Change array_push and array_cat so that they retain the lower bound of

the array (for array_push) or higher-dimensional array (for array_cat)
rather than decrementing it as before.  This avoids generating lower
bounds other than one for any array operation within the SQL spec.  Per
recent discussion.
Interestingly, this seems to have been the original behavior, because
while updating the docs I noticed that a large fraction of relevant
examples were *wrong* for the old behavior and are now right.  Is it
worth correcting this in the back-branch docs?

doc/src/sgml/array.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.47 2005/11/17 22:14:50 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.48 2005/11/19 01:50:08 tgl Exp $ -->
 
 <sect1 id="arrays">
  <title>Arrays</title>
@@ -391,13 +391,11 @@ SELECT ARRAY[5,6] || ARRAY[[1,2],[3,4]];
  </para>
 
  <para>
-  When a single element is pushed on to the beginning of a one-dimensional
-  array, the result is an array with a lower bound subscript equal to
-  the right-hand operand's lower bound subscript, minus one. When a single
-  element is pushed on to the end of a one-dimensional array, the result is
-  an array retaining the lower bound of the left-hand operand. For example:
+  When a single element is pushed on to either the beginning or end of a
+  one-dimensional array, the result is an array with the same lower bound
+  subscript as the array operand. For example:
 <programlisting>
-SELECT array_dims(1 || ARRAY[2,3]);
+SELECT array_dims(1 || '[0:1]={2,3}'::int[]);
  array_dims
 ------------
  [0:2]
@@ -441,7 +439,7 @@ SELECT array_dims(ARRAY[[1,2],[3,4]] || ARRAY[[5,6],[7,8],[9,0]]);
 SELECT array_dims(ARRAY[1,2] || ARRAY[[3,4],[5,6]]);
  array_dims
 ------------
- [0:2][1:2]
+ [1:3][1:2]
 (1 row)
 </programlisting>
  </para>

doc/src/sgml/func.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.293 2005/11/17 22:14:50 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.294 2005/11/19 01:50:08 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -7484,7 +7484,7 @@ SELECT NULLIF(value, '(none)') ...
     </entry>
         <entry><type>int</type></entry>
         <entry>returns lower bound of the requested array dimension</entry>
-        <entry><literal>array_lower(array_prepend(0, ARRAY[1,2,3]), 1)</literal></entry>
+        <entry><literal>array_lower('[0:2]={1,2,3}'::int[], 1)</literal></entry>
         <entry><literal>0</literal></entry>
        </row>
        <row>

src/backend/utils/adt/array_userfuncs.c

@@ -6,7 +6,7 @@
  * Copyright (c) 2003-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/array_userfuncs.c,v 1.17 2005/11/17 22:14:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/array_userfuncs.c,v 1.18 2005/11/19 01:50:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -152,6 +152,13 @@ array_push(PG_FUNCTION_ARGS)
 	result = array_set(v, 1, &indx, newelem, isNull,
 					   -1, typlen, typbyval, typalign);
 
+	/*
+	 * Readjust result's LB to match the input's.  This does nothing in the
+	 * append case, but it's the simplest way to implement the prepend case.
+	 */
+	if (ARR_NDIM(v) == 1)
+		ARR_LBOUND(result)[0] = ARR_LBOUND(v)[0];
+
 	PG_RETURN_ARRAYTYPE_P(result);
 }
 
@@ -305,7 +312,7 @@ array_cat(PG_FUNCTION_ARGS)
 	{
 		/*
 		 * resulting array has the second argument as the outer array, with
-		 * the first argument appended to the front of the outer dimension
+		 * the first argument inserted at the front of the outer dimension
 		 */
 		ndims = ndims2;
 		dims = (int *) palloc(ndims * sizeof(int));
@@ -316,9 +323,6 @@ array_cat(PG_FUNCTION_ARGS)
 		/* increment number of elements in outer array */
 		dims[0] += 1;
 
-		/* decrement outer array lower bound */
-		lbs[0] -= 1;
-
 		/* make sure the added element matches our existing elements */
 		for (i = 0; i < ndims1; i++)
 		{

src/test/regress/expected/arrays.out

@@ -224,9 +224,9 @@ SELECT array_append(array[42], 6) AS "{42,6}";
 (1 row)
 
 SELECT array_prepend(6, array[42]) AS "{6,42}";
-    {6,42}    
---------------
- [0:1]={6,42}
+ {6,42} 
+--------
+ {6,42}
 (1 row)
 
 SELECT array_cat(ARRAY[1,2], ARRAY[3,4]) AS "{1,2,3,4}";
@@ -236,9 +236,9 @@ SELECT array_cat(ARRAY[1,2], ARRAY[3,4]) AS "{1,2,3,4}";
 (1 row)
 
 SELECT array_cat(ARRAY[1,2], ARRAY[[3,4],[5,6]]) AS "{{1,2},{3,4},{5,6}}";
-      {{1,2},{3,4},{5,6}}       
---------------------------------
- [0:2][1:2]={{1,2},{3,4},{5,6}}
+ {{1,2},{3,4},{5,6}} 
+---------------------
+ {{1,2},{3,4},{5,6}}
 (1 row)
 
 SELECT array_cat(ARRAY[[3,4],[5,6]], ARRAY[1,2]) AS "{{3,4},{5,6},{1,2}}";
@@ -267,9 +267,9 @@ SELECT ARRAY[1,2] || 3 AS "{1,2,3}";
 (1 row)
 
 SELECT 0 || ARRAY[1,2] AS "{0,1,2}";
-    {0,1,2}    
----------------
- [0:2]={0,1,2}
+ {0,1,2} 
+---------
+ {0,1,2}
 (1 row)
 
 SELECT ARRAY[1,2] || ARRAY[3,4] AS "{1,2,3,4}";
@@ -297,9 +297,9 @@ SELECT ARRAY[0,0] || ARRAY[1,1] || ARRAY[2,2] AS "{0,0,1,1,2,2}";
 (1 row)
 
 SELECT 0 || ARRAY[1,2] || 3 AS "{0,1,2,3}";
-    {0,1,2,3}    
------------------
- [0:3]={0,1,2,3}
+ {0,1,2,3} 
+-----------
+ {0,1,2,3}
 (1 row)
 
 -- array casts