Re: [sqlite] Multi-master replication with updated Versioning extension

MD5 hashes can still collide. How does this implementation deal with 
hash collisions?

----- Original Message ----- 
From: "Alexey Pechnikov" <pechnikov@xxxxxxxxxxxx>
To: "General Discussion of SQLite Database" <sqlite-users@xxxxxxxxxx>
Sent: Thursday, July 30, 2009 7:11 AM
Subject: Re: [sqlite] Multi-master replication with updated Versioning 
extension


> Hello!
>
> On Thursday 30 July 2009 17:25:15 P Kishor wrote:
>> > I haven't looked at your work in depth, but I am interested in 
>> > this. I
>> > have implemented a very simple versioning system with TRIGGERs 
>> > whereby
>> > every change (INSERT, UPDATE, DELETE) in a column in a table is 
>> > stored
>> > in a versions table along with its primary key, allowing me to go 
>> > back
>> > and examine any version and roll back to it, if desired.
>
> Yes, the primary key field is good enough for master-slave 
> replication but not for
> multi-master because each master has self sequence counter. And full 
> record
> hash may be used for master-slave replication on tables without 
> primary keys.
>
> As table-independant way extension use ROWID field and md5 hash of 
> all fields.
> So multi-master is possible with some restrictions such as 
> non-unique records
> is denied. But may be ROWID + hash of record can help for this 
> situation too.
>
> Best regards, Alexey Pechnikov.
> http://pechnikov.tel/
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