Hi, On Thu, Nov 10, 2022 at 06:27:21PM -0800, Kirk Parker wrote: > I came across what seems like anomalous behavior regarding > implicit conversion from a numeric type to text. You can write: > > select 3.1416 || '?'; > > and the number implicitly converts to text and concatenates just fine, but > writing: > > select trim(3.1416); > > fails with an error message. This seems odd to me--in both cases a float > literal is used in a context expecting text; in one case it implicitly > converts, in the other it doesn't. > > *This brings up my real question*: are the details of this documented > anywhere? Chapter 10 refers to ' implicit conversions' but I can't see > anywhere that the docs explain the details of how it is done, that would > explain the observed difference in behavior described above.
There are actually no cast defined from numeric to text, so you won't find a documentation for that. The first example is working as documented at https://www.postgresql.org/docs/current/functions-string.html: anynonarray || text → text Converts the non-string input to text, then concatenates the two strings. (The non-string input cannot be of an array type, because that would create ambiguity with the array || operators. If you want to concatenate an array's text equivalent, cast it to text explicitly.)
