Distributed Database System Providing Data and Space Management Methodology

Abstract

A distributed database system providing data and space management methodology. In one embodiment, for example, a method for transferring a data structure in cache at a first database server to a second database server in a distributed database system comprises steps of: determining a first database server having a data structure in cache in response to a request for the data structure from a second database server, the request including a request for a lock on the data structure; providing the request for the data structure to the first database server; in response, sending the data structure from the first database server to the second database server; and receiving and using the data structure at the second database server without waiting for the lock request to be explicitly granted.

1 . A method for transferring a data structure in cache at a first database server to a second database server in a distributed database system, the method comprising:
 determining a first database server having a data structure in cache in response to a request for the data structure from a second database server;   providing the request for the data structure to the first database server;   in response, sending the data structure and a message containing an address where the data structure needs to be copied on the second database server to the second database server; and   receiving the data structure at the second database server using the data structure address included with the message.   
   
   
       2 . The method of  claim 1 , wherein the data structure comprises a data page. 
   
   
       3 . The method of  claim 1 , wherein said request for the data structure includes a lock request for the data structure from the second database server. 
   
   
       4 . The method of  claim 3 , wherein said sending step includes granting the lock request based on sending the message including the data structure address. 
   
   
       5 . The method of  claim 1 , further comprising:
 providing a resource master for tracking data structures in cache at database servers in the distributed database system.   
   
   
       6 . The method of  claim 5 , wherein said determining step includes consulting the resource master for determining the first database server having the data structure in cache. 
   
   
       7 . The method of  claim 5 , wherein said providing step includes receiving a lock request for the data structure from the second database server at the resource master and sending the lock request to the first database server. 
   
   
       8 . The method of  claim 7 , wherein said resource master determines whether to grant the lock request. 
   
   
       9 . The method of  claim 7 , wherein the resource master sends a lock downgrade message to the first database server. 
   
   
       10 . The method of  claim 9 , wherein the resource master sends a lock granted message to the second database server after receiving a reply from the first database server that it has downgraded the lock. 
   
   
       11 . A computer-readable medium having processor-executable instructions for performing the method of  claim 1 . 
   
   
       12 . A method for transferring a data structure in cache at a first database server to a second database server in a distributed database system, the method comprising:
 determining a first database server having a data structure in cache in response to a request for the data structure from a second database server, the request including a request for a lock on the data structure;   providing the request for the data structure to the first database server;   in response, sending the data structure from the first database server to the second database server; and   receiving and using the data structure at the second database server without waiting for the lock request to be explicitly granted.   
   
   
       13 . The method of  claim 12 , wherein said sending step includes indicating the request for a lock on the data structure is to be granted to the second database server. 
   
   
       14 . The method of  claim 12 , further comprising:
 providing a resource master for tracking data structures in cache at database servers in the distributed database system.   
   
   
       15 . The method of  claim 14 , wherein said determining step includes consulting the resource master for determining the first database server having the data structure in cache. 
   
   
       16 . The method of  claim 14 , wherein said providing step includes receiving the request for a lock on the data structure at the resource master and sending the lock request to the first database server. 
   
   
       17 . The method of  claim 16 , wherein said resource master determines whether to grant the request for a lock. 
   
   
       18 . The method of  claim 16 , wherein the resource master sends a lock downgrade message to the first database server. 
   
   
       19 . The method of  claim 18 , wherein the resource master sends a lock granted message to the second database server after receiving a reply from the first database server that it has downgraded the lock. 
   
   
       20 . A computer-readable medium having processor-executable instructions for performing the method of  claim 12 . 
   
   
       21 . In a distributed database system having a plurality of database servers, a system for transferring a data structure in cache at a first database server to a second database server, the system comprising:
 a resource master for determining a first database server having a data structure in cache in response to a request for the data structure from a second database server, the request including a request for a lock on the data structure and for providing the request for the data structure to the first database server;   a first database server which sends the data structure to the second database server in response to the request received from the resource master; and   a second database server which receives and uses the data structure sent by the first database server without waiting for the lock request to be explicitly granted.   
   
   
       22 . The system of  claim 21 , wherein the resource master determines whether the request for a lock on the data structure is to be granted to the second database server. 
   
   
       23 . The system of  claim 21 , wherein the resource master tracks data structures in cache at a plurality of database servers of the distributed database system. 
   
   
       24 . The system of  claim 21 , wherein said resource master determines whether to grant the request for a lock received from the second database server. 
   
   
       25 . The system of  claim 24 , wherein the resource master sends the lock request received to the first database server if it grants the request for the lock received from the second database server. 
   
   
       26 . The system of  claim 24 , wherein the resource master sends a lock downgrade message to the first database server if it grants the request for the lock received from the second database server. 
   
   
       27 . The system of  claim 26 , wherein the resource master sends a lock granted message to the second database server after receiving a reply from the first database server that it has downgraded the lock. 
   
   
       28 . In a distributed database system comprising a plurality of nodes sharing access to data, a method for regulating access to data objects in cache at nodes of the distributed database system, the method comprising:
 providing a lock master at one of said plurality of nodes for regulating access to data objects in cache at said plurality of nodes;   submitting a lock request for a given data object requested at a first node of the distributed database system to the lock master, the lock request including an address to which the given data object is to reside at the first node;   forwarding the lock request from the lock master to a second node having the given data object in cache; and   in response, transferring the data object from the second node to the first node using the address included with the lock request without waiting for the lock request to be explicitly granted.   
   
   
       29 . The method of  claim 28 , wherein the data object comprises a data page. 
   
   
       30 . The method of  claim 28 , wherein said lock master determines whether to grant the lock request. 
   
   
       31 . The method of  claim 30 , wherein said lock master determines whether to grant the lock request based, at least in part, on whether a lock is maintained on the given data object at the second node. 
   
   
       32 . The method of  claim 31 , wherein said lock master determines whether to grant the lock request based, at least in part, on type of lock maintained on the given data object. 
   
   
       33 . The method of  claim 31 , wherein said forwarding step includes implicitly granting the lock request based on forwarding the lock request to the second node. 
   
   
       34 . The method of  claim 28 , wherein said forwarding step includes sending a lock downgrade message to the second node together with the lock request. 
   
   
       35 . The method of  claim 34 , further comprising:
 sending a lock granted message to the first node after the lock master receives a reply from the second node to the lock downgrade message.   
   
   
       36 . The method of  claim 28 , wherein the lock master runs at a selected one of the first node, the second node and a third node. 
   
   
       37 . A computer-readable medium having processor-executable instructions for performing the method of  claim 28 .