Re: Which file does the SELECT? - Mailing list pgsql-hackers

From Martijn van Oosterhout
Subject Re: Which file does the SELECT?
Date
Msg-id 20101010202330.GA9578@svana.org
Whole thread Raw
In response to Re: Which file does the SELECT?  (Vaibhav Kaushal <vaibhavkaushal123@gmail.com>)
List pgsql-hackers
On Sun, Oct 10, 2010 at 10:51:54PM +0530, Vaibhav Kaushal wrote:
> However, I find too many references to the Data structure "datum" what is it
> and where is it defined? Can someone tell me please? Also, what role does it
> play?

"Datum" is the singular form of "data". It refers to a single item of
any type. So it may be an integer, text type, geometry type, anything.
A row is a list of datums. (A datum can also be a composite type).

Normally in the planner code you don't need to worry to much about what
it explicitly refers to, but if you do, you need to know the type of a
datum before you can manipulate it. The type is not stored inside the
datum.

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Patriotism is when love of your own people comes first; nationalism,
> when hate for people other than your own comes first.
>                                       - Charles de Gaulle

pgsql-hackers by date:

Previous
From: Tom Lane
Date:
Subject: Re: WIP: Triggers on VIEWs
Next
From: Dimitri Fontaine
Date:
Subject: Debugging initdb breakage