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https://issues.apache.org/jira/browse/PHOENIX-2601?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Maryann Xue resolved PHOENIX-2601.
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Resolution: Fixed
> Query result is incorrect when both index hint and limit are used
> -----------------------------------------------------------------
>
> Key: PHOENIX-2601
> URL: https://issues.apache.org/jira/browse/PHOENIX-2601
> Project: Phoenix
> Issue Type: Bug
> Affects Versions: 4.4.0
> Environment: Linux
> Reporter: Simon Lee
> Assignee: Maryann Xue
> Fix For: 4.7.0
>
> Attachments: PHOENIX-2601.patch
>
>
> Query result is incorrect when both index hint and limit are used.
> To reproduce the problem,
> 1. Create an HBase table with a column family. The column family has 4
> columns (a1, a2, a3, a4). Create an index on (a1, a2).
> 2. Populate the table with the following data
> {code}
> a1 a2 a3 a4
> -- ----- ----- -----
> 1 Small Red USA
> 1 Small Yellow UK
> 1 Small Green China
> {code}
> 3. Run the following Phoenix queries, and the query results are correct.
> {code}
> select a1, a2, a3, a4 from table where a1 = '1' and a2 = 'Small' ;
> {code}
> Three rows are returned as expected
> {code}
> select a1, a2, a3, a4 from table where a1 = '1' and a2 = 'Small' and a3 =
> "Yellow" limit 1;
> {code}
> One row is returned as expected
> {code}
> select /*+ INDEX(add_index_hint_here) */ a1, a2, a3, a4 from table where a1 =
> '1' and a2 = 'Small' and a3 = "Yellow";
> {code}
> One row is returned as expected
> 4. However, with the combination of index hint and limit clause, the query
> result is incorrect.
> {code}
> select /*+ INDEX(add_index_hint_here) */ a1, a2, a3, a4 from table where a1 =
> '1' and a2 = 'Small' and a3 = "Yellow" limit 1;
> {code}
> Zero row is returned. The expected result is 1 row (i.e. the second row in
> the example).
> *The explain plan of the problematic query*
> {code}
> +------------------------------------------+
> | PLAN |
> +------------------------------------------+
> | CLIENT 11-CHUNK PARALLEL 1-WAY ... MY_TABLE |
> | SERVER FILTER BY A.A3 = 'Yellow' |
> | CLIENT 1 ROW LIMIT |
> | SKIP-SCAN-JOIN TABLE 0 |
> | CLIENT 1-CHUNK SERIAL 1-WAY RANGE SCAN OVER MY_INDEX
> [[52,48,48,45,69,79,84,45,48,48,57],23] |
> | SERVER FILTER BY FIRST KEY ONLY |
> | SERVER 1 ROW LIMIT |
> | CLIENT 1 ROW LIMIT |
> | DYNAMIC SERVER FILTER BY ("MY_ROW_KEY") IN (($148.$150, $1 |
> | JOIN-SCANNER 1 ROW LIMIT |
> +------------------------------------------+
> {code}
> It looks like the query plan uses the index first. Although all three rows
> match the index (a1 = '1' and 'a2 = 'Small'), but the intermediate result
> only has the first row due the "limit 1" clause. In this case, the
> intermediate result has one row (a3 = 'Red'). Then the query engine tries to
> apply the (a3 = 'Yellow') to the intermediate result, and get zero row as the
> final result.
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