> LOG: statement: UPDATE Transactions
> SET previous_value = previous_value(id)
> WHERE new_value IS NOT NULL
> AND new_value <> ''
> AND node_id IN (SELECT node_id FROM NodeSegments)
> LOG: duration: 16687993.067 ms
I hope that I can presume some suggestions that I gleened after finishing my
celko book. I don't
know if the suggestions presented will help in your case.
>From the reading WHERE conditions such as <> '' or IS NOT NULL can be
>preformance killers as these
may discourge the optimizer from using an index scan. The suggest was to
replace this with:
new_value > '<some minimum value possible in this field i.e. A>'
this WHERE conditions should only find non-NULL and non-empty strings.
Also, the IN is also know as a killer so the suggestion was to reform the query
like so:
UPDATE Transactions
SET previous_value = previous_value(id)
FROM NodeSegments
WHERE Transactions.Node_id = NodeSegments.Node_id
AND Transactions.new_value > 'A'; --assuming A is a minimum value
I hope this can help.
Regards,
Richard Broersma Jr.
---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to [EMAIL PROTECTED] so that your
message can get through to the mailing list cleanly
