| From: | Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> |
|---|---|
| To: | Samuel Williams <space(dot)ship(dot)traveller(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Index size |
| Date: | 2016-11-29 23:41:48 |
| Message-ID: | 4ec3b7b3-014b-1780-12ba-41974a39e369@aklaver.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
On 11/29/2016 03:30 PM, Samuel Williams wrote:
> I'd like to understand a bit more about indexes in PG.
https://www.postgresql.org/docs/9.5/static/indexam.html
"An index is effectively a mapping from some data key values to tuple
identifiers, or TIDs, of row versions (tuples) in the index's parent
table. A TID consists of a block number and an item number within that
block (see Section 63.6). This is sufficient information to fetch a
particular row version from the table. ..."
>
> When I have a row in a table, and an index, say, for a single column,
> does that duplicate the entire row on disk? Or is there some kind of
> id lookup involved?
>
> Thanks.
>
>
--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Michael Sheaver | 2016-11-30 00:10:59 | "Fuzzy" Matches on Nicknames |
| Previous Message | Patrick B | 2016-11-29 23:31:25 | Monitoring Replication - Postgres 9.2 |