nill <nillx87@hotmail.com> writes:
> I am analyzing query plans generated by the view in the database PostgreSQL
> 8.3, looking for missing information "constraints not explicitly registrants
> in the tables."
You realize of course that 8.3 is nearly 7 years old and has been out of
support for awhile.
> In the analysis of the query plan and its subplane, I can not understand
> what the parameter $0 represents, without looking the SQL query. My question
> is: looking only at the query plan product, you can understand what is the
> parameter $0?
It's a variable passed down from the outer query level. It's true that
you can't tell which variable, in 8.3. Less obsolete versions produce
more readable output though. (I won't claim it's perfect; we still don't
try very hard to decompile ANY/ALL subplans.)
regards, tom lane