コード例 #1
0
  public Double getDistinctRowCount(Project rel, ImmutableBitSet groupKey, RexNode predicate) {
    if (predicate == null || predicate.isAlwaysTrue()) {
      if (groupKey.isEmpty()) {
        return 1D;
      }
    }
    ImmutableBitSet.Builder baseCols = ImmutableBitSet.builder();
    ImmutableBitSet.Builder projCols = ImmutableBitSet.builder();
    List<RexNode> projExprs = rel.getProjects();
    RelMdUtil.splitCols(projExprs, groupKey, baseCols, projCols);

    List<RexNode> notPushable = new ArrayList<RexNode>();
    List<RexNode> pushable = new ArrayList<RexNode>();
    RelOptUtil.splitFilters(
        ImmutableBitSet.range(rel.getRowType().getFieldCount()), predicate, pushable, notPushable);
    final RexBuilder rexBuilder = rel.getCluster().getRexBuilder();

    // get the distinct row count of the child input, passing in the
    // columns and filters that only reference the child; convert the
    // filter to reference the children projection expressions
    RexNode childPred = RexUtil.composeConjunction(rexBuilder, pushable, true);
    RexNode modifiedPred;
    if (childPred == null) {
      modifiedPred = null;
    } else {
      modifiedPred = RelOptUtil.pushPastProject(childPred, rel);
    }
    Double distinctRowCount =
        RelMetadataQuery.getDistinctRowCount(rel.getInput(), baseCols.build(), modifiedPred);

    if (distinctRowCount == null) {
      return null;
    } else if (!notPushable.isEmpty()) {
      RexNode preds = RexUtil.composeConjunction(rexBuilder, notPushable, true);
      distinctRowCount *= RelMdUtil.guessSelectivity(preds);
    }

    // No further computation required if the projection expressions
    // are all column references
    if (projCols.cardinality() == 0) {
      return distinctRowCount;
    }

    // multiply by the cardinality of the non-child projection expressions
    for (int bit : projCols.build()) {
      Double subRowCount = RelMdUtil.cardOfProjExpr(rel, projExprs.get(bit));
      if (subRowCount == null) {
        return null;
      }
      distinctRowCount *= subRowCount;
    }

    return RelMdUtil.numDistinctVals(distinctRowCount, RelMetadataQuery.getRowCount(rel));
  }
コード例 #2
0
  public Double getDistinctRowCount(Values rel, ImmutableBitSet groupKey, RexNode predicate) {
    if (predicate == null || predicate.isAlwaysTrue()) {
      if (groupKey.isEmpty()) {
        return 1D;
      }
    }
    Double selectivity = RelMdUtil.guessSelectivity(predicate);

    // assume half the rows are duplicates
    Double nRows = rel.getRows() / 2;
    return RelMdUtil.numDistinctVals(nRows, nRows * selectivity);
  }