/**
* Creates a relational expression which permutes the output fields of a relational expression
* according to a permutation.
*
* <p>Optimizations:
*
* <ul>
* <li>If the relational expression is a {@link CalcRel} or {@link ProjectRel} which is already
* acting as a permutation, combines the new permutation with the old;
* <li>If the permutation is the identity, returns the original relational expression.
* </ul>
*
* <p>If a permutation is combined with its inverse, these optimizations would combine to remove
* them both.
*
* @param rel Relational expression
* @param permutation Permutation to apply to fields
* @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 permutes its input fields
*/
public static RelNode permute(RelNode rel, Permutation permutation, List<String> fieldNames) {
if (permutation.isIdentity()) {
return rel;
}
if (rel instanceof CalcRel) {
CalcRel calcRel = (CalcRel) rel;
Permutation permutation1 = calcRel.getProgram().getPermutation();
if (permutation1 != null) {
Permutation permutation2 = permutation.product(permutation1);
return permute(rel, permutation2, null);
}
}
if (rel instanceof ProjectRel) {
Permutation permutation1 = ((ProjectRel) rel).getPermutation();
if (permutation1 != null) {
Permutation permutation2 = permutation.product(permutation1);
return permute(rel, permutation2, null);
}
}
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 < permutation.getTargetCount(); i++) {
int target = permutation.getTarget(i);
final RelDataTypeField targetField = fields.get(target);
outputTypeList.add(targetField.getType());
outputNameList.add(
((fieldNames == null) || (fieldNames.size() <= i) || (fieldNames.get(i) == null))
? targetField.getName()
: fieldNames.get(i));
exprList.add(rel.getCluster().getRexBuilder().makeInputRef(fields.get(i).getType(), i));
final int source = permutation.getSource(i);
projectRefList.add(new RexLocalRef(source, fields.get(source).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());
}
public static RelNode createProject(final RelNode child, final List<Integer> posList) {
return CalcRel.createProject(
child,
new AbstractList<RexNode>() {
public int size() {
return posList.size();
}
public RexNode get(int index) {
final int pos = posList.get(index);
return child
.getCluster()
.getRexBuilder()
.makeInputRef(child.getRowType().getFieldList().get(pos).getType(), pos);
}
},
null);
}
/**
* Creates new RelNodes replacing/removing the original project/row scan
*
* @param projectedScan new scan that is now projected
* @param origProject original projection
* @param needRename true if fields from the row scan need to be renamed
* @param newProject projection that contains the new projection expressions, in the case where
* the original projection cannot be removed because it projects expressions
* @return new RelNode
*/
public RelNode createNewRelNode(
RelNode projectedScan, ProjectRel origProject, boolean needRename, ProjectRel newProject) {
RelNode scanRel;
if (needRename) {
// Replace calling convention with FENNEL_EXEC_CONVENTION
RelTraitSet traits = RelOptUtil.clone(origProject.getTraits());
traits.setTrait(CallingConventionTraitDef.instance, FennelRel.FENNEL_EXEC_CONVENTION);
if (!traits.equals(projectedScan.getTraits())) {
RelNode mergedProjectedScan = convert(projectedScan, traits);
RelOptPlanner planner = projectedScan.getCluster().getPlanner();
// register projectedScan == mergedProjectedScan
// so mergedProjectedScan will have a set later on
projectedScan = planner.ensureRegistered(mergedProjectedScan, projectedScan);
}
scanRel =
new FennelRenameRel(
origProject.getCluster(),
projectedScan,
RelOptUtil.getFieldNames(origProject.getRowType()),
traits);
} else {
scanRel = projectedScan;
}
if (newProject == null) {
return scanRel;
} else {
// in the case where the projection had expressions, put the
// new, modified projection on top of the projected row scan
return (ProjectRel)
CalcRel.createProject(
scanRel,
newProject.getProjectExps(),
RelOptUtil.getFieldNames(newProject.getRowType()));
}
}
