Abstract: Techniques are described herein for replacing a part of an expression in a query to a database with a virtual column. A virtual column is defined by the database to contain results of a defining expression. A part of an expression in a query is replaced with a virtual column whose defining expression is equal to the part of the expression in the query. The part of an expression in a query can be the entire expression. When an expression in a query can be replaced with more than one replacement expression involving virtual columns, the replacement expression with the least cost of query processing is selected.

Abstract: The concept of portioning is expanded with a variety of techniques. In particular, one technique involves partitioning an object at multiple levels, where at least one of the levels uses list-based partitioning. Further, a partitioning technique is provided which involves storing a data item in a default partition when the item does not map to any one of the list-based partitions for which a key value group has been defined. Techniques are also provided for efficiently splitting a partition.

Abstract: The concept of portioning is expanded with a variety of techniques. In particular, one technique involves partitioning an object at multiple levels, where at least one of the levels uses list-based partitioning. Further, a partitioning technique is provided which involves storing a data item in a default partition when the item does not map to any one of the list-based partitions for which a key value group has been defined. Techniques are also provided for efficiently splitting a partition.

Abstract: The concept of partitioning is expanded with a variety of techniques. In particular, one technique involves partitioning an object at multiple levels, where at least one of the levels uses list-based partitioning. Further, a partitioning technique is provided which involves storing a data item in a default partition when the item does not map to any one of the list-based partitions for which a key value group has been defined. Techniques are also provided for efficiently splitting a partition.

Abstract: A system, method, computer program and article of manufacture for sharing metadata among cursors is provided. A metadata object marked as a versioned object can have multiple versions. Program units can share these versions of object metadata as opposed to copying the non-versioned object metadata into their memory. These program units may contain a pointer to an object's metadata but are otherwise void of the metadata information for the object. A locking protocol for the metadata ensures concurrency control and triggers dependency tracking. A locking protocol for the cursors controls cursor dependency status.

Abstract: Versioned metadata allows multiple versions of metadata for a given object to exist concurrently on a system thereby supporting the parallel execution of operations which would otherwise be mutually exclusive. Metadata updates are permitted while other objects maintain access to another version of the metadata through a versioning infrastructure. The versioning infrastructure allows the creation of new versions of metadata, maintains obsolete versions in the system as long as they are being used by any object, and deletes the obsolete versions once they are no longer in use.