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Biggest relief from NOSQL to SQL migration

This year my biggest accomplishment was to move our old NOSQL system from BDB/Cassandra to Mysql and so far its holding billions of rows and working fine.  Though this move has given me and my buddy peace and good sleep and I can now focus on other fires. But the biggest relief comes from being able to delegate some tasks to junior team and also being able to quickly script adhoc requirements quickly.

For e.g. today I got an adhoc requirement to find list of customers with > 1000 versions of a single file.  Had it been BDB I would have to write a program and then run it on each app node to find the answer and it would have taken days to get this info.  But with mysql all I had to do was to write a script that will execute a federated query and get me the output so all I need to do is run something like

nohup python sweep_all_shards.py "select pid, max(cnt) from (select customerid,file_id,count(version_id) cnt from \${SCHEMA_NAME}.version_\${TBL_SUFFIX} group by customer_id,file_id having count(version_id) >1000)a group by customerid" &


and within 6 hours the script had sweepeed all the shards and got me the result. So I had to just do some grep/awk/sed to get the answer.

Few weeks back I got some adhoc requirement to find max size of file uploaded by each customer and same I got it in less than one day whereas earlier I would have spent days getting this info.


Also one more advantage I see is that I have created a read only user on each mysql slave and  given access to production support people and as everyone knows relational database very few requirements come to me so I get more free time to work on more interesting things.

Also last night mysql server crashed twice while creating index on a 85M record table and boy the DBAs knew how to recover it whereas when it was BDB it was an Achilles hill to recover data out of it and this time Ops team did it without involving everyone and they were all confident and relaxed and BDB/Cassandra was always panic mode.

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