Re: Multithreaded prob

Hi Doug,

On 16 Nov 2014, at 05:19, Doug Service wrote:

99% of the time the threads will be writing to completely different tables. However, occasionally they may insert or update a record in a common table to indicate the start or end of a job. If two threads happen by chance to do this concurrently, will this cause a transaction abort as you describe? Possibly. Just make sure your code retries transactions, and all should be well. I expect no big problems in your use case. Best,

Hannes

On 11/14/2014 10:20 AM, Hannes Mühleisen wrote:

...

Hi List,

Multithreaded read access should work great. However, sending updates to a single table concurrently will trigger transaction aborts due to the concurrency model that MonetDB uses. So, if you are doing reads, run as many(*) threads as you like in parallel. If you are doing a lot of writes to a single table, it might be best combining those on a single connection.

Best,

Hannes

(*) We get best results in throughput when using around the same number of threads as there are hardware contexts on the CPU.

...

On 14 Nov 2014, at 17:28, Alastair McKinley wrote:

Hi Doug,

I did have a problem with a similar configuration

I don't believe concurrent access using MAPI (or any interface) is currently supported unless things have changed since approx version 11.17.

I had to serialise requests at the client end.

Best regards,

Alastair

On Fri, 2014-11-14 at 08:13 -0800, Doug Service wrote:

...

I have installed MonetDB and and started using it through MAPI. The documentation indicates that opening multiple connections from separate threads in a single process is supported. I perused the MAPI source and it appears that all of the Monet data structures used are associated with the connection.

In our application the threads will be independent and processing similar but unique data sets each with its own connection to the database. No threads will share a database connection nor attempt to use another threads connection. Does anyone have experience using multiple threads in a single process each accessing a separate database MonetDB MAPI connection they would like to share? Did you have any problems?

Doug Service

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