liyafan82 opened a new pull request #2146:
URL: https://github.com/apache/calcite/pull/2146
1. For {{RelMdColumnUniqueness#areColumnsUnique(RelSubset, RelMetadataQuery,
ImmutableBitSet, boolean)}}, we can return early as we encounter the first
null.
2. For {{RelMdDistinctRowCount#getDistinctRowCount(Values, RelMetadataQuery,
ImmutableBitSet, RexNode)}}, we can get the distinct row count accurately,
instead of guessing that half of the elements are distinct.
3. In class RelMdUtil, areColumnsDefinitelyUnique and
areColumnsDefinitelyUniqueWhenNullsFiltered have identical behaviors, so we
should use the formmer, which is more efficient.
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