Horton

Re: Sparse bit set data structure

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Adrien NAYRAT <adrien.nayrat@anayrat.info>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Julien Rouhaud <rjuju123@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Andrey Borodin <x4mmm@yandex-team.ru>, Claudio Freire <klaussfreire@gmail.com>
Date: 2019-04-08T23:38:11Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add IntegerSet, to hold large sets of 64-bit ints efficiently.

Uh, should this be applied?

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On Thu, Mar 28, 2019 at 03:46:03PM +0100, Adrien NAYRAT wrote:
> Hello,
> 
> According to the draw and simple8b_mode struct comment, it seems there is a
> typo:
> 
> > *      20-bit integer       20-bit integer       20-bit integer
> >  * 1101 00000000000000010010 01111010000100100000 00000000000000010100
> >  * ^
> >  * selector
> >  *
> >  * The selector 1101 is 13 in decimal.  From the modes table below, we see
> >  * that it means that the codeword encodes three 12-bit integers.  In decimal,
> >  * those integers are 18, 500000 and 20.  Because we encode deltas rather than
> >  * absolute values, the actual values that they represent are 18, 500018 and
> >  * 500038.
> [...]
> >     {20, 3},                    /* mode 13: three 20-bit integers */
> 
> 
> The comment should be "the codeword encodes three *20-bit* integers" ?
> 
> Patch attached.
> 
> Regards,

> diff --git a/src/backend/lib/integerset.c b/src/backend/lib/integerset.c
> index 28b4a38609..9984fd55e8 100644
> --- a/src/backend/lib/integerset.c
> +++ b/src/backend/lib/integerset.c
> @@ -805,7 +805,7 @@ intset_binsrch_leaf(uint64 item, leaf_item *arr, int arr_elems, bool nextkey)
>   * selector
>   *
>   * The selector 1101 is 13 in decimal.  From the modes table below, we see
> - * that it means that the codeword encodes three 12-bit integers.  In decimal,
> + * that it means that the codeword encodes three 20-bit integers.  In decimal,
>   * those integers are 18, 500000 and 20.  Because we encode deltas rather than
>   * absolute values, the actual values that they represent are 18, 500018 and
>   * 500038.


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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
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