System for estimating a first access time of transactions accessing a database object

Abstract

A system and a computer readable medium for estimating the first access time of a plurality of currently active transactions accessing at least one database object is disclosed. According to varying embodiments of the system and computer readable medium disclosed herein, the present invention may provide an efficient mechanism for tracking the earliest first access time of the set of all currently active transactions accessing an object in a database system.

1 . A computer readable storage medium for storing instructions that, when executed by a computer cause the computer to perform a method for estimating an earliest first access time of a plurality of currently active transactions accessing at least one database object, the method comprising:
 placing each of plurality of currently active transactions accessing the object in a group of a plurality of groups, the plurality of groups corresponding to a plurality of time intervals, each of the plurality of currently active transactions accessing the at least one database object being placed in the group based upon a first access time of the at least one database object by each of the plurality of currently active transactions and the particular time interval; and   storing a group first access time for the group, the group first access time corresponding to the earliest first access time for any of the plurality of currently active transactions in the group; and   defining the earliest first access time for any of the plurality of currently active transactions in the group as a commit log sequence number.   
   
   
       2 . The computer readable storage medium of  claim 1  wherein the program further includes instructions for:
 providing a storage area of a particular size to store data for the plurality of groups corresponding to the at least one database object.   
   
   
       3 . The computer readable storage medium of  claim 1  wherein the first access time further includes a claim time for each of the plurality of currently active transactions. 
   
   
       4 . The computer readable storage medium of  claim 1  wherein accessing instructions further include instructions for:
 accessing a database object for a read access or write access.   
   
   
       5 . The computer readable storage medium of  claim 1  wherein the first access time is represented by a log sequence number. 
   
   
       6 . The computer readable storage medium of  claim 1  wherein the storing instructions further include instructions for:
 storing the group first access time as the minimum first access time for all the currently active transactions in the group.   
   
   
       7 . The computer readable storage medium of  claim 1  wherein the program further includes:
 approximating the first access time of the each of the plurality of currently active transactions in the group as the group first access time.   
   
   
       8 . The computer readable storage medium of  claim 1  wherein the program further includes instructions for:
 defining an earliest group first access time for the plurality of groups as an object first access time of the at least one database object.   
   
   
       9 . The computer readable storage medium of  claim 8  further comprising:
 updating the identity of the group of the plurality of groups having the earliest group access time to a group having a next earliest group first access time in response to the group having the earliest group first access time becoming empty.   
   
   
       10 . A system for estimating an earliest first access time of plurality of currently active transactions accessing at least one database object, the system comprising:
 a processor; and   a storage area, coupled with the processor and having a particular size, the storage area for storing data for a plurality of groups corresponding to the at least one database object, each of the plurality of groups corresponding to a particular time interval, each of plurality of currently active transactions being stored in a group of the plurality of groups based upon a time of a first access of the at least one database object by each of the plurality of currently active transactions and the particular time interval;   wherein the at least one transaction includes at least one of a read transaction and a write transaction and the each of the at least one transaction is stored in the group having the particular time interval corresponding to the time of the first access of the at least one database object by each of the at least one transaction;   wherein the earliest first access time for any of the plurality of currently active transactions in the group is defined as a commit log sequence number.   
   
   
       11 . The system of  claim 10  wherein the first access time further includes a claim time for each of the plurality of currently active transactions and the first access includes acquiring a lock for a table. 
   
   
       12 . The system of  claim 10  wherein a group first access time for the group is stored in the storage area, the group first access time being a minimum first access time for all of the plurality of currently active transactions in the group. 
   
   
       13 . The system of  claim 12  wherein the first access time of the each of the plurality of currently active transactions in the group is defined as the group first access time. 
   
   
       14 . The system of  claim 11  wherein an earliest group first access time for the plurality of groups is stored in the storage area as an object first access time for the database object. 
   
   
       15 . The system of  claim 14  wherein the identity of the group of the plurality of groups having the earliest group access time is updated to a group having a next earliest group first access time in response to the group having the earliest group first access time becoming empty.