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Finding cache candidatesA statement should be considered for caching if it is executed often and has a long run time. Cache candidates are found by creating a list of statements sorted by the product of the number of executions multiplied by the statements run time. The function mysqlnd_qc_get_query_trace_log returns a query log which help with the task. Collecting a query trace is a slow operation. Thus, it is disabled by default. The PHP configuration directive mysqlnd_qc.collect_query_trace is used to enable it. The functions trace contains one entry for every query issued before the function is called.
Example #1 Collecting a query trace mysqlnd_qc.enable_qc=1 mysqlnd_qc.collect_query_trace=1
<?php The above examples will output: array(2) { [0]=> array(8) { ["query"]=> string(26) "SELECT 1 AS _one FROM DUAL" ["origin"]=> string(102) "#0 qc.php(7): mysqli->query('SELECT 1 AS _on...') #1 {main}" ["run_time"]=> int(0) ["store_time"]=> int(25) ["eligible_for_caching"]=> bool(false) ["no_table"]=> bool(false) ["was_added"]=> bool(false) ["was_already_in_cache"]=> bool(false) } [1]=> array(8) { ["query"]=> string(26) "SELECT 1 AS _one FROM DUAL" ["origin"]=> string(102) "#0 qc.php(7): mysqli->query('SELECT 1 AS _on...') #1 {main}" ["run_time"]=> int(0) ["store_time"]=> int(8) ["eligible_for_caching"]=> bool(false) ["no_table"]=> bool(false) ["was_added"]=> bool(false) ["was_already_in_cache"]=> bool(false) } } Assorted information is given in the trace. Among them timings and the origin of the query call. The origin property holds a code backtrace to identify the source of the query. The depth of the backtrace can be limited with the PHP configuration directive mysqlnd_qc.query_trace_bt_depth. The default depth is 3.
Example #2 Setting the backtrace depth with the mysqlnd_qc.query_trace_bt_depth ini setting mysqlnd_qc.enable_qc=1 mysqlnd_qc.collect_query_trace=1
<?php The above examples will output something similar to: DROP TABLE IF EXISTS test: 0ms (1x) CREATE TABLE test(id INT): 0ms (1x) INSERT INTO test(id) VALUES (1), (2), (3): 0ms (1x) SELECT id FROM test WHERE id = 0: 25ms (1x) SELECT id FROM test WHERE id = 1: 10ms (1x) SELECT id FROM test WHERE id = 2: 9ms (1x) |