On 10/28/2012 11:05 AM, Chris Corbyn wrote:
Would this introduce problems finding rows where the stored value is NaN? You'd
need to add a function or operator to avoid that.
I guess it should behave similar to NULL-s
That is IS NOT DISTINCT FROM should still return true
test=# select NULL IS NOT DISTINCT FROM NULL as must_be_true;
must_be_true
--------------
t
(1 row)
I guess making the NaN comparison IEEE compliant could introduce
some problems with indexes, so I propose that index operators would
treat NaNs like NULLs
Hannu
Il giorno 28/ott/2012, alle ore 20:43, Hannu Krosing ha scritto:
This is how PostgreSQL currently works -
test=# select 'NaN'::float = 'NaN'::float as must_be_false;
must_be_false
----------
t
(1 row)
I think that PostgreSQL's behaviour of comparing two
NaN-s as equal is wrong and Iwe should follow the IEEE 754 spec here
As per IEEE 754 a NaN behaves similar to NULL in SQL.
There is some discussion of why it is so at:
http://stackoverflow.com/questions/1565164/what-is-the-rationale-for-all-comparisons-returning-false-for-ieee754-nan-values
especially the first comment
---------
Hannu
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