[ZODB-Dev] ReadConflictError while re-indexing big fat index

Chris Withers chris at simplistix.co.uk
Mon Aug 2 06:41:49 EDT 2004

Hi All,

I'm pretty sure this has been gone over before, but I thought I'd spark 
off another discussion 'cos this is a little bit disturbing.

I'm currently getting this:

     * Module Products.ZCatalog.ZCatalog, line 649, in searchResults
     * Module Products.ZCatalog.Catalog, line 753, in searchResults
     * Module Products.ZCatalog.Catalog, line 496, in search
     * Module Products.PluginIndexes.PathIndex.PathIndex, line 234, in 
     * Module Products.PluginIndexes.PathIndex.PathIndex, line 185, in 
     * Module ZODB.Connection, line 561, in setstate
     * Module ZODB.Connection, line 590, in _is_invalidated

ReadConflictError: database read conflict error (oid 000000000001ff36, 
class BTrees.IIBTree.IISet)

...while re-indexing a big text index (nb: not a PathIndex)

The indexing is happening on a dedicated ZEO client so as not to impact 
on the site's performance, however, getting the above error on every 
page impacts somewhat more on the Site's performance ;-)

This raises some questions for me:

1. What is the above error message really trying to tell me?
    (it's a pretty obscure message ;-)

2. How SHOULD I try and re-index a large text index without effectively
    taking down the whole site for an hour or two.

3. (Because I figure it's kinda relevent here and I like asking
     questions in 3's ;-)
    When is MVCC due to land and will it help with this problem?



Simplistix - Content Management, Zope & Python Consulting
            - http://www.simplistix.co.uk

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