Hello,
I am playing with the "INHERITS" functionality of create table to
determine its suitability to my needs and I've hit a roadblock (hopefully
minor)...
If I have two tables like this:
CREATE TABLE tablea (
id SERIAL
);
CREATE TABLE tableb () INHERITS (tablea);
#1. Now first of all, I notice that if I insert something into tableb, it
appears in tablea and if I insert something in tablea, it does not appear
in tableb... Is this correct and will the use of the "SERIAL" type
cause any confusion or can I insert rows in each table without being
concerned about any internal ramifications of this?
#2. If I do "explain select id from tablea where id=4", I get something
like this:
QUERY PLAN
-------------------------------------------------------
Seq Scan on jobdata (cost=0.00..1.04 rows=1 width=4)
Filter: (id = 4)
...If, however, I do "explain select id from tableb where id=4":
-------------------------------------
------------------------------------------------
Result (cost=0.00..2.08 rows=2 width=4)
-> Append (cost=0.00..2.08 rows=2 width=4)
-> Seq Scan on jobdata_revisions (cost=0.00..1.04 rows=1 width=4)
Filter: (id = 4)
-> Seq Scan on jobdata jobdata_revisions (cost=0.00..1.04
rows=1 width=4)
Filter: (id = 4)
I'm a bit mystified by the results of tableb, I don't understand what the
"Append" and the second "Seq Scan" is for... More importantly, I'm not
sure how to optimize this properly...
Any ideas what I can do here?...
Thanks!
- Greg
