cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Benjamin Lerer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9631) Unnecessary required filtering for query on indexed clustering key
Date Wed, 24 Jun 2015 12:58:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14599347#comment-14599347
] 

Benjamin Lerer commented on CASSANDRA-9631:
-------------------------------------------

{quote}Now, using the index on b for that query is not smart and C* should always stick to
the index on e for that query as it will be faster and won't require filtering. It's just
not what happens in 2.1.{quote}

I had a look at the code of 2.1 and it seems that it used to ignore the index on {{b}} for
this specific case. I broke that behaviour when I implemented CASSANDRA-8275. The 2.2/trunk
behaviour was not affected by my patch.

I will provide some patches to fix the problem in 2.0 and 2.1 and add some extra unit tests
to all the versions.

> Unnecessary required filtering for query on indexed clustering key
> ------------------------------------------------------------------
>
>                 Key: CASSANDRA-9631
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9631
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: Cassandra 2.1.6 vanilla; 3-node local cluster; OSX Yosemite 10.10.3;
Installed with CCM.
>            Reporter: Kevin Deldycke
>            Assignee: Benjamin Lerer
>              Labels: CQL, query, secondaryIndex
>
> Let's create and populate a simple table composed of one partition key {{a}}, two clustering
keys {{b}} & {{c}}, and one secondary index on a standard column {{e}}:
> {code:sql}
> $ cqlsh 127.0.0.1
> Connected to test21 at 127.0.0.1:9160.
> [cqlsh 4.1.1 | Cassandra 2.1.6-SNAPSHOT | CQL spec 3.1.1 | Thrift protocol 19.39.0]
> Use HELP for help.
> cqlsh> CREATE KEYSPACE test WITH REPLICATION={'class': 'SimpleStrategy', 'replication_factor':
3};
> cqlsh> CREATE TABLE test.table1 (
>    ...     a int,
>    ...     b int,
>    ...     c int,
>    ...     d int,
>    ...     e int,
>    ...     PRIMARY KEY (a, b, c)
>    ... );
> cqlsh> CREATE INDEX table1_e ON test.table1 (e);
> cqlsh> INSERT INTO test.table1 (a, b, c, d, e) VALUES (1, 1, 1, 1, 1);
> (...)
> cqlsh> SELECT * FROM test.table1;
>  a | b | c | d | e
> ---+---+---+---+---
>  1 | 1 | 1 | 1 | 1
>  1 | 1 | 2 | 2 | 2
>  1 | 1 | 3 | 3 | 3
>  1 | 2 | 1 | 1 | 3
>  1 | 3 | 1 | 1 | 1
>  2 | 4 | 1 | 1 | 1
> (6 rows)
> {code}
> With such a schema, I am allowed to query on the indexed column without filtering by
providing the first two elements of the primary key:
> {code:sql}
> cqlsh> SELECT * FROM test.table1 WHERE a=1 AND b=1 AND e=3;
>  a | b | c | d | e
> ---+---+---+---+---
>  1 | 1 | 3 | 3 | 3
> (1 rows)
> {code}
> Let's now introduce an index on the first clustering key:
> {code:sql}
> cqlsh> CREATE INDEX table1_b ON test.table1 (b);
> {code}
> Now, I expect the same query as above to work without filtering, but it's not:
> {code:sql}
> cqlsh> SELECT * FROM test.table1 WHERE a=1 AND b=1 AND e=3;
> Bad Request: Cannot execute this query as it might involve data filtering and thus may
have unpredictable performance. If you want to execute this query despite the performance
unpredictability, use ALLOW FILTERING
> {code}
> I think this is a bug on the way secondary indexes are accounted for when checking for
unfiltered queries.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message