Hi, The merge policy has to tell IndexWriter, which segments it needs to merge. For upgrading indexes it just only returns the segments that are old. And those are forceMerged to 1 segment afterwards. That is just a hack to trigger correct merges in IndexUpgrader. The use of forceMerge for that is just an implementation detail.
What's your issue with that? IndexUpgrader does what it should: after the upgrade you have an index with only recent segment versions. Uwe Am 22. Mai 2017 07:39:54 MESZ schrieb Trejkaz <trej...@trypticon.org>: >On Mon, May 22, 2017 at 3:36 PM, Uwe Schindler <u...@thetaphi.de> wrote: >> Hi Trejkaz, >> >> yes, it calls forceMerge, but this is just a "trick" to look at each >segment while merging. But finally it >> decides on the version number of each segment, if it gets merged as >part of the forceMerge(1). If the >> version number of an segment is already on the latest version >(because the index was already used >> with 4.10 and new documents were added/updated), it will just remove >it from the list of the segs to >> merge. It looks like the index in 4.10.4 already has a lot of >segments on 4.10 version. When you >> upgrade it directly after that to 5.5.2, of course it has to merge >all segments, as all segs are "only >> on 4.10". >> >> The whole trick is in the IndexUpgraderMergePolicy. This one >implements the algorithm above. > >So a MergePolicy can override the desire of the caller to have a >single segment? I thought the caller would ultimately get the power of >veto, but I guess not. :) > >It turns out we were relying on this for a later migration, but I >guess it might be easier to somehow make it work regardless of the >number of segments which came out the end. Because all indexes before >this were created on v3 and the migration goes all the way to v5, it >took quite a while to run into an index which didn't end up as a >single segment after both passes... (I guess it would have to have >over 100 segments?) > >TX > >--------------------------------------------------------------------- >To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org >For additional commands, e-mail: java-user-h...@lucene.apache.org -- Uwe Schindler Achterdiek 19, 28357 Bremen https://www.thetaphi.de
