Abstract: This invention relates generally to a system for processing database queries, and more particularly to a method for generating high level language or machine code to implement query execution plans. The present invention provides a method for generating executable machine code for query execution plans, that is adaptive to dynamic runtime conditions, that is compiled just in time for execution and most importantly, that avoids the bounds checking, pointer indirection, materialization and other similar kinds of overhead that are typical in interpretive runtime execution engines.

Abstract: A disk is segmented into a first data segment and a secondary data segment. The secondary data segment stores a logical mirror of the first data segment of another disk. Upon detecting a failure, the logical mirror of data stored in the first data segment of the failed disk is accessible from the secondary data segment of a non-failed disk. The first data segment can be rebuilt quickly on another disk from the logical mirror stored in the secondary data segment. During regenerating, accesses to the first data segment on the disk containing the logical mirror are handled by its own logical mirror, which is not involved in the regenerating process.

Abstract: A large information space is divided into many smaller information extents. These extents are annotated with statistics about the information they contain. When a search for information includes a restriction based on value, the desired value ranges can be compared to the value ranges of each extent. If the desired value range lies outside the range of the extent, then the extent cannot hold the desired value and does not need to be included in the search.