Mark pageinspect's disk-accessing functions as parallel restricted.

These functions have been marked parallel safe, but the buildfarm's
response to commit e2933a6 exposed the flaw in that thinking:
if you try to use them on a temporary table, and they run inside
a parallel worker, they'll fail with "cannot access temporary tables
during a parallel operation".

Fix that by marking them parallel restricted instead.  Maybe someday
we'll have a better answer and can reverse this decision.

Back-patch to v15.  To go back further, we'd have to devise variant
versions of pre-1.10 pageinspect versions.  Given the lack of field
complaints, it doesn't seem worth the trouble.  We'll just deem
this case unsupported pre-v15.  (If anyone does complain, it might
be good enough to update the markings manually in their DBs.)

Discussion: https://postgr.es/m/E1ox94a-000EHu-VH@gemulon.postgresql.org

Author: tglsfdc

contrib/pageinspect/Makefile

@@ -13,7 +13,8 @@ OBJS = \
 	rawpage.o
 
 EXTENSION = pageinspect
-DATA =  pageinspect--1.9--1.10.sql pageinspect--1.8--1.9.sql \
+DATA =  pageinspect--1.10--1.11.sql \
+	pageinspect--1.9--1.10.sql pageinspect--1.8--1.9.sql \
 	pageinspect--1.7--1.8.sql pageinspect--1.6--1.7.sql \
 	pageinspect--1.5.sql pageinspect--1.5--1.6.sql \
 	pageinspect--1.4--1.5.sql pageinspect--1.3--1.4.sql \

contrib/pageinspect/pageinspect--1.10--1.11.sql

@@ -0,0 +1,28 @@
+/* contrib/pageinspect/pageinspect--1.10--1.11.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pageinspect UPDATE TO '1.11'" to load this file. \quit
+
+--
+-- Functions that fetch relation pages must be PARALLEL RESTRICTED,
+-- not PARALLEL SAFE, otherwise they will fail when run on a
+-- temporary table in a parallel worker process.
+--
+
+ALTER FUNCTION get_raw_page(text, int8) PARALLEL RESTRICTED;
+ALTER FUNCTION get_raw_page(text, text, int8) PARALLEL RESTRICTED;
+-- tuple_data_split must be restricted because it may fetch TOAST data.
+ALTER FUNCTION tuple_data_split(oid, bytea, integer, integer, text) PARALLEL RESTRICTED;
+ALTER FUNCTION tuple_data_split(oid, bytea, integer, integer, text, bool) PARALLEL RESTRICTED;
+-- heap_page_item_attrs must be restricted because it calls tuple_data_split.
+ALTER FUNCTION heap_page_item_attrs(bytea, regclass, bool) PARALLEL RESTRICTED;
+ALTER FUNCTION heap_page_item_attrs(bytea, regclass) PARALLEL RESTRICTED;
+ALTER FUNCTION bt_metap(text) PARALLEL RESTRICTED;
+ALTER FUNCTION bt_page_stats(text, int8) PARALLEL RESTRICTED;
+ALTER FUNCTION bt_page_items(text, int8) PARALLEL RESTRICTED;
+ALTER FUNCTION hash_bitmap_info(regclass, int8) PARALLEL RESTRICTED;
+-- brin_page_items might be parallel safe, because it seems to touch
+-- only index metadata, but I don't think there's a point in risking it.
+-- Likewise for gist_page_items.
+ALTER FUNCTION brin_page_items(bytea, regclass) PARALLEL RESTRICTED;
+ALTER FUNCTION gist_page_items(bytea, regclass) PARALLEL RESTRICTED;

contrib/pageinspect/pageinspect.control

@@ -1,5 +1,5 @@
 # pageinspect extension
 comment = 'inspect the contents of database pages at a low level'
-default_version = '1.10'
+default_version = '1.11'
 module_pathname = '$libdir/pageinspect'
 relocatable = true