PostgreSQL Discussion - Column descriptions - could they be propagated to new tables?

Author

Column descriptions - could they be propagated to new tables?

Clive Page

2006-04-05, 9:30 am

Since I discovered the facilities in Postgres for providing and listing
column descrptions, I have found them very useful, especially for adding a
string showing physical units to my columns. For example:

\d+ cat
Table "public.cat"
Column | Type | Modifiers | Description
-----------------+------------------+-----------+--------------
src_num | integer | |
ra | double precision | | deg
decl | double precision | | deg
radec_err | real | | arcsec
lii | double precision | | deg
bii | double precision | | deg
pn_cts | real | | counts

However if one performs a JOIN creating a new table, all these
descriptions fail to transfer. I haven't been able to find any easy way
of propagating the descriptions - would it be a useful facility to have
them propagated automatically? I would have thought that things like
units would be useful even in many scientific applications, e.g. to have
monetary columns described as dollars/pounds/euros or whatever.

--
Clive Page
Dept of Physics & Astronomy,
University of Leicester,
Leicester, LE1 7RH, U.K.

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Merlin Moncure

2006-04-05, 11:31 am

On 4/5/06, Clive Page <cgp@star.le.ac.uk> wrote:
> Since I discovered the facilities in Postgres for providing and listing
> column descrptions, I have found them very useful, especially for adding a
> string showing physical units to my columns.

Have you considered using domains for these types? You can comment
the domain appropriately. While the domain description will not show
in \d+. to get the description you can do \dT on the domain.

Based on your background I also think you might appreciate domains
from a design perspective. There are a couple of disadvantages to
using them so I'd suggest reading about them.

merlin

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Jim Nasby

2006-04-07, 3:36 am

On Apr 5, 2006, at 12:15 PM, Merlin Moncure wrote:
> On 4/5/06, Clive Page <cgp@star.le.ac.uk> wrote:
>
> Have you considered using domains for these types? You can comment
> the domain appropriately. While the domain description will not show
> in \d+. to get the description you can do \dT on the domain.
>
> Based on your background I also think you might appreciate domains
> from a design perspective. There are a couple of disadvantages to
> using them so I'd suggest reading about them.

I seem to recall some astronomer having created some custom types for
storing astronomical data in PostgreSQL. Or perhaps he was using
PostGIS. I know that other astronomers are using PostgreSQL/PostGIS
so if you look around you might be able to save yourself quite a bit
of work.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461

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