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From Denis Magda <dma...@gridgain.com>
Subject Re: SQL: Index hints
Date Fri, 21 Apr 2017 06:58:55 GMT
If multiple indexes are listed then H2 will pick only one of them like
MySql does, right?

Denis

On Thursday, April 20, 2017, Sergi Vladykin <sergi.vladykin@gmail.com>
wrote:

> No, it must be USE INDEX without underscore. Also mention that multiple
> indexes can be listed.
>
> http://h2database.com/html/grammar.html#table_expression
>
> Sergi
>
>
> 2017-04-21 4:25 GMT+03:00 Denis Magda <dmagda@apache.org <javascript:;>>:
>
> > Sergi, I’ve documented this feature for 2.0. Please confirm that the text
> > below is technically correct:
> >
> > Index hints are useful in scenarios when it's known that one index is
> more
> > selective for certain queries than another and it's needed to instruct
> the
> > query optimizer to choose a more efficient execution plan. To do this
> trick
> > in Apache Ignite use USE_INDEX(index_list) statement that tells Ignite to
> > take only one of the named indexes for query execution.
> >
> > Below is an example that leverages from this capability:
> >
> > SELECT * FROM table1 USE_INDEX(index_age)
> >   WHERE salary > 150000 AND age < 35;
> >
> > —
> > Denis
> >
> > > On Jan 23, 2017, at 12:19 PM, Denis Magda <dmagda@apache.org
> <javascript:;>> wrote:
> > >
> > > Created a ticket so that we don’t forget about this new H2 capability.
> > > https://issues.apache.org/jira/browse/IGNITE-4594 <
> > https://issues.apache.org/jira/browse/IGNITE-4594>
> > >
> > > Alexander P. feel free to assign it on yourself.
> > >
> > > —
> > > Denis
> > >
> > >> On Jan 23, 2017, at 10:05 AM, Dmitriy Setrakyan <
> dsetrakyan@apache.org <javascript:;>>
> > wrote:
> > >>
> > >> Very cool! Would be nice to add it to Ignite.
> > >>
> > >> On Mon, Jan 23, 2017 at 3:17 AM, Sergi Vladykin <
> > sergi.vladykin@gmail.com <javascript:;>>
> > >> wrote:
> > >>
> > >>> Guys,
> > >>>
> > >>> Recently in H2 we've merged a very important feature: index hints.
It
> > is an
> > >>> additional MySQL-like syntax:
> > >>>
> > >>> SELECT * FROM  my_table USE INDEX (index_a) WHERE A = 1
> > >>>
> > >>> It will be very easy to support this in Ignite.
> > >>>
> > >>> Alex,
> > >>>
> > >>> Since you are working on better SQL Enum support and it will require
> H2
> > >>> upgrade anyways, you can add this stuff to Ignite as well.
> > >>>
> > >>> Sergi
> > >>>
> > >
> >
> >
>

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