[
https://issues.apache.org/jira/browse/LUCENE-10616?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17561823#comment-17561823
]
fang hou commented on LUCENE-10616:
-----------------------------------
hi [~jpountz] i tried to resolve this by changing the decompress loop in
LZ4WithPresetDictCompressionMode to return early when we got all fields we
need. But i'm a little bit hesitated to do so because it may break the api
design of decompress that it may not return enough length bytes than we
expected. Besides, i'm not sure if it's the right direction to change logics in
LZ4WithPresetDictCompressionMode. Should this decompression optimization happen
in Lucene90CompressingStoredFieldsReader(but i haven't found an easy solution
to do)? here is a WIP pr to demo my current thoughts
[https://github.com/apache/lucene/pull/1003.] PLZ give me some insights thanks!
> Moving to dictionaries has made stored fields slower at skipping
> ----------------------------------------------------------------
>
> Key: LUCENE-10616
> URL: https://issues.apache.org/jira/browse/LUCENE-10616
> Project: Lucene - Core
> Issue Type: Bug
> Reporter: Adrien Grand
> Priority: Minor
> Time Spent: 10m
> Remaining Estimate: 0h
>
> [~ywelsch] has been digging into a regression of stored fields retrieval that
> is caused by LUCENE-9486.
> Say your documents have two stored fields, one that is 100B and is stored
> first, and the other one that is 100kB, and you are only interested in the
> first one. While the idea behind blocks of stored fields is to store multiple
> documents in the same block to leverage redundancy across documents,
> sometimes documents are larger than the block size. As soon as documents are
> larger than 2x the block size, our stored fields format splits such large
> documents into multiple blocks, so that you wouldn't need to decompress
> everything only to retrieve a couple small fields.
> Before LUCENE-9486, BEST_SPEED had a block size of 16kB, so only retrieving
> the first field value would only need to decompress 16kB of data. With the
> move to preset dictionaries in LUCENE-9486 and then LUCENE-9917, we now have
> blocks of 80kB, so stored fields would now need to decompress 80kB of data,
> 5x more than before.
> With dictionaries, our blocks are now split into 10 sub blocks. We happen to
> eagerly decompress all sub blocks that intersect with the stored document,
> which is why we would decompress 80kB of data, but this is an implementation
> detail. It should be possible to decompress these sub blocks lazily so that
> we would only decompress those that intersect with one of the field values
> that the user is interested in retrieving?
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org
For additional commands, e-mail: issues-h...@lucene.apache.org
