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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 01:56:01 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16252832#comment-16252832
] 

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_r151016226
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/execute/AggregatePlan.java ---
    @@ -112,7 +114,26 @@ private AggregatePlan(StatementContext context, FilterableStatement
statement, T
         public Expression getHaving() {
             return having;
         }
    -    
    +
    +    @Override
    +    public Cost getCost() throws SQLException {
    +        Long byteCount = getEstimatedBytesToScan();
    +        if (byteCount == null) {
    +            return Cost.ZERO;
    +        }
    +
    +        int parallelLevel = 10;
    --- End diff --
    
    How about passing in groupBy instead of just groupBy.isUngroupedAggregate() as I think
we'd want to get more info eventually out of the groupBy (for example, if it's ordered or
unordered which impacts memory usage substantially)? This might help keep the interfaces a
little more stable.


> 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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