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:
Show quoted text
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.htmlregards, 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