Re: About adding an attribute to a system catalog

Robert Haas <robertmhaas@gmail.com> writes:
> Adding attributes to bootstrap tables is a whole lot more fiddly than
> for other system tables.  I suggest looking at a patch that did this
> to see what's involved. For example, commit
> 76a47c0e7423891d4b4f0977312f46fec6c5c416 removed and replaced a column
> in pg_attribute, so by looking through there you could see all of the
> places that had to be updated.

One way in which that particular commit isn't a great example is that,
since the number of columns didn't change, it didn't expose the need to
update pg_attribute's handmade row in pg_class.h.  Failing to update the
column count in that DATA line is a standard gotcha when adding columns to
one of the BKI_BOOTSTRAP tables.

In general, though, Robert's advice is good: find a previous commit that
did something similar to what you need.  And grep is your friend in any
case.
        regards, tom lane