Thread: primary key display in psql
When you look at a table definition with psql \d, one of the arguably most important pieces of information -- the primary key -- is hidden somewhere below under "indexes": Table "public.test2"Column | Type | Modifiers --------+---------+-----------a | integer | not nullb | integer | not null Indexes: "test2_pkey" PRIMARY KEY, btree (a, b) I think we could easily improve that by having it look something like this instead: Table "public.test2"Column | Type | Modifiers --------+---------+-----------a | integer | PKb | integer | PK Indexes: "test2_pkey" PRIMARY KEY, btree (a, b) Since there can only be one primary key, this should be unambiguous. I don't have time to code this up right now, but maybe someone feels inspired. What do you think?
Peter Eisentraut <peter_e@gmx.net> writes:
> I think we could easily improve that by having it look something like
> this instead:
> Table "public.test2"
> Column | Type | Modifiers
> --------+---------+-----------
> a | integer | PK
> b | integer | PK
> Indexes:
> "test2_pkey" PRIMARY KEY, btree (a, b)
Spelling out "primary key" would seem to be more in keeping with existing
entries in that column, eg we have "not null" not "NN".
I think this is a sensible proposal for a single-column PK, but am less
sure that it makes sense for multi-col. The modifiers column is
intended to describe column constraints; which a multi-col PK is not,
by definition.
regards, tom lane
On Wed, Jan 13, 2010 at 4:47 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Peter Eisentraut <peter_e@gmx.net> writes: >> I think we could easily improve that by having it look something like >> this instead: > >> Table "public.test2" >> Column | Type | Modifiers >> --------+---------+----------- >> a | integer | PK >> b | integer | PK >> Indexes: >> "test2_pkey" PRIMARY KEY, btree (a, b) > > Spelling out "primary key" would seem to be more in keeping with existing > entries in that column, eg we have "not null" not "NN". > > I think this is a sensible proposal for a single-column PK, but am less > sure that it makes sense for multi-col. The modifiers column is > intended to describe column constraints; which a multi-col PK is not, > by definition. Yeah, IIRC, MySQL shows PRI for each column of a multi-column primary key, and I think it's horribly confusing. I wouldn't even be in favor of doing this just for the single-column case, on the grounds that it makes the single and multiple column cases asymmetrical. IMO, the \d output has too many bells and whistles already; the last thing we should do is add more. ...Robert
On Wed, Jan 13, 2010 at 05:03:33PM -0500, Robert Haas wrote: > On Wed, Jan 13, 2010 at 4:47 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > > > > Spelling out "primary key" would seem to be more in keeping with existing > > entries in that column, eg we have "not null" not "NN". > > > > I think this is a sensible proposal for a single-column PK, but am less > > sure that it makes sense for multi-col. The modifiers column is > > intended to describe column constraints; which a multi-col PK is not, > > by definition. > > Yeah, IIRC, MySQL shows PRI for each column of a multi-column primary > key, and I think it's horribly confusing. I wouldn't even be in favor > of doing this just for the single-column case, on the grounds that it > makes the single and multiple column cases asymmetrical. IMO, the \d > output has too many bells and whistles already; the last thing we > should do is add more. How about spelling it as so: Table "public.test" Column | Type | Modifiers--------+---------+----------- a | integer | primary key b |integer | Indexes: "test1_pkey" PRIMARY KEY, btree (a) Table "public.test2" Column | Type | Modifiers--------+---------+----------- a | integer | primary key (compound) b | integer | primary key (compound)Indexes: "test2_pkey" PRIMARY KEY, btree (a, b) As to Tom's point that a compound primary key is a table level restriction, by definition, participating in such a key is still a restriction on what values that column can take. When introspecting someone else's schema, with a very wide table, seeing '(compound)' is a nice strong hint to go looking for the other members of the PK. Ross -- Ross Reedstrom, Ph.D. reedstrm@rice.edu Systems Engineer & Admin, Research Scientist phone: 713-348-6166 The Connexions Project http://cnx.org fax: 713-348-3665 Rice University MS-375, Houston, TX 77005 GPG Key fingerprint = F023 82C8 9B0E 2CC6 0D8E F888 D3AE 810E 88F0 BEDE