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 |
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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
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