Re: How much clustered?

Tom Lane wrote:
> Carlos Henrique Reimer <carlosreimer@yahoo.com.br> writes:
> >   I would like to know how much clustered is a table related to some index.... How can I discover?
>
> You could do
>     select ctid from mytable order by indexcolumns
> and then do whatever sort of calculation strikes your fancy on the
> sequence of page numbers.  (It's probably fair to ignore the row
> numbers, considering an index to be fully clustered if the page
> reference sequence is perfect.)

Currently we output the ctid as a string:

    snprintf(buf, sizeof(buf), "(%u,%u)", blockNumber, offsetNumber);

Perhaps someday we should consider outputting that as an array or a
result set:

    test=> select x from (select 1, 2) as x;
       x
    -------
     (1,2)
    (1 row)

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  Bruce Momjian   http://candle.pha.pa.us
  SRA OSS, Inc.   http://www.sraoss.com

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