Hi, The SQL function log() returns incorrect results in these cases: ``` evantest=# SELECT log(0.5::numeric, 'Infinity'::numeric); log ---------- Infinity (1 row)
evantest=# SELECT log(1::numeric, 'Infinity'::numeric);
log
----------
Infinity
(1 row)
```
log(base, value) = ln(value) / ln(base)
ln(0.5) is negative, so the first should return negative infinity; ln(1) is
zero, so the second should fail with division by zero.
Verifying in Python:
```
>>> print(math.log(math.inf, 0.5))
-inf
>>> print(math.log(math.inf, 1));
Traceback (most recent call last):
File "<python-input-3>", line 1, in <module>
print(math.log(math.inf, 1));
~~~~~~~~^^^^^^^^^^^^^
ZeroDivisionError: division by zero
```
Also, verifying with PG itself using division:
```
evantest=# select ln('Infinity'::numeric)/ln(0.5::numeric);
?column?
-----------
-Infinity
(1 row)
evantest=# select ln('Infinity'::numeric)/ln(1::numeric);
ERROR: division by zero
```
This issue was introduced in v14.
Please see the attached patch for the fix.
Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/
v1-0001-Fix-numeric-log-with-an-infinite-argument-and-a-b.patch
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