摘要:
A method, database system and computer program are disclosed for optimizing a SQL query, in which the SQL query includes an IN-List. The method includes utilizing an array insert to insert the IN-List into a spool and piggybacking IN-List rows into a join step.
摘要:
A SQL query that includes an IN-List is optimized by utilizing an array insert to insert the IN-List into a spool and piggybacking IN-List rows into a join step.
摘要:
An optimization technique involves optimizing a SQL query, in which the SQL query includes a large IN-List query to access data in a table. The technique includes determining whether an IN-List exceeds a predetermined size, and, if so, removing the IN-List query statement and inserting a new query statement including a join operation.
摘要:
A database query is optimized for a star database schema that includes at least one fact table and at least one dimension table, where the database query includes an IN-List condition. During optimization, the IN-List is transformed into a relation and the relation is joined with the dimension table to produce a join result. The join result is then joined to the fact table.
摘要:
A SQL query that includes an IN-List is optimized by (1) performing an evaluation to determine whether access to a table can be performed as a join operation, (2) converting the IN-List to an IN-LIST relation, and (3) joining the IN-List relation with the table to access the data in the table.
摘要:
A database query is optimized for a star database schema that includes at least one fact table and at least one dimension table, where the database query includes an IN-List condition. During optimization, the IN-List is transformed into a relation and the relation is joined with the dimension table to produce a join result. The join result is then joined to the fact table.
摘要:
A method, database system and computer program are disclosed for optimizing a SQL query, in which the SQL query includes an IN-List. An evaluation is performed to determine whether the IN-List query can be performed as a join operation. If so, a new access path that converting IN-List to a relation, and subsequently joined with the table to complete the IN-List query is cost and competes with other access paths.
摘要:
Demographics for data are determined. A compression ratio (“CR”) is determined for each of a plurality of compression techniques. CR is a size of the data before compression divided into a predicted size of the data after compression. The predicted size of the data after compression is determined as a function of the determined demographics. An access efficiency of each of the compression techniques is determined as a function of the determined demographics. The compression techniques are ranked by CR and access efficiency. A compression technique is selected based on the ranking. The data is compressed using the selected compression technique. The compressed data is stored.
摘要:
Methods, computer programs, and database systems for performing a database query to join a column A and a column B on an inequality condition are disclosed. A database includes value-count indexes for columns A and B. Minimum and a maximum values for A and B are determined, using the value-count indexes for A and B, respectively. The method includes defining three or more sets of values in A and B, relative to the minimum and maximum values for B and A, respectively. The method includes generating one or more Cartesian products between values in A and B. The database query is performed on a set of values in A and a set of values in B to generate a partial query result. The method includes merging one or more Cartesian products and the partial query result.
摘要:
Processing of a request is optimized. The request has one or more predicates. A list of the one or more predicates in the request is created and predicates for which an actual cost has not been stored or for which a cost cannot be estimated are pruned from the list. An access path for the each of the predicates is selected. The request is processed using the selected access paths producing one or more actual predicate costs. The one or more actual predicate costs are stored.