Abstract: An information retrieval system is adapted to process a query having an associated plan that includes applying predicates comprising local predicates and a join predicate, to at least two tables. Index ANDing is used to construct a filter for filtering a first of the tables in accordance with the local predicates. The join predicate is applied to the tables for determining row identifiers of rows satisfying the join predicate. The row identifiers are used to probe the filter for determining whether the rows satisfying the join predicate also satisfy the local predicates. The rows that satisfy both the join and local predicates are fetched and the join predicate is completed. Results of the join predicate are then returned.

Abstract: In an information retrieval system, a query optimization method transforms maximum or minimum function aggregation predicates on a non-indexed column into a single sort function. The method evaluates the query to identify a table and a predicate equating a column of the table to a sub-query that applies a maximum or minimum aggregation function to the column to return an aggregate value for the column. The aggregate value is used for selecting rows from the table to produce a query result. A determination is then made whether an index has not been created using the column of the table. In response to these steps of evaluating and determining, the method reforms the query as a sort function on the column. The sort function scans the table once to provide the query result.

Abstract: A query rewrite optimization method eliminates condition predicates of conditional expressions defining the values of a column that is referenced in the predicate of an SQL query on a view. The method evaluates the query to identify a view and a predicate referencing a column of the view. The column has values selected by a conditional expression having condition predicates defining respective mutually exclusive ranges of values. The predicate defines a first range of values. A determination is made as to whether one of the condition predicates defines a mutually exclusive range of values that comprises the first range of values. In response, the query is rewritten to eliminate the condition predicates other than the one condition predicate. The predicate is thus applied directly to the base tables without evaluating the conditional expression.

Abstract: The objects of this invention are accomplished by combinging the inverse DCT of an appropriate size with scaling on the resulting reconstructed image. In particular, if the data is stored as DCT values of blocks of size P.times.Q and an output image is to be scaled by a factor of R in one dimension and S in the second dimension, then the process is performed in two stages. First a scaling of factor K1/P in the first dimension and a scaling of factor L1/Q in the second dimension are done by inverse transforming with 2-dimensional DCTs of size K1.times.L1. A factor .sqroot.(K1/P).times..sqroot.(L1/Q) is absorbed into a dequantization process prior to the inverse transorm process. Then a scaling of factor K2/K3 in the first dimension and a scaling of factor L2/L3 in the second dimension is done in the spatial domain. The integers K1, K2, K3, L1, L2, L3 are chosen so the (K1K2/K3)=R, (L1L2/L3)=S, (K1/P).gtoreq.R, (L1/Q).gtoreq.S, and the ratios (K2/K3) and (L1/L2) are close to 1.