public static SqlOpQuery makeSelectOrTable(SqlOpQuery node) {
String alias = aliasGenerator.next();
SqlOpQuery result = new SqlOpQuery(node.getSchema(), node.getQueryString(), alias);
return result;
}
/**
* Builds up the one triple that states where the actual data for the target mapping comes from.
* Such a source can be simply a database table or an SQL query.
*
* @param r2rml the target com.hp.hpl.jena.rdf.model.Model
* @param relation the data source (table name or SQL query)
* @return the whole Statement stating where the data comes from, e.g. '[] rr:tableName "EMP"'
*/
private Statement buildLogicalTableTriple(Model r2rml, SqlOpBase relation) {
// subject (a blank node [])
Resource logicalTableSubject = ResourceFactory.createResource();
// predicate (rr:tableName or rr:sqlQuery)
Property logicalTablePredicate;
// object (a Literal like "SELECT DEPTNO FROM DEPT WHERE DEPTNO > 23" or
// simply a table name like "DEPTNO"
Literal logicalTableObject;
// it's a table
if (relation instanceof SqlOpTable) {
SqlOpTable tbl = (SqlOpTable) relation;
logicalTablePredicate = ResourceFactory.createProperty(rrNamespace, "tableName");
logicalTableObject = ResourceFactory.createPlainLiteral(tbl.getTableName());
// it's a query
} else if (relation instanceof SqlOpQuery) {
SqlOpQuery query = (SqlOpQuery) relation;
logicalTablePredicate = ResourceFactory.createProperty(rrNamespace, "sqlQuery");
logicalTableObject = ResourceFactory.createPlainLiteral(query.getQueryString());
// it's not possible
} else {
// should never be called since a relation can either be a table
// or a query
logicalTablePredicate = ResourceFactory.createProperty("");
logicalTableObject = ResourceFactory.createPlainLiteral("");
}
Statement logicalTblStatement =
r2rml.createStatement(logicalTableSubject, logicalTablePredicate, logicalTableObject);
return logicalTblStatement;
}
public static SqlOpSelectBlock makeSelect(SqlOpQuery node) {
SqlOpQuery opQuery = makeSelectOrTable(node);
SqlOpSelectBlock result = SqlOpSelectBlock.create(opQuery);
for (String columnName : opQuery.getSchema().getColumnNames()) {
result
.getProjection()
.put(columnName, new ExprVar(opQuery.getAliasName() + "." + columnName));
}
return result;
}
