Обсуждение: INHERIT

If I try to get the columns from pg_attribute using the oid of a child
table created with INHERIT I get its columns AND all of its inherited
columns.

How do I just get the columns added by the child table?

I figure I could check each column to see if they also exist in
pg_attribute under a parent table but I figure there must be an
easier/faster way? Another pg_* table perhaps? Besides; I am not certian
this would work if there is a common column between a child and one of
its parents (if that is even allowed)?

As usual, any help would be greatly appreciated.

Peter

BTW: I checked pg_dump source and did not see an answer.

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Peter Harvey wrote: >If I try to get the columns from pg_attribute using the oid of a child >table created with INHERIT
Iget its columns AND all of its inherited >columns. > >How do I just get the columns added by the child table? > >I
figureI could check each column to see if they also exist in >pg_attribute under a parent table but I figure there must
bean >easier/faster way? Another pg_* table perhaps? Besides; I am not certian >this would work if there is a common
columnbetween a child and one of >its parents (if that is even allowed)? > >As usual, any help would be greatly
appreciated.
 

SELECT a.attname FROM pg_attribute AS a,      pg_class AS c,      pg_inherits AS i WHERE a.attrelid = c.oid AND
i.inhrelid= c.oid AND       c.relname = 'child_table'       AND a.attname NOT IN ( SELECT a.attname   FROM pg_attribute
ASa,        pg_class AS c,        pg_inherits AS i   WHERE i.inhrelid = c.oid AND         a.attrelid = i.inhparent AND
      c.relname = 'child_table' )
 


-- 
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
PGP: 1024R/32B8FAA1: 97 EA 1D 47 72 3F 28 47  6B 7E 39 CC 56 E4 C1 47
GPG: 1024D/3E1D0C1C: CA12 09E0 E8D5 8870 5839  932A 614D 4C34 3E1D 0C1C
========================================   "Submit yourselves therefore to God. Resist the devil,      and he will flee
fromyou."        James 4:7 
 

Oliver Elphick wrote:
> 
> Peter Harvey wrote:
>   >If I try to get the columns from pg_attribute using the oid of a child
>   >table created with INHERIT I get its columns AND all of its inherited
>   >columns.
>   >
>   >How do I just get the columns added by the child table?
>   >
>   >I figure I could check each column to see if they also exist in
>   >pg_attribute under a parent table but I figure there must be an
>   >easier/faster way? Another pg_* table perhaps? Besides; I am not certian
>   >this would work if there is a common column between a child and one of
>   >its parents (if that is even allowed)?

hannu=# \d parent         Table "parent"Attribute |  Type   | Modifier 
-----------+---------+----------parid     | integer | not null
Index: parent_pkey

hannu=# create table badchild (parid text) inherits (parent);
NOTICE:  CREATE TABLE: merging attribute "parid" with inherited
definition
ERROR:  CREATE TABLE: attribute "parid" type conflict (int4 and text)
hannu=# 

And anyway, in the current state I would advise you not to put too much 
hope in postgreSQL's OO features, especially inheritance ;)

-------------
Hannu