/**
* Creates projection list for scan. If the projection contains expressions, then the input
* references from those expressions are extracted and that list of references becomes the
* projection list.
*
* @param origScan row scan underneath the project
* @param projRel ProjectRel that we will be creating the projection for
* @param projectedColumns returns a list of the projected column ordinals, if it is possible to
* project
* @param preserveExprCondition condition that identifies special expressions that should be
* preserved in the projection
* @param defaultExpr expression to be used in the projection if no fields or special columns are
* selected
* @param newProjList returns a new projection RelNode corresponding to a projection that now
* references a rowscan that is projecting the input references that were extracted from the
* original projection expressions; if the original expression didn't contain expressions,
* then this list is returned empty
* @return true if columns in projection list from the scan need to be renamed
*/
public boolean createProjectionList(
FennelRel origScan,
ProjectRel projRel,
List<Integer> projectedColumns,
PushProjector.ExprCondition preserveExprCondition,
RexNode defaultExpr,
List<ProjectRel> newProjList) {
// REVIEW: what about AnonFields?
int n = projRel.getChildExps().length;
RelDataType rowType = origScan.getRowType();
RelDataType projType = projRel.getRowType();
RelDataTypeField[] projFields = projType.getFields();
List<Integer> tempProjList = new ArrayList<Integer>();
boolean needRename = false;
for (int i = 0; i < n; ++i) {
RexNode exp = projRel.getChildExps()[i];
List<String> origFieldName = new ArrayList<String>();
Integer projIndex = mapProjCol(exp, origFieldName, rowType);
if (projIndex == null) {
// there are expressions in the projection; we need to extract
// all input references and any special expressions from the
// projection
PushProjector pushProject =
new PushProjector(projRel, null, origScan, preserveExprCondition);
ProjectRel newProject = pushProject.convertProject(defaultExpr);
if (newProject == null) {
// can't do any further projection
return false;
}
newProjList.add(newProject);
// using the input references we just extracted, it should now
// be possible to create a projection for the row scan
needRename =
createProjectionList(
origScan,
(ProjectRel) newProject.getChild(),
projectedColumns,
preserveExprCondition,
defaultExpr,
newProjList);
assert (projectedColumns.size() > 0);
return needRename;
}
String projFieldName = projFields[i].getName();
if (!projFieldName.equals(origFieldName.get(0))) {
needRename = true;
}
tempProjList.add(projIndex);
}
// now that we've determined it is possible to project, add the
// ordinals to the return list
projectedColumns.addAll(tempProjList);
return needRename;
}
/**
* 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());
}
/**
* 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());
}
protected Integer mapFieldRef(RexNode exp, List<String> origFieldName, RelDataType rowType) {
RexInputRef fieldAccess = (RexInputRef) exp;
origFieldName.add(rowType.getFields()[fieldAccess.getIndex()].getName());
return fieldAccess.getIndex();
}
