Bruno Wolff III <bruno@wolff.to> writes:
> On Fri, Jan 07, 2005 at 19:36:47 -0800,
> "Loren M. Lang" <lorenl@alzatex.com> wrote:
>> Do large TEXT or VARCHAR entries in postgresql cause any performance
>> degradation when a query is being executed to search for data in a table
>> where the TEXT/VARCHAR fields aren't being searched themselves?
> Yes in that the data is more spread out because of the wider rows and that
> results in more disk blocks being looked at to get the desired data.
You are overlooking the effects of TOAST. Fields wider than a kilobyte
or two will be pushed out-of-line and will thereby not impose a penalty
on queries that only access the other fields in the table.
(If Loren's notion of "large" is "a hundred bytes" then there may be a
measurable impact. If it's "a hundred K" then there won't be.)
regards, tom lane
