RE: Untested Developer Code - lack of concurrency testing

From: Amar Kumar Padhi <>
Date: Wed, 13 May 2009 10:05:50 +0400 (GST)
Message-ID: <488841.101242194833325.JavaMail.seven_at_aomfe4p1>

The most problematic stuff I have come across is lack of developers ability to think from concurrent session or multiple sessions running the same code. Most developers design and test code from a single session, not analyzing the outcome if the code is executed in parallel for the same set of data. In my case this has resulted in deadlock and even duplicate data processing. Imagine, two users running the same accounting process that generates duplicate Entries in the system and then you have to dig and sort the issue. Yes this also results in arguments whether the developers missed something or the users are disorganized. I make use of custom designed application locks as well as dbms_lock to prevent such issues. Developers now follow it as a standard. Haven't seen any more issues in this area. Users are also happy as the application prompts who is holding the lock before they even start processing the data.

2) the other one is order of columns in a composite index, as well as the choice to make the right index on the right columns that does not conflict with already existing index.

That is all I can immediately think of and jot down.


-original message-
 Untested Developer Code - lack of concurrency testing From: "kyle Hailey" <> Date: 12-05-2009 19:17

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

-- Received on Wed May 13 2009 - 01:05:50 CDT

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