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Date: Wed, 29 May 2013 06:02:20 +0000 (UTC)
From: "Owen O'Malley (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Message-ID: <JIRA.12648530.1369093925515.33565.1369807340133@arcas>
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Subject: [jira] [Commented] (HIVE-4579) Create a SARG interface for
 RecordReaders
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    [ https://issues.apache.org/jira/browse/HIVE-4579?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13669027#comment-13669027 ] 

Owen O'Malley commented on HIVE-4579:
-------------------------------------

I need to add the null-safe equals as an primitive clause. Having NULL as a boolean value makes things strange and I need to keep in mind that:

* P and not P is not always false (it may be null)
* P or not P is not always true (it may be null)

I see why you wanted HIVE-4478 since if a column has no nulls, the rules for predicate evaluation are much tighter. :) Although we are going to want it in the index as well as in the stripe metadata.


> Create a SARG interface for RecordReaders
> -----------------------------------------
>
>                 Key: HIVE-4579
>                 URL: https://issues.apache.org/jira/browse/HIVE-4579
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Owen O'Malley
>            Assignee: Owen O'Malley
>         Attachments: h-4579.patch, pushdown.pdf
>
>
> I think we should create a SARG (http://en.wikipedia.org/wiki/Sargable) interface for RecordReaders. For a first pass, I'll create an API that uses the value stored in hive.io.filter.expr.serialized.
> The desire is to define an simpler interface that the direct AST expression that is provided by hive.io.filter.expr.serialized so that the code to evaluate expressions can be generalized instead of put inside a particular RecordReader.

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