FST should allow controlling how hard builder tries to share suffixes ---------------------------------------------------------------------
Key: LUCENE-3289 URL: https://issues.apache.org/jira/browse/LUCENE-3289 Project: Lucene - Java Issue Type: Improvement Reporter: Michael McCandless Assignee: Michael McCandless Fix For: 3.4, 4.0 Today we have a boolean option to the FST builder telling it whether it should share suffixes. If you turn this off, building is much faster, uses much less RAM, and the resulting FST is a prefix trie. But, the FST is larger than it needs to be. When it's on, the builder maintains a node hash holding every node seen so far in the FST -- this uses up RAM and slows things down. On a dataset that Elmer (see java-user thread "Autocompletion on large index" on Jul 6 2011) provided (thank you!), which is 1.32 M titles avg 67.3 chars per title, building with suffix sharing on took 22.5 seconds, required 1.25 GB heap, and produced 91.6 MB FST. With suffix sharing off, it was 8.2 seconds, 450 MB heap and 129 MB FST. I think we should allow this boolean to be shade-of-gray instead: usually, how well suffixes can share is a function of how far they are from the end of the string, so, by adding a tunable N to only share when suffix length < N, we can let caller make reasonable tradeoffs. -- This message is automatically generated by JIRA. For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org