Пример #1
0
 /**
  * Creates a relational expression which permutes the output fields of a relational expression
  * according to a permutation.
  *
  * <p>Optimizations:
  *
  * <ul>
  *   <li>If the relational expression is a {@link CalcRel} or {@link ProjectRel} which is already
  *       acting as a permutation, combines the new permutation with the old;
  *   <li>If the permutation is the identity, returns the original relational expression.
  * </ul>
  *
  * <p>If a permutation is combined with its inverse, these optimizations would combine to remove
  * them both.
  *
  * @param rel Relational expression
  * @param permutation Permutation to apply to fields
  * @param fieldNames Field names; if null, or if a particular entry is null, the name of the
  *     permuted field is used
  * @return relational expression which permutes its input fields
  */
 public static RelNode permute(RelNode rel, Permutation permutation, List<String> fieldNames) {
   if (permutation.isIdentity()) {
     return rel;
   }
   if (rel instanceof CalcRel) {
     CalcRel calcRel = (CalcRel) rel;
     Permutation permutation1 = calcRel.getProgram().getPermutation();
     if (permutation1 != null) {
       Permutation permutation2 = permutation.product(permutation1);
       return permute(rel, permutation2, null);
     }
   }
   if (rel instanceof ProjectRel) {
     Permutation permutation1 = ((ProjectRel) rel).getPermutation();
     if (permutation1 != null) {
       Permutation permutation2 = permutation.product(permutation1);
       return permute(rel, permutation2, null);
     }
   }
   final List<RelDataType> outputTypeList = new ArrayList<RelDataType>();
   final List<String> outputNameList = new ArrayList<String>();
   final List<RexNode> exprList = new ArrayList<RexNode>();
   final List<RexLocalRef> projectRefList = new ArrayList<RexLocalRef>();
   final List<RelDataTypeField> fields = rel.getRowType().getFieldList();
   for (int i = 0; i < permutation.getTargetCount(); i++) {
     int target = permutation.getTarget(i);
     final RelDataTypeField targetField = fields.get(target);
     outputTypeList.add(targetField.getType());
     outputNameList.add(
         ((fieldNames == null) || (fieldNames.size() <= i) || (fieldNames.get(i) == null))
             ? targetField.getName()
             : fieldNames.get(i));
     exprList.add(rel.getCluster().getRexBuilder().makeInputRef(fields.get(i).getType(), i));
     final int source = permutation.getSource(i);
     projectRefList.add(new RexLocalRef(source, fields.get(source).getType()));
   }
   final RexProgram program =
       new RexProgram(
           rel.getRowType(),
           exprList,
           projectRefList,
           null,
           rel.getCluster().getTypeFactory().createStructType(outputTypeList, outputNameList));
   return new CalcRel(
       rel.getCluster(),
       rel.getTraitSet(),
       rel,
       program.getOutputRowType(),
       program,
       Collections.<RelCollation>emptyList());
 }
Пример #2
0
  /**
   * Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link SetOpRel} (including UNION and
   * UNION ALL).
   */
  public TrimResult trimFields(
      SetOpRel setOp, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
    final RelDataType rowType = setOp.getRowType();
    final int fieldCount = rowType.getFieldCount();
    int changeCount = 0;

    // Fennel abhors an empty row type, so pretend that the parent rel
    // wants the last field. (The last field is the least likely to be a
    // system field.)
    if (fieldsUsed.isEmpty()) {
      fieldsUsed.set(rowType.getFieldCount() - 1);
    }

    // Compute the desired field mapping. Give the consumer the fields they
    // want, in the order that they appear in the bitset.
    final Mapping mapping = createMapping(fieldsUsed, fieldCount);

    // Create input with trimmed columns.
    final List<RelNode> newInputs = new ArrayList<RelNode>();
    for (RelNode input : setOp.getInputs()) {
      TrimResult trimResult = trimChild(setOp, input, fieldsUsed, extraFields);
      RelNode newInput = trimResult.left;
      final Mapping inputMapping = trimResult.right;

      // We want "mapping", the input gave us "inputMapping", compute
      // "remaining" mapping.
      //    |                   |                |
      //    |---------------- mapping ---------->|
      //    |-- inputMapping -->|                |
      //    |                   |-- remaining -->|
      //
      // For instance, suppose we have columns [a, b, c, d],
      // the consumer asked for mapping = [b, d],
      // and the transformed input has columns inputMapping = [d, a, b].
      // remaining will permute [b, d] to [d, a, b].
      Mapping remaining = Mappings.divide(mapping, inputMapping);

      // Create a projection; does nothing if remaining is identity.
      newInput = CalcRel.projectMapping(newInput, remaining, null);

      if (input != newInput) {
        ++changeCount;
      }
      newInputs.add(newInput);
    }

    // If the input is unchanged, and we need to project all columns,
    // there's to do.
    if (changeCount == 0 && mapping.isIdentity()) {
      return new TrimResult(setOp, mapping);
    }

    RelNode newSetOp = setOp.copy(setOp.getTraitSet(), newInputs);
    return new TrimResult(newSetOp, mapping);
  }
Пример #3
0
  public static RelNode createProject(final RelNode child, final List<Integer> posList) {
    return CalcRel.createProject(
        child,
        new AbstractList<RexNode>() {
          public int size() {
            return posList.size();
          }

          public RexNode get(int index) {
            final int pos = posList.get(index);
            return child
                .getCluster()
                .getRexBuilder()
                .makeInputRef(child.getRowType().getFieldList().get(pos).getType(), pos);
          }
        },
        null);
  }
Пример #4
0
 /**
  * Trims a child relational expression, then adds back a dummy project to restore the fields that
  * were removed.
  *
  * <p>Sounds pointless? It causes unused fields to be removed further down the tree (towards the
  * leaves), but it ensure that the consuming relational expression continues to see the same
  * fields.
  *
  * @param rel Relational expression
  * @param input Input relational expression, whose fields to trim
  * @param fieldsUsed Bitmap of fields needed by the consumer
  * @return New relational expression and its field mapping
  */
 protected TrimResult trimChildRestore(
     RelNode rel, RelNode input, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
   TrimResult trimResult = trimChild(rel, input, fieldsUsed, extraFields);
   if (trimResult.right.isIdentity()) {
     return trimResult;
   }
   final RelDataType rowType = input.getRowType();
   List<RelDataTypeField> fieldList = rowType.getFieldList();
   final List<RexNode> exprList = new ArrayList<RexNode>();
   final List<String> nameList = rowType.getFieldNames();
   RexBuilder rexBuilder = rel.getCluster().getRexBuilder();
   assert trimResult.right.getSourceCount() == fieldList.size();
   for (int i = 0; i < fieldList.size(); i++) {
     int source = trimResult.right.getTargetOpt(i);
     RelDataTypeField field = fieldList.get(i);
     exprList.add(
         source < 0
             ? rexBuilder.makeZeroLiteral(field.getType())
             : rexBuilder.makeInputRef(field.getType(), source));
   }
   RelNode project = CalcRel.createProject(trimResult.left, exprList, nameList);
   return new TrimResult(project, Mappings.createIdentity(fieldList.size()));
 }