Recently I was troubleshooting a system using Relstorage/MySQL with a
history free schema. The zope application became unresponsive and a
show processlist on the server showed a REPLACE INTO query taking a
long time. The mysql process had saturated the cores on the box. The
server had 64GB RAM, 300 GB SAN storage, 3.6 GHz Xeon x 8 cores.


As soon as I killed the REPLACE INTO query the web application became
responsive. I patched relstorage with this patch:


>From my research it appears REPLACE INTO deletes the rows from the
table first, then inserts new rows. It appears that INSERT...ON DUPLICATE
KEY UPDATE has better performance.

1. How do I run the unit tests for this project? (what are the dependencies)

2. What's the process for submitting patches to this project?

Daniel Garcia
For more information about ZODB, see http://zodb.org/

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