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https://issues.apache.org/jira/browse/CALCITE-2247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16469219#comment-16469219
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Julian Hyde commented on CALCITE-2247:
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It helps to use a truth table. For {{b = 1 OR b != 1}} it is sufficient to
consider 3 values: null, 0, 1:
|| b || b = 1 || b != 1 || b = 1 OR b != 1
| null | unknown | unknown | unknown
| 0 | false | true | true
| 1 | true | false | true
So, {{b=1 OR b is not null}} is valid rewrite but {{b is not null}} gives the
wrong answer when b = null.
Are you talking about the test where an expression used to simplify to
"OR(=($7, 20), =($7, 30))" and now simplifies to "OR(=($7, 20), null, =($7,
30))"? I agree that the null should be there. Before your change it was
"AND(null, ...)"
> Add rule to push in condition condition into a related disjunctive expression
> -----------------------------------------------------------------------------
>
> Key: CALCITE-2247
> URL: https://issues.apache.org/jira/browse/CALCITE-2247
> Project: Calcite
> Issue Type: Improvement
> Reporter: Zoltan Haindrich
> Assignee: Zoltan Haindrich
> Priority: Major
>
> Simplify expressions like: {code}a = 1 AND (a = 1 OR a = 2){code} to {code}a
> = 1{code}
> Conditions to apply will be:
> * in an AND condition there exists a comparison(c) and an OR (o)
> * o and c only reference 1 variable
> See HIVE-19097 for more info.
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