Previously entries which were accessed only 1 time weren't cached.
It has been appeared that some rarely executed heavy queries may read indexdb block twice
in a row instead of once. There is no need in caching such a block then.
This change should eliminate cache size spikes for indexdb/dataBlocks when such heavy queries are executed.
Expose -blockcache.missesBeforeCaching command-line flag, which can be used for fine-tuning
the number of cache misses needed before storing the block in the caching.
* lib/{storage,regexpcache}: replaces regexpCacheMap with LRU cache
It should decrease memory usage for regexp caching
with storing cacheEntry by pointer - golang map should be able to effectivly shrink it's size
original issue with this case - unexpected map grows and storage OOM
Apply suggestions from code review
Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>
Adds missing metrics for regexp cache and regexpPrefixes cache
* wip
* wip
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
