/** Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link TableFunctionRel}. */
public TrimResult trimFields(
TableFunctionRel tabFun, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
final RelDataType rowType = tabFun.getRowType();
final int fieldCount = rowType.getFieldCount();
List<RelNode> newInputs = new ArrayList<RelNode>();
for (RelNode input : tabFun.getInputs()) {
final int inputFieldCount = input.getRowType().getFieldCount();
BitSet inputFieldsUsed = Util.bitSetBetween(0, inputFieldCount);
// Create input with trimmed columns.
final Set<RelDataTypeField> inputExtraFields = Collections.emptySet();
TrimResult trimResult = trimChildRestore(tabFun, input, inputFieldsUsed, inputExtraFields);
assert trimResult.right.isIdentity();
newInputs.add(trimResult.left);
}
TableFunctionRel newTabFun = tabFun;
if (!tabFun.getInputs().equals(newInputs)) {
newTabFun = tabFun.copy(tabFun.getTraitSet(), newInputs);
}
assert newTabFun.getClass() == tabFun.getClass();
// Always project all fields.
Mapping mapping = Mappings.createIdentity(fieldCount);
return new TrimResult(newTabFun, mapping);
}
/** Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link SortRel}. */
public TrimResult trimFields(SortRel sort, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
final RelDataType rowType = sort.getRowType();
final int fieldCount = rowType.getFieldCount();
final RelCollation collation = sort.getCollation();
final RelNode input = sort.getChild();
// We use the fields used by the consumer, plus any fields used as sort
// keys.
BitSet inputFieldsUsed = (BitSet) fieldsUsed.clone();
for (RelFieldCollation field : collation.getFieldCollations()) {
inputFieldsUsed.set(field.getFieldIndex());
}
// Create input with trimmed columns.
final Set<RelDataTypeField> inputExtraFields = Collections.emptySet();
TrimResult trimResult = trimChild(sort, input, inputFieldsUsed, inputExtraFields);
RelNode newInput = trimResult.left;
final Mapping inputMapping = trimResult.right;
// If the input is unchanged, and we need to project all columns,
// there's nothing we can do.
if (newInput == input && inputMapping.isIdentity() && fieldsUsed.cardinality() == fieldCount) {
return new TrimResult(sort, Mappings.createIdentity(fieldCount));
}
final SortRel newSort =
sort.copy(sort.getTraitSet(), newInput, RexUtil.apply(inputMapping, collation));
assert newSort.getClass() == sort.getClass();
// The result has the same mapping as the input gave us. Sometimes we
// return fields that the consumer didn't ask for, because the filter
// needs them for its condition.
return new TrimResult(newSort, inputMapping);
}
/** Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link TableModificationRel}. */
public TrimResult trimFields(
TableModificationRel modifier, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
// Ignore what consumer wants. We always project all columns.
Util.discard(fieldsUsed);
final RelDataType rowType = modifier.getRowType();
final int fieldCount = rowType.getFieldCount();
RelNode input = modifier.getChild();
// We want all fields from the child.
final int inputFieldCount = input.getRowType().getFieldCount();
BitSet inputFieldsUsed = Util.bitSetBetween(0, inputFieldCount);
// Create input with trimmed columns.
final Set<RelDataTypeField> inputExtraFields = Collections.emptySet();
TrimResult trimResult = trimChild(modifier, input, inputFieldsUsed, inputExtraFields);
RelNode newInput = trimResult.left;
final Mapping inputMapping = trimResult.right;
if (!inputMapping.isIdentity()) {
// We asked for all fields. Can't believe that the child decided
// to permute them!
throw Util.newInternal("Expected identity mapping, got " + inputMapping);
}
TableModificationRel newModifier = modifier;
if (newInput != input) {
newModifier = modifier.copy(modifier.getTraitSet(), Collections.singletonList(newInput));
}
assert newModifier.getClass() == modifier.getClass();
// Always project all fields.
