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@> (contains)
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Commits from this thread:
  2019-09-23 13cd97e6c8 216bcf5838 7cd99d3947 184b5fad00 65cddf70aa 70c1245064 0652c3992e  Doc: clarify handling of duplicate elements in array containment tests.

* @> (contains)
@ 2019-08-18 15:13  PG Doc comments form <noreply@postgresql.org>
  0 siblings, 1 reply; 3+ messages in thread

From: PG Doc comments form @ 2019-08-18 15:13 UTC (permalink / raw)
  To: pgsql-docs@lists.postgresql.org; +Cc: php.pl.prices@gmail.com

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.6/functions-array.html
Description:

Hi.
Noticed strange thin with @>
Query "select '{1,2}'::int[] @> '{1,2,2,2,2,2,2,2}'::int[]" returns true,
but first array contains even less elements then second.
I think it's a bug in "contains" logic, but don't know where to submit it.


^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: @> (contains)
@ 2019-08-18 16:19  David G. Johnston <david.g.johnston@gmail.com>
  parent: PG Doc comments form <noreply@postgresql.org>
  0 siblings, 1 reply; 3+ messages in thread

From: David G. Johnston @ 2019-08-18 16:19 UTC (permalink / raw)
  To: php.pl.prices@gmail.com; pgsql-docs@lists.postgresql.org

On Sun, Aug 18, 2019 at 8:53 AM PG Doc comments form <noreply@postgresql.org>
wrote:

> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/9.6/functions-array.html
> Description:
>
> Hi.
> Noticed strange thin with @>
> Query "select '{1,2}'::int[] @> '{1,2,2,2,2,2,2,2}'::int[]" returns true,
> but first array contains even less elements then second.
> I think it's a bug in "contains" logic, but don't know where to submit it.
>

Its a valid interpretation of "contains", for this purpose each array is
treated like a set (ignoring the cardinality of elements, and overall
dimensionality), but it needs to be documented as behaving that way on that
page.  I don't see that its documented anywhere for that matter.  The
source code documents that dimensions are ignored but is silent on
duplication of elements:

array_contain_compare:
/*-----------------------------------------------------------------------------
 * array overlap/containment comparisons
 * These use the same methods of comparing array elements as array_eq.
 * We consider only the elements of the arrays, ignoring dimensionality.
 *----------------------------------------------------------------------------
 */

David J.

^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: @> (contains)
@ 2019-09-23 16:56  Tom Lane <tgl@sss.pgh.pa.us>
  parent: David G. Johnston <david.g.johnston@gmail.com>
  0 siblings, 0 replies; 3+ messages in thread

From: Tom Lane @ 2019-09-23 16:56 UTC (permalink / raw)
  To: David G. Johnston <david.g.johnston@gmail.com>; +Cc: php.pl.prices@gmail.com; pgsql-docs@lists.postgresql.org

"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Sun, Aug 18, 2019 at 8:53 AM PG Doc comments form <noreply@postgresql.org>
>> Noticed strange thin with @>
>> Query "select '{1,2}'::int[] @> '{1,2,2,2,2,2,2,2}'::int[]" returns true,
>> but first array contains even less elements then second.
>> I think it's a bug in "contains" logic, but don't know where to submit it.

> Its a valid interpretation of "contains", for this purpose each array is
> treated like a set (ignoring the cardinality of elements, and overall
> dimensionality), but it needs to be documented as behaving that way on that
> page.

Done now.

			regards, tom lane





^ permalink  raw  reply  [nested|flat] 3+ messages in thread

end of thread, other threads:[~2019-09-23 16:56 UTC | newest]

Thread overview: 3+ messages (download: mbox mbox.gz follow: Atom feed)
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2019-08-18 15:13 @> (contains) PG Doc comments form <noreply@postgresql.org>
2019-08-18 16:19 ` David G. Johnston <david.g.johnston@gmail.com>
2019-09-23 16:56   ` Tom Lane <tgl@sss.pgh.pa.us>

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