Remove <@ from contrib/intarray's GiST operator classes.

Since commit efc77cf5, an indexed query using <@ has required a
full-index scan, so that it actually performs worse than a plain seqscan
would do.  As I noted at the time, we'd be better off to not treat <@ as
being indexable by such indexes at all; and that's what this patch does.

It would have been difficult to remove these opclass members without
dropping the whole opclass before commit 9f968278 fixed GiST opclass
member dependency rules, but now it's quite simple, so let's do it.

I left the existing support code in place for the time being, with
comments noting it's now unreachable.  At some point, perhaps we should
remove that code in favor of throwing an error telling people to upgrade
the extension version.

Discussion: https://postgr.es/m/2176979.1596389859@sss.pgh.pa.us
Discussion: https://postgr.es/m/458.1565114141@sss.pgh.pa.us

contrib/intarray/Makefile

@@ -12,7 +12,8 @@ OBJS = \
 	_intbig_gist.o
 
 EXTENSION = intarray
-DATA = intarray--1.2--1.3.sql intarray--1.2.sql intarray--1.1--1.2.sql \
+DATA = intarray--1.3--1.4.sql intarray--1.2--1.3.sql \
+	intarray--1.2.sql intarray--1.1--1.2.sql \
 	intarray--1.0--1.1.sql
 PGFILEDESC = "intarray - functions and operators for arrays of integers"
 

contrib/intarray/_int_gist.c

@@ -93,6 +93,12 @@ g_int_consistent(PG_FUNCTION_ARGS)
 			break;
 		case RTContainedByStrategyNumber:
 		case RTOldContainedByStrategyNumber:
+
+			/*
+			 * This code is unreachable as of intarray 1.4, because the <@
+			 * operator has been removed from the opclass.  We keep it for now
+			 * to support older versions of the SQL definitions.
+			 */
 			if (GIST_LEAF(entry))
 				retval = inner_int_contains(query,
 											(ArrayType *) DatumGetPointer(entry->key));

contrib/intarray/_intbig_gist.c

@@ -533,6 +533,12 @@ g_intbig_consistent(PG_FUNCTION_ARGS)
 			break;
 		case RTContainedByStrategyNumber:
 		case RTOldContainedByStrategyNumber:
+
+			/*
+			 * This code is unreachable as of intarray 1.4, because the <@
+			 * operator has been removed from the opclass.  We keep it for now
+			 * to support older versions of the SQL definitions.
+			 */
 			if (GIST_LEAF(entry))
 			{
 				int			i,

contrib/intarray/intarray--1.3--1.4.sql

+/* contrib/intarray/intarray--1.3--1.4.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION intarray UPDATE TO '1.4'" to load this file. \quit
+
+-- Remove <@ from the GiST opclasses, as it's not usefully indexable
+-- due to mishandling of empty arrays.  (It's OK in GIN.)
+
+ALTER OPERATOR FAMILY gist__int_ops USING gist
+DROP OPERATOR 8 (_int4, _int4);
+
+ALTER OPERATOR FAMILY gist__intbig_ops USING gist
+DROP OPERATOR 8 (_int4, _int4);
+
+-- Likewise for the old spelling ~.
+
+ALTER OPERATOR FAMILY gist__int_ops USING gist
+DROP OPERATOR 14 (_int4, _int4);
+
+ALTER OPERATOR FAMILY gist__intbig_ops USING gist
+DROP OPERATOR 14 (_int4, _int4);

contrib/intarray/intarray.control

 # intarray extension
 comment = 'functions, operators, and index support for 1-D arrays of integers'
-default_version = '1.3'
+default_version = '1.4'
 module_pathname = '$libdir/_int'
 relocatable = true
 trusted = true

doc/src/sgml/intarray.sgml

@@ -399,7 +399,7 @@
 
   <para>
    <filename>intarray</filename> provides index support for the
-   <literal>&amp;&amp;</literal>, <literal>@&gt;</literal>, <literal>&lt;@</literal>,
+   <literal>&amp;&amp;</literal>, <literal>@&gt;</literal>,
    and <literal>@@</literal> operators, as well as regular array equality.
   </para>
 
@@ -436,7 +436,8 @@
 
   <para>
    There is also a non-default GIN operator class
-   <literal>gin__int_ops</literal> supporting the same operators.
+   <literal>gin__int_ops</literal>, which supports these operators as well
+   as <literal>&lt;@</literal>.
   </para>
 
   <para>