Mapping mapping = Mappings.createIdentity(fieldCount);
return new TrimResult(newModifier, mapping);
}
/** Overrides the default behaviour to including binding of Grails domain classes. */
@Override
protected void secondPassCompile() throws MappingException {
final Thread currentThread = Thread.currentThread();
final ClassLoader originalContextLoader = currentThread.getContextClassLoader();
if (!configLocked) {
if (LOG.isDebugEnabled())
LOG.debug(
"[GrailsAnnotationConfiguration] ["
+ domainClasses.size()
+ "] Grails domain classes to bind to persistence runtime");
// do Grails class configuration
configureDomainBinder(binder, grailsApplication, domainClasses);
for (GrailsDomainClass domainClass : domainClasses) {
final String fullClassName = domainClass.getFullName();
String hibernateConfig = fullClassName.replace('.', '/') + ".hbm.xml";
final ClassLoader loader = originalContextLoader;
// don't configure Hibernate mapped classes
if (loader.getResource(hibernateConfig) != null) continue;
final Mappings mappings = super.createMappings();
if (!GrailsHibernateUtil.usesDatasource(domainClass, dataSourceName)) {
continue;
}
LOG.debug(
"[GrailsAnnotationConfiguration] Binding persistent class [" + fullClassName + "]");
Mapping m = binder.getMapping(domainClass);
mappings.setAutoImport(m == null || m.getAutoImport());
binder.bindClass(domainClass, mappings, sessionFactoryBeanName);
}
}
try {
currentThread.setContextClassLoader(grailsApplication.getClassLoader());
super.secondPassCompile();
createSubclassForeignKeys();
} finally {
currentThread.setContextClassLoader(originalContextLoader);
}
configLocked = true;
}
private Mapping createMapping(BitSet fieldsUsed, int fieldCount) {
final Mapping mapping =
Mappings.create(MappingType.InverseSurjection, fieldCount, fieldsUsed.cardinality());
int i = 0;
for (int field : Util.toIter(fieldsUsed)) {
mapping.set(field, i++);
}
return mapping;
}
/**
* 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);
}
/**
* Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link org.eigenbase.rel.ValuesRel}.
*/
public TrimResult trimFields(
ValuesRel values, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
final RelDataType rowType = values.getRowType();
final int fieldCount = rowType.getFieldCount();
// If they are asking for no fields, we can't give them what they want,
// because zero-column records are illegal. Give them the last field,
// which is unlikely to be a system field.
if (fieldsUsed.isEmpty()) {
fieldsUsed = Util.bitSetBetween(fieldCount - 1, fieldCount);
}
// If all fields are used, return unchanged.
if (fieldsUsed.equals(Util.bitSetBetween(0, fieldCount))) {
Mapping mapping = Mappings.createIdentity(fieldCount);
return new TrimResult(values, mapping);
}
List<List<RexLiteral>> newTuples = new ArrayList<List<RexLiteral>>();
for (List<RexLiteral> tuple : values.getTuples()) {
List<RexLiteral> newTuple = new ArrayList<RexLiteral>();
for (int field : Util.toIter(fieldsUsed)) {
newTuple.add(tuple.get(field));
}
newTuples.add(newTuple);
}
final Mapping mapping = createMapping(fieldsUsed, fieldCount);
RelDataType newRowType =
values
.getCluster()
.getTypeFactory()
.createStructType(Mappings.apply3(mapping, rowType.getFieldList()));
final ValuesRel newValues = new ValuesRel(values.getCluster(), newRowType, newTuples);
return new TrimResult(newValues, mapping);
}
/** Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link FilterRel}. */
public TrimResult trimFields(
FilterRel filter, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
final RelDataType rowType = filter.getRowType();
final int fieldCount = rowType.getFieldCount();
final RexNode conditionExpr = filter.getCondition();
final RelNode input = filter.getChild();
// We use the fields used by the consumer, plus any fields used in the
// filter.
BitSet inputFieldsUsed = (BitSet) fieldsUsed.clone();
final Set<RelDataTypeField> inputExtraFields = new LinkedHashSet<RelDataTypeField>(extraFields);
RelOptUtil.InputFinder inputFinder =
new RelOptUtil.InputFinder(inputFieldsUsed, inputExtraFields);
conditionExpr.accept(inputFinder);
// Create input with trimmed columns.
