Kirill Kozlov created CALCITE-3571:
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Summary: RelBuilder#shouldMergeProject throws an exception for
JOIN with complex conditions
Key: CALCITE-3571
URL: https://issues.apache.org/jira/browse/CALCITE-3571
Project: Calcite
Issue Type: Bug
Components: core
Affects Versions: 1.21.0
Reporter: Kirill Kozlov
Before joins are created left and right paths are pared first. For the 1st
query above they are as follows:
{code:java}
Left:
LogicalProject with RecordType(VARBINARY id, VARCHAR fA1, VARCHAR fA1_2)
LogicalTableScan with RecordType(VARBINARY id, VARCHAR fA1)
Right:
LogicalTableScan with RecordType(VARCHAR id, VARCHAR fB1){code}
As they are processed - they are registered as leaves (added to the Array).
When Join node is being created it knows what the `condition expressions` is:
{code:java}
=(TO_HEX($0), $3)
{code}
Since TO_HEX is not computed anywhere - it modifies the left input to be as
follows (via RelOptUtil#pushDownJoinConditions) because
RelBuilder#shouldMergeProject always return true.
{code:java}
LogicalProject with RecordType(VARBINARY id, VARCHAR fA1, VARCHAR fA1_2,
VARCHAR $f3)
{code}
where `VARCHAR $f3` is a result of TO_HEX. Note that the list of leaves is not
updated.
[https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql2rel/SqlToRelConverter.java#L2571]
Finally, when identifier "query.fA1_2" is being converted (via
SqlToRelConverter#convertIdentifier) for the top-most node
{code:java}
top-most node:
LogicalProject with RecordType(VARBINARY id, VARCHAR fA1, VARCHAR fA1_2,
VARCHAR id0, VARCHAR fB1)
LogicalJoin with RecordType(VARBINARY id, VARCHAR fA1, VARCHAR fA1_2, VARCHAR
$f3, VARCHAR id0, VARCHAR fB1)
LogicalProject with RecordType(VARBINARY id, VARCHAR fA1, VARCHAR fA1_2,
VARCHAR $f3)
LogicalTableScan with RecordType(VARBINARY id, VARCHAR fA1)
LogicalTableScan with RecordType(VARCHAR id, VARCHAR fB1){code}
Blackboard perform a lookup (via SqlToRelConverter#lookupExp), in process of
which LookupContext is created.
In a constructor, LookupContext performs flatten, which recursively traverses
tree of nodes (from above codeblock) and checks the leaves to see if they
contain such expression. When it does get to the modified left input of a join
it does not get a match on it and continues further down to a TableScan.
When it finally flattens the result, TableScan's RecordType knows nothing about
a duplicated field `fA1_2`, causing an error above.
I think a viable solution would be to modify Join creation to register a
resulting join inputs as leaves (when they are modified). Alternative approach
would be to not merge Projects when join needs to modify an input.
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