protected static class RelFieldTrimmer.TrimResult extends Pair<RelNode,Mapping>
The mapping describes where to find the columns wanted by the parent of the current relational expression.
The mapping is a
Mappings.SourceMapping
, which means
that no column can be used more than once, and some columns are not used.
columnsUsed.getSource(i)
returns the source of the i'th output
field.
For example, consider the mapping for a relational expression that has 4 output columns but only two are being used. The mapping {2 → 1, 3 → 0} would give the following behavior:
Constructor and Description |
---|
TrimResult(RelNode left,
Mapping right)
Creates a TrimResult.
|
adjacents, compareTo, equals, firstAnd, getKey, getValue, hashCode, left, left, of, of, right, right, setValue, toMap, toString, zip, zip, zip, zip
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