From: Dan Harris <fbsd@drivefaster.net>
To: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: General advice on user functions
Date: Wed, 21 Feb 2007 11:33:24 -0700
Message-ID: <45DC9074.3040901@drivefaster.net> (raw)
I have a new task of automating the export of a very complex Crystal
Report. One thing I have learned in the last 36 hours is that the
export process to PDF is really, really, slooww..
Anyway, that is none of your concern. But, I am thinking that I can
somehow utilize some of PG's strengths to work around the bottleneck in
Crystal. The main problem seems to be that tens of thousands of rows of
data must be summarized in the report and calculations made. Based on
my recent experience, I'd say that this task would be better suited to
PG than relying on Crystal Reports to do the summarizing.
The difficulty I'm having is that the data needed is from about 50
different "snapshots" of counts over time. The queries are very simple,
however I believe I am going to need to combine all of these queries
into a single function that runs all 50 and then returns just the
count(*) of each as a separate "column" in a single row.
I have been Googling for hours and reading about PL/pgsql functions in
the PG docs and I have yet to find examples that returns multiple items
in a single row. I have seen cases that return "sets of", but that
appears to be returning multiple rows, not columns. Maybe this I'm
barking up the wrong tree?
Here's the gist of what I need to do:
1) query count of rows that occurred between 14 months ago and 12 months
ago for a given criteria, then count the rows that occurred between 2
months ago and current. Repeat for 50 different where clauses.
2) return each count(*) as a "column" so that in the end I can say:
select count_everything( ending_date );
and have it return to me:
count_a_lastyear count_a_last60 count_b_lastyear count_b_last60
---------------- -------------- ---------------- --------------
100 150 200 250
I'm not even sure if a function is what I'm after, maybe this can be
done in a view? I am embarrassed to ask something that seems like it
should be easy, but some key piece of knowledge is escaping me on this.
I don't expect someone to write this for me, I just need a nudge in the
right direction and maybe a URL or two to get me started.
Thank you for reading this far.
-Dan
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To: pgsql-performance@postgresql.org
Cc: fbsd@drivefaster.net
Subject: Re: General advice on user functions
In-Reply-To: <45DC9074.3040901@drivefaster.net>
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