[jira] [Commented] (OAK-1263) optimize oak index to support 'fast ORDER BY' queries to support sorting & pagination for large set of children

["Davide Giannella (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-1263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13897731#comment-13897731 ] 

Davide Giannella commented on OAK-1263:
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I'm currently working on a prototype that can be found on my [github fork|https://github.com/davidegiannella/jackrabbit-oak/tree/OAK-1263]. It works by the extensions of the current PropertyIndex.

Is currently implementing a single LinkedList approach with the aim of optimise it later on into a [skiplist|http://en.wikipedia.org/wiki/Skip_list].

There are benchmarks too for measuring the throughput of inserts (for now) and comparing the three use-cases: [no index|https://github.com/davidegiannella/jackrabbit-oak/blob/OAK-1263/oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/NoIndexesOrderByInsertTest.java], [standard property|https://github.com/davidegiannella/jackrabbit-oak/blob/OAK-1263/oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/StandardPropertyIndexOrderByInsertTest.java] and [ordered property|https://github.com/davidegiannella/jackrabbit-oak/blob/OAK-1263/oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/OrderedPropertyIndexOrderByInsertTest.java].

> optimize oak index to support 'fast ORDER BY' queries to support sorting & pagination for large set of children
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: OAK-1263
>                 URL: https://issues.apache.org/jira/browse/OAK-1263
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: query
>    Affects Versions: 0.12
>            Reporter: Stefan Egli
>            Assignee: Alex Parvulescu
>             Fix For: 0.17
>
>
> We have a use case where we'd like to be able to use an index in a "pagination-like" fashion. That is, we'd like to be able to have an index on a subtree on a certain property, and then run a query which does ORDER BY that property combined with OFFSET. That way, essentially allowing pagination of child nodes of a particular parent based on 'sorted by a certain property'.
> AFAIU currently the oak index is not optimized to support ORDER BY queries in a fast manner. The index keeps 'the child nodes unsorted', ie to process an ORDER BY, the child nodes would have to be 'manually sorted' which can result in bad performance given a large number of child nodes.



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