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From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2122) Optimize ContainerLock.isCompatible()
Date Tue, 28 Nov 2006 20:26:22 GMT
     [ http://issues.apache.org/jira/browse/DERBY-2122?page=all ]

Mike Matrigali updated DERBY-2122:

I think you should add back some sort of compatibility "table" documentation.  It may just
be me but I often refer to this 
source code to figure out what locks are compatible with what.  Since the previous implementation
had it as a 2-d array
with true/false I didn't need extra comments.  But I find it harder to read the code encoding
into bit maps. I wouldn't hold
up a commit for this. 

I hand checked all the compatibility conversions and they all looked right.  

> Optimize ContainerLock.isCompatible()
> -------------------------------------
>                 Key: DERBY-2122
>                 URL: http://issues.apache.org/jira/browse/DERBY-2122
>             Project: Derby
>          Issue Type: Improvement
>          Components: Store, Performance
>    Affects Versions:
>            Reporter: Knut Anders Hatlen
>         Assigned To: Knut Anders Hatlen
>            Priority: Trivial
>         Attachments: derby-2122-v1.diff, derby-2122-v1.stat
> The numbers at http://wiki.apache.org/db-derby/Derby1961MethodCalls indicate that ContainerLock.isCompatible()
is called many times per transaction, at least when there are multiple concurrent clients
operating on the same containers. Currently, it looks into a two-dimensional array to find
out whether two locks are compatible. This could be implemented more efficiently, for instance
by having a bit pattern in each ContainerLock object representing which lock types it is compatible

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