TrimResult trimResult = trimChild(filter, input, inputFieldsUsed, inputExtraFields);
RelNode newInput = trimResult.left;
final Mapping inputMapping = trimResult.right;
// If the input is unchanged, and we need to project all columns,
// there's nothing we can do.
if (newInput == input && fieldsUsed.cardinality() == fieldCount) {
return new TrimResult(filter, Mappings.createIdentity(fieldCount));
}
// Build new project expressions, and populate the mapping.
final RexVisitor<RexNode> shuttle = new RexPermuteInputsShuttle(inputMapping, newInput);
RexNode newConditionExpr = conditionExpr.accept(shuttle);
final FilterRel newFilter = new FilterRel(filter.getCluster(), newInput, newConditionExpr);
assert newFilter.getClass() == filter.getClass();
// The result has the same mapping as the input gave us. Sometimes we
// return fields that the consumer didn't ask for, because the filter
// needs them for its condition.
return new TrimResult(newFilter, inputMapping);
}
/**
* 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()));
}
/** Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link AggregateRel}. */
public TrimResult trimFields(
AggregateRel aggregate, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
// Fields:
//
// | sys fields | group fields | agg functions |
//
// Two kinds of trimming:
//
// 1. If agg rel has system fields but none of these are used, create an
// agg rel with no system fields.
//
// 2. If aggregate functions are not used, remove them.
//
// But grouping fields stay, even if they are not used.
final RelDataType rowType = aggregate.getRowType();
// Compute which input fields are used.
BitSet inputFieldsUsed = new BitSet();
// 1. group fields are always used
for (int i : Util.toIter(aggregate.getGroupSet())) {
inputFieldsUsed.set(i);
}
// 2. agg functions
for (AggregateCall aggCall : aggregate.getAggCallList()) {
for (int i : aggCall.getArgList()) {
inputFieldsUsed.set(i);
}
}
// Create input with trimmed columns.
final RelNode input = aggregate.getInput(0);
final Set<RelDataTypeField> inputExtraFields = Collections.emptySet();
final TrimResult trimResult = trimChild(aggregate, input, inputFieldsUsed, inputExtraFields);
final RelNode newInput = trimResult.left;
final Mapping inputMapping = trimResult.right;
// If the input is unchanged, and we need to project all columns,
// there's nothing to do.
if (input == newInput && fieldsUsed.equals(Util.bitSetBetween(0, rowType.getFieldCount()))) {
return new TrimResult(aggregate, Mappings.createIdentity(rowType.getFieldCount()));
}
// Which agg calls are used by our consumer?
final int groupCount = aggregate.getGroupSet().cardinality();
int j = groupCount;
int usedAggCallCount = 0;
for (int i = 0; i < aggregate.getAggCallList().size(); i++) {
if (fieldsUsed.get(j++)) {
++usedAggCallCount;
}
}
// Offset due to the number of system fields having changed.
Mapping mapping =
Mappings.create(
MappingType.InverseSurjection, rowType.getFieldCount(), groupCount + usedAggCallCount);
final BitSet newGroupSet = Mappings.apply(inputMapping, aggregate.getGroupSet());
// Populate mapping of where to find the fields. System and grouping
// fields first.
for (IntPair pair : inputMapping) {
if (pair.source < groupCount) {
mapping.set(pair.source, pair.target);
}
}
// Now create new agg calls, and populate mapping for them.
final List<AggregateCall> newAggCallList = new ArrayList<AggregateCall>();
j = groupCount;
for (AggregateCall aggCall : aggregate.getAggCallList()) {
if (fieldsUsed.get(j)) {
AggregateCall newAggCall =
new AggregateCall(
aggCall.getAggregation(),
aggCall.isDistinct(),
Mappings.apply2(inputMapping, aggCall.getArgList()),
aggCall.getType(),
aggCall.getName());
if (newAggCall.equals(aggCall)) {
newAggCall = aggCall; // immutable -> canonize to save space
}
mapping.set(j, groupCount + newAggCallList.size());
newAggCallList.add(newAggCall);
}
++j;
}
RelNode newAggregate =
new AggregateRel(aggregate.getCluster(), newInput, newGroupSet, newAggCallList);
assert newAggregate.getClass() == aggregate.getClass();
return new TrimResult(newAggregate, mapping);
}
/** 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);
}
/** Variant of {@link #trimFields(RelNode, BitSet, Set)} for {@link ProjectRel}. */
public TrimResult trimFields(
ProjectRel project, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
final RelDataType rowType = project.getRowType();
final int fieldCount = rowType.getFieldCount();
final RelNode input = project.getChild();
final RelDataType inputRowType = input.getRowType();
// Which fields are required from the input?
