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List:       postgresql-general
Subject:    Re: [HACKERS] 9.3: Empty arrays returned by array_remove()
From:       Dean Rasheed <dean.a.rasheed () gmail ! com>
Date:       2013-05-31 7:55:49
Message-ID: CAEZATCUOkyz=VszVRVWCWLvJdxRTjKgODMhj-GqX1yEaQNQ7ew () mail ! gmail ! com
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On 31 May 2013 08:34, Brendan Jurd <direvus@gmail.com> wrote:
> On 31 May 2013 02:52, Dean Rasheed <dean.a.rasheed@gmail.com> wrote:
>> Testing 9.3beta, it seems that array_remove() may return an empty 1-d
>> array whose upper bound is lower than its lower bound. I know that we
>> discussed allowing this kind of array, but I don't think that
>> discussion reached any conclusion, other than to agree that the
>> current empty 0-d array behaviour would be kept in 9.3.
>>
>
> That's right, zero-D is still the only supported representation of an
> empty array, so when array_remove() yields an empty array it ought to
> be zero-D.  Good catch.
>

Yeah, that's what I thought. Here's a patch to fix it, plus a new
regression test to confirm that the result is a zero-D array.

Regards,
Dean

["array_remove.patch" (application/octet-stream)]

diff --git a/src/backend/utils/adt/arrayfuncs.c b/src/backend/utils/adt/arrayfuncs.c
new file mode 100644
index f53a0d2..c2dc1fb
*** a/src/backend/utils/adt/arrayfuncs.c
--- b/src/backend/utils/adt/arrayfuncs.c
*************** array_replace_internal(ArrayType *array,
*** 5398,5403 ****
--- 5398,5411 ----
  		return array;
  	}
  
+ 	/* If all elements were removed return an empty array */
+ 	if (nresult == 0)
+ 	{
+ 		pfree(values);
+ 		pfree(nulls);
+ 		return construct_empty_array(element_type);
+ 	}
+ 
  	/* Allocate and initialize the result array */
  	if (hasnulls)
  	{
diff --git a/src/test/regress/expected/arrays.out b/src/test/regress/expected/arrays.out
new file mode 100644
index 051bac9..4ac1e08
*** a/src/test/regress/expected/arrays.out
--- b/src/test/regress/expected/arrays.out
*************** select array_remove(array['A','CC','D','
*** 1568,1573 ****
--- 1568,1579 ----
  
  select array_remove('{{1,2,2},{1,4,3}}', 2); -- not allowed
  ERROR:  removing elements from multidimensional arrays is not supported
+ select array_remove(array['X','X','X'], 'X') = '{}';
+  ?column? 
+ ----------
+  t
+ (1 row)
+ 
  select array_replace(array[1,2,5,4],5,3);
   array_replace 
  ---------------
diff --git a/src/test/regress/sql/arrays.sql b/src/test/regress/sql/arrays.sql
new file mode 100644
index 04e9725..6dce0dc
*** a/src/test/regress/sql/arrays.sql
--- b/src/test/regress/sql/arrays.sql
*************** select array_remove(array[1,2,2,3], 5);
*** 437,442 ****
--- 437,443 ----
  select array_remove(array[1,NULL,NULL,3], NULL);
  select array_remove(array['A','CC','D','C','RR'], 'RR');
  select array_remove('{{1,2,2},{1,4,3}}', 2); -- not allowed
+ select array_remove(array['X','X','X'], 'X') = '{}';
  select array_replace(array[1,2,5,4],5,3);
  select array_replace(array[1,2,5,4],5,NULL);
  select array_replace(array[1,2,NULL,4,NULL],NULL,5);


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