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List:       postgresql-admin
Subject:    [ADMIN] RE: [SQL] float4
From:       JT Kirkpatrick <jt-kirkpatrick () mpsllc ! com>
Date:       1999-06-30 12:30:46
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ahh, so 6.5 has an answer!  for our "cash and accounts payable" database i 
converted the float4 field to int4, and altered the input mask on the front 
end to show a decimal point, but not save it with the data.  so now i am 
saving $35.99 as 3599.  i had to alter all reports to divide by 100.  works 
fine.  i'd really like to get it sincerely stable in 6.4.2 before upgrading 
to 6.5, unless a reason for instability is solved in 6.5.  we are still 
having problems with it locking up daily. . .

jt

-----Original Message-----
From:	Tom Lane [SMTP:tgl@sss.pgh.pa.us]
Sent:	Monday, June 28, 1999 7:32 PM
To:	JT Kirkpatrick
Cc:	'pgsql-admin@hub.org'; 'pgsql-sql@hub.org'
Subject:	Re: [SQL] float4

JT Kirkpatrick <jt-kirkpatrick@mpsllc.com> writes:
> we made all monetary fields FLOAT4's.  weird stuff -- or maybe not to you 
> -- we insert 23516.69 into a float4 field directly in psql, and then 
select
> it, and it shows 23516.7.  this is not good for a field used for MONEY!!! 

Yup, no surprise.  float4 is good to about 6 decimal digits on most
machines, and yours is evidently right in there with the pack.

float8 is good to about 16 digits on most hardware, but I wouldn't
really recommend it either if you need guaranteed-exact calculations.

The money type in Postgres is a fairly crude hack that I can't recommend
(it's basically an int4 representing cents, and will therefore poop out
at 2^31 cents or about $20million).

What you really want is the general "numeric" type added in Postgres 6.5
--- decimal representation with as many digit positions as you specify.
It's a good deal slower for calculations than native floats,
unfortunately, especially if you use a very wide numeric field.
But calculations per-se are seldom the bottleneck for a database
application...

BTW, the current plan is to phase out the money type in favor of numeric
in some future release.

			regards, tom lane

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