PostgreSQL performance issues

Hi all,

I'm working for a brazillian company developing and maintaining a ERP sw
that uses PostgreSQL as it main OLTP database system. We're just to start
the migration to IBM DB2 because of many performance issues.

I searched the solution for these performance problems, and can't find
anything on the other web foruns.

I'll put them in this post as topics, but first I'll describe how's the ERP
database's schema:
- More than 200 tables;
- About 10 tables with about 10,000 transactions and 15,000 new rows per
day;
- These 10 tables has at least 12 table indexes and 3 triggers;
- Many of our customer servers uses AMD64 processors running Red Hat
Enterprise (with EXT3), but we have some using Xeon processors and Windows
2003 Server (NTFS), and the issues still the same;
- All servers have at least 1 Gb of dedicated RAM, with no virtualization;
- All servers uses at least 2 disks on RAID 0 (Ultra-SCSI disks);
- Database encoding: LATIN 1.

The issue topics:
1) As the database grows on our customers, lower performance occurs. After
one week of use, the I/O on database is extremely high. It appears that
VACUUM FULL and/or VACUUM ANALYZE doesn't work on this databases.

2) We have a very complex view mount on other views. When we cancel a simple
SELECT on this top-level view (expecting return a max. of 100 rows for
example) the PostgreSQL process starts a infinite loop (we left more than 4
days and the loop doesn't stops), using 100% of all processors on the
server.

3) On these servers, the disk usage grows very small than the records loaded
into database. For example, after restoring a backup, the database DIR have
about 40 Gb (with all indexes created). After one week of use, and about
500,000 new records on tables, the database size grows to about 42 Gb, but
on Windows 2003 Server we can see the high fragmentation of disk (maybe on
linux this occurs too).

4) VACUUM FULL and/or VACUUM ANALYZE appears to doesn't work perfectly.

The temporary (but extensive) solution:
I have seem that one action could solve this problems for a short time. It
is as follows:
1) Create a database dump into a .SQL plain text file;
2) Drop the OTLP original database;
3) Create a new database using the original name;
4) Restores the .SQL file with psql.

The cost of use PostgreSQL database on our sw came to a very high levels, so
we're evaluating the same database schema and data on other databases as IBM
DB2 9, and these issues doesn't work. However, we need solve this problems
on PgSQL, as exists many customers who will not migrate to DB2.

Anyone can help me?
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