/**
* 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);
}
public Void visitInputRef(RexInputRef inputRef) {
super.visitInputRef(inputRef);
if (inputRef.getIndex() >= inputRowType.getFieldCount()) {
throw new IllegalForwardRefException();
}
return null;
}
public RelDataType inferReturnType(SqlOperatorBinding opBinding) {
assert opBinding.getOperandCount() == 1;
final RelDataType recordType = opBinding.getOperandType(0);
boolean isStruct = recordType.isStruct();
int fieldCount = recordType.getFieldCount();
assert isStruct && (fieldCount == 1);
RelDataTypeField fieldType = recordType.getFieldList().get(0);
assert fieldType != null : "expected a record type with one field: " + recordType;
final RelDataType firstColType = fieldType.getType();
return opBinding.getTypeFactory().createTypeWithNullability(firstColType, true);
}