Floating point exceptions.

From: Keith Parks <emkxp01(at)mtcc(dot)demon(dot)co(dot)uk>
To: hackers(at)postgresql(dot)org
Subject: Floating point exceptions.
Date: 1998-01-07 16:11:09
Message-ID: 199801071611.QAA27856@mtcc.demon.co.uk
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Hi All,

I suspect this is an O/S or platform problem but can anyone offer any
suggestions as to how I might locate the cause.

DROP TABLE FLOAT8_TBL;
DROP

CREATE TABLE FLOAT8_TBL(f1 float8);
CREATE

INSERT INTO FLOAT8_TBL(f1) VALUES ('1.2345678901234e-200');
INSERT 277993 1

SELECT '' AS bad, : (f.f1) from FLOAT8_TBL f;
ABORT: floating point exception! The last floating point operation either
exceeded legal ranges or was a divide by zero

The ABORT message comes from tcop.c when we are hit by a FPE signal by
the operating system.

.....

Here's some additional tests that seem to show the threshold.

postgres=> CREATE TABLE FLOAT8_TBL(f1 float8);
CREATE
postgres=> INSERT INTO FLOAT8_TBL(f1) VALUES ('1.2345678901234e-150');
INSERT 278057 1
postgres=> SELECT '' AS bad, : (f.f1) from FLOAT8_TBL f;
bad|?column?
---+--------
| 1
(1 row)

postgres=> INSERT INTO FLOAT8_TBL(f1) VALUES ('1.2345678901234e-151');
INSERT 278058 1
postgres=> SELECT '' AS bad, : (f.f1) from FLOAT8_TBL f;
ABORT: floating point exception! The last floating point operation either
exceeded legal ranges or was a divide by zero

Keith.

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