/**
* Determines if a projection is simple.
*
* @param calcRel CalcRel containing the projection
* @param projOrdinals if the projection is simple, returns the ordinals of the projection inputs
* @return rowtype corresponding to the projection, provided it is simple; otherwise null is
* returned
*/
private RelDataType isProjectSimple(CalcRel calcRel, List<Integer> projOrdinals) {
// Loop through projection expressions. If we find a non-simple
// projection expression, simply return.
RexProgram program = calcRel.getProgram();
List<RexLocalRef> projList = program.getProjectList();
int nProjExprs = projList.size();
RelDataType[] types = new RelDataType[nProjExprs];
String[] fieldNames = new String[nProjExprs];
RelDataTypeField[] projFields = calcRel.getRowType().getFields();
for (int i = 0; i < nProjExprs; i++) {
RexNode projExpr = program.expandLocalRef(projList.get(i));
if (projExpr instanceof RexInputRef) {
projOrdinals.add(((RexInputRef) projExpr).getIndex());
types[i] = projExpr.getType();
fieldNames[i] = projFields[i].getName();
continue;
} else if (!(projExpr instanceof RexCall)) {
return null;
}
RexCall rexCall = (RexCall) projExpr;
if (rexCall.getOperator() != SqlStdOperatorTable.castFunc) {
return null;
}
RexNode castOperand = rexCall.getOperands()[0];
if (!(castOperand instanceof RexInputRef)) {
return null;
}
RelDataType castType = projExpr.getType();
RelDataType origType = castOperand.getType();
if (isCastSimple(origType, castType)) {
projOrdinals.add(((RexInputRef) castOperand).getIndex());
types[i] = castType;
fieldNames[i] = projFields[i].getName();
} else {
return null;
}
}
// return the rowtype corresponding to the output of the projection
return calcRel.getCluster().getTypeFactory().createStructType(types, fieldNames);
}
