/**
* Check if a tuple attribute reference is valid. Disambiguate if needed. Also set the
* RelationSchema for the TupleAttribute. *
*/
boolean analyzeTupleAttribute(TupleAttribute ta) {
if (ta.tableName == null) {
BaseRelationSchema found_in = null;
for (BaseRelationSchema rs : query_relations) {
// System.out.println("searching for " + ta.attributeName + " in " + rs);
if (rs.hasAttribute(ta.attributeName)) {
if (found_in == null) {
found_in = rs;
} else {
System.out.println("=========> Attribute " + ta.attributeName + " ambiguous");
return false;
}
}
}
if (found_in != null) {
ta.tableName = found_in.getName();
ta.setRelationSchema(found_in);
return true;
} else {
System.out.println(
"=========> Attribute "
+ ta.attributeName
+ " not found in any of the tables in the FROM clause");
return false;
}
} else {
if (!checkRelationContainedInFromClause(ta.tableName)) {
System.out.println("=========> Relation " + ta.tableName + " not in the From Clause");
return false;
}
ta.setRelationSchema(Globals.getRelationSchema(ta.tableName));
if (!ta.rs.hasAttribute(ta.attributeName)) {
System.out.println(
"=========> Attribute "
+ ta.attributeName
+ " not present in the relation "
+ ta.tableName);
return false;
}
return true;
}
}
/* Construct the query object. Analyze, check for errors etc. */
boolean analyze() {
/* Get the relation schemas, and make sure the relations exist. */
query_relations = new Vector<BaseRelationSchema>();
for (String name : query_relation_names) {
BaseRelationSchema rs;
if ((rs = Globals.getRelationSchema(name)) == null) {
System.out.println("=========> Relation " + name + " does not exist");
return false;
}
query_relations.add(rs);
}
/* Now check all the predicates. */
for (Predicate p : query_predicates) {
/* Check the validity of the attributes. */
if ((p.lhs() instanceof TupleAttribute) && (!analyzeTupleAttribute((TupleAttribute) p.lhs())))
return false;
if ((p.rhs() instanceof TupleAttribute) && (!analyzeTupleAttribute((TupleAttribute) p.rhs())))
return false;
}
/* Finally check the select list. */
if (select_attributes.size() != 0) {
for (TupleAttribute ta : select_attributes) {
/* Check the validity of the attribute. */
if (!analyzeTupleAttribute(ta)) return false;
}
} else {
for (BaseRelationSchema rs : query_relations) {
for (String attrName : rs.attributeNames) {
TupleAttribute ta = new TupleAttribute(rs.getName(), attrName);
ta.setRelationSchema(rs);
select_attributes.add(ta);
}
}
}
return true;
}
/** Is the argument relation contained in the From Clause ? * */
boolean checkRelationContainedInFromClause(String name) {
for (BaseRelationSchema rs : query_relations) if (rs.getName().equals(name)) return true;
return false;
}