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second execution of the query is faster even the query cache is disabled
Posted by: David raj
Date: November 08, 2013 01:21AM

Hi,
Query caching is disabled in my server and when I ran the query second time the execution is much much faster than the first time.

But if I change the value what I gave in my query again the query is taking more time but only for the first execution.

MySQL version: 5.5.30
And all my tables are in MyISAM.

I am pasting the profiler output. Can anyone have any idea about this behaviour?

You can see the difference in "Copying to tmp table"

First time of execution:
+-------------------------+------------+-----------------------+---------------+-------------+
| Status | Duration | Source_function | Source_file | Source_line |
+-------------------------+------------+-----------------------+---------------+-------------+
| starting | 0.009494 | NULL | NULL | NULL |
| checking permissions | 0.000005 | check_access | sql_parse.cc | 4751 |
| checking permissions | 0.000001 | check_access | sql_parse.cc | 4751 |
| checking permissions | 0.000002 | check_access | sql_parse.cc | 4751 |
| checking permissions | 0.000004 | check_access | sql_parse.cc | 4751 |
| Opening tables | 0.028032 | open_tables | sql_base.cc | 4831 |
| System lock | 0.000021 | mysql_lock_tables | lock.cc | 299 |
| init | 0.013522 | mysql_select | sql_select.cc | 2579 |
| optimizing | 0.000341 | optimize | sql_select.cc | 865 |
| statistics | 0.315518 | optimize | sql_select.cc | 1056 |
| preparing | 0.000049 | optimize | sql_select.cc | 1078 |
| FULLTEXT initialization | 0.000276 | init_ftfuncs | sql_base.cc | 9032 |
| Creating tmp table | 0.000037 | optimize | sql_select.cc | 1601 |
| executing | 0.000004 | exec | sql_select.cc | 1836 |
| Copying to tmp table | 138.033982 | exec | sql_select.cc | 1983 |
| Sorting result | 0.000073 | exec | sql_select.cc | 2267 |
| Sending data | 0.005455 | exec | sql_select.cc | 2380 |
| end | 0.001783 | mysql_select | sql_select.cc | 2615 |
| removing tmp table | 0.000008 | free_tmp_table | sql_select.cc | 11219 |
| end | 0.000003 | free_tmp_table | sql_select.cc | 11244 |
| query end | 0.000003 | mysql_execute_command | sql_parse.cc | 4440 |
| closing tables | 0.000009 | mysql_execute_command | sql_parse.cc | 4492 |
| freeing items | 0.000029 | mysql_parse | sql_parse.cc | 5640 |
| logging slow query | 0.000002 | log_slow_statement | sql_parse.cc | 1461 |
| logging slow query | 0.016585 | log_slow_statement | sql_parse.cc | 1470 |
| cleaning up | 0.000005 | dispatch_command | sql_parse.cc | 1417 |
+-------------------------+------------+-----------------------+---------------+-------------+

Second time of execution:
+-------------------------+----------+-----------------------+---------------+-------------+
| Status | Duration | Source_function | Source_file | Source_line |
+-------------------------+----------+-----------------------+---------------+-------------+
| starting | 0.000175 | NULL | NULL | NULL |
| checking permissions | 0.000004 | check_access | sql_parse.cc | 4751 |
| checking permissions | 0.000001 | check_access | sql_parse.cc | 4751 |
| checking permissions | 0.000002 | check_access | sql_parse.cc | 4751 |
| checking permissions | 0.000004 | check_access | sql_parse.cc | 4751 |
| Opening tables | 0.000030 | open_tables | sql_base.cc | 4831 |
| System lock | 0.000014 | mysql_lock_tables | lock.cc | 299 |
| init | 0.000081 | mysql_select | sql_select.cc | 2579 |
| optimizing | 0.000022 | optimize | sql_select.cc | 865 |
| statistics | 0.000859 | optimize | sql_select.cc | 1056 |
| preparing | 0.000042 | optimize | sql_select.cc | 1078 |
| FULLTEXT initialization | 0.000011 | init_ftfuncs | sql_base.cc | 9032 |
| Creating tmp table | 0.000023 | optimize | sql_select.cc | 1601 |
| executing | 0.000002 | exec | sql_select.cc | 1836 |
| Copying to tmp table | 4.428463 | exec | sql_select.cc | 1983 |
| Sorting result | 0.000068 | exec | sql_select.cc | 2267 |
| Sending data | 0.000024 | exec | sql_select.cc | 2380 |
| end | 0.000003 | mysql_select | sql_select.cc | 2615 |
| removing tmp table | 0.000008 | free_tmp_table | sql_select.cc | 11219 |
| end | 0.000003 | free_tmp_table | sql_select.cc | 11244 |
| query end | 0.000004 | mysql_execute_command | sql_parse.cc | 4440 |
| closing tables | 0.000013 | mysql_execute_command | sql_parse.cc | 4492 |
| freeing items | 0.000026 | mysql_parse | sql_parse.cc | 5640 |
| logging slow query | 0.000002 | log_slow_statement | sql_parse.cc | 1461 |
| cleaning up | 0.000003 | dispatch_command | sql_parse.cc | 1417 |
+-------------------------+----------+-----------------------+---------------+-------------+

Regards,
David

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second execution of the query is faster even the query cache is disabled
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