On 11 April 2012 00:35, Robert Haas <robertmh...@gmail.com> wrote: > If people need something like that, couldn't they create it by hashing > the normalized query text with an arbitrary algorithm?
That supposes that the normalised query text is perfectly stable. It may well not be, particularly for things like ad-hoc queries or queries generated by ORMs, across database clusters and over long periods of time - you're basically throwing the benefit of all of that intelligent normalisation out of the window, because it's pretty close to free to expose it. What if a developer tweaks an alias in the application for clarity? Also, as you point out, it has additional utility in advertising when a collision has happened, and setting the user's expectations appropriately. I assume that collisions are very rare, but when they do happen, this gives you a fighting chance of noticing them. As Tom points out, the query hash will vary according to platform specific characteristics, including endianness, and will require OIDs are the same on every node. However, it is still going to be useful in clusters that use streaming replication, though not a third party trigger based replication system for example, because streaming replication does of course require that those factors (and rather a lot more) will be identical across the cluster anyway. Realistically, I'd expect a large majority of people interested in this feature to only want to use it with streaming replication anyway. -- Peter Geoghegan http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training and Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
