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From Sergey Shelukhin <ser...@hortonworks.com>
Subject Re: adding ANSI flag for hive
Date Tue, 17 Dec 2013 23:53:48 GMT
Agree on both points. For now, what I had in mind was double vs decimal,
and other such backward compat vs SQL compat and potentially perf vs SQL
compact cases.


I think one flag would not be so bad...


On Mon, Dec 16, 2013 at 8:29 AM, Alan Gates <gates@hortonworks.com> wrote:

> A couple of thoughts on this:
>
> 1) If we did this I think we should have one flag, not many.  As Thejas
> points out, your test matrix goes insane when you have too many flags and
> hence things don't get properly tested.
>
> 2) We could do this in an incremental way, where we create this new ANSI
> flag and are clear with users that for a while this will be evolving.  That
> is, as we find new issues with data types, semantics, whatever, we will
> continue to change the behavior of this flag.  At some point in the future
> (as Thejas suggests, at a 1.0 release) we could make this the default
> behavior.  This avoids having to do a full sweep now and find everything
> that we want to change and make ANSI compliant and living with whatever we
> miss.
>
> Alan.
>
> On Dec 11, 2013, at 5:14 PM, Thejas Nair wrote:
>
> > Having too many configs complicates things for the user, and also
> > complicates the code, and you also end up having many untested
> > combinations of config flags.
> > I think we should identify a bunch of non compatible changes that we
> > think are important, fix it in a branch and make a major version
> > release (say 1.x).
> >
> > This is also related to HIVE-5875, where there is a discussion on
> > switching the defaults for some of the configs to more desirable
> > values, but non backward compatible values.
> >
> > On Wed, Dec 11, 2013 at 4:33 PM, Sergey Shelukhin
> > <sergey@hortonworks.com> wrote:
> >> Hi.
> >>
> >> There's recently been some discussion about data type changes in Hive
> >> (double to decimal), and result changes for special cases like division
> by
> >> zero, etc., to bring it in compliance with MySQL (that's what JIRAs use
> an
> >> example; I am assuming ANSI SQL is meant).
> >> The latter are non-controversial (I guess), but for the former,
> performance
> >> may suffer and/or backward compat may be broken if Hive is brought in
> >> compliance.
> >> If fuller ANSI compat is sought in the future, there may be some even
> >> hairier issues such as double-quoted identifiers.
> >>
> >> In light of that, and also following MySQL, I wonder if we should add a
> >> flag, or set of flags, to HIVE to be able to force ANSI compliance.
> >> When this/ese flag/s is/are not set, for example, int/int division could
> >> return double for backward compat/perf, vectorization can skip the
> special
> >> case handling for division by zero/etc., etc.
> >> Wdyt?
> >>
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