Re: Index size

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.klaver@aklaver.com