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Re: Large Tables(>1 Gb)

From: Fred_Zellinger(at)seagate(dot)com
To: pgsql-general(at)hub(dot)org
Subject: Re: Large Tables(>1 Gb)
Date: 2000-06-30 18:53:35
Message-ID: OF0A2CE73B.6C82F8EE-ON8625690E.0066595B@stsv.seagate.com (view raw or flat)
Thread:
Lists: pgsql-general

Thanks for all the great responses on this(doing select * from large tables
and hanging psql).

Here is what I have:
--- psql uses libpq which tries to load everything into memory before
spooling it.
--- use cursors to FETCH selected amount of rows and then spool those.
--- use "select * from big_table limit 1000 offset 0;" for simple queries.

Sometimes you want to do a simple select * from mytable just to get a look
at the data, but you don't care which data.

I am about to go take my multiple broken up tables and dump them back into
one table(and then shut off all those BASH shell scripts I wrote which
checked the system date and created new monthly tables if needed...good
scripting practice but a waste of time).

However, there is still something bugging me.  Even though many people
related stories of 7.5 Gb+ Dbs, I still can't make that little voice in me
quit saying "breaking things into smaller chunks means faster work"
theories.

There must exist a relationship between file sizes and DB performance.
This relationship can be broken into 3 parts:
1.  How the hardware is arranged to pull in large files(fragmentation,
partitions, etc)
2.  How the underlying OS deals with large files
3.  How Postgres deals with(or is affected by) large files.

I imagine that the first two are the dominant factors in the relationship,
but does anyone have any experience with how small/removed of a factor the
internals Postgres are?  Are there any internal coding concerns that have
had to deal with this(like the one mentioned about files being split at
about 1Gb)?

(Curious) Fred



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