Abstract: A method and apparatus for transforming queries is provided. A select-project-join query Q that specifies an antijoin is rewritten into another query that references the materialized view M. The common section includes the tables being antijoined, and may be one-to-many lossless with respect to the join with the materialized view delta.

Abstract: A method and apparatus for transforming queries is provided. A select-project-join query Q is rewritten into another query that joins a materialized view M and a subset of the tables from Q not in the common section portion of Q. The common section may be one-to-many lossless with respect to the join with the materialized view delta. As compared to one-to-one rewrites, the one-to-many rewrites described herein provide a more general class of rewrites.

Abstract: A query containing an outer join of a view based on a join of two tables is transformed by pushing one or more predicates of the outer join into the view. The pushed predicates provide new access paths and join methods that are used by a database server in generating an access plan to evaluate the view. In one embodiment, costs for processing the original and transformed queries are estimated and the lower cost query is processed.

Abstract: A method and system for performing spreadsheet-like operations in a database system is described herein. As explained, a database language is extended to introduce new clauses (“spreadsheet-like clauses”), for defining and executing spreadsheet-like operations on data contained within a RDBMS. According to one aspect of the invention, in response to receiving a database query that specifies an operation for manipulating data, data from a relational structure is retrieved and stored in a non-relational structure that can be addressed as a multi-dimensional array. The operation specified in the database query is the performed on then data.

Abstract: Queries having a outer query block enclosing an inner query block, such as a reference to a view or a subquery, with a grouping operator, such as GROUP or DISTINCT, are transformed by merging the inner query block into the outer query block. The FROM clause of the transformed query includes the tables referenced in the FROM clauses of the outer query block and the inner query block. A new GROUP BY clause is created for the outer query block that contains the rowids of tables referenced in the FROM list of the original query and the expressions in the GROUP BY clause of the inner query block. The outer query block can be split if the outer query block also contains a GROUP BY or HAVING clause.

Abstract: Concurrency control for maintenance of materialized view defined as a join on a plurality of base tables is provided by obtaining different types of locks. The base table being updated is locked with one type of lock, and the other base tables of the materialized view is locked with a different type of lock. These lock types are defined so that another process attempting to update another base table simultaneously is blocked until the update on the base table is committed. On the other hand, another process attempting to update the same base table is allowed to perform that update concurrently.

Abstract: A method and apparatus are provided for rewriting aggregate queries to access a materialized view when (1) the queries place a restriction on an ordered dimension, (2) the materialized view aggregates the information referenced in the query and groups by the same dimension, and (3) the materialized view groups the information at a coarser level of granularity than the granularity associated with the restriction contained in the aggregate queries.

Abstract: A method and apparatus are provided for performing incremental refreshes to materialized views defined by one-to-one lossless joins. Each base table of the materialized view is selected to be processed as the current "selected table". During the processing, if the selected table is the right table of an outer join, then selected columns of rows of the materialized view are set to NULL based on rows of the selected table that have been updated or deleted in the selected table after a prior refresh operation. Then, NULL values in selected columns of the materialized view are updated to reflect new values caused by updates and inserts into the selected table that occurred after the prior refresh operation. If the selected table is not the right table of an outer join, then rows from the materialized view are deleted based on rows of the selected table that have been updated or deleted in the selected table after the prior refresh operation.

Abstract: A method and apparatus are provided for performing incremental refreshes to materialized views defined by one-to-N lossless joins. Each base table of the materialized view is selected to be processed as the current "selected table". The processing of the current selected table varies depending on whether the selected table is the right side table of an outer join. If the selected table is not the right table of an outer join, then the selected table is processed by (1) deleting rows from the materialized view based on rows of the selected table that have been updated or deleted in the selected table during the batch window, and (2) inserting rows into the materialized view based on updates and inserts into the selected table that occurred during the batch window. If the selected table is the right table of an outer join, then changes made to the selected table are processed in a way that reduces the number of changes that have to be made to the materialized view.

Abstract: Techniques for maintaining an approximate histogram of a relation in a database, in the presence of updates to the relation. The histogram includes a number of subsets, or "buckets," each representing at least one possible value of an attribute of the relation. Each of the subsets has a count associated therewith indicative of the frequency of occurrence of the corresponding value of the attribute. After an update to the relation, the counts associated with the subsets are compared to a threshold. If the count associated with a given subset exceeds the threshold, the given subset is separated at its median into two separate subsets. After the separation operation, the two subsets with the lowest counts are combined such that a constant number of subsets are maintained in the histogram, if the total combined count of the subsets does not exceed the threshold. If no two subsets have a total combined count which does not exceed the threshold, the histogram is recomputed from a random sample of the relation.

Abstract: A method maintains information associated with items in a database of limited memory which information is used to generate representations of the information such as high-biased histograms. In a first embodiment of the inventive method, information associated with all items with sales above a threshold, together with approximate counts of the items, is maintained. Appropriate choice of a threshold limits the amount of information required to be maintained so as to generate accurate representations of the information with high probability. In a second embodiment of the inventive method, information used to generate a high-biased histogram is maintained within a fixed allotment of memory by dynamic adjusting a threshold which threshold is used to determine a probability with which information is retained in the database.