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From Sergi Vladykin <sergi.vlady...@gmail.com>
Subject Re: SQL: Index hints
Date Fri, 21 Apr 2017 07:11:25 GMT
Exactly, this syntax was taken from MySQL.

Sergi

2017-04-21 9:58 GMT+03:00 Denis Magda <dmagda@gridgain.com>:

> 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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