/**
* RelMdColumnUniqueness supplies a default implementation of {@link
* RelMetadataQuery#areColumnsUnique} for the standard logical algebra.
*/
public class RelMdColumnUniqueness {
public static final RelMetadataProvider SOURCE =
ReflectiveRelMetadataProvider.reflectiveSource(
BuiltinMethod.COLUMN_UNIQUENESS.method, new RelMdColumnUniqueness());
// ~ Constructors -----------------------------------------------------------
private RelMdColumnUniqueness() {}
// ~ Methods ----------------------------------------------------------------
public Boolean areColumnsUnique(FilterRelBase rel, BitSet columns, boolean ignoreNulls) {
return RelMetadataQuery.areColumnsUnique(rel.getChild(), columns, ignoreNulls);
}
public Boolean areColumnsUnique(SortRel rel, BitSet columns, boolean ignoreNulls) {
return RelMetadataQuery.areColumnsUnique(rel.getChild(), columns, ignoreNulls);
}
public Boolean areColumnsUnique(CorrelatorRel rel, BitSet columns, boolean ignoreNulls) {
return RelMetadataQuery.areColumnsUnique(rel.getLeft(), columns, ignoreNulls);
}
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);
}
public Boolean areColumnsUnique(JoinRelBase rel, BitSet columns, boolean ignoreNulls) {
if (columns.cardinality() == 0) {
return false;
}
final RelNode left = rel.getLeft();
final RelNode right = rel.getRight();
// Divide up the input column mask into column masks for the left and
// right sides of the join
BitSet leftColumns = new BitSet();
BitSet rightColumns = new BitSet();
int nLeftColumns = left.getRowType().getFieldCount();
for (int bit : BitSets.toIter(columns)) {
if (bit < nLeftColumns) {
leftColumns.set(bit);
} else {
rightColumns.set(bit - nLeftColumns);
}
}
// If the original column mask contains columns from both the left and
// right hand side, then the columns are unique if and only if they're
// unique for their respective join inputs
Boolean leftUnique = RelMetadataQuery.areColumnsUnique(left, leftColumns, ignoreNulls);
Boolean rightUnique = RelMetadataQuery.areColumnsUnique(right, rightColumns, ignoreNulls);
if ((leftColumns.cardinality() > 0) && (rightColumns.cardinality() > 0)) {
if ((leftUnique == null) || (rightUnique == null)) {
return null;
} else {
return leftUnique && rightUnique;
}
}
// If we're only trying to determine uniqueness for columns that
// originate from one join input, then determine if the equijoin
// columns from the other join input are unique. If they are, then
// the columns are unique for the entire join if they're unique for
// the corresponding join input, provided that input is not null
// generating.
final JoinInfo joinInfo = rel.analyzeCondition();
if (leftColumns.cardinality() > 0) {
if (rel.getJoinType().generatesNullsOnLeft()) {
return false;
}
Boolean rightJoinColsUnique =
RelMetadataQuery.areColumnsUnique(right, joinInfo.rightSet(), ignoreNulls);
if ((rightJoinColsUnique == null) || (leftUnique == null)) {
return null;
}
return rightJoinColsUnique && leftUnique;
} else if (rightColumns.cardinality() > 0) {
if (rel.getJoinType().generatesNullsOnRight()) {
return false;
}
Boolean leftJoinColsUnique =
RelMetadataQuery.areColumnsUnique(left, joinInfo.leftSet(), ignoreNulls);
if ((leftJoinColsUnique == null) || (rightUnique == null)) {
return null;
}
return leftJoinColsUnique && rightUnique;
}
throw new AssertionError();
}
public Boolean areColumnsUnique(SemiJoinRel rel, BitSet columns, boolean ignoreNulls) {
// only return the unique keys from the LHS since a semijoin only
// returns the LHS
return RelMetadataQuery.areColumnsUnique(rel.getLeft(), columns, ignoreNulls);
}
public Boolean areColumnsUnique(AggregateRelBase rel, BitSet columns, boolean ignoreNulls) {
// group by keys form a unique key
if (rel.getGroupCount() > 0) {
BitSet groupKey = new BitSet();
for (int i = 0; i < rel.getGroupCount(); i++) {
groupKey.set(i);
}
return BitSets.contains(columns, groupKey);
} else {
// interpret an empty set as asking whether the aggregation is full
// table (in which case it returns at most one row);
// TODO jvs 1-Sept-2008: apply this convention consistently
// to other relational expressions, as well as to
// RelMetadataQuery.getUniqueKeys
return columns.isEmpty();
}
}
// Catch-all rule when none of the others apply.
public Boolean areColumnsUnique(RelNode rel, BitSet columns, boolean ignoreNulls) {
// no information available
return null;
}
}