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https://issues.apache.org/jira/browse/DRILL-6844?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16683055#comment-16683055
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ASF GitHub Bot commented on DRILL-6844:
---------------------------------------
HanumathRao opened a new pull request #1534: DRILL-6844: Query with ORDER BY
DESC on indexed column does not pick …
URL: https://github.com/apache/drill/pull/1534
…secondary index.
This PR fixes the issue related to query not picking index when desc is used
in the order by clause.
The code is changed to create the sort collation with nulls first when
indexed field is desc otherwise it creates nulls last.
@amansinha100 Can you please review this PR.
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> Query with ORDER BY DESC on indexed column does not pick secondary index
> ------------------------------------------------------------------------
>
> Key: DRILL-6844
> URL: https://issues.apache.org/jira/browse/DRILL-6844
> Project: Apache Drill
> Issue Type: Bug
> Components: Query Planning & Optimization
> Affects Versions: 1.14.0
> Reporter: Hanumath Rao Maduri
> Assignee: Hanumath Rao Maduri
> Priority: Major
>
> Query with ORDER BY DESC on indexed column does not pick secondary index
> {noformat}
> // Query that uses the secondary index defined on ts.
> 0: jdbc:drill:schema=dfs.tmp> explain plan for
> . . . . . . . . . . . . . . > select ts from dfs.`/c8/test3` order by ts
> limit 1;
> +------+------+
> | text | json |
> +------+------+
> | 00-00 Screen
> 00-01 Project(ts=[$0])
> 00-02 SelectionVectorRemover
> 00-03 Limit(fetch=[1])
> 00-04 Scan(table=[[dfs, /c8/test3]], groupscan=[JsonTableGroupScan
> [ScanSpec=JsonScanSpec [tableName=maprfs:///c8/test3, condition=null,
> indexName=ts], columns=[`ts`], limit=1, maxwidth=125]])
> {noformat}
> // Same query with ORDER BY ts DESC does not use the secondary index defined
> on ts.
> 0: jdbc:drill:schema=dfs.tmp> explain plan for
> . . . . . . . . . . . . . . > select ts from dfs.`/c8/test3` order by ts desc
> limit 1;
> +------+------+
> | text | json |
> +------+------+
> | 00-00 Screen
> 00-01 Project(ts=[$0])
> 00-02 SelectionVectorRemover
> 00-03 Limit(fetch=[1])
> 00-04 SingleMergeExchange(sort0=[0 DESC])
> 01-01 OrderedMuxExchange(sort0=[0 DESC])
> 02-01 SelectionVectorRemover
> 02-02 Limit(fetch=[1])
> 02-03 SelectionVectorRemover
> 02-04 TopN(limit=[1])
> 02-05 HashToRandomExchange(dist0=[[$0]])
> 03-01 Scan(table=[[dfs, /c8/test3]], groupscan=[JsonTableGroupScan
> [ScanSpec=JsonScanSpec [tableName=maprfs:///c8/test3, condition=null],
> columns=[`ts`], maxwidth=8554]])
> {noformat}
> { noformat}
> Index definition is,
> maprcli table index list -path /c8/test3 -json
> {
> "timestamp":1538066303932,
> "timeofday":"2018-09-27 04:38:23.932 GMT+0000 PM",
> "status":"OK",
> "total":2,
> "data":[
> {
> "cluster":"c8",
> "type":"maprdb.si",
> "indexFid":"2176.68.131294",
> "indexName":"ts",
> "hashed":false,
> "indexState":"REPLICA_STATE_REPLICATING",
> "idx":1,
> "indexedFields":"ts:ASC",
> "isUptodate":false,
> "minPendingTS":1538066077,
> "maxPendingTS":1538066077,
> "bytesPending":0,
> "putsPending":0,
> "bucketsPending":1,
> "copyTableCompletionPercentage":100,
> "numTablets":32,
> "numRows":80574368,
> "totalSize":4854052160
> },
> {
> "cluster":"c8",
> "type":"maprdb.si",
> "indexFid":"2176.72.131302",
> "indexName":"ts_desc",
> "hashed":false,
> "indexState":"REPLICA_STATE_REPLICATING",
> "idx":2,
> "indexedFields":"ts:DESC",
> "isUptodate":false,
> "minPendingTS":1538066077,
> "maxPendingTS":1538066077,
> "bytesPending":0,
> "putsPending":0,
> "bucketsPending":1,
> "copyTableCompletionPercentage":100,
> "numTablets":32,
> "numRows":80081344,
> "totalSize":4937154560
> }
> ]
> }
> {noformat}
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