Re: array support patch phase 1 patch

Tom Lane wrote:
> Another problem is:
>
> regression=# select distinct array(select * from text_tbl) from foo;
> ERROR: Unable to identify an equality operator for type text[]
>
> This DISTINCT query would fail anyway of course, for lack of a '<'
> operator for arrays, but it seems like we ought to be able to find the
> polymorphic '=' operator.

The attached small patch addresses the above concern (finding
polymorphic "=" operator) by introducing a new function,
IsPolymorphicCoercible().

Now, as predicted, I get:

regression=# select distinct array(select f1 from tse);
ERROR: Unable to identify an ordering operator for type integer[]
Use an explicit ordering operator or modify the query

If there are no objections, please apply.

Next question this begs is, should I work on a '<' operator for arrays?
And if so, how is the behavior defined? Hannu suggested
element-by-element, analogous to character-by-character text string
comparison. Comments?

Thanks,

Joe