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

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These functions have been marked parallel safe, but the buildfarm's
response to commit e2933a6e1 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
This commit is contained in:
Tom Lane 2022-11-21 15:37:10 -05:00
parent 51b5834cd5
commit aeaaf520f4
4 changed files with 32 additions and 2 deletions
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3
contrib/pageinspect/Makefile
View File

@ -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 \

1
contrib/pageinspect/meson.build
View File

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

28
contrib/pageinspect/pageinspect--1.10--1.11.sql Normal file
View File

@ -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;

2
contrib/pageinspect/pageinspect.control
View File

@ -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