I think using pg_dump in some cases is a good option , but not all the time, having a function makes it much cleaner to use

Consider pgAdmin lets say (and there are many such applications out there) , you need to show object DDL on the RHP and its nicely formatted and you can copy paste it and then perhaps export it in an SQL file.

Now imagine you need to spawn a new process from inside the app for pg_dump, and then make it write to a file and then read the file to display the object DDL, which is possible but very messy looking code. Then there are issues with launching external processes on certain platforms (for example in Java if you start a new process from the runtime(), you need to make sure you properly flush out its stdout and stderr streams otherwise it can go in a deadlock etc), i would use a function, if available anyday

Additionally  there are such functions for other objects, but for tables you needed to construct it manually, so i also thought this would just complete the set and make it easier to write an SQL / DDL exporting app.

Naz Gassiep wrote:
Just a question, is there any advantage to having this then building a
function in applications that wrap and use pg_dump with a few options?
Surely that's a more appropriate way to achieve this functionality?
- Naz.

Usama Munir wrote:

i was following a thread some time ago where adding a function
*pg_get_tabledef* was one of the TODOs for 8.2, but it somehow didn't
make it to the release perhaps because the functionality was not
clearly defined? not sure.

Anyway  i happen to come up with a function for pg_get_tabledef which
works something like following

/postgres=# select pg_get_tabledef(16388) ;
 CREATE TABLE  public.dept
  deptno numeric(2,0) NOT NULL,
  dname  character varying(14),
  loc    character varying(13)
/(1 row)

i wanted to submit a patch for this, IFF the community wants this
function. The rationale is obviously to help Application developers
writing applications like pgAdmin. Currently this part of SQL needs to
be constructed manually for postgres by the tools.

it is arguable that a table defintion will have constraints , triggers
etc as well, and they can be added without much problem, but i think
if a tool needs to construct an SQL for all table related objects then
functions are already available for them like pg_get_constraintdef,
pg_get_ruledef, pg_get_indexdef, pg_get_triggerdef etc

i understand that you guys don't like someone to develop a patch in
isolation and just come up with it one day, but it really came out as
a by-product of some other work , and i thought you guys might be
interested in it.

if it is desired,  i will submit  a patch for it, within a day or so.

Usama Munir
EnterpriseDB (www.enterprisedb.com)


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