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https://issues.apache.org/jira/browse/PHOENIX-3451?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15644761#comment-15644761
]
James Taylor commented on PHOENIX-3451:
---------------------------------------
When the index is used, the final sort is not being done:
{code}
0: jdbc:phoenix:> explain SELECT DISTINCT entity_id, score FROM test.test2
WHERE organization_id = 'org2' AND container_id IN (
'container1','container2','container3' ) ORDER BY score DESC LIMIT 2;
+--------------------------------------------------------------------------------------------------------------------------------------------------------+
| PLAN
|
+--------------------------------------------------------------------------------------------------------------------------------------------------------+
| CLIENT 1-CHUNK PARALLEL 1-WAY SKIP SCAN ON 3 KEYS OVER TEST.TEST_SCORE2
['org2 ','container1 '] - ['org2 ','container3 '] |
| SERVER FILTER BY FIRST KEY ONLY
|
| SERVER AGGREGATE INTO DISTINCT ROWS BY ["ENTITY_ID", "SCORE"] LIMIT 2
GROUPS |
| CLIENT MERGE SORT
|
| CLIENT 2 ROW LIMIT
|
+--------------------------------------------------------------------------------------------------------------------------------------------------------+
{code}
If the query is hinted to not use the index, the output is fine:
{code}
0: jdbc:phoenix:> explain SELECT /*+ NO_INDEX */ DISTINCT entity_id, score FROM
test.test2 WHERE organization_id = 'org2' AND container_id IN (
'container1','container2','container3' ) ORDER BY score DESC LIMIT 2;
+--------------------------------------------------------------------------------------------------------------------------------------------------+
| PLAN
|
+--------------------------------------------------------------------------------------------------------------------------------------------------+
| CLIENT 1-CHUNK PARALLEL 1-WAY SKIP SCAN ON 3 KEYS OVER TEST.TEST2 ['org2
','container1 '] - ['org2 ','container3 '] |
| SERVER AGGREGATE INTO DISTINCT ROWS BY [ENTITY_ID, SCORE]
|
| CLIENT MERGE SORT
|
| CLIENT TOP 2 ROWS SORTED BY [SCORE DESC]
|
+--------------------------------------------------------------------------------------------------------------------------------------------------+
{code}
Do you need that index, [~jpalmert]? For the above query, it's not buying you
anything.
Also, do you know about the FIRST_VALUE aggregate function:
https://phoenix.apache.org/language/functions.html#first_value, as this may
help you.
> Secondary index and query using distinct: LIMIT doesn't return the first rows
> -----------------------------------------------------------------------------
>
> Key: PHOENIX-3451
> URL: https://issues.apache.org/jira/browse/PHOENIX-3451
> Project: Phoenix
> Issue Type: Bug
> Affects Versions: 4.8.0
> Reporter: Joel Palmert
>
> This may be related to PHOENIX-3452 but the behavior is different so filing
> it separately.
> Steps to repro:
> CREATE TABLE IF NOT EXISTS TEST.TEST (
> ORGANIZATION_ID CHAR(15) NOT NULL,
> CONTAINER_ID CHAR(15) NOT NULL,
> ENTITY_ID CHAR(15) NOT NULL,
> SCORE DOUBLE,
> CONSTRAINT TEST_PK PRIMARY KEY (
> ORGANIZATION_ID,
> CONTAINER_ID,
> ENTITY_ID
> )
> ) VERSIONS=1, MULTI_TENANT=TRUE, REPLICATION_SCOPE=1, TTL=31536000;
> CREATE INDEX IF NOT EXISTS TEST_SCORE ON TEST.TEST (CONTAINER_ID, SCORE DESC,
> ENTITY_ID DESC);
> UPSERT INTO test.test VALUES ('org2','container2','entityId6',1.1);
> UPSERT INTO test.test VALUES ('org2','container1','entityId5',1.2);
> UPSERT INTO test.test VALUES ('org2','container2','entityId4',1.3);
> UPSERT INTO test.test VALUES ('org2','container1','entityId3',1.4);
> UPSERT INTO test.test VALUES ('org2','container3','entityId7',1.35);
> UPSERT INTO test.test VALUES ('org2','container3','entityId8',1.45);
> EXPLAIN
> SELECT DISTINCT entity_id, score
> FROM test.test
> WHERE organization_id = 'org2'
> AND container_id IN ( 'container1','container2','container3' )
> ORDER BY score DESC
> LIMIT 2
> OUTPUT
> entityId5 1.2
> entityId3 1.4
> The expected out out would be
> entityId8 1.45
> entityId3 1.4
> You will get the expected output if you remove the secondary index from the
> table or remove distinct from the query.
> As described in PHOENIX-3452 if you run the query without the LIMIT the
> ordering is not correct. However, the 2first results in that ordering is
> still not the onces returned by the limit clause, which makes me think there
> are multiple issues here and why I filed both separately. The rows being
> returned are the ones assigned to container1. It looks like Phoenix is first
> getting the rows from the first container and when it finds that to be enough
> it stops the scan. What it should be doing is getting 2 results for each
> container and then merge then and then limit again.
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