Re: Default fill factor for tables?

> Roberts, Jon escribió:
> 
> > Why would you set the fillfactor to anything other than 100 for a
> > PostgreSQL table?
> 
> To favor HOT updates.
> 
> --

I can find very little information on hot updates but I found this: http://archives.postgresql.org/pgsql-patches/2006-11/msg00059.php

It states, "This design optimizies the updates when none of the index columns are modified and length of the tuple remains the same after update."  

How can a row's length change?  I think it must mean the size (in bytes) of the row remains the same.

If this is the constraint, then I still don't see the benefit.  If the size can vary, I can see the benefit because the new column value may be larger than the old value thus needing the space.  

Why isn't the hot update documented in these locations?
http://www.postgresql.org/docs/8.3/interactive/sql-createtable.html
http://www.postgresql.org/docs/8.3/interactive/sql-update.html
http://www.postgresql.org/docs/8.3/interactive/sql-altertable.html



Jon