Dmitry Lychagin created ASTERIXDB-2951:
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Summary: Support IS [NOT] DISTINCT FROM operator
Key: ASTERIXDB-2951
URL: https://issues.apache.org/jira/browse/ASTERIXDB-2951
Project: Apache AsterixDB
Issue Type: Bug
Components: COMP - Compiler
Affects Versions: 0.9.7
Reporter: Dmitry Lychagin
Assignee: Dmitry Lychagin
Fix For: 0.9.8
SQL supports IS NOT DISTINCT FROM operator which is a comparison operator that
also returns TRUE if both values are NULL.
See SQL:1999 feature T151, “DISTINCT predicate” and SQL:2003 feature T152,
“DISTINCT predicate with negation”.
We need to implement IS [NOT] DISTINCT FROM operator in SQL++ extending it to
support MISSING values as follows.
"x IS NOT DISTINCT FROM y" returns true
1. if x and y are not unknown and x = y,
2. if both x and y are null,
3. if both x and y are missing
otherwise it returns false.
"x IS DISTINCT FROM y" returns: NOT(x IS NOT DISTINCT FROM y)
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