rubenada commented on a change in pull request #1987:
URL: https://github.com/apache/calcite/pull/1987#discussion_r439257255
##########
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);
+ }
+
+ // Build new project expressions, and populate the mapping.
+ final List<RexNode> newProjects = new ArrayList<>();
+ final RexVisitor<RexNode> shuttle =
+ new RexPermuteInputsShuttle(
+ inputMapping, newInput);
+ final Mapping mapping =
+ Mappings.create(
+ MappingType.INVERSE_SURJECTION,
+ fieldCount,
+ fieldsUsed.cardinality());
+ for (Ord<RexNode> ord : Ord.zip(projs)) {
+ if (fieldsUsed.get(ord.i)) {
+ mapping.set(ord.i, newProjects.size());
+ RexNode newProjectExpr = ord.e.accept(shuttle);
+ newProjects.add(newProjectExpr);
+ }
+ }
+
+ final RelDataType newRowType =
+ RelOptUtil.permute(calc.getCluster().getTypeFactory(), rowType,
+ mapping);
+
+ final RelNode newInputRelNode = relBuilder.push(newInput).build();
+ if (rexProgram.getCondition() != null) {
+ final List<RexNode> filter = Lists.transform(
+ ImmutableList.of(
+ rexProgram.getCondition()), rexProgram::expandLocalRef);
+ assert filter.size() == 1;
+ final RexNode conditionExpr = filter.get(0);
+
+ final RexNode newConditionExpr =
+ conditionExpr.accept(shuttle);
+ final RexProgram newRexProgram =
RexProgram.create(newInputRelNode.getRowType(),
+ newProjects, newConditionExpr, newRowType.getFieldNames(),
+ newInputRelNode.getCluster().getRexBuilder());
+ LogicalCalc logicalCalc = LogicalCalc.create(newInputRelNode,
newRexProgram);
+
+ return result(logicalCalc, mapping);
+ } else {
+ final RexProgram newRexProgram = RexProgram
+ .create(newInputRelNode.getRowType(), newProjects, null,
+ newRowType.getFieldNames(),
newInputRelNode.getCluster().getRexBuilder());
+
+ LogicalCalc logicalCalc = LogicalCalc.create(newInputRelNode,
newRexProgram);
+ return result(logicalCalc, mapping);
Review comment:
Hints need to be transferred from the original Calc to the new Calc (see
CALCITE-4055).
Also, IMHO this piece of code could be refactored, to avoid duplicating
instructions at the end of the "if" and "else" block, something like:
```
RexNode newConditionExpr = null;
if (rexProgram.getCondition() != null) {
...
newConditionExpr = conditionExpr.accept(shuttle);
}
final RexProgram newRexProgram = ...
final LogicalCalc logicalCalc = LogicalCalc.create(newInputRelNode,
newRexProgram);
logicalCalc.withHints(calc.getHints()); // transfer hints
return result(logicalCalc, mapping);
```
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