Abstract: A method, computer program and database system are disclosed for performing an exclusion join of at least a first table T1 and a second table T2, where each of the tables has an associated Star Map, S1 and S2, respectively. Each Star Map includes bitmap entries having locations indexed by the hash of one or more values associated with one or more join key columns of its associated table. The method, computer program, and database system include a) performing one or more Boolean operations using the bitmap entries of the Star Maps S1 and S2 to produce bitmap entries in a Star Map SJ where there is a corresponding set bitmap entry in S1 and no corresponding set bitmap entry in S2; b) using SJ to identify qualifying rows from the first table T1; and c) providing the qualifying rows as an exclusion join result.

Abstract: A method, computer program and database system are disclosed for performing an outer join of at least a first table T1 and a second table T2. The join has join conditions. Each of the tables has an associated Star Map, S1 and S2, respectively. Each Star Map includes bitmap entries which have locations indexed by the hash of one or more values associated with one or more join key columns of its associated table. A bitmap entry in a Star Map, if set, indicates the presence of a row in its associated table that has entries in the one or more join key columns that together hash to the location of the bitmap entry.

Abstract: A method for retrieving information from a database includes identifying a cylinder. The cylinder includes a plurality of data segments. The method also includes retrieving the plurality of data segments from the cylinder during a single retrieval operation. In addition, the method includes storing the plurality of data segments in a cache.

Abstract: A method and computer program for allocating storage for a header and one or more data elements in a data storage facility are disclosed. The method and computer program include computing a hole size B that is a portion of a word that would be unallocated if storage were allocated to the header and to the data elements in a preferred order. The method and computer program include finding a subset of data elements S={Fi1, Fi2, . . . , Fin} that satisfy the equation (SizeModN(Fi1)+SizeModN(Fi2)+ . . . +SizeModN(Fin))mod N=B where N is the largest alignment requirement associated with any data element. The method and computer program include allocating storage to data elements in S first and allocating storage to the remaining elements in the preferred order. A lookup table and a method for building the lookup table are also disclosed.

Abstract: A method, apparatus, and article of manufacture for optimizing SQL queries in a relational database management system involving aggregate and grouping functions. A local aggregation operation is performed on one or more processors of a massively parallel processor (MPP) computer system, wherein rows of the table that are local to each processor are locally aggregated to create one or more aggregate result rows. The aggregate result rows created by each of the local aggregation operations are then re-distributed to one or more processors and coalesced into a global aggregate result row by a global aggregation operation.