I'm noticing some inconsistent behavior regarding empty arrays and IS NULL status. For example:
net_test=# select array_upper('{}'::INT[], 1) IS NULL;
?column?
----------
t
(1 row)
This is correct. There are no dimensions to an empty array by definition. The only other way to handle this would be an ERROR. I followed the lead of (the pre-existing function) array_dims() when creating array_upper() and array_lower().
net_test=# select '{}'::INT[] IS NULL;
?column?
----------
f
(1 row)
This is also correct, and completely orthogonal to the first example. There is a difference between an empty array and NULL, just like there is between an empty string and NULL.
I feel that this is confusing; an empty array should be considered NULL everywhere or nowhere.
As I said above, that makes no more sense than saying '' == NULL
For that matter, the new array declaration syntax does not support empty arrays: net_test=# select ARRAY[ ]::INT[]; ERROR: syntax error at or near "]" at character 15
This is a known issue, and will not be easily fixed. We discussed it at some length last June/July. See especially:
http://archives.postgresql.org/pgsql-hackers/2003-06/msg01174.php http://archives.postgresql.org/pgsql-hackers/2003-06/msg01195.php http://archives.postgresql.org/pgsql-hackers/2003-06/msg01196.php http://archives.postgresql.org/pgsql-hackers/2003-06/msg01298.php
Joe
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