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From "Sam Tunnicliffe (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-10217) Support custom query expressions in SELECT
Date Fri, 04 Dec 2015 20:08:11 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-10217?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sam Tunnicliffe updated CASSANDRA-10217:
----------------------------------------
    Component/s: CQL

> Support custom query expressions in SELECT
> ------------------------------------------
>
>                 Key: CASSANDRA-10217
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10217
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: CQL
>            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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