[jira] [Commented] (PHOENIX-3941) Filter regions to scan for local indexes based on data table leading pk filter conditions

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PHOENIX-3941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16739127#comment-16739127 ] 

Lars Hofhansl commented on PHOENIX-3941:
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Perhaps I am missing something here.

From the examples in the test it seems that this assumes that pk columns of the table are included in the index.
I.e. if the table's pk is (A, B, C), and also has a column D, that this prune regions only if the index itself contains a prefix of the pk, i.e. the index would need to defined as ON table(A,D).

This is not necessary, right? We can *always* prune regions based on the prefix of the PK, no?

I.e. in the above example if the index was define ON table(D) only, and we now have a query
WHERE D = x, and A = b; we can still use A = b to prune the regions? Why does the A need to included in the index?! That seems like a bug.


> Filter regions to scan for local indexes based on data table leading pk filter conditions
> -----------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-3941
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-3941
>             Project: Phoenix
>          Issue Type: Improvement
>            Reporter: James Taylor
>            Assignee: James Taylor
>            Priority: Major
>              Labels: SFDC, localIndex
>             Fix For: 4.14.0, 5.0.0
>
>         Attachments: PHOENIX-3941_v1.patch, PHOENIX-3941_v2.patch, PHOENIX-3941_v3.patch, PHOENIX-3941_v4.patch
>
>
> Had a good offline conversation with [~ndimiduk] at PhoenixCon about local indexes. Depending on the query, we can often times prune the regions we need to scan over based on the where conditions against the data table pk. For example, with a multi-tenant table, we only need to scan the regions that are prefixed by the tenant ID.
> We can easily get this information from the compilation of the query against the data table (which we always do), through the statementContext.getScanRanges() structure. We'd just want to keep a pointer to the data table QueryPlan from the local index QueryPlan.



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