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From Julian Hyde <jh...@apache.org>
Subject Re: Simplifying literal comparison literal
Date Mon, 20 Feb 2017 19:58:32 GMT
I do think it’s worth considering. Can you log a JIRA case please?

Also, if you add a test — probably a few extra lines in RexProgramTest will suffice —
I will accept your PR. I think it will be efficient enough.

Julian


> On Feb 19, 2017, at 7:14 PM, Kevin Risden <compuwizard123@gmail.com> wrote:
> 
> Thanks Julian. I looked in the existing rules but didn't come across the
> ReduceExpressionsRule.FILTER_INSTANCE. Adding that rule to the planner
> seems to do the same thing that I was trying to do in simplify. I don't
> think there is any reason to change simplify. It was just the first way to
> found to try to work around the issue I was facing.
> 
> Would you still want a JIRA case logged since that would result in multiple
> ways of doing the same thing?
> 
> Kevin Risden
> 
> On Sun, Feb 19, 2017 at 8:13 PM, Julian Hyde <jhyde@apache.org <mailto:jhyde@apache.org>>
wrote:
> 
>> We have support for this in planner rules -- I’m pretty sure that
>> ReduceExpressionsRule.FILTER_INSTANCE will convert ‘where 1 = 0’ to
>> ‘where false’, then PruneEmptyRules.FILTER_INSTANCE will make the Filter
>> disappear altogether — but arguably it could happen in RexUtil.simplify
>> also.
>> 
>> The purpose of RexUtil.simplify is to simplify (only) patterns that are
>> commonly occurring, easy to recognize, and will produce a quick win in
>> terms of the size of the RelNode/RexNode tree. I don’t know yet whether
>> this passes that threshold. Can you log a JIRA case for this and we can
>> discuss further?
>> 
>> By the way, https://issues.apache.org/jira/browse/CALCITE-1638 <
>> https://issues.apache.org/jira/browse/CALCITE-1638 <https://issues.apache.org/jira/browse/CALCITE-1638>>
is related. It
>> changed the result of a test that was doing ‘where 1 = 1’.
>> 
>> Julian
>> 
>> 
>> 
>> 
>>> On Feb 19, 2017, at 2:03 PM, Kevin Risden <compuwizard123@gmail.com>
>> wrote:
>>> 
>>> While working on Solr and Calcite integration, I found that there is a
>> case
>>> where some tools issue a sql query like "where 1 = 0" just to get
>> metadata
>>> information back. Spark SQL is one of the ones that does this.
>>> 
>>> Calcite doesn't seem to optimize away the literal comparison literal case
>>> with RexUtil.simplify. In my understanding any literal comparison literal
>>> results in a simple TRUE/FALSE result.
>>> 
>>> I'm not sure this is valid in the general case, but I put together a
>> simple
>>> example of doing this on the RexUtil simplifyCall.
>>> 
>>> https://github.com/apache/calcite/pull/376
>>> 
>>> I would love to hear any feedback related to this. I need to run through
>>> the full Calcite test suite, but wondering if this is even viable.
>>> 
>>> Thanks!
>>> 
>>> Kevin Risden


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