BitSet inputFieldsUsed = new BitSet(inputRowType.getFieldCount());
final Set<RelDataTypeField> inputExtraFields = new LinkedHashSet<RelDataTypeField>(extraFields);
RelOptUtil.InputFinder inputFinder =
new RelOptUtil.InputFinder(inputFieldsUsed, inputExtraFields);
for (Ord<RexNode> ord : Ord.zip(project.getProjects())) {
if (fieldsUsed.get(ord.i)) {
ord.e.accept(inputFinder);
}
}
// Create input with trimmed columns.
TrimResult trimResult = trimChild(project, input, inputFieldsUsed, inputExtraFields);
RelNode newInput = trimResult.left;
final Mapping inputMapping = trimResult.right;
// If the input is unchanged, and we need to project all columns,
// there's nothing we can do.
if (newInput == input && fieldsUsed.cardinality() == fieldCount) {
return new TrimResult(project, Mappings.createIdentity(fieldCount));
}
// Some parts of the system can't handle rows with zero fields, so
// pretend that one field is used.
if (fieldsUsed.cardinality() == 0) {
final Mapping mapping = Mappings.create(MappingType.InverseSurjection, fieldCount, 1);
final RexLiteral expr =
project.getCluster().getRexBuilder().makeExactLiteral(BigDecimal.ZERO);
RelDataType newRowType =
project
.getCluster()
.getTypeFactory()
.createStructType(
Collections.singletonList(expr.getType()), Collections.singletonList("DUMMY"));
ProjectRel newProject =
new ProjectRel(
project.getCluster(),
project.getCluster().traitSetOf(RelCollationImpl.EMPTY),
newInput,
Collections.<RexNode>singletonList(expr),
newRowType,
project.getFlags());
return new TrimResult(newProject, mapping);
}
// Build new project expressions, and populate the mapping.
List<RexNode> newProjectExprList = new ArrayList<RexNode>();
final RexVisitor<RexNode> shuttle = new RexPermuteInputsShuttle(inputMapping, newInput);
final Mapping mapping =
Mappings.create(MappingType.InverseSurjection, fieldCount, fieldsUsed.cardinality());
for (Ord<RexNode> ord : Ord.zip(project.getProjects())) {
if (fieldsUsed.get(ord.i)) {
mapping.set(ord.i, newProjectExprList.size());
RexNode newProjectExpr = ord.e.accept(shuttle);
newProjectExprList.add(newProjectExpr);
}
}
final RelDataType newRowType =
project
.getCluster()
.getTypeFactory()
.createStructType(Mappings.apply3(mapping, rowType.getFieldList()));
final List<RelCollation> newCollations =
RexUtil.apply(inputMapping, project.getCollationList());
final RelNode newProject;
if (RemoveTrivialProjectRule.isIdentity(
newProjectExprList, newRowType, newInput.getRowType())) {
// The new project would be the identity. It is equivalent to return
// its child.
newProject = newInput;
} else {
newProject =
new ProjectRel(
project.getCluster(),
project
.getCluster()
.traitSetOf(
newCollations.isEmpty() ? RelCollationImpl.EMPTY : newCollations.get(0)),
newInput,
newProjectExprList,
newRowType,
project.getFlags());
assert newProject.getClass() == project.getClass();
}
return new TrimResult(newProject, mapping);
}
/**
* Visit method, per {@link org.eigenbase.util.ReflectiveVisitor}.
*
* <p>This method is invoked reflectively, so there may not be any apparent calls to it. The class
* (or derived classes) may contain overloads of this method with more specific types for the
* {@code rel} parameter.
*
* <p>Returns a pair: the relational expression created, and the mapping between the original
* fields and the fields of the newly created relational expression.
*
* @param rel Relational expression
* @param fieldsUsed Fields needed by the consumer
* @return relational expression and mapping
*/
public TrimResult trimFields(RelNode rel, BitSet fieldsUsed, Set<RelDataTypeField> extraFields) {
// We don't know how to trim this kind of relational expression, so give
// it back intact.
Util.discard(fieldsUsed);
return new TrimResult(rel, Mappings.createIdentity(rel.getRowType().getFieldCount()));
}