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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
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4 files changed

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‎contrib/pageinspect/Makefile

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

‎contrib/pageinspect/meson.build

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@@ -33,6 +33,7 @@ install_data(
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'pageinspect--1.7--1.8.sql',
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'pageinspect--1.8--1.9.sql',
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'pageinspect--1.9--1.10.sql',
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'pageinspect--1.10--1.11.sql',
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'pageinspect.control',
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kwargs: contrib_data_args,
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)

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

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

‎contrib/pageinspect/pageinspect.control

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

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