Tom Lane wrote:
Joe Conway <[EMAIL PROTECTED]> writes:
Tom Lane wrote:
In the long run maybe we should choose some other name for the
array_append and array_prepend operators to avoid the confusion with
concatenation.  It seems to me that "concatenation" normally implies
"stringing together similar objects", which these two operators
definitely don't do, and so you could argue that || was a bad name
for them from the get-go.

Originally I saw this situation as as requiring the concatenation operator per SQL 2003:

Maybe I am missing something, but the only such construct I see in
SQL2003 is concatenation of arrays of equal rank.  There is nothing
corresponding to array_prepend or array_append.

Well, I've never claimed to be particularly good at interpreting the SQL spec, but as an example...

<array concatenation> ::=
   <array value expression 1> || <array primary>
<array primary> ::=
<value expression primary> ::=
<nonparenthesized value expression primary> ::=
<unsigned value specification> ::=
<unsigned literal> ::=
    <unsigned numeric literal>

Doesn't this mean that array concatenation should include things like:

   <array value expression> || <unsigned numeric literal>


  ARRAY[1,2,3] || 42

I do have a plan B if people don't want to rename the operators, though.
It looks to me like we could eliminate the conflict if we invented a new
polymorphic pseudotype called "anynonarray" or some such, which would
act like anyelement *except* it would not match an array.  Then,
declaring the capturing operators as text||anynonarray and
anynonarray||text would prevent them from matching any case where either
side was known to be an array type.  But they would (I think) still win
out in cases such as scalar || 'unknown literal'.  The end result would
be that concatenations involving a known-array value would be array
concatenation, but you could force them to be text concatenation, if
that's what you wanted, by explicitly casting the array value(s) to text.

That sounds reasonable to me.


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