mirror/postgresql
2
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2025-03-01 19:45:33 +08:00
Code Issues Packages Projects Releases Wiki Activity

Remove underflow error in float division with infinite divisor.

Browse Source 
float4_div and float8_div correctly produced zero for zero divided
by infinity, but threw an underflow error for nonzero finite values
divided by infinity.  This seems wrong; at the very least it's
inconsistent with the behavior recently implemented for numeric
infinities.  Remove the error and allow zero to be returned.

This patch also removes a useless isinf() test from the overflow
checks in these functions (non-Inf divided by Inf can't produce Inf).

Extracted from a larger patch; this seems significant outside the
context of geometric operators, so it deserves its own commit.

Kyotaro Horiguchi

Discussion: https://postgr.es/m/CAGf+fX70rWFOk5cd00uMfa__0yP+vtQg5ck7c2Onb-Yczp0URA@mail.gmail.com
This commit is contained in:
Tom Lane 2020-11-04 18:11:15 -05:00
parent 9e38c2bb50
commit fac83dbd6f
6 changed files with 24 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
src/include/utils/float.h
View File

@ -225,9 +225,9 @@ float4_div(const float4 val1, const float4 val2)
if (unlikely(val2 == 0.0f) && !isnan(val1))
float_zero_divide_error();
result = val1 / val2;
if (unlikely(isinf(result)) && !isinf(val1) && !isinf(val2))
if (unlikely(isinf(result)) && !isinf(val1))
float_overflow_error();
if (unlikely(result == 0.0f) && val1 != 0.0f)
if (unlikely(result == 0.0f) && val1 != 0.0f && !isinf(val2))
float_underflow_error();
return result;
@ -241,9 +241,9 @@ float8_div(const float8 val1, const float8 val2)
if (unlikely(val2 == 0.0) && !isnan(val1))
float_zero_divide_error();
result = val1 / val2;
if (unlikely(isinf(result)) && !isinf(val1) && !isinf(val2))
if (unlikely(isinf(result)) && !isinf(val1))
float_overflow_error();
if (unlikely(result == 0.0) && val1 != 0.0)
if (unlikely(result == 0.0) && val1 != 0.0 && !isinf(val2))
float_underflow_error();
return result;

6
src/test/regress/expected/float4-misrounded-input.out
View File

@ -137,6 +137,12 @@ SELECT 'Infinity'::float4 / 'Infinity'::float4;
NaN
(1 row)
SELECT '42'::float4 / 'Infinity'::float4;
?column?
----------
0
(1 row)
SELECT 'nan'::float4 / 'nan'::float4;
?column?
----------

6
src/test/regress/expected/float4.out
View File

@ -137,6 +137,12 @@ SELECT 'Infinity'::float4 / 'Infinity'::float4;
NaN
(1 row)
SELECT '42'::float4 / 'Infinity'::float4;
?column?
----------
0
(1 row)
SELECT 'nan'::float4 / 'nan'::float4;
?column?
----------

6
src/test/regress/expected/float8.out
View File

@ -120,6 +120,12 @@ SELECT 'Infinity'::float8 / 'Infinity'::float8;
NaN
(1 row)
SELECT '42'::float8 / 'Infinity'::float8;
?column?
----------
0
(1 row)
SELECT 'nan'::float8 / 'nan'::float8;
?column?
----------

1
src/test/regress/sql/float4.sql
View File

@ -49,6 +49,7 @@ SELECT ' INFINITY x'::float4;
SELECT 'Infinity'::float4 + 100.0;
SELECT 'Infinity'::float4 / 'Infinity'::float4;
SELECT '42'::float4 / 'Infinity'::float4;
SELECT 'nan'::float4 / 'nan'::float4;
SELECT 'nan'::float4 / '0'::float4;
SELECT 'nan'::numeric::float4;

1
src/test/regress/sql/float8.sql
View File

@ -42,6 +42,7 @@ SELECT ' INFINITY x'::float8;
SELECT 'Infinity'::float8 + 100.0;
SELECT 'Infinity'::float8 / 'Infinity'::float8;
SELECT '42'::float8 / 'Infinity'::float8;
SELECT 'nan'::float8 / 'nan'::float8;
SELECT 'nan'::float8 / '0'::float8;
SELECT 'nan'::numeric::float8;