rubenada commented on a change in pull request #1987:
URL: https://github.com/apache/calcite/pull/1987#discussion_r439258169
##########
File path: core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java
##########
@@ -350,6 +354,100 @@ public TrimResult trimFields(
Mappings.createIdentity(rel.getRowType().getFieldCount()));
}
+ /**
+ * Variant of {@link #trimFields(RelNode, ImmutableBitSet, Set)} for
+ * {@link org.apache.calcite.rel.logical.LogicalCalc}.
+ */
+ public TrimResult trimFields(
+ Calc calc,
+ ImmutableBitSet fieldsUsed,
+ Set<RelDataTypeField> extraFields) {
+ final RexProgram rexProgram = calc.getProgram();
+ final List<RexNode> projs = Lists.transform(rexProgram.getProjectList(),
+ rexProgram::expandLocalRef);
+
+ final RelDataType rowType = calc.getRowType();
+ final int fieldCount = rowType.getFieldCount();
+ final RelNode input = calc.getInput();
+
+ final Set<RelDataTypeField> inputExtraFields =
+ new LinkedHashSet<>(extraFields);
+ RelOptUtil.InputFinder inputFinder =
+ new RelOptUtil.InputFinder(inputExtraFields);
+ for (Ord<RexNode> ord : Ord.zip(projs)) {
+ if (fieldsUsed.get(ord.i)) {
+ ord.e.accept(inputFinder);
+ }
+ }
+ ImmutableBitSet inputFieldsUsed = inputFinder.inputBitSet.build();
+
+ // Create input with trimmed columns.
+ TrimResult trimResult =
+ trimChild(calc, input, inputFieldsUsed, inputExtraFields);
+ RelNode newInput = trimResult.left;
+ final Mapping inputMapping = trimResult.right;
+
+ // If the input is unchanged, and we need to project all columns,
+ // there's nothing we can do.
+ if (newInput == input
+ && fieldsUsed.cardinality() == fieldCount) {
+ return result(calc, Mappings.createIdentity(fieldCount));
+ }
+
+ // Some parts of the system can't handle rows with zero fields, so
+ // pretend that one field is used.
+ if (fieldsUsed.cardinality() == 0) {
+ return dummyProject(fieldCount, newInput);
Review comment:
I am not sure if, in this situation, the hints from the original Calc
must / can be transferred into the new "dummy Project". What do you think
@danny0405 ?
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
