Re: trouble selecting from array

On Thu, Mar 27, 2008 at 8:58 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> If you want a sub-array you need to use the slice notation, eg
> tdr_tags[2:2][1:2]

The slice approach is not a general solution...in fact there seems to
be no way to convert an array of N dimensions to N-1 dimensions except
in the special case of N=1. One side effect of this is that the
_pg_expand_array approaches which I was about to suggest to the OP
only work for one dimensional arrays.

reading the archives, you wrote:
"Because it isn't a slice expression --- you used colon nowhere, so the
result type is going to be text not text[]. (Remember that the parser
must determine the expression's result type at parse time, so whether
there are enough subscripts can't enter into this.) Our alternatives
here are to throw a subscripting error or return NULL. I'd personally
have gone with throwing an error, I think, but it seems far too late to
revisit that decision."

is there not enough information available to the parser to reduce the
expression dimensions by one?

merlin