Change array_offset to return subscripts, not offsets

... and rename it and its sibling array_offsets to array_position and
array_positions, to account for the changed behavior.

Having the functions return subscripts better matches existing practice,
and is better suited to using the result value as a subscript into the
array directly.  For one-based arrays, the new definition is identical
to what was originally committed.

(We use the term "subscript" in the documentation, which is what we use
whenever we talk about arrays; but the functions themselves are named
using the word "position" to match the standard-defined POSITION()
functions.)

Author: Pavel Stěhule
Behavioral problem noted by Dean Rasheed.

Author: alvherre

doc/src/sgml/array.sgml

@@ -601,20 +601,20 @@ SELECT * FROM sal_emp WHERE pay_by_quarter && ARRAY[10000];
  </para>
 
  <para>
-  You can also search for specific values in an array using the <function>array_offset</>
-  and <function>array_offsets</> functions. The former returns the position of
+  You can also search for specific values in an array using the <function>array_position</>
+  and <function>array_positions</> functions. The former returns the subscript of
   the first occurrence of a value in an array; the latter returns an array with the
-  positions of all occurrences of the value in the array.  For example:
+  subscripts of all occurrences of the value in the array.  For example:
 
 <programlisting>
-SELECT array_offset(ARRAY['sun','mon','tue','wed','thu','fri','sat'], 'mon');
- array_offset
---------------
+SELECT array_position(ARRAY['sun','mon','tue','wed','thu','fri','sat'], 'mon');
+ array_positions
+-----------------
  2
 
-SELECT array_offsets(ARRAY[1, 4, 3, 1, 3, 4, 2, 1], 1);
- array_offsets 
----------------
+SELECT array_positions(ARRAY[1, 4, 3, 1, 3, 4, 2, 1], 1);
+ array_positions
+-----------------
  {1,4,8}
 </programlisting>
  </para>

doc/src/sgml/func.sgml

@@ -11481,10 +11481,10 @@ SELECT NULLIF(value, '(none)') ...
     <primary>array_lower</primary>
   </indexterm>
   <indexterm>
-    <primary>array_offset</primary>
+    <primary>array_position</primary>
   </indexterm>
   <indexterm>
-    <primary>array_offsets</primary>
+    <primary>array_positions</primary>
   </indexterm>
   <indexterm>
     <primary>array_prepend</primary>
@@ -11606,27 +11606,27 @@ SELECT NULLIF(value, '(none)') ...
        <row>
         <entry>
          <literal>
-          <function>array_offset</function>(<type>anyarray</type>, <type>anyelement</type> <optional>, <type>int</type></optional>)
+          <function>array_position</function>(<type>anyarray</type>, <type>anyelement</type> <optional>, <type>int</type></optional>)
          </literal>
         </entry>
         <entry><type>int</type></entry>
-        <entry>returns the offset of the first occurrence of the second
+        <entry>returns the subscript of the first occurrence of the second
         argument in the array, starting at the element indicated by the third
         argument or at the first element (array must be one-dimensional)</entry>
-        <entry><literal>array_offset(ARRAY['sun','mon','tue','wed','thu','fri','sat'], 'mon')</literal></entry>
+        <entry><literal>array_position(ARRAY['sun','mon','tue','wed','thu','fri','sat'], 'mon')</literal></entry>
         <entry><literal>2</literal></entry>
        </row>
        <row>
         <entry>
          <literal>
-          <function>array_offsets</function>(<type>anyarray</type>, <type>anyelement</type>)
+          <function>array_positions</function>(<type>anyarray</type>, <type>anyelement</type>)
          </literal>
         </entry>
         <entry><type>int[]</type></entry>
-        <entry>returns an array of offsets of all occurrences of the second
+        <entry>returns an array of subscripts of all occurrences of the second
         argument in the array given as first argument (array must be
         one-dimensional)</entry>
-        <entry><literal>array_offsets(ARRAY['A','A','B','A'], 'A')</literal></entry>
+        <entry><literal>array_positions(ARRAY['A','A','B','A'], 'A')</literal></entry>
         <entry><literal>{1,2,4}</literal></entry>
        </row>
        <row>
@@ -11741,18 +11741,18 @@ NULL baz</literallayout>(3 rows)</entry>
     </table>
 
    <para>
-    In <function>array_offset</function> and <function>array_offsets</>,
+    In <function>array_position</function> and <function>array_positions</>,
     each array element is compared to the searched value using
     <literal>IS NOT DISTINCT FROM</literal> semantics.
    </para>
 
    <para>
-    In <function>array_offset</function>, <literal>NULL</literal> is returned
+    In <function>array_position</function>, <literal>NULL</literal> is returned
     if the value is not found.
    </para>
 
