Add test with multirange type for pg_restore_attribute_stats()

This commit adds a test for pg_restore_attribute_stats() with the
injection of statistics related to a multirange type.  This case is
supported in statatt_get_type() since its introduction in ce207d2a79,
but there was no test in the main regression test suite to check for the
case where attribute stats is restored for a multirange type, as done by
multirange_typanalyze().

Note that this has been originally applied as d4504d6f60 in v19 and
newer branches.  This will be used for the test of a follow-up commit.

Author: Corey Huinker <corey.huinker@gmail.com>
Discussion: https://postgr.es/m/CADkLM=c3JivzHNXLt-X_JicYknRYwLTiOCHOPiKagm2_vdrFUg@mail.gmail.com
Security: CVE-2026-16238
Backpatch-through: 18

src/test/regress/expected/stats_import.out

@@ -12,6 +12,11 @@ CREATE TABLE stats_import.test(
     arange int4range,
     tags text[]
 ) WITH (autovacuum_enabled = false);
+CREATE TABLE stats_import.test_mr(
+    id INTEGER PRIMARY KEY,
+    name text,
+    mrange int4multirange
+) WITH (autovacuum_enabled = false);
 SELECT
     pg_catalog.pg_restore_relation_stats(
         'schemaname', 'stats_import',
@@ -1227,6 +1232,27 @@ AND attname = 'id';
  stats_import | test      | id      | f         |      0.36 |         5 |        0.6 | {2,1,3}          | {0.3,0.25,0.05}   | {1,2,3,4}        |             |                   |                        |                      |                        |                  | 
 (1 row)
 
+-- test for multiranges
+INSERT INTO stats_import.test_mr
+VALUES
+  (1, 'red', '{[1,3),[5,9),[20,30)}'::int4multirange),
+  (2, 'red', '{[11,13),[15,19),[20,30)}'::int4multirange),
+  (3, 'red', '{[21,23),[25,29),[120,130)}'::int4multirange);
+-- ensure that we set attribute stats for a multirange
+SELECT pg_catalog.pg_restore_attribute_stats(
+  'schemaname', 'stats_import',
+  'relname', 'test_mr',
+  'attname', 'mrange',
+  'inherited', false,
+  'range_length_histogram', '{19,29,109}'::text,
+  'range_empty_frac', '0'::real,
+  'range_bounds_histogram', '{"[1,30)","[11,30)","[21,130)"}'::text
+);
+ pg_restore_attribute_stats 
+----------------------------
+ t
+(1 row)
+
 --
 -- Test the ability to exactly copy data from one table to an identical table,
 -- correctly reconstructing the stakind order as well as the staopN and
@@ -1503,9 +1529,10 @@ AND attname = 'i';
 
 DROP TABLE stats_temp;
 DROP SCHEMA stats_import CASCADE;
-NOTICE:  drop cascades to 6 other objects
+NOTICE:  drop cascades to 7 other objects
 DETAIL:  drop cascades to type stats_import.complex_type
 drop cascades to table stats_import.test
+drop cascades to table stats_import.test_mr
 drop cascades to table stats_import.part_parent
 drop cascades to sequence stats_import.testseq
 drop cascades to view stats_import.testview

src/test/regress/sql/stats_import.sql

@@ -15,6 +15,12 @@ CREATE TABLE stats_import.test(
     tags text[]
 ) WITH (autovacuum_enabled = false);
 
+CREATE TABLE stats_import.test_mr(
+    id INTEGER PRIMARY KEY,
+    name text,
+    mrange int4multirange
+) WITH (autovacuum_enabled = false);
+
 SELECT
     pg_catalog.pg_restore_relation_stats(
         'schemaname', 'stats_import',
@@ -844,6 +850,24 @@ AND tablename = 'test'
 AND inherited = false
 AND attname = 'id';
 
+-- test for multiranges
+INSERT INTO stats_import.test_mr
+VALUES
+  (1, 'red', '{[1,3),[5,9),[20,30)}'::int4multirange),
+  (2, 'red', '{[11,13),[15,19),[20,30)}'::int4multirange),
+  (3, 'red', '{[21,23),[25,29),[120,130)}'::int4multirange);
+
+-- ensure that we set attribute stats for a multirange
+SELECT pg_catalog.pg_restore_attribute_stats(
+  'schemaname', 'stats_import',
+  'relname', 'test_mr',
+  'attname', 'mrange',
+  'inherited', false,
+  'range_length_histogram', '{19,29,109}'::text,
+  'range_empty_frac', '0'::real,
+  'range_bounds_histogram', '{"[1,30)","[11,30)","[21,130)"}'::text
+);
+
 --
 -- Test the ability to exactly copy data from one table to an identical table,
 -- correctly reconstructing the stakind order as well as the staopN and