[TYPO3-core] RFC: #11271: Use 2 level cache for BEgetRootLine

[Niels Fröhling]

Martin Kutschker wrote:

> And, when do these caches expire?

  Never. You'd need to kill the current way xml2array and force everybody (TV, 
flex, I don't want to know what else) to use appropriate tags.

  For a 2.5GB OLAP I implemented a query-result cache that measured runtime 
performance of queries and always put the 200 slowest into the cache, always 
dropping/reusing the then "fastest" query-result. Like LRU, just LSU (least 
slowest used) prunning. I basically was able to reduce it to a single INSERT 
UPDATE cache-update query, but that was mySQL-specific.

  You can make relative good worst-case estimates about it, and also add size 
heuristics to the prunning (but then you have two queries).
  Another advantage is that possibly very fast xml2array-calls (which possibly 
are faster than going through the cache) won't end up it the cache at all.

  Ciao
	Niels