/**
* Generates a cast from one row type to another
*
* @param rexBuilder RexBuilder to use for constructing casts
* @param lhsRowType target row type
* @param rhsRowType source row type; fields must be 1-to-1 with lhsRowType, in same order
* @return cast expressions
*/
public static RexNode[] generateCastExpressions(
RexBuilder rexBuilder, RelDataType lhsRowType, RelDataType rhsRowType) {
int n = rhsRowType.getFieldCount();
assert n == lhsRowType.getFieldCount()
: "field count: lhs [" + lhsRowType + "] rhs [" + rhsRowType + "]";
RexNode[] rhsExps = new RexNode[n];
for (int i = 0; i < n; ++i) {
rhsExps[i] = rexBuilder.makeInputRef(rhsRowType.getFields()[i].getType(), i);
}
return generateCastExpressions(rexBuilder, lhsRowType, rhsExps);
}
/**
* 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()));
}