    <para>
-    In <function>array_offsets</function>, <literal>NULL</literal> is returned
+    In <function>array_positions</function>, <literal>NULL</literal> is returned
     only if the array is <literal>NULL</literal>; if the value is not found in
     the array, an empty array is returned instead.
    </para>

src/backend/utils/adt/array_userfuncs.c

@@ -19,7 +19,7 @@
 #include "utils/typcache.h"
 
 
-static Datum array_offset_common(FunctionCallInfo fcinfo);
+static Datum array_position_common(FunctionCallInfo fcinfo);
 
 
 /*
@@ -659,43 +659,43 @@ array_agg_array_finalfn(PG_FUNCTION_ARGS)
 }
 
 /*-----------------------------------------------------------------------------
- * array_offset, array_offset_start :
+ * array_position, array_position_start :
  *			return the offset of a value in an array.
  *
  * IS NOT DISTINCT FROM semantics are used for comparisons.  Return NULL when
  * the value is not found.
  *-----------------------------------------------------------------------------
  */
 Datum
-array_offset(PG_FUNCTION_ARGS)
+array_position(PG_FUNCTION_ARGS)
 {
-	return array_offset_common(fcinfo);
+	return array_position_common(fcinfo);
 }
 
 Datum
-array_offset_start(PG_FUNCTION_ARGS)
+array_position_start(PG_FUNCTION_ARGS)
 {
-	return array_offset_common(fcinfo);
+	return array_position_common(fcinfo);
 }
 
 /*
- * array_offset_common
- * 		Common code for array_offset and array_offset_start
+ * array_position_common
+ * 		Common code for array_position and array_position_start
  *
  * These are separate wrappers for the sake of opr_sanity regression test.
  * They are not strict so we have to test for null inputs explicitly.
  */
 static Datum
-array_offset_common(FunctionCallInfo fcinfo)
+array_position_common(FunctionCallInfo fcinfo)
 {
 	ArrayType  *array;
 	Oid			collation = PG_GET_COLLATION();
 	Oid			element_type;
 	Datum		searched_element,
 				value;
 	bool		isnull;
-	int			offset = 0,
-				offset_min;
+	int			position,
+				position_min;
 	bool		found = false;
 	TypeCacheEntry *typentry;
 	ArrayMetaState *my_extra;
@@ -731,18 +731,20 @@ array_offset_common(FunctionCallInfo fcinfo)
 		null_search = false;
 	}
 
+	position = (ARR_LBOUND(array))[0] - 1;
+
 	/* figure out where to start */
 	if (PG_NARGS() == 3)
 	{
 		if (PG_ARGISNULL(2))
 			ereport(ERROR,
 					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
-					 errmsg("initial offset should not be NULL")));
+					 errmsg("initial position should not be NULL")));
 
-		offset_min = PG_GETARG_INT32(2);
+		position_min = PG_GETARG_INT32(2);
 	}
 	else
-		offset_min = 1;
+		position_min = (ARR_LBOUND(array))[0];
 
 	/*
 	 * We arrange to look up type info for array_create_iterator only once per
@@ -780,10 +782,10 @@ array_offset_common(FunctionCallInfo fcinfo)
 	array_iterator = array_create_iterator(array, 0, my_extra);
 	while (array_iterate(array_iterator, &value, &isnull))
 	{
-		offset += 1;
+		position++;
 
 		/* skip initial elements if caller requested so */
-		if (offset < offset_min)
+		if (position < position_min)
 			continue;
 
 		/*
@@ -818,12 +820,12 @@ array_offset_common(FunctionCallInfo fcinfo)
 	if (!found)
 		PG_RETURN_NULL();
 
-	PG_RETURN_INT32(offset);
+	PG_RETURN_INT32(position);
 }
 
 /*-----------------------------------------------------------------------------
- * array_offsets :
- *			return an array of offsets of a value in an array.
+ * array_positions :
+ *			return an array of positions of a value in an array.
  *
  * IS NOT DISTINCT FROM semantics are used for comparisons.  Returns NULL when
  * the input array is NULL.  When the value is not found in the array, returns
@@ -833,15 +835,15 @@ array_offset_common(FunctionCallInfo fcinfo)
  *-----------------------------------------------------------------------------
  */
 Datum
-array_offsets(PG_FUNCTION_ARGS)
+array_positions(PG_FUNCTION_ARGS)
 {
 	ArrayType  *array;
 	Oid			collation = PG_GET_COLLATION();
 	Oid			element_type;
 	Datum		searched_element,
 				value;
 	bool		isnull;
-	int			offset = 0;
+	int			position;
 	TypeCacheEntry *typentry;
 	ArrayMetaState *my_extra;
 	bool		null_search;
@@ -854,6 +856,8 @@ array_offsets(PG_FUNCTION_ARGS)
 	array = PG_GETARG_ARRAYTYPE_P(0);
 	element_type = ARR_ELEMTYPE(array);
 
