Tino Wildenhain escribió:
> Which makes me think if the solution would be to just run CLUSTER under
> the hood when VACUUM FULL is requested. Would that introduce any
> other problems?
The difference is that CLUSTER requires double the disk space in table +
indexes. VACUUM FULL has no such requirement.
A possibly approach would be to do an ANALYZE (to have fresh stats about
dead tuple density), and do a CLUSTER if the density is too high.
There has been talk about rewriting VACUUM FULL anyway; it's complex
code and it introduces extra complications in other parts of code that
would be otherwise unneeded, e.g. HOT. I have no idea what a rewritten
VACUUM FULL would look like, though.
Another thing we should do in this area is rewrite CLUSTER to use a
seqscan + sort instead of indexscan when the heap/index order
correlation is low.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
