[
https://issues.apache.org/jira/browse/LUCENE-10216?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17439330#comment-17439330
]
Adrien Grand commented on LUCENE-10216:
---------------------------------------
bq. How do you feel about making this configurable in the API with a param that
defines the number of segments merged together
I worry that it would make the API too complicated.
Thinking about it more: Ideally addIndexes would do the right thing based on
the configured MergePolicy (to know how to group CodecReaders together) and
MergeScheduler (to know how many threads it may use) so that we could hopefully
keep the same API as today and experts users like Amazon product search could
use a MergePolicy that favors many segments for search concurrency, plus
possibly a ConcurrentMergeScheduler that is allowed to use many threads, and
you would get the desired behavior? This might be a high-hanging fruit though.
> Add concurrency to addIndexes(CodecReader…) API
> -----------------------------------------------
>
> Key: LUCENE-10216
> URL: https://issues.apache.org/jira/browse/LUCENE-10216
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/index
> Reporter: Vigya Sharma
> Priority: Major
>
> I work at Amazon Product Search, and we use Lucene to power search for the
> e-commerce platform. I’m working on a project that involves applying
> metadata+ETL transforms and indexing documents on n different _indexing_
> boxes, combining them into a single index on a separate _reducer_ box, and
> making it available for queries on m different _search_ boxes (replicas).
> Segments are asynchronously copied from indexers to reducers to searchers as
> they become available for the next layer to consume.
> I am using the addIndexes API to combine multiple indexes into one on the
> reducer boxes. Since we also have taxonomy data, we need to remap facet field
> ordinals, which means I need to use the {{addIndexes(CodecReader…)}} version
> of this API. The API leverages {{SegmentMerger.merge()}} to create segments
> with new ordinal values while also merging all provided segments in the
> process.
> _This is however a blocking call that runs in a single thread._ Until we have
> written segments with new ordinal values, we cannot copy them to searcher
> boxes, which increases the time to make documents available for search.
> I was playing around with the API by creating multiple concurrent merges,
> each with only a single reader, creating a concurrently running 1:1
> conversion from old segments to new ones (with new ordinal values). We follow
> this up with non-blocking background merges. This lets us copy the segments
> to searchers and replicas as soon as they are available, and later replace
> them with merged segments as background jobs complete. On the Amazon dataset
> I profiled, this gave us around 2.5 to 3x improvement in addIndexes() time.
> Each call was given about 5 readers to add on average.
> This might be useful add to Lucene. We could create another {{addIndexes()}}
> API with a {{boolean}} flag for concurrency, that internally submits multiple
> merge jobs (each with a single reader) to the {{ConcurrentMergeScheduler}},
> and waits for them to complete before returning.
> While this is doable from outside Lucene by using your thread pool, starting
> multiple addIndexes() calls and waiting for them to complete, I felt it needs
> some understanding of what addIndexes does, why you need to wait on the merge
> and why it makes sense to pass a single reader in the addIndexes API.
> Out of box support in Lucene could simplify this for folks a similar use case.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org
For additional commands, e-mail: issues-h...@lucene.apache.org
