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https://issues.apache.org/jira/browse/SOLR-16546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17636235#comment-17636235
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Shawn Heisey commented on SOLR-16546:
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{quote}Hopefully CaffeineCache's algorithm will easily identify this as an
eviction candidate if it's not re-used.
{quote}
I wonder what happens if say your cache size is set to 100 and you get 5000
different queries with a facet. Is the cache going to choose to evict the
facet-related "q parameter" entries with low hitcounts, leaving the
filter-related entries with many hits, or will it eventually evict ALL the
entries including the filters? [~ben.manes] has already indicated on my cache
dumper issue that Caffeine does not track an explicit per-entry hitcount, it
figures out which entry to evict through some fuzzy logic. Hopefully it will
always choose to evict the facet-related entries.
> Faceting puts an entry for each q into the filterCache
> -------------------------------------------------------
>
> Key: SOLR-16546
> URL: https://issues.apache.org/jira/browse/SOLR-16546
> Project: Solr
> Issue Type: Improvement
> Security Level: Public(Default Security Level. Issues are Public)
> Components: faceting
> Affects Versions: 9.0
> Reporter: Andy Lester
> Priority: Minor
>
> I noticed that I was getting far more entries in the filterCache than I was
> expecting. All my app's FQs are driven by the app itself. There are only a
> couple dozen FQs possible in our queries, but I'd be getting ~10K cache
> ejections every hour. That didn't make any sense.
> So I investigated and discovered that making a query using facets adds an
> entry to the filterCache. Here's my demonstration.
> The script show-results is this:
> {{curl -s "$URL/twit/admin/cache" | jq -S .queries
> curl -s "$URL/admin/metrics" | jq
> '.metrics."solr.core.twit"."CACHE.searcher.filterCache".inserts'
> }}
> The /admin/cache handler is Shawn Heisey's cache dumper he's working on in
> ticket SOLR-15859.
> {{# Freshly started Solr. No cache entries.
> $ ./show-results
> {}
> 0
> # Query on "alpha" with facets on.
> $ curl -s $URL/twit/select?q=title:alpha&rows=0&facet=on&facet.field=grouping
> # Now there is a filter cache entry.
> $ ./show-results
> {
> "title:alpha": 0
> }
> 1
> # Query on "beta" with facets on. "beta" shows up in the cache.
> $ curl -s $URL/twit/select?q=title:beta&rows=0&facet=on&facet.field=grouping
> $ ./show-results
> {
> "title:alpha": 0,
> "title:beta": 0
> }
> 2
> # Now query on "gamma" with facets OFF.
> $ curl -s $URL/twit/select?q=title:gamma&rows=0&facet=off&facet.field=grouping
> # The "gamma" does not show up in the filter cache.
> $ ./show-results
> {
> "title:alpha": 0,
> "title:beta": 0
> }
> 2
> # Now do same query on "gamma" with facets ON.
> $ curl -s $URL/twit/select?q=title:gamma&rows=0&facet=on&facet.field=grouping
> # The "gamma" shows up.
> $ ./show-results
> {
> "title:alpha": 0,
> "title:beta": 0,
> "title:gamma": 0
> }
> 3
> }}
> Is this correct behavior? Do I need to adjust my filterCache to allow for
> this?
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