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From "Sylvain Lebresne (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-9664) Allow MV's select statements to be more complex
Date Thu, 03 Sep 2015 08:22:46 GMT


Sylvain Lebresne commented on CASSANDRA-9664:

The schema I settled on was this:
where_clause frozen<list<tuple<list<text>, int, list<text>>>>
I'm actually a little bit worried about this for 2 reasons:
# it's incomprehensible by a human being and will be a bit of a pain for external tools (like,
say, the {{DESCRIBE}} of cqlsh). We've done extensive and painful work to make the schema
tables more understandable and more easy to translate to their original statement, and this
feels like a step backward.
# it's not future proof. For instance, and while the exact plans are not fully fleshed out,
I strongly suspect we'll start to support at least some form of {{OR}} in the medium-ish term
(I also have some ideas for allowing some custom form of expressions for the sake of custom
index that might or might not pan out, but probably wouldn't work with this if they do).

bq. I also considered storing a single string of the WHERE clause

That would have my preference, mainly for my 2nd reason above: it makes no assumption on what
a WHERE clause may end up supporting in the future. It also solves my 1st point, even though
in all honestly, it does makes it a little harder for external tools that _would_ prefer a
most "parsed" version of the WHERE clause (but then again, a WHERE clause parser is not _that_
hard if you really care). Overall, I'd be much more comfortable with it. It does mean we'd
need to modify the parser to parse WHERE clauses separately, but is it really _that_ hard?

> Allow MV's select statements to be more complex
> -----------------------------------------------
>                 Key: CASSANDRA-9664
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Carl Yeksigian
>            Assignee: Tyler Hobbs
>              Labels: client-impacting, doc-impacting
>             Fix For: 3.0.0 rc1
> [Materialized Views|] add support
for a syntax which includes a {{SELECT}} statement, but only allows selection of direct columns,
and does not allow any filtering to take place.
> We should add support to the MV {{SELECT}} statement to bring better parity with the
normal CQL {{SELECT}} statement, specifically simple functions in the selected columns, as
well as specifying a {{WHERE}} clause.

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