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

[Martin Schoenbeck]

Hi Dmitry,

Dmitry Dulepov schrieb:

> 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.
> --------

That means, mysql will follow the explained plan as far as the plan works.
At the point where it doesn't work any longer mysql knows, all data to
deliver (may be none) are put together. It won't take another plan than
that explained as long as the data aren't changed.

> Yes... I did two days of tests with "ab"... Even simple indexes on
> "delete" and "hidden" increase request rate.

Depending on the requests and the scattering of them any index may help.
But even there are really statements selecting solely for 'deleted' or
'hidden', which I don't believe, it would be better to create a combined
index, which works for statements selecting yet another field, too.

To do that right, you really have to analyze the select statements causing
performance penalties.

Martin
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