/**
* Invokes {@link #trimFields}, or the appropriate method for the type of the rel parameter, using
* multi-method dispatch.
*
* @param rel Relational expression
* @param fieldsUsed Bitmap of fields needed by the consumer
* @return New relational expression and its field mapping
*/
protected final TrimResult dispatchTrimFields(
RelNode rel, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
final TrimResult trimResult = trimFieldsDispatcher.invoke(rel, fieldsUsed, extraFields);
final RelNode newRel = trimResult.left;
final Mapping mapping = trimResult.right;
final int fieldCount = rel.getRowType().getFieldCount();
assert mapping.getSourceCount() == fieldCount
: "source: " + mapping.getSourceCount() + " != " + fieldCount;
final int newFieldCount = newRel.getRowType().getFieldCount();
assert mapping.getTargetCount() + extraFields.size() == newFieldCount
: "target: "
+ mapping.getTargetCount()
+ " + "
+ extraFields.size()
+ " != "
+ newFieldCount;
if (Bug.TodoFixed) assert newFieldCount > 0 : "rel has no fields after trim: " + rel;
if (newRel.equals(rel)) {
return new TrimResult(rel, mapping);
}
return trimResult;
}
/**
* Creates a relational expression which projects the output fields of a relational expression
* according to a partial mapping.
*
* <p>A partial mapping is weaker than a permutation: every target has one source, but a source
* may have 0, 1 or more than one targets. Usually the result will have fewer fields than the
* source, unless some source fields are projected multiple times.
*
* <p>This method could optimize the result as {@link #permute} does, but does not at present.
*
* @param rel Relational expression
* @param mapping Mapping from source fields to target fields. The mapping type must obey the
* constaints {@link MappingType#isMandatorySource()} and {@link
* MappingType#isSingleSource()}, as does {@link MappingType#InverseFunction}.
* @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 projects a subset of the input fields
*/
public static RelNode projectMapping(RelNode rel, Mapping mapping, List<String> fieldNames) {
assert mapping.getMappingType().isSingleSource();
assert mapping.getMappingType().isMandatorySource();
if (mapping.isIdentity()) {
return rel;
}
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 < fields.size(); i++) {
final RelDataTypeField field = fields.get(i);
exprList.add(rel.getCluster().getRexBuilder().makeInputRef(field.getType(), i));
}
for (int i = 0; i < mapping.getTargetCount(); i++) {
int source = mapping.getSource(i);
final RelDataTypeField sourceField = fields.get(source);
outputTypeList.add(sourceField.getType());
outputNameList.add(
((fieldNames == null) || (fieldNames.size() <= i) || (fieldNames.get(i) == null))
? sourceField.getName()
: fieldNames.get(i));
projectRefList.add(new RexLocalRef(source, sourceField.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());
}
/** Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link JoinRel}. */
public TrimResult trimFields(JoinRel join, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
final RelDataType rowType = join.getRowType();
final int fieldCount = rowType.getFieldCount();
final RexNode conditionExpr = join.getCondition();
final int systemFieldCount = join.getSystemFieldList().size();
// Add in fields used in the condition.
BitSet fieldsUsedPlus = (BitSet) fieldsUsed.clone();
final Set<RelDataTypeField> combinedInputExtraFields =
new LinkedHashSet<RelDataTypeField>(extraFields);
RelOptUtil.InputFinder inputFinder =
new RelOptUtil.InputFinder(fieldsUsedPlus, combinedInputExtraFields);
conditionExpr.accept(inputFinder);
// If no system fields are used, we can remove them.
int systemFieldUsedCount = 0;
for (int i = 0; i < systemFieldCount; ++i) {
if (fieldsUsed.get(i)) {
++systemFieldUsedCount;
}
}
final int newSystemFieldCount;
if (systemFieldUsedCount == 0) {
newSystemFieldCount = 0;
} else {
newSystemFieldCount = systemFieldCount;
}
int offset = systemFieldCount;
int changeCount = 0;
int newFieldCount = newSystemFieldCount;
List<RelNode> newInputs = new ArrayList<RelNode>(2);
List<Mapping> inputMappings = new ArrayList<Mapping>();
List<Integer> inputExtraFieldCounts = new ArrayList<Integer>();
for (RelNode input : join.getInputs()) {
final RelDataType inputRowType = input.getRowType();
final int inputFieldCount = inputRowType.getFieldCount();
// Compute required mapping.
BitSet inputFieldsUsed = new BitSet(inputFieldCount);
for (int bit : Util.toIter(fieldsUsedPlus)) {
if (bit >= offset && bit < offset + inputFieldCount) {
inputFieldsUsed.set(bit - offset);
}
}
// If there are system fields, we automatically use the
// corresponding field in each input.
if (newSystemFieldCount > 0) {
// calling with newSystemFieldCount == 0 should be safe but hits
// http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6222207
inputFieldsUsed.set(0, newSystemFieldCount);
}
// FIXME: We ought to collect extra fields for each input
// individually. For now, we assume that just one input has
// on-demand fields.
Set<RelDataTypeField> inputExtraFields =
input.getRowType().getField("_extra") == null
? Collections.<RelDataTypeField>emptySet()
: combinedInputExtraFields;
inputExtraFieldCounts.add(inputExtraFields.size());
TrimResult trimResult = trimChild(join, input, inputFieldsUsed, inputExtraFields);
newInputs.add(trimResult.left);
if (trimResult.left != input) {
++changeCount;
}
final Mapping inputMapping = trimResult.right;
inputMappings.add(inputMapping);
// Move offset to point to start of next input.
offset += inputFieldCount;
newFieldCount += inputMapping.getTargetCount() + inputExtraFields.size();
}
Mapping mapping = Mappings.create(MappingType.InverseSurjection, fieldCount, newFieldCount);
for (int i = 0; i < newSystemFieldCount; ++i) {
mapping.set(i, i);
}
offset = systemFieldCount;
int newOffset = newSystemFieldCount;
for (int i = 0; i < inputMappings.size(); i++) {
Mapping inputMapping = inputMappings.get(i);
for (IntPair pair : inputMapping) {
mapping.set(pair.source + offset, pair.target + newOffset);
}
offset += inputMapping.getSourceCount();
newOffset += inputMapping.getTargetCount() + inputExtraFieldCounts.get(i);
}
if (changeCount == 0 && mapping.isIdentity()) {
return new TrimResult(join, Mappings.createIdentity(fieldCount));
}
// Build new join.
final RexVisitor<RexNode> shuttle =
new RexPermuteInputsShuttle(mapping, newInputs.get(0), newInputs.get(1));
RexNode newConditionExpr = conditionExpr.accept(shuttle);
final JoinRel newJoin =
join.copy(join.getTraitSet(), newConditionExpr, newInputs.get(0), newInputs.get(1));
return new TrimResult(newJoin, mapping);
}
