On Sat, Dec 4, 2010 at 6:48 AM, Robert Haas <robertmh...@gmail.com> wrote:
> On Dec 4, 2010, at 1:30 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > "Ross J. Reedstrom" <reeds...@rice.edu> writes: > >> If you consider that an index basically is, in some sense, a pre-canned > >> column list, then: > > > >> ALTER TABLE table_name ADD PRIMARY KEY (column_list); > >> ALTER TABLE table_name ADD PRIMARY KEY USING index_name; > > > >> are parallel constructions. And it avoids the error case of the user > >> providing a column list that doesn't match the index. > > > > +1 for that approach. One other thought is that ordinarily, the > > add-constraint syntax ensures that the constraint is named the same as > > its underlying index; in fact we go so far as to keep them in sync if > > you rename the index later. But after > > > > ALTER TABLE table_name ADD CONSTRAINT con_name PRIMARY KEY USING > index_name; > > > > they'd be named differently, unless we (a) throw an error or (b) > > forcibly rename the index. Neither of those ideas seems to satisfy the > > principle of least surprise, but leaving it alone seems like it will > > also lead to confusion later. > > I think that might be the best way though. > Haas, are you promoting to leave them different? I'd be comfortable with that. I'd also be comfortable with B (renaming with notice, similar to the notice when creating a constraint). Given we rename the constraint when we rename the index, I would not find the reverse behavior terribly surprising. Actually I think I'd even be comfortable with A, either you must name the constraint after the index, or you can leave the constraint name out, and we'll use the index name. > > > I wonder whether, in the same spirit as not letting the user write a > > column name list that might not match, we should pick a syntax that > > doesn't allow specifying a constraint name different from the index > > name. In the case where you say CONSTRAINT it'd be a bit plausible > > to write something like > > > > ALTER TABLE table_name ADD CONSTRAINT con_name PRIMARY KEY USING EXISTING > INDEX; > > > > (implying that the index to use is named con_name) but I don't know > > what to do if you want to leave off the "CONSTRAINT name" clause. > > Because this seems plain weird. > > +1 Robert Treat play: http://www.xzilla.net work: http://www.omniti.com/is/hiring
