[Koha-zebra] A few Zebra Questions

[Sebastian Hammer]

Mike Taylor wrote:

>>Date: Thu, 29 Dec 2005 15:55:10 -0500
>>From: Sebastian Hammer <quinn at indexdata.com>
>>
>>    
>>
>>>Does Zebra allow any kind of database replication, master/slave or
>>>master/master relationships? (or alternatively, are there methods
>>>to communicate between two or more Zebra servers?)
>>>      
>>>
>>Oooh.. serious dream project. I have fantasized about this for
>>years.  But no, there is nothing built into Zebra today.
>>
>>One somewhat obvious way to approach this would be using
>>OAI-PMH.. the LoC is presently contemplating awarding us a little
>>money to support an OAI server function in Zebra.
>>    
>>
>
>Why?!  What on earth does OAI-PMH bring to the party that Zebra
>doesn't already support natively through Z39.50 and/or SRU?  For
>example to search for records updated since 15th December:
>
>	rec.lastModificationDate >= 2005-12-15
>  
>
I'm not always hip to the latest changes to Zebra, but last I looked, it 
didn't support searching by record update timestamp. The other thing 
missing is the ability to retrieve information about records that have 
been deleted. At present, these just disappear without a trace.. there 
needs to be some mechanism to retrieve information (at least a sysno) 
about records deleted since a given date.

Whether the updating happens through OAI (which has only the benefit of 
being specifically made for this purpose) or SRU (Rob Sanderson and 
Ralph Levan have put forward a SRU profile to support OAI-like 
activities -- don't recall if they deal with delete records, though) 
doesn't matter much in the great scheme of things.. except when you 
follow standards, there is always a hope that other standards-compliant 
software will interoperate with you.

>It would be the work of a moment to set up a periodic polling daemon
>that use a query such as this to check for changes to a master Zebra
>database and propagates them to a slave.
>
>  
>
>>>Is there any foreseeable way to get around the speed issues with
>>>updating that would make it feasible to store status data quickly?
>>>      
>>>
>>What is the issue here -- the ability to use circulation status as a
>>filter in bibliographic searching, or what?
>>    
>>
>
>Another question that immediately occurs is: _what_ speed issues?
>Have you actually seen any?  Do you have any numbers?
>  
>
I'd like to hear the answer to this too. But my sense is that updating a 
single record in a multimillion record database does take some 
significant period of a time -- much more than updating a single row in 
an RDBMS, for sure. It matters if you're scaling to a major library with 
multiple circulation desks.

--Sebastian

> _/|_	 ___________________________________________________________________
>/o ) \/  Mike Taylor  <mike at miketaylor.org.uk>  http://www.miketaylor.org.uk
>)_v__/\  "Press any key to continue or any other key to quit" -- Jeff
>	 Covey.
>
>
>  
>

-- 
Sebastian Hammer, Index Data
quinn at indexdata.com   www.indexdata.com
Ph: (603) 209-6853