Oracle International Corporation

Robert J Jenkins, Jr

Kenneth R Jacobs

Juan R Loaiza

Ekrem Soylemez

Gary Hallmark

Adiel Yoaz

Hasan Rizvi

An approach for using functional indexes as a primary filter is provided. A database query that contains a reference to a column of a table, but does not contain any reference to a functional index based on that column, is received by a database server. The database server adds to the database query a reference to the functional index on the column. The database server determines if the database query should be executed using the functional index. If the database server determines that the database query should be executed using the functional index, then the database query is executed with the functional index. If the database server determines that the database query should not be executed using the functional index, then data that indicates that the functional index is not to be evaluated when the database query is executed is stored.

Automatic use of a functional index as a primary filter

A method and apparatus is disclosed for implementing descending indexes in a database management system. A key value to be inserted within an index is decomposed into individual data bytes, such as an integer character value, that make up the key value and dictate the location where the key value will be inserted relative to other key values. A first function is applied to the data sequences in order to generate a reversed key value having reversed sorting properties. The reversed key values are then inserted into the index. The resulting index thus contains key values that are sorted in descending order. Additionally, indexes may be created on multiple key columns, with the sub_keys being independently sorted in either ascending or descending order. The present invention also discloses transformations that may be performed by a server in order to properly interpret statements that require the creation of standard or functional indexes in descending order.

Implementing descending indexes with a descend function

A method and system for recovering after failure of a first server to which a client was connected for accessing a resource is provided. When it is detected that a connection between the first server and the client has failed, the client is automatically connected with a second server that has access to the resource. After automatically connecting the client, the client accesses the resource through the second server. The client stores information about the state of the session with the first server so that processing can continue where it left off after the client connects with the second server. The client may be pre-connected to the second server prior to the failure of the first server to reduce the latency caused by switching in response to a failure. The second server may be configured to pre-parse the commands that the client issues to the first server to further reduce the latency associated with switching to the second server.

Automatic failover for clients accessing a resource through a server

The present invention provides a uniqueness-required index and a corresponding non-uniqueness count to support deferred uniqueness constraint enforcement. A uniqueness-required index stores duplicate occurrences of indexed data values that occur during statement or transaction processing. The non-uniqueness count associated with the uniqueness-required index provides a count of the number of indexed data values that occur more than once in the index. Where a non-uniqueness count is not equal to zero, a uniqueness constraint violation remains unresolved. Where an unresolved constraint violation exists at enforcement time, the effects of the processing are removed. A currently non-unique count can be used to represent the number of uniqueness-required indexes that are 'currently non-unique'. The currently non-unique count can be examined to determine whether there are any unresolved uniqueness constraint violations. Constraints can be enforced at the end of the processing of a statement, a transaction, or within a transaction at a savepoint.

Method for using an index as a workspace for deferred enforcement of

A method and apparatus for executing queries on a set of data that has been partitioned into a plurality of partitions based on a partitioning key is provided. A query is received that includes a reference to a second key. The second key is not part of the partitioning key but has a predetermined correlation with the partitioning key. This second key is referred to as an overlapping partition key. A subset of the plurality of partitions is selected to be scanned based on the reference to the second key and the predetermined correlation with the partitioning key. The query is then executed by scanning only those partitions of the plurality of partitions that belong to the subset of partitions. The overlapping partition key provides for reduced query execution time even when the partitioning key is not directly involved in the query. Specifically, the overlapping partition key permits a partial table scan in situations that would require a fill table scan with partitioning alone.

Using overlapping partitions of data for query optimization

A method and apparatus are disclosed for enabling a constraint without prohibiting updates to the constrained data during the validation portion of the enablement process. A constraint is first enforced. While the constraint is being enforced, the pre-existing data are inspected to determine whether the constraint is valid. Because the constraint is in force for all changes to the data during the validation process, the constraint will be enabled if the pre-existing data conforms with the constraint. A serialization value is stored in the constraint definition. Whenever the constraint definition is changed, the serialization value is changed. The serialization value of a constraint definition is recorded before validating the constraint. After validating the constraint, the serialization value in the constraint definition is compared to the recorded serialization value to determine whether the constraint definition was changed during the validation process.

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Foster City, CA, United States of America

Robert J Jenkins, Jr