Thread: Text field performance
We are having some performance issues we think may be related to large text field values, and many records. So, a couple questions... 1) Are text values always stored in the companion text file, or only if they exceed a certain size? What size? 2) When the query executer reads tuples during a query, does it always read the text companion file too? For example, the executer finds an index match and then goes after the heap tuple to continue field matching. Now, assuming the query does not contain any conditions involving a text field, does the executer read the text field in even if the tuple does not match and won't be included in the result set? 3) Is there any eqivelent to the CLUSTER functionality for text companion files? Is there any such thing planned? What's the best way to reduce fragmentation in a text companion file? TIA -Glen
Glen Parker <glenebob@nwlink.com> writes: > We are having some performance issues we think may be related to large > text field values, and many records. So, a couple questions... See http://www.postgresql.org/docs/8.1/static/storage-toast.html regards, tom lane
We're still on 7.4 (sorry, probly should have mentioned that). Does that documentation apply to the 7.4 series as well? Maybe an easier question is, can we expect a TOAST performance increase when upgrading to 8.1? Thx again... -Glen Tom Lane wrote: > Glen Parker <glenebob@nwlink.com> writes: > >>We are having some performance issues we think may be related to large >>text field values, and many records. So, a couple questions... > > > See > http://www.postgresql.org/docs/8.1/static/storage-toast.html > > regards, tom lane > >
On Tue, 2006-01-17 at 15:01 -0800, Glen Parker wrote: > We're still on 7.4 (sorry, probly should have mentioned that). Does > that documentation apply to the 7.4 series as well? AFAIK, there haven't been any major changes to TOAST since 7.4, so most of that documentation should be applicable. > Maybe an easier question is, can we expect a TOAST performance increase > when upgrading to 8.1? A lot of performance improvements have been made since since 7.4, but I don't believe any of them have affected TOAST in particular. -Neil