Re: join tables vs. denormalization by trigger

Hello,

I had a similar issue and -atfer testing - decided to merge the tables
B and C into a single table.
In my case the resulting table contains a large proportion of nulls
which limits the size increase...
You'll have to do some testing with your data to evaluate the
performance gain.

Hope to help,

Marc

-----Original Message-----
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Walter
Mauritz
Sent: Tuesday, September 04, 2007 8:53 PM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] join tables vs. denormalization by trigger

Hi,

I wonder about differences in performance between two scenarios:

Background:
Table A, ~50,000 records
Table B, ~3,000,000 records (~20 cols)
Table C, ~30,000,000 records (~10 cols)

a query every 3sec. with limit 10

Table C depends on Table B wich depends on Table A, int8 foreign key,
btree index

* consider it a read only scenario (load data only in night, with time
for vacuum analyze daily)
* im required to show records from Table C, but also with some (~5cols)
info from Table B
* where clause always contains the foreign key to Table A
* where clause may contain further 1-10 search parameter


Scenario A)
simply inner join Table B + C

Scenario B)
with use of trigger on insert/update I could push the required
information from table B down to table C.
-> so i would only require to select from table C.


My question:
1) From your experience ... how much faster (approximately) in percent
do you regard Scenario B faster than A ?

2) any other tips for such a read only scenario

Thx for any attention :-)
Walter
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TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not
       match