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Re: Postgres inherited table, some questions...

From: "Net Virtual Mailing Lists" <mailinglists(at)net-virtual(dot)com>
To: <pgsql-general(at)postgresql(dot)org>
Subject: Re: Postgres inherited table, some questions...
Date: 2004-09-29 16:10:35
Message-ID: 20040929161035.8962@mail.net-virtual.com (view raw or flat)
Thread:
Lists: pgsql-general
Hello,

I hate to re-ask this again (sorry to be repetitive!)... I really could
use some help with this, if anyone is familiar with table inheritance as
it applies to my questions....

Thanks!

- Greg

>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
>



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Subject: Re: Composite Type Argument Construction to a Function
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Subject: Re: EXTRACT Clarification

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