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From "Alexander Paschenko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IGNITE-5382) SQL: frequent switch between schemas cause severe slowdown
Date Wed, 26 Jul 2017 18:43:00 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-5382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16102093#comment-16102093
] 

Alexander Paschenko commented on IGNITE-5382:
---------------------------------------------

[~skalashnikov]
my comments:

- please see my changes (removed weak map, made {{H2ConnectionWrapper}} immutable)
- refactor duplicate code in {{IgniteH2Indexing}} (added a TODO on this)
- add javadocs to {{H2ConnectionCache}}
- please refactor {{IgniteH2Indexing}} to bind statements cache and its corresponding connection
together in the thread scope. Currently we drop all thread's cached statements when we change
a schema and I don't think it's right. I believe we better store thread local maps of following
structure schema name -> [connection; statement cache] and clean them up by timeout like
it's done now for statement caches.

> SQL: frequent switch between schemas cause severe slowdown
> ----------------------------------------------------------
>
>                 Key: IGNITE-5382
>                 URL: https://issues.apache.org/jira/browse/IGNITE-5382
>             Project: Ignite
>          Issue Type: Task
>          Components: cache, sql
>            Reporter: Vladimir Ozerov
>            Assignee: Sergey Kalashnikov
>              Labels: important, performance
>             Fix For: 2.2
>
>
> We have thread-bound cached connection to H2 database which is bound to specific schema.
See {{IgniteH2Indexing.connectionForThread}}.
> When query with different schema is executed, we call {{SET SCHEMA}} command, which is
rather expensive and may cause slowdown when queries form different caches are executed.
> To avoid this we should maintain thread-local map of such connections. Be careful with
concurrency and resource leaks.



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