Chengxiang Li created FLINK-3141:
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Summary: Design of NULL values handling in operation
Key: FLINK-3141
URL: https://issues.apache.org/jira/browse/FLINK-3141
Project: Flink
Issue Type: Sub-task
Reporter: Chengxiang Li
We discuss and finalize how NULL value is handled in specified cases here. this
is the first proposal:
# NULL compare. In ascending order, NULL is smaller than any other value, and
NULL == NULL return false.
# NULL exists in GroupBy Key, all NULL values are grouped as a single group.
# NULL exists in Aggregate columns, ignore NULL in aggregation function.
# NULL exists in both side Join key, refer to #i, NULL == NULL return false, no
output for NULL Join key.
# NULL in Scalar expression, expression within NULL(eg. 1 + NULL) return NULL.
# NULL in Boolean expression, add an extra result: UNKNOWN, more semantic for
Boolean expression in reference #1.
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