Kevin Field wrote:
Section 9.2 in the docs say, 'The ordinary comparison operators yield null (signifying "unknown") when either input is null.' This applies to other operators too. For example, the result of tacking an unknown value onto a known one is unknown, because you don't know what exactly you just tacked on. Soselect null::text || 'hello'; ...returns NULL, which makes sense. But then this select array_cat(null::integer[], '{3}'::integer[]); ...doesn't return NULL, which it should, for consistency.
Doesn't make sense to me either. I found that this was changed between 8.1 (where it returns null) and 8.2, but I find nothing in the respective release notes or commit messages about this change. Tom?
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