Horton

Re: Overhead cost of Serializable Snapshot Isolation

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

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From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
To: Simon Riggs <simon@2ndQuadrant.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>, Robert Haas <robertmhaas@gmail.com>, Greg Sabino Mullane <greg@endpoint.com>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2011-10-12T05:34:22Z
Lists: pgsql-hackers 
On 11.10.2011 23:21, Simon Riggs wrote:
> If the normal default_transaction_isolation = read committed and all
> transactions that require serializable are explicitly marked in the
> application then there is no way to turn off SSI without altering the
> application. That is not acceptable, since it causes changes in
> application behaviour and possibly also performance issues.

I don't get that. If all the transactions that require serializability 
are marked as such, why would you disable SSI for them? That would just 
break the application, since the transactions would no longer be 
serializable.

If they don't actually need serializability, but repeatable read is 
enough, then mark them that way.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com