+	position = (ARR_LBOUND(array))[0] - 1;
+
 	/*
 	 * We refuse to search for elements in multi-dimensional arrays, since we
 	 * have no good way to report the element's location in the array.
@@ -912,12 +916,12 @@ array_offsets(PG_FUNCTION_ARGS)
 	}
 
 	/*
-	 * Accumulate each array offset iff the element matches the given element.
+	 * Accumulate each array position iff the element matches the given element.
 	 */
 	array_iterator = array_create_iterator(array, 0, my_extra);
 	while (array_iterate(array_iterator, &value, &isnull))
 	{
-		offset += 1;
+		position += 1;
 
 		/*
 		 * Can't look at the array element's value if it's null; but if we
@@ -927,7 +931,7 @@ array_offsets(PG_FUNCTION_ARGS)
 		{
 			if (isnull && null_search)
 				astate =
-					accumArrayResult(astate, Int32GetDatum(offset), false,
+					accumArrayResult(astate, Int32GetDatum(position), false,
 									 INT4OID, CurrentMemoryContext);
 
 			continue;
@@ -937,7 +941,7 @@ array_offsets(PG_FUNCTION_ARGS)
 		if (DatumGetBool(FunctionCall2Coll(&my_extra->proc, collation,
 										   searched_element, value)))
 			astate =
-				accumArrayResult(astate, Int32GetDatum(offset), false,
+				accumArrayResult(astate, Int32GetDatum(position), false,
 								 INT4OID, CurrentMemoryContext);
 	}
 

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201503301
+#define CATALOG_VERSION_NO	201503302
 
 #endif

src/include/catalog/pg_proc.h

@@ -895,11 +895,11 @@ DATA(insert OID = 515 (  array_larger	   PGNSP PGUID 12 1 0 0 0 f f f f t f i 2
 DESCR("larger of two");
 DATA(insert OID = 516 (  array_smaller	   PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 2277 "2277 2277" _null_ _null_ _null_ _null_ array_smaller _null_ _null_ _null_ ));
 DESCR("smaller of two");
-DATA(insert OID = 3277 (  array_offset		   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 23 "2277 2283" _null_ _null_ _null_ _null_ array_offset _null_ _null_ _null_ ));
+DATA(insert OID = 3277 (  array_position		   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 23 "2277 2283" _null_ _null_ _null_ _null_ array_position _null_ _null_ _null_ ));
 DESCR("returns a offset of value in array");
-DATA(insert OID = 3278 (  array_offset		   PGNSP PGUID 12 1 0 0 0 f f f f f f i 3 0 23 "2277 2283 23" _null_ _null_ _null_ _null_ array_offset_start _null_ _null_ _null_ ));
+DATA(insert OID = 3278 (  array_position		   PGNSP PGUID 12 1 0 0 0 f f f f f f i 3 0 23 "2277 2283 23" _null_ _null_ _null_ _null_ array_position_start _null_ _null_ _null_ ));
 DESCR("returns a offset of value in array with start index");
-DATA(insert OID = 3279 (  array_offsets		   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 1007 "2277 2283" _null_ _null_ _null_ _null_ array_offsets _null_ _null_ _null_ ));
+DATA(insert OID = 3279 (  array_positions		   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 1007 "2277 2283" _null_ _null_ _null_ _null_ array_positions _null_ _null_ _null_ ));
 DESCR("returns a array of offsets of some value in array");
 DATA(insert OID = 1191 (  generate_subscripts PGNSP PGUID 12 1 1000 0 0 f f f f t t i 3 0 23 "2277 23 16" _null_ _null_ _null_ _null_ generate_subscripts _null_ _null_ _null_ ));
 DESCR("array subscripts generator");

src/include/utils/array.h

@@ -358,9 +358,9 @@ extern Datum array_agg_finalfn(PG_FUNCTION_ARGS);
 extern Datum array_agg_array_transfn(PG_FUNCTION_ARGS);
 extern Datum array_agg_array_finalfn(PG_FUNCTION_ARGS);
 
-extern Datum array_offset(PG_FUNCTION_ARGS);
-extern Datum array_offset_start(PG_FUNCTION_ARGS);
-extern Datum array_offsets(PG_FUNCTION_ARGS);
+extern Datum array_position(PG_FUNCTION_ARGS);
+extern Datum array_position_start(PG_FUNCTION_ARGS);
+extern Datum array_positions(PG_FUNCTION_ARGS);
 
 /*
  * prototypes for functions defined in array_typanalyze.c