Correct me if I’m wrong, I don’t know if there is an upside of splitting an already merged segment, afaik a single big segment helps with queries and multiple small segments help with indexing but the benefit is only during the indexing so splitting an already merged index shouldn’t make indexing faster, because the hard work is already done and finished long ago.
About your original question I’m sorry that I can’t say yes or no without testing and confirming but I’d be surprised if Solr goes back to a merged index and splits it. It is like fragmenting an already defragmented hard drive. From the documentation: “If creating a new segment would cause the number of lowest level segments to exceed the mergeFactor value, then all those segments are merged together to form a single large segment.” What I understand from the above is Solr tries to merge them to 1 all the time, you can only set how many segments will trigger the initial merge. If the limit is low, merges are triggered frequently so it puts additional load on the node during heavy indexing. -ufuk — > On Dec 11, 2024, at 0:02, Kevin Liang (BLOOMBERG/ 919 3RD A) > <klian...@bloomberg.net> wrote: > > Yes - I am wondering if solr will split segments when the config is updated > to reduce the max segment size > > From: users@solr.apache.org At: 12/09/24 20:53:10 UTC-5:00To: > users@solr.apache.org > Subject: Re: Merge Policy Max Segment Size + Reindexing > > Do you mean if Solr will go back to the old already merged segments and split > them after the change? > > — > >>> On Dec 10, 2024, at 2:27, Kevin Liang (BLOOMBERG/ 919 3RD A) >> <klian...@bloomberg.net> wrote: >> >> Sorry, I didn't word my original message very well. The situation is we > have a larger max segment size currently configured (let's say 10GB) and we > want to update the config to reduce the max segment size (let's say 5GB). > Will > we need to reindex for that reduction to take effect? I have only seen > code/explanations around merging (i.e. Joining two segments into larger > segments) but never anything about segment splitting (which I imagine doesn't > happen?) >> >> From: users@solr.apache.org At: 12/09/24 12:22:38 UTC-5:00To: > users@solr.apache.org >> Subject: Re: Merge Policy Max Segment Size + Reindexing >> >> As far as I know it does not require reindexing. But not sure if there is >> no NRT is happening will the above take effect . >> >> It is good to read. >> > https://blog.mikemccandless.com/2011/02/visualizing-lucenes-segment-merges.html >> >> >> Thanks, >> Ramesh >> >>> On Mon, Dec 9, 2024 at 11:57 AM Kevin Liang (BLOOMBERG/ 919 3RD A) < >>> klian...@bloomberg.net> wrote: >>> >>> Hello, >>> >>> We've configured a merge policy factory such that max segment size is >>> greater than the default. If we update the configuration and restart the >>> cloud, will the lucene segments automatically be split to meet the smaller >>> max segment size? Or will this require a full reindex of the data? >>> >>> -Kevin Liang >> >> >> -- >> Thanks, >> Ramesh >> >> > >
