[jira] [Updated] (IGNITE-5991) SQL: lazy ResultSet for map query

["Vladimir Ozerov (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IGNITE-5991?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vladimir Ozerov updated IGNITE-5991:
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    Summary: SQL: lazy ResultSet for map query  (was: SQL: create prototype for map query execution without moving full ResultSet to memory)

> SQL: lazy ResultSet for map query
> ---------------------------------
>
>                 Key: IGNITE-5991
>                 URL: https://issues.apache.org/jira/browse/IGNITE-5991
>             Project: Ignite
>          Issue Type: Improvement
>          Components: sql
>    Affects Versions: 2.1
>            Reporter: Vladimir Ozerov
>            Assignee: Vladimir Ozerov
>            Priority: Critical
>             Fix For: 2.2
>
>
> Currently we move the whole {{ResultSet}} to memory when executing SQL query on mapper. If result set is large enough, this could easily bring server down due to high GC pressure or even OOME. 
> To avoid that we should stream H2's {{ResultSet}} to our own consumer, which will construct a page and send it to the client  When a page is sent, consumer will block current thread until "next page request" is received. This approach has disadvantage - query thread will be blocked. However, implementation should be fairly easy and will allow us to avoid OOMEs on server. In future we will improve it to minimize blocking (or even avoid it completely).



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