Hello, As a result of frequent java OOM exceptions, I try to investigate more into the solr jvm memory heap usage. Please correct me if I am mistaking, this is my understanding of usages for the heap (per replica on a solr instance): 1. Buffers for indexing - bounded by ramBufferSize 2. Solr caches 3. Segment merge 4. Miscellaneous- buffers for Tlogs, servlet overhead etc.
Particularly I'm concerned by Solr caches and segment merges. 1. How much memory consuming (bytes per doc) are FilterCaches (bitDocSet) and queryResultCaches (DocList)? I understand it is related to the skip spaces between doc id's that match (so it's not saved as a bitmap). But basically, is every id saved as a java int? 2. QueryResultMaxDocsCached - (for example = 100) means that any query resulting in more than 100 docs will not be cached (at all) in the queryResultCache? Or does it have to do with the documentCache? 3. DocumentCache - written on the wiki it should be greater than max_results*concurrent_queries. Max result is just the num of rows displayed (rows-start) param, right? Not the queryResultWindow. 4. LazyFieldLoading=true - when quering for id's only (fl=id) will this cache be used? (on the expense of eviction of docs that were already loaded with stored fields) 5. How large is the heap used by mergings? Assuming we have a merge of 10 segments of 500MB each (half inverted files - *.pos *.doc etc, half non inverted files - *.fdt, *.tvd), how much heap should be left unused for this merge? Thanks in advance, Manu
