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https://issues.apache.org/jira/browse/CALCITE-4203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17188173#comment-17188173
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Chunwei Lei commented on CALCITE-4203:
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Thanks for your review, Julian.
> Is there any benefit in delegating to {{getUniqueKeys((SetOp) r, mq,
>ignoreNulls)}}?
For reusing the code.
> In fact I think {{getUniqueKeys(SetOp, RelMetadataQuery, boolean)}} should be
> changed to {{getUniqueKeys(Union, RelMetadataQuery, boolean)}}
I don't do this in case it may break the downstream project if it has a
subclass of SetOp except Minus and Intersect.
> Use {{LinkedHashSet}} or {{TreeSet}} rather than {{HashSet}}, for determinism.
> Add tests
> Some comments would be nice. The unique keys of Minus are precisely the
>unique keys of its first input. Any unique key of any input of Intersect is a
>unique key of the Intersect.
Makes sense.
> Are your methods consistent with {{RelMdColumnUniqueness}} for {{Intersect}}
>and {{Minus?}}
I think so.
> RelMdUniqueKeys should not return empty when meeting Intersect and Minus if
> its input has unique keys
> -----------------------------------------------------------------------------------------------------
>
> Key: CALCITE-4203
> URL: https://issues.apache.org/jira/browse/CALCITE-4203
> Project: Calcite
> Issue Type: Improvement
> Reporter: Chunwei Lei
> Assignee: Chunwei Lei
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Currently, we get an empty unique key for Intersect and Minus if its all is
> true.
>
> {code:java}
> // code placeholder
> public Set<ImmutableBitSet> getUniqueKeys(SetOp rel, RelMetadataQuery mq,
> boolean ignoreNulls) {
> if (!rel.all) {
> return ImmutableSet.of(
> ImmutableBitSet.range(rel.getRowType().getFieldCount()));
> }
> return ImmutableSet.of();
> }
> {code}
> However, from the semantic of Intersect and Minus, we can get their unique
> keys from its input even if its all is true.
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