Обсуждение: @> (contains)
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.
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.
*----------------------------------------------------------------------------
*/
* 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.
"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