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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4288) Indexes not used when ordering by primary key
Date Wed, 15 Nov 2017 01:56:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16252823#comment-16252823
] 

ASF GitHub Bot commented on PHOENIX-4288:
-----------------------------------------

Github user JamesRTaylor commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/281#discussion_r151014001
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/execute/BaseQueryPlan.java ---
    @@ -500,7 +500,10 @@ public ExplainPlan getExplainPlan() throws SQLException {
             if (context.getScanRanges() == ScanRanges.NOTHING) {
                 return new ExplainPlan(Collections.singletonList("DEGENERATE SCAN OVER "
+ getTableRef().getTable().getName().getString()));
             }
    -        
    +
    +        // Initialize dummy iterator to get the stats.
    --- End diff --
    
    Comment that you need the stats prior to optimization as they help drive cost based decisions.


> Indexes not used when ordering by primary key
> ---------------------------------------------
>
>                 Key: PHOENIX-4288
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4288
>             Project: Phoenix
>          Issue Type: Sub-task
>            Reporter: Marcin Januszkiewicz
>            Assignee: Maryann Xue
>              Labels: CostBasedOptimization
>
> We have a table
> CREATE TABLE t (
>   rowkey VARCHAR PRIMARY KEY,
>   c1 VARCHAR,
>   c2 VARCHAR
> )
> which we want to query by doing partial matches on c1, and keep the ordering of the source
table:
> SELECT rowkey, c1, c2 FROM t where c1 LIKE 'X0%' ORDER BY rowkey;
> We expect most queries to select a small subset of the table, so we create an index to
speed up searches:
> CREATE LOCAL INDEX t_c1_ix ON t (c1);
> However, this index will not be used since Phoenix will always choose not to resort the
data.
> In our actual use case, adding index hints is not a practical solution.
> See also discussion at:
> https://lists.apache.org/thread.html/26ab58288eb811d2f074c3f89067163d341e5531fb581f3b2486cf43@%3Cuser.phoenix.apache.org%3E



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