Tom, Folks: I am having a rather interesting time getting performance out of my database. I'd really appreciate some feedback from the list on this.
As you may recall, I've gotten around Postgres' lack of rowset-returning stored procedures by constructing "pointer tables" which simply hold lists of primary keys related to the user's current search. This is an excellent approach for a browser-based application, and I have since used this idea on other databases, even one that supports stored procedures. However, this means that I clear all of these pointer tables on a periodic basis (how frequently depends on usage). Just clearing the records didn't work, because of the Postgres "padded index" problem where eventually the indexes on these tables becomes full of deleted rows. Which gives me problem 1: 1. INDEXES: I discovered, the hard way, a peculiar problem. If you drop and re-create a table within the same transaction (in a function, for example) the indexes do not get dropped completely. Doing this to several tables, I had the disturbing experience of seeing incorrect rows in response to some queries. Specifically dropping each of the indexes, dropping the tables, re-creating the tables, and re-creating the indexes seems to work. However, this seems to me to indicate a potential problem with DDL commands within transactions. The second problem is giving me severe grief right now: 2. I have a very complex view designed for browsing client information. This view involves 2 other views, and two custom aggregates which are based on sub-queries (could only do it in Postgres!). The query plan is as long as this e-mail, but thanks to optimization and good indexing it runs in about 2 seconds right after a VACUUM. Unfortunately, 6 hours after a VACUUM, the query bogs down. The query plan does not seem to have changed much, but somehow what took 50% of the processor for 2 seconds at 8:30AM flattens the processor for a full 45 seconds at 3:30 pm. Once VACUUM can be run in the background, I suppose that this can be dealt with, but until then does anyone have any suggestions? -Josh Berkus ______AGLIO DATABASE SOLUTIONS___________________________ Josh Berkus Complete information technology [EMAIL PROTECTED] and data management solutions (415) 565-7293 for law firms, small businesses fax 621-2533 and non-profit organizations. San Francisco
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