Isidor Zeuner wrote:

Dear MonetDB developers, Dear Isidor,

MonetDB/SQL follows an optimistic concurrency control scheme. One of the properties of OCC is that it does not lock the database, except for validation of potential conflicts between the r/w sets. As such, it favors low update frequency. There are no facilities to control, take control over this behavior. If you aim for a (extreme) high update rates you could consider a master/slave setup, where the master executes the update in serial way. In most cases this is more efficient as well. Alternatively, a middleware layer can perform a coarse grain locking scheme. regards, Martin

on concurrently running writing transactions, I am getting a rather narrowly descriptive error message: "!SQLException:sql.trans:COMMIT: failed".

My first attempts to deal with this issue suggest that it happens exactly in those cases where the concurrent writes create some sort of conflict.

I am aware that MonetDB does not focus on concurrency, and of the suggestion to serialize multiple writers. However, I'd like to know what the current status of concurrency is. To what extent are SQL primitives implemented which allow to let the server take care of serializing writes, for example through explicit table locking or transaction isolation?

Best regards,

Isidor Zeuner

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