[jira] [Updated] (IGNITE-6202) SQL: support hash join

["Nikolay Izhikov (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IGNITE-6202?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nikolay Izhikov updated IGNITE-6202:
------------------------------------
    Labels: h2-limitation performance sql-engine  (was: performance sql-engine)

> SQL: support hash join
> ----------------------
>
>                 Key: IGNITE-6202
>                 URL: https://issues.apache.org/jira/browse/IGNITE-6202
>             Project: Ignite
>          Issue Type: Task
>          Components: sql
>    Affects Versions: 2.1
>            Reporter: Vladimir Ozerov
>            Priority: Major
>              Labels: h2-limitation, performance, sql-engine
>
> Justification is the same as for IGNITE-6201 (merge joins). If join is equijoin, and participating attributes are not sorted in advance, then instead of executing nested loops, we can do the following:
> 1) Get the table with smaller number of entries
> 2) Build a hash table from target attribute to the list of matching entries
> 3) Iterate over larger table and perform lookup into hash table
> Note that this operation might be memory-intensive in case smaller table is large enough still. For this reason we should provide a mechanism to avoid out-of-memory errors. Let's avoid spilling to disk in the first iteration, and try to set a kind of hard limit on how much data can be kept in memory. If we see that this limit cannot be satisfied, then fallback to nested loops.



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