RE: Untested Developer Code - lack of concurrency testing

From: Herring Dave - dherri <>
Date: Tue, 12 May 2009 15:55:24 -0500
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Got one from the DW side of the world. I had a developer build a view for an application that joined a 1/2 billion row table to a number of small tables, one of which included a many-to-many join. This failed in a number of ways in production, mostly due to lack of temp space (400 GB+ per query), when multiple people hit it. Needless to say that view has been banned. That was years ago and ever since DBAs attend all code reviews.

David C. Herring | DBA, Acxiom Automotive  

630-944-4762 office | 630-430-5988 cell | 630-944-4989 fax 1501 Opus Pl | Downers Grove, IL, 60515 | U.S.A. |  

-----Original Message-----

From: kyle Hailey [] Sent: Tuesday, May 12, 2009 10:12 AM
Subject: Untested Developer Code - lack of concurrency testing

with one user and it runs fine and then gets put into production and only to hit a huge performance snafu. I'm putting together a demo on this kind of situation and was
thinking of some examples. One example that came to mind is a Nesedt Loops join that hammers the root node of an index. Might work fine for one user, but when multiple users start running it, the query runs into cache buffers chains latch issues with the high concurrency access to the index's root block which might be resolved by doing a hash join or moving the lookup table to a hash cluster for example. Wondering if anyone else had good examples of developer code that worked fine with one user and broke in the multi user production environment.
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Kyle Hailey

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-- Received on Tue May 12 2009 - 15:55:24 CDT

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