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Michael Sun commented on SOLR-9764: ----------------------------------- Here are some single user test results for the amount of memory saved. Setup: Solr with a collection alias mapping to two collections, each with 4 days of data. Test: Restart Solr, run query with filter for last 7 days and collect memory histogram on one server afterwards. The filter hits both collections, with one match all and the other match partially. Result (extracted from histogram) |Patched|#BitDocSet instances|#MatchAllDocSet instances|# bytes for [J| |Y|2|2|10001833664| |N|4|0|10008701640| Validation: The difference of bytes for long[] is 6867976 bytes (6.9M). That's the total amount of memory saved by MatchAllDocSet for one query. Since there are 2 MatchedDocSet are used, each saves 3433988 (3.4M). The the other side, The core under study has 27M documents, which requires a long[] at the size of 3.4M (27M/8), which is aligned with the memory saved from histogram. > Design a memory efficient DocSet if a query returns all docs > ------------------------------------------------------------ > > Key: SOLR-9764 > URL: https://issues.apache.org/jira/browse/SOLR-9764 > Project: Solr > Issue Type: Improvement > Security Level: Public(Default Security Level. Issues are Public) > Reporter: Michael Sun > Attachments: SOLR-9764.patch, SOLR-9764.patch, SOLR-9764.patch, > SOLR_9764_no_cloneMe.patch > > > In some use cases, particularly use cases with time series data, using > collection alias and partitioning data into multiple small collections using > timestamp, a filter query can match all documents in a collection. Currently > BitDocSet is used which contains a large array of long integers with every > bits set to 1. After querying, the resulted DocSet saved in filter cache is > large and becomes one of the main memory consumers in these use cases. > For example. suppose a Solr setup has 14 collections for data in last 14 > days, each collection with one day of data. A filter query for last one week > data would result in at least six DocSet in filter cache which matches all > documents in six collections respectively. > This is to design a new DocSet that is memory efficient for such a use case. > The new DocSet removes the large array, reduces memory usage and GC pressure > without losing advantage of large filter cache. > In particular, for use cases when using time series data, collection alias > and partition data into multiple small collections using timestamp, the gain > can be large. > For further optimization, it may be helpful to design a DocSet with run > length encoding. Thanks [~mmokhtar] for suggestion. -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org