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From Michael Mior <mm...@uwaterloo.ca>
Subject Re: Materialized view rewriting
Date Fri, 26 Feb 2016 18:26:16 GMT
Thanks for the suggestion Maryann!  While it's obvious from this thread
that this isn't the ideal way to define materialized views, it did work in
this case. I'll be watching the JIRA for a better solution. I managed to
automated materialized view definitions in Cassandra in the case where
the original view has no WHERE clause defined. The somewhat tricky part
there is converting the clause written in CQL to SQL which Calcite can use.

Cheers,
--
Michael Mior
mmior@uwaterloo.ca

2016-02-25 11:46 GMT-05:00 Maryann Xue <maryann.xue@gmail.com>:

> Hi Michael,
>
> We had a little difficulty defining our secondary indices as materialized
> views with our Schema SPI implementation too, and this made the code pretty
> hacky. In order to call that defineMaterialization method, we hold the
> parent SchemaPlus object within our own Schema impl object so that we can
> get its own corresponding SchemaPlus object by calling "parentSchema
> .getSubSchema(this.name)" later on. We do this after the schema/table
> resolving phase (that is when the entire schema tree incl. your own schema
> objects have been initiated) and call defineMaterialization for each
> secondary index under each subSchema. We add a hook in "Hook.TRIMMED" for
> this, which sounds pretty weird, but this is exactly a point after you have
> the whole schema tree ready and before the materializations are asked for
> by the planner.
>
> Anyway, I do hope the interface can be modified to avoid all this trouble.
>
>
> Thanks,
> Maryann
>
> On Thu, Feb 25, 2016 at 9:24 AM, Michael Mior <mmior@uwaterloo.ca> wrote:
>
> > Any suggestions on the best place to hook in and add the materialized
> > views? It seems like doing so requires the SchemaPlus object
> corresponding
> > to the current schema. The current best approach I see is to save a
> > reference to the parent schema and then pull out the appropriate
> SchemaPlus
> > object in getTableMap. This seems like a bit of a hack though.
> >
> > --
> > Michael Mior
> > mmior@uwaterloo.ca
> >
> > 2016-02-24 17:22 GMT-05:00 Julian Hyde <jhyde@apache.org>:
> >
> > > By the way, interesting that you are interested in Cassandra and
> > > materialized views. Cassandra announced materialized view support
> > > recently[1] but they solved only half of a problem (not an
> > > insignificant half, I hasten to add), namely materialized view
> > > maintenance. They don't transparently substitute them into the query -
> > > you have to reference the materialized view explicitly in y our query
> > > - so in my book they've not delivered materialized view support. If
> > > you're planning to deliver REAL materialized view support to Cassandra
> > > that would be awesome.
> > >
> > > Julian
> > >
> > > [1]
> > >
> http://www.datastax.com/dev/blog/new-in-cassandra-3-0-materialized-views
> > >
> > >
> > > On Wed, Feb 24, 2016 at 2:17 PM, Julian Hyde <jhyde@apache.org> wrote:
> > > > As is typical for complex pieces of code like this, the documentation
> > > > is in the code (and the unit test). It's probably not what you wanted
> > > > to hear, but the code mutates quite fast and so if we'd written a
> > > > design doc a few months ago it would be partially inaccurate.
> > > >
> > > > I, Maryann Xue and Amogh Margoor are the main authors of this code.
> > > >
> > > > Suggest you find a relevant test case in MaterializationTest (or
> write
> > > > a new one) and run it with trace enabled and/or in a debugger. You
> > > > will see the process of matching an expression to a MV bottom up if
> > > > you watch each call to UnifyRule.unify.
> > > >
> > > > Julian
> > > >
> > > >
> > > > On Wed, Feb 24, 2016 at 1:40 PM, Michael Mior <mmior@uwaterloo.ca>
> > > wrote:
> > > >> Is there any documentation anywhere on how the current
> implementation
> > of
> > > >> query rewriting for materialized views work? Mostly I'm referring
> > > >> to MaterializedViewSubstitutionVisitor. There's a lot of code to
> > digest
> > > >> with not a lot of documentation and it would be helpful to have a
> > > reference
> > > >> to refer. Thanks!
> > > >>
> > > >> Cheers,
> > > >> --
> > > >> Michael Mior
> > > >> mmior@uwaterloo.ca
> > >
> >
>

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