Re: When is an explicit cast necessary?

On 9 Apr 2010, at 16:57, Alan Millington wrote:

> However, every language that I have ever used will implicitly convert an integer 1 to a smallint (or short) 1 when required to do so. How can such a cast be called "surprising behaviour", or produce "misleading results", to quote the first article?

No, they probably don't cast integer values down to smallint. What they do is cast the smallint up to integer, as that's a safe cast. After all, numbers that fit in an int may not fit in a smallint (try "select 75000::smallint;" for example) and you'd lose data casting it down, but it's fine the other way around.

Since your function has smallint as one of its parameter types the database can't cast the smallint up to an int like it would normally do in such cases as the function doesn't accept integer values for that parameter. PG can't do much but throw an error.

Alban Hertroys

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