
  ["query_aggr_store_time_total"]=>
  string(2) "10"
  ["receive_bytes_recorded"]=>
  string(2) "65"
  ["receive_bytes_replayed"]=>
  string(2) "65"
  ["send_bytes_recorded"]=>
  string(2) "29"
  ["send_bytes_replayed"]=>
  string(2) "29"
  ["slam_stale_refresh"]=>
  string(1) "0"
  ["slam_stale_hit"]=>
  string(1) "0"
  ["request_counter"]=>
  int(1)
  ["process_hash"]=>
  int(3547549858)
}

See Also