Abstract: In a database system, a mechanism is provided to enable parsing of a query into plural objects stored in respective plural tables. One or more characteristics of the query is modified using content of the plural tables based on one or more predefined rules for the purpose of recomposing the query.

Abstract: A database system includes an enhanced technique for performing sorts in which removals of duplicate records are performed to compact the size of segments being sorted. To enhance a query plan, the duplicate record removal is performed as early in the query plan as possible. By removing duplicate records early in the query plan, the number of input/output (I/O) operations is reduced, resulting in more efficient usage of database system resources. In example implementations, two type of sorts are performed: a heap sort (to sort successive segments of an input file, with the sorting associated with concurrent removal of duplicate records to compact each segment so that a smaller number of I/O accesses is needed); and a merge sort (in which output files from prior sorting passes are merged and sorted, with the merge sort process also associated with the removal of duplicate records to further compact the data segments and reduce the number of I/O accesses).

Abstract: A database system includes a storage that contains plural tables as well as a predefined data structure. The database system is able to, in response to a join query, perform a join of two or more tables. The database system also is able to determine, based on values contained in the predefined data structure, whether a group-by operation can be skipped.

Abstract: A database system includes an enhanced optimizer module that is able to consider group-by operations as part of the optimization of a join. Given a query that performs a join of multiple tables and that includes an aggregation function as well as at one of a Where clause and a Group-by clause, a partial group-by is performed on at least one of the tables of the join query to reduce the number of rows for the join. Group-by can also be performed on intermediate results of intermediate joins.

Abstract: A database system includes an enhanced optimizer module that is able to consider group-by operations as part of the optimization of a join. Given a query that performs a join of multiple tables and that includes an aggregation function as well as at one of a Where clause and a Group-by clause, a partial group-by is performed on at least one of the tables of the join query to reduce the number of rows for the join. Group-by can also be performed on intermediate results of intermediate joins.

Abstract: A database system includes a storage that contains plural tables as well as a predefined data structure. The database system is able to, in response to a join query, perform a join of two or more tables. The database system also is able to determine, based on values contained in the predefined data structure, whether a group-by operation can be skipped.