[TYPO3-dev] Testing TYPO3 caching vs.[FE][pageCacheToExternalFiles]

[Dmitry Dulepov]

Hi!

Martin Kutschker wrote:
>> EXPLAIN is only a guess. It is not authorative and depends on the
>> current state of the database, number of records, "ANALYZE" status, etc.
> 
> Huh? But you can only make indices for your data. EXPLAIN tells you
> something about the data and what Mysql thinks of it.

Indexes are build from data but you do them for the table ;)

EXPLAIN tells you what mysql _thinks_ he will do if he really executes
this query. Nothing more. Quotation from mysql manual:
--------
When you precede a SELECT statement with the keyword EXPLAIN, MySQL
displays information from the optimizer about the query execution
_plan_. That is, MySQL explains how it _would_ process the SELECT,
including information about how tables are joined and in which order.
--------

> Adding indices without checking EXPLAIN before and after making changes
> to indices is IMHO only wild guessing.

I agree. My point is that EXPLAIN is not to be trusted for 100% because
it depends on the existing database data and it is difficult to build
proper indexes unless there is real data in the database.

> PS: Don't forget that various chaches in Mysql and in the OS affect your
> tests! A rerun may show different results.

Yes... I did two days of tests with "ab"... Even simple indexes on
"delete" and "hidden" increase request rate. Though moving cache, stats
and other updating table to innodb increased it much more.

Dmitry.
-- 
"It is our choices, that show what we truly are,
far more than our abilities." (A.P.W.B.D.)