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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4666) Add a subquery cache that persists beyond the life of a query
Date Mon, 18 Jun 2018 19:00:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4666?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16516160#comment-16516160
] 

ASF GitHub Bot commented on PHOENIX-4666:
-----------------------------------------

Github user ortutay commented on the issue:

    https://github.com/apache/phoenix/pull/298
  
    @JamesRTaylor almost ready, we've been testing/deploying this internally and have a few
small changes that I'll push out before it's ready to merge


> Add a subquery cache that persists beyond the life of a query
> -------------------------------------------------------------
>
>                 Key: PHOENIX-4666
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4666
>             Project: Phoenix
>          Issue Type: Improvement
>            Reporter: Marcell Ortutay
>            Assignee: Marcell Ortutay
>            Priority: Major
>
> The user list thread for additional context is here: [https://lists.apache.org/thread.html/e62a6f5d79bdf7cd238ea79aed8886816d21224d12b0f1fe9b6bb075@%3Cuser.phoenix.apache.org%3E]
> ----
> A Phoenix query may contain expensive subqueries, and moreover those expensive subqueries
may be used across multiple different queries. While whole result caching is possible at the
application level, it is not possible to cache subresults in the application. This can cause
bad performance for queries in which the subquery is the most expensive part of the query,
and the application is powerless to do anything at the query level. It would be good if Phoenix
provided a way to cache subquery results, as it would provide a significant performance gain.
> An illustrative example:
>     SELECT * FROM table1 JOIN (SELECT id_1 FROM large_table WHERE x = 10) expensive_result
ON table1.id_1 = expensive_result.id_2 AND table1.id_1 = \{id}
> In this case, the subquery "expensive_result" is expensive to compute, but it doesn't
change between queries. The rest of the query does because of the \{id} parameter. This means
the application can't cache it, but it would be good if there was a way to cache expensive_result.
> Note that there is currently a coprocessor based "server cache", but the data in this
"cache" is not persisted across queries. It is deleted after a TTL expires (30sec by default),
or when the query completes.
> This is issue is fairly high priority for us at 23andMe and we'd be happy to provide
a patch with some guidance from Phoenix maintainers. We are currently putting together a design
document for a solution, and we'll post it to this Jira ticket for review in a few days.



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