[GitHub] [calcite] xy2953396112 commented on a change in pull request #1987: [CALCITE-4020] Support Calc operator in RelFieldTrimmer

[GitBox <gi...@apache.org>]

xy2953396112 commented on a change in pull request #1987:
URL: https://github.com/apache/calcite/pull/1987#discussion_r439726414



##########
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:
       Thanks, clean up the code.




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