Hi I want to know the internal of solr filter cache, especially its memory usage.
I googled some pages: https://teaspoon-consulting.com/articles/solr-cache-tuning.html https://lucene.472066.n3.nabble.com/Solr-Filter-Cache-Size-td4120912.html (Erick Erickson's answer) All of them said its structure is: fq => a bitmap (total doc number bits), but I think it's not so simple, reason: Given total doc number is 1 billion, each filter cache entry will use nearly 1GB(1000000000/8 bit), it's too big and very easy to make solr OOM (I have a 1 billion doc cluster, looks it works well) And I also checked solr node, but cannot find the details (only saw using DocSets structure) So far, I guess: * degenerate into an doc id array/list when the bitmap is sparse * using some compressed bitmap, e.g. roaring bitmaps which one is correct? or another answer, thanks you very much!
