Partitioning ownership of a database among different database servers to control access to the database

Abstract

A database or some portion thereof is partitioned into ownership groups. Each ownership group is assigned one or more database servers as owners of the ownership group. The database servers that are assigned as owners of an ownership group are treated as the owners of all data items that belong to the ownership group. That is, they are allowed to directly access the data items within the ownership group, while other database servers are not allowed to directly access those data items. Accordingly, at least a portion of the database is partitioned into a plurality of ownership groups. Each ownership group is assigned an owner set. Only processes that are executing on database servers that are members of the owner set of an ownership group are allowed to directly access data within the ownership group.

1 . A method comprising performing a machine-executed operation involving instructions, wherein the machine-executed operation is at least one of: 
 A) sending said instructions over transmission media;    B) receiving said instructions over transmission media;    C) storing said instructions onto a machine-readable storage medium; and    D) executing the instructions;    wherein said instructions are instructions which, when executed by one or more processors, causes: 
 maintaining a plurality of persistent data items on persistent storage accessible to a plurality of nodes;  
 assigning ownership of each of the persistent data items to at least one of the plurality of nodes;  
 shipping an operation that involves a particular data item of said plurality of persistent data items to a particular node assigned to the particular data item to cause the particular node to perform the operation on the particular data item, wherein said particular data item resides at a particular location on said persistent storage;  
 reassigning ownership of the particular data item from the particular node to another node without moving the particular data item from said particular location on said persistent storage;  
 after the reassignment, when any node wants an operation performed that involves said particular data item, the node that desires the operation to be performed ships the operation to said other node for the other node to perform the operation on the particular data item while said particular data item continues to reside at said particular location.  
   
   
   
       2 . The method of  claim 1  wherein the plurality of nodes are nodes of a multi-node database system.  
   
   
       3 . The method of  claim 2  wherein the multi-node database system includes nodes that do not have access to said persistent storage.  
   
   
       4 . The method of  claim 2  wherein the step of reassigning ownership of the particular data item from the particular node to another node is performed as part of a gradual transfer of ownership from said particular node to one or more other nodes.  
   
   
       5 . The method of  claim 4  wherein the gradual transfer is initiated in response to detecting that said particular node is overworked relative to one or more other nodes in said multi-node database system.  
   
   
       6 . The method of  claim 1  wherein method includes the step of: 
 determining whether the particular node held exclusive-mode or shared-mode access to the data item;    
   
   
       7 . The method of  claim 1  further comprising the step of: 
 in response to transferring ownership of said particular data item to said other node, aborting an in-progress operation that involves said particular data item;    
   
   
       8 . The method of  claim 7 , further comprising the step of: 
 after ownership of the particular data item has been transferred to said particular node, re-executing the in-progress operation.    
   
   
       9 . The method of  claim 1  wherein: 
 an operation that involves said particular data item is in-progress at the time the transfer of ownership of said particular data item is to be performed;    the method further includes the step of determining whether to wait for said in-progress operation to complete based on a set of one or more factors; and    if it is determined to not wait for said in-progress operation to complete, aborting said in-progress operation.    
   
   
       10 . The method of  claim 9  wherein said set of one of more factors includes how much work has already been performed by said in-progress operation.  
   
   
       11 . A method comprising performing a machine-executed operation involving instructions, wherein the machine-executed operation is at least one of: 
 A) sending said instructions over transmission media;    B) receiving said instructions over transmission media;    C) storing said instructions onto a machine-readable storage medium; and    D) executing the instructions;    wherein said instructions are instructions which, when executed by one or more processors, causes: 
 maintaining a plurality of persistent data items on persistent storage accessible to a plurality of nodes, wherein a particular data item, of said plurality of persistent data items, resides at a particular location on said persistent storage;  
 assigning ownership of each of the persistent data items to at least one of the plurality of nodes;  
 shipping an operation that involves said particular data item to a particular node assigned to the particular data item to cause the particular node to perform the operation on the particular data item;  
 while the first node continues to operate, reassigning ownership of the particular data item from the particular node to another node;  
 after the reassignment, when any node wants an operation performed that involves said particular data item, the node that desires the operation to be performed ships the operation to said other node for the other node to perform the operation on the particular data item.  
   
   
   
       12 . The method of  claim 11  wherein the plurality of nodes are nodes of a multi-node database system.  
   
   
       13 . The method of  claim 12  wherein the multi-node database system includes nodes that do not have access to said persistent storage.  
   
   
       14 . The method of  claim 12  wherein the step of reassigning ownership of the particular data item from the particular node to another node is performed as part of a gradual transfer of ownership from said particular node to one or more other nodes.  
   
   
       15 . The method of  claim 14  wherein the gradual transfer is initiated in response to detecting that said particular node is overworked relative to one or more other nodes in said multi-node database system.  
   
   
       16 . The method of  claim 11  wherein method includes the step of: 
 determining whether the particular node held exclusive-mode or shared-mode access to the data item;    
   
   
       17 . The method of  claim 11  further comprising the step of: 
 in response to transferring ownership of said particular data item to said other node, aborting an in-progress operation that involves said particular data item;    
   
   
       18 . The method of  claim 17 , further comprising the step of: 
 after ownership of the particular data item has been transferred to said particular node, re-executing the in-progress operation.    
   
   
       19 . The method of  claim 11  wherein: 
 an operation that involves said particular data item is in-progress at the time the transfer of ownership of said particular data item is to be performed;    the method further includes the step of determining whether to wait for said in-progress operation to complete based on a set of one or more factors; and    if it is determined to not wait for said in-progress operation to complete, aborting said in-progress operation.    
   
   
       20 . The method of  claim 19  wherein said set of one of more factors includes how much work has already been performed by said in-progress operation.