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From "Damian Steer (JIRA)" <>
Subject [jira] [Commented] (JENA-118) SDB can't concurrently write (duplicate key error)
Date Wed, 21 Sep 2011 14:45:08 GMT


Damian Steer commented on JENA-118:

Unlocking occurs at the end of the transaction in postgresql. Other databases (mysql, db2,
oracle) have something similar, but (surprise!) details vary. MySQL appears to need an explicit

I should clarify the 'heavy' bit: it holds the lock longer than it strictly needs to (after
node table modification is complete), and I think it prevents 'safe' concurrent reads, i.e.
sparql queries. However it enables concurrent (ish :-) writes, so I'm inclined to enable it.
Original reporter doesn't seem to have tried it.

> SDB can't concurrently write (duplicate key error)
> --------------------------------------------------
>                 Key: JENA-118
>                 URL:
>             Project: Jena
>          Issue Type: Improvement
>          Components: SDB
>            Reporter: Damian Steer
>            Assignee: Damian Steer
>         Attachments: lock-pg.patch
>   Original Estimate: 96h
>  Remaining Estimate: 96h
> Multiple concurrent writes in SDB can break because duplicates can appear despite the
join-based duplicate suppression. Typically the users sees something like:
> org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint

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