Re: PG index architecture

> -----Original Message-----
> From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-
> owner@postgresql.org] On Behalf Of Andy Colson
> Sent: Tuesday, July 15, 2014 4:27 PM
> To: pgsql
> Subject: [GENERAL] PG index architecture
>
> I was thinking about indexes, and am kinda curious about sequential access.
>
> I know nothing of PG guts, so this might even be a dumb question.
>
> As I understand indexes, they are a key value pair, that contain a value and a
> position.  You lookup the value then use the position to seek into the
> database to load the record.
>
> Do we, or could we, load all the the matching index records, then sort them
> by position?  (maybe not all, maybe large batches)
>
> When loading from the database, if access was slightly more sequential (vs
> very random), would it increase performance?
>
> Said another way:
>
> I think of table scanning as sequential, and fast.  That would be loading db
> record 1,2,3, etc.
>
> Would it be faster to load db records "mostly sequential": 1,3,4,7,10
> compared to randomly: 7,3,10,1,4
>
> -Andy
>

It is called CLUSTER:

http://www.postgresql.org/docs/9.2/static/sql-cluster.html

Regards,
Igor Neyman