Re: operator dependency of commutator and negator

Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Excerpts from Itagaki Takahiro's message of mi sep 29 03:56:33 -0400 2010:
>> When we drop an operator used by other operators as COMMUTATOR or NEGATOR,
>> pg_dump generates an invalid SQL command for the operators depending on
>> the dropped one. Is it an unavoidable restriction?

> Maybe we need a pg_depend entry from each pg_operator entry to the other
> one. The problem is that this creates a cycle in the depends graph; not
> sure how well these are handled in the code, if at all.

See the comment in catalog/pg_operator.c:

/*
* NOTE: we do not consider the operator to depend on the associated
* operators oprcom and oprnegate. We would not want to delete this
* operator if those go away, but only reset the link fields; which is not
* a function that the dependency code can presently handle. (Something
* could perhaps be done with objectSubId though.) For now, it's okay to
* let those links dangle if a referenced operator is removed.
*/

I'm not sure that fixing this case is worth the amount of work it'd
take. How often do you drop just one member of a commutator pair?

regards, tom lane