[Zope-CMF] is there a conflict error resistent index

Dieter Maurer dieter at handshake.de
Sun Jun 17 14:13:11 EDT 2007

Joachim Schmitz wrote at 2007-6-16 13:35 +0200:
> ...
>during our recent search for the cause of the many conflict errors, we 
>discovered that nearly all of them where caused during indexing the 
>portal_catalog, when the same values are indexed. This can happen easily 
>with date_indexes, since the dates are only stored with a resolution of 
>1 minute.

Usually, this will not cause a conflict -- only when in addition
the first objects that use a new date value are created
in concurrent transactions. I expect that the probability is not
too high for this....

>Even more conflict error prone is the reviewstate. Since there 
>are only a few reviewstates.

Again, only the initial "filling" of the document list for
a given state is critical. Once there is a document list,
this list (an "IITreeSet", usually) can concurrently add elements
(using application specific conflict resolution -- reducing the
conflict probability by a factor of about 120).

For one of our internal projects, I have created a set
of "conflict reduced indexes". These indexes do not delete
a document list one it has been created. However, it turned
out that this additional conflict protection is not worth the effort.
My special indexes have been phased out meanwhile....


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