public Boolean areColumnsUnique(ProjectRelBase rel, BitSet columns, boolean ignoreNulls) {
// ProjectRel maps a set of rows to a different set;
// Without knowledge of the mapping function(whether it
// preserves uniqueness), it is only safe to derive uniqueness
// info from the child of a project when the mapping is f(a) => a.
//
// Also need to map the input column set to the corresponding child
// references
List<RexNode> projExprs = rel.getProjects();
BitSet childColumns = new BitSet();
for (int bit : BitSets.toIter(columns)) {
RexNode projExpr = projExprs.get(bit);
if (projExpr instanceof RexInputRef) {
childColumns.set(((RexInputRef) projExpr).getIndex());
} else if (projExpr instanceof RexCall && ignoreNulls) {
// If the expression is a cast such that the types are the same
// except for the nullability, then if we're ignoring nulls,
// it doesn't matter whether the underlying column reference
// is nullable. Check that the types are the same by making a
// nullable copy of both types and then comparing them.
RexCall call = (RexCall) projExpr;
if (call.getOperator() != SqlStdOperatorTable.CAST) {
continue;
}
RexNode castOperand = call.getOperands().get(0);
if (!(castOperand instanceof RexInputRef)) {
continue;
}
RelDataTypeFactory typeFactory = rel.getCluster().getTypeFactory();
RelDataType castType = typeFactory.createTypeWithNullability(projExpr.getType(), true);
RelDataType origType = typeFactory.createTypeWithNullability(castOperand.getType(), true);
if (castType.equals(origType)) {
childColumns.set(((RexInputRef) castOperand).getIndex());
}
} else {
// If the expression will not influence uniqueness of the
// projection, then skip it.
continue;
}
}
// If no columns can affect uniqueness, then return unknown
if (childColumns.cardinality() == 0) {
return null;
}
return RelMetadataQuery.areColumnsUnique(rel.getChild(), childColumns, ignoreNulls);
}
// implement RelOptRule
public void onMatch(RelOptRuleCall call) {
final FilterRelBase filterRel = call.rel(0);
final ProjectRelBase projRel = call.rel(1);
// convert the filter to one that references the child of the project
RexNode newCondition = RelOptUtil.pushFilterPastProject(filterRel.getCondition(), projRel);
RelNode newFilterRel =
filterFactory == null
? filterRel.copy(filterRel.getTraitSet(), projRel.getChild(), newCondition)
: filterFactory.createFilter(projRel.getChild(), newCondition);
RelNode newProjRel =
projectFactory == null
? projRel.copy(
projRel.getTraitSet(), newFilterRel, projRel.getProjects(), projRel.getRowType())
: projectFactory.createProject(
newFilterRel, projRel.getProjects(), projRel.getRowType().getFieldNames());
call.transformTo(newProjRel);
}
