Index managing method in database managing system

• US 5,806,058 A
• Filed: 06/24/1996
• Issued: 09/08/1998
• Est. Priority Date: 06/26/1995
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kawamura, Nobuo, Mori, Yasuharu
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): WALLACE, MICHAEL J
• Application Number:
  US08/668,684
• Time in Patent Office: 806 Days
• Field of Search: 707/1, 707/2, 707/3, 707/200
• US Class Current: 1/1
• CPC Class Codes: G06F 16/2272 Management thereof
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing

Abstract

A database managing system for effecting management in accessing data stored in a database via an index is so configured so as to prevent duplication of index key values and increase of index key values from degrading the access performance and lowering the storage efficiency of the index. Upon receiving, from an application program, a request to add a data record, a database manager adds this data record to a data portion and effects addition and update of an index record in an index portion. An index manager intervenes in this processing and excepts, from the index portion, an index record containing an index key value which has reached an upper limit value of the number of duplications preset in an exception key managing table. At the time of recreation of the index, the index manager refers to access time contained in index records and excepts index records which have not been accessed during an elapse of a fixed period of time.

Claims

1. In a database managing system having a database for storing a plurality of data records, data processing being conducted by using an index including a plurality of index records, each of said index records being created by associating an index key value with a storage location of at least one data record in said database relating to said index key value, an index managing method executed by a processor, comprising the steps of:

(a) in response to a processing request on a certain data record, checking on a number of associated data records belonging to an index record relating to said data record requested to be processed, on the basis of an index key value defined in said data record requested to be processed;

(b) comparing said number of associated data records with a predetermined upper limit number; and

(c) in response to arrival of said number of associated data records at said upper limit number, accessing said data record requested to be processed stored in said database without using said storage location in said database stored in said relating index record.

2. An index managing method according to claim 1, wherein said processor deletes an index record having said number of associated data records which has reached said upper limit number.

3. An index managing method according to claim 1, wherein each of said index records has a field for setting therein said number of associated data records belonging to the index record.

4. An index managing method according to claim 1, wherein said database managing system includes an exception key value table having a list of index key values of index records each having said number of associated data records which has reached said upper limit number, and

at said step (c), said processor determines whether said number of associated data records has reached said upper limit number by referring to said exception key table.

5. An index managing method according to claim 4, wherein said upper limit number is set beforehand in said exception key value table.

6. In a database managing system having a database for storing a plurality of data records, data processing being conducted by using an index including a plurlaity of index records, each of said index records being created by associating an index key value with a storage location of at least one data record in said database relating to said index key value, an index managing method executed by a processor, comprising the steps of:

(a) checking on nonaccess period of time of an index record;

(b) comparing said nonaccess period of time with a predetermined upper limit holding period of time; and

(c) in response to arrival of said nonaccess period of time at said upper limit holding period of time, deleting said index record.

7. An index managing method according to claim 6, wherein each of said index records has a field for setting therein latest access time of data records belonging to the index record, and

at said step (b), said nonaccess period of time is calculated on the basis of a difference between current time and said latest access time.

8. An index managing method according to claim 6, wherein said database managing system includes an exception key value table having a list of index key values of index records deleted at said step (c), and

at said step (c), said processor determines whether said nonaccess period of time has reached said upper limit holding period of time by referring to said exception key table.

9. An index managing method according to claim 8, wherein said upper limit holding period of time is set beforehand in said exception key value table.

10. An index managing method according to claim 8, wherein said processor periodically conducts said steps (a), (b) and (c) for each of index records included in the same index.

11. A database managing system comprising:

a database storing a plurality of data records and storing an index including a plurality of index records, each of said index records being created by associating an index key value with a storage location of at least one data record in said database relating to said index key value; and

a processor for conducting processing of said plurality of data records by using said index, said processor comprising;

(a) means, responsive to a processing request on a certain data record, for checking on the number of associated data records belonging to an index record relating to said data record requested to be processed, on the basis of an index key value defined in said data record requested to be processed;

(b) means for comparing said number of associated data records with a predetermined upper limit number; and

(c) means, responsive to arrival of said number of associated data records at said upper limit number, for accessing said data record requested to be processed stored in said database without using said storage location in said database stored in said relating index record.

12. A database managing system comprising:

a database storing a plurality of data records and storing an index including a plurality of index records, each of said index records being created by associating an index key value with a storage location of at least one data record in said database relating to said index key value; and

a processor for conducting data processing by using said index, said processor comprising;

(a) means for checking on nonaccess period of time of an index record;

(b) means for comparing said nonaccess period of time with a predetermined upper limit holding period of time; and

(c) means, responsive to arrival of said nonaccess period of time at said upper limit holding period of time, for deleting said index record.

13. A medium for use in a database managing system having a database for storing a plurality of data records, data processing being conducted by using an index including a plurality of index records, each of said index records being created by associating an index key value with a storage location of at least one data record in said database relating to said index key value, said medium comprising:

a first code portion, responsive to a processing request on a certain data record, for causing a processor to check on a number of associated data records belonging to an index record relating to said data record requested to be processed, on the basis of an index key value defined in said data record requested to be processed;

a second code portion for causing said processor to compare said number of associated data records with a predetermined upper limit number; and

a third code portion, responsive to arrival of said number of associated data records at said upper limit number, for causing said processor to access said data record requested to be processed stored in said database without using said storage location in said database stored in said relating index record.

14. A medium for use in a database managing system having a database for storing a plurality of data records, data processing being conducted by using an index including a plurality of index records, each of said index records being created by associating an index key value with a storage location of at least one data record in said database relating to said index key value, said medium comprising:

a first code portion for causing a processor to check on nonaccess period of time of an index record;

a second code portion for causing said processor to compare said nonaccess period of time with a predetermined upper limit holding period of time; and

a third code portion, responsive to arrival of said nonaccess period of time at said upper limit holding period of time, for causing said processor to delete said index record.

15. An index managing method in a database managing system, said database managing system having a database including an index portion and a data portion, data stored in said data portion being accessed by tracing association of index key values stored in said index portion with data storage locations, a plurality of data being associated with a single index key value, said index managing method comprising the steps of:

counting data associated with a single index key value as a number of associated data; and

in response to arrival of said number of associated data at a predetermined number, deleting said index key value and a data storage location associated therewith from said index portion.

16. An index managing method in a database managing system having a database including an index portion and a data portion, data stored in said data portion being accessed by tracing association of index key values stored in said index portion with data storage locations, said index managing method comprising the steps of:

registering last accessed time as access time for each index key value of said index portion; and

in response to an elapse of a predetermined time from said access time of an index key value, deleting the index key value and a data storage location associated therewith from said index portion.

17. An index managing method in a database managing system having a database including an index portion and a data portion, data stored in said data portion being accessed by tracing association of index key values stored in said index portion with data storage locations, a plurality of data being associated with a single index key value, said index managing method comprising the steps of:

counting data associated with a single index key value as a number of associated data;

in response to arrival of said number of associated data at a predetermined number, deleting said index key value and a data storage location associated therewith from said index portion;

registering last accessed time as access time for each index key value of said index portion; and

in response to an elapse of a predetermined time from said access time of an index key value, deleting the index key value and a data storage location associated therewith from said index portion.