Re: auto_explain causes regression failures

I wrote:
> If you're lost about the point here, it's this: an ArrayExpr can
> represent the result of an array assignment. For example, given
> UPDATE foo SET a[42] = x, what is generated is an ArrayExpr
> with refexpr = a, refupperindexpr = 42, refassgnexpr = x.
> On execution that generates the updated array value that needs to
> get stored back into the "a" column. How would you like to print
> that in EXPLAIN? Same deal for FieldStore: it can represent generating
> the new value of a composite column after replacing one field.

After thinking about this for awhile, the best representation I can
come up with is to let the EXPLAIN output look like an UPDATE
assignment. That is, from something like

UPDATE foo SET arraycol[42] = x WHERE ...

an EXPLAIN VERBOSE would include this in the targetlist display:

Output: ... , arraycol[42] = x , ...

An alternative possibility is to strip the indirection node(s) and
just show "x"; but that seems to leave a good deal of information
hidden, especially if the subscript expressions are complicated.

Objections, better ideas?

regards, tom lane