BUG #19715: pg_restore_attribute_stats() rejects range statistics for a domain over int4multirange

The following bug has been logged on the website:

Bug reference: 19715
Logged by: Qifan Liu
Email address: imchifan(at)163(dot)com
PostgreSQL version: 18.6
Operating system: Linux/amd64
Description:

pg_restore_attribute_stats() rejects range length and bounds histograms for
a column whose type is a domain over int4multirange. It returns false and
warns that the column is not a range type. However, ANALYZE generates both
range-specific statistic kinds 6 and 7 for a column of the same domain type.

As a result, statistics exported for a domain over a multirange type cannot
be faithfully restored to an equivalent column.

Steps to reproduce
------------------
Run the following input with psql -X:

\set ON_ERROR_STOP on
CREATE DOMAIN restore_stats_mr AS int4multirange;
CREATE TABLE restore_stats_src (v restore_stats_mr);
CREATE TABLE restore_stats_dst (v restore_stats_mr);

INSERT INTO restore_stats_src VALUES
('{[1,3)}'), ('{[5,9)}'), ('{[11,15)}');
ANALYZE restore_stats_src;

SELECT array_agg(k ORDER BY k) AS analyze_range_kinds
FROM (
SELECT unnest(ARRAY[stakind1, stakind2, stakind3, stakind4, stakind5]) AS
k
FROM pg_statistic
WHERE starelid = 'restore_stats_src'::regclass
AND staattnum = 1
) s
WHERE k IN (6, 7);

SELECT pg_catalog.pg_restore_attribute_stats(
'schemaname', 'public',
'relname', 'restore_stats_dst',
'attname', 'v',
'inherited', false,
'range_length_histogram', '{2,4,4}'::text,
'range_empty_frac', 0::real,
'range_bounds_histogram', ARRAY['[1,3)', '[5,9)', '[11,15)']::text
) AS restore_ok;

SELECT count(*) = 2 AS restored_both_range_kinds
FROM (
SELECT unnest(ARRAY[stakind1, stakind2, stakind3, stakind4, stakind5]) AS
k
FROM pg_statistic
WHERE starelid = 'restore_stats_dst'::regclass
AND staattnum = 1
) s
WHERE k IN (6, 7);

Actual result
-------------
analyze_range_kinds
---------------------
{6,7}

WARNING: column "v" is not a range type
DETAIL: Cannot set STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM or
STATISTIC_KIND_BOUNDS_HISTOGRAM.
restore_ok
------------
f

restored_both_range_kinds
---------------------------
f

Expected result
---------------
pg_restore_attribute_stats() should return true and restore statistic kinds
6 and 7. ANALYZE produces those range statistics for the same domain type,
so the restoration path should not reject them as belonging to a non-range
column.

Additional information
----------------------
The issue was reproduced on PostgreSQL 20devel and PostgreSQL 18.6.
PostgreSQL 17.11 does not provide pg_restore_attribute_stats().