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Posted to commits@cassandra.apache.org by "Jonathan Ellis (JIRA)" <ji...@apache.org> on 2015/08/31 16:55:46 UTC
[jira] [Updated] (CASSANDRA-10217) Support custom query expressions
in SELECT
[ https://issues.apache.org/jira/browse/CASSANDRA-10217?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jonathan Ellis updated CASSANDRA-10217:
---------------------------------------
Fix Version/s: (was: 3.0 beta 2)
3.0.0 rc1
> Support custom query expressions in SELECT
> ------------------------------------------
>
> Key: CASSANDRA-10217
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10217
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Sam Tunnicliffe
> Assignee: Sam Tunnicliffe
> Fix For: 3.0.0 rc1
>
>
> (Broken out of CASSANDRA-10124)
> Custom index implementations often support query expressions which do not fit the structure of CQL. To support these, it has been necessary to add a fake column to the base table and query that using the custom syntax. Taking an example from the [Stratio docs|https://github.com/Stratio/cassandra-lucene-index]:
> {code}
> SELECT * FROM tweets WHERE lucene='{
> filter : {type:"range", field:"time", lower:"2014/04/25", upper:"2014/05/1"},
> query : {type:"phrase", field:"body", value:"big data gives organizations", slop:1}
> }'
> {code}
> The {{lucene}} field is a dummy column that has to be added to the table in order to associate the pre-3.0 row-based index with the {{tweets}} table. We could rewrite this query as:
> {code}
> SELECT * FROM tweets
> WHERE expr(lucene, '{filter : {type:"range", field:"time", lower:"2014/04/25", upper:"2014/05/1"},
> query : {type:"phrase", field:"body", value:"big data gives organizations", slop:1}}');
> {code}
> In this version the {{expr}} function takes 2 arguments: the first is the name of the index being targetted, {{lucene}} and the second is the query string itself.
> Parsing and validation of those expressions would be delegated to the custom index implementations which support them.
> One thing to consider is index selection. If a query contains custom expressions, but the target index is not selected, C* has no way to use the custom expressions as a post-query filter, like it does with standard expressions & {{ALLOW FILTERING}}. To compensate for that, index selection should be weighted in favour of indexes targetted by custom expressions. At least in the first instance, we should also restrict queries to targetting a single index via custom expressions, i.e. disallow queries like {{SELECT * FROM t WHERE expr(index1, 'foo') AND expr(index2, 'bar')}}
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