VoltXMLElement voltGetXMLExpression(QueryExpression queryExpr, Session session)
throws HSQLParseException {
// "select" statements/clauses are always represented by a QueryExpression of type
// QuerySpecification.
// The only other instances of QueryExpression are direct QueryExpression instances instantiated
// in XreadSetOperation
// to represent UNION, etc.
int exprType = queryExpr.getUnionType();
if (exprType == QueryExpression.NOUNION) {
// "select" statements/clauses are always represented by a QueryExpression of type
// QuerySpecification.
if (!(queryExpr instanceof QuerySpecification)) {
throw new HSQLParseException(queryExpr.operatorName() + " is not supported.");
}
QuerySpecification select = (QuerySpecification) queryExpr;
return voltGetXMLSpecification(select, session);
} else if (exprType == QueryExpression.UNION
|| exprType == QueryExpression.UNION_ALL
|| exprType == QueryExpression.EXCEPT
|| exprType == QueryExpression.EXCEPT_ALL
|| exprType == QueryExpression.INTERSECT
|| exprType == QueryExpression.INTERSECT_ALL) {
VoltXMLElement unionExpr = new VoltXMLElement("union");
unionExpr.attributes.put("uniontype", queryExpr.operatorName());
VoltXMLElement leftExpr = voltGetXMLExpression(queryExpr.getLeftQueryExpression(), session);
VoltXMLElement rightExpr = voltGetXMLExpression(queryExpr.getRightQueryExpression(), session);
/**
* Try to merge parent and the child nodes for UNION and INTERSECT (ALL) set operation. In
* case of EXCEPT(ALL) operation only the left child can be merged with the parent in order to
* preserve associativity - (Select1 EXCEPT Select2) EXCEPT Select3 vs. Select1 EXCEPT
* (Select2 EXCEPT Select3)
*/
if ("union".equalsIgnoreCase(leftExpr.name)
&& queryExpr.operatorName().equalsIgnoreCase(leftExpr.attributes.get("uniontype"))) {
unionExpr.children.addAll(leftExpr.children);
} else {
unionExpr.children.add(leftExpr);
}
if (exprType != QueryExpression.EXCEPT
&& exprType != QueryExpression.EXCEPT_ALL
&& "union".equalsIgnoreCase(rightExpr.name)
&& queryExpr.operatorName().equalsIgnoreCase(rightExpr.attributes.get("uniontype"))) {
unionExpr.children.addAll(rightExpr.children);
} else {
unionExpr.children.add(rightExpr);
}
return unionExpr;
} else {
throw new HSQLParseException(
queryExpression.operatorName() + " tuple set operator is not supported.");
}
}
