From: Michael Paquier Date: Wed, 6 Aug 2025 08:22:03 +0000 (+0900) Subject: Add regression test for short varlenas saved in TOAST relations X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=225ebfe30a1ae9fda74f3d8f98ea6fa511b60624;p=thirdparty%2Fpostgresql.git Add regression test for short varlenas saved in TOAST relations toast_save_datum() has for a very long time some code able to handle short varlenas (values up to 126 bytes reduced to a 1-byte header), converting such varlenas to an external on-disk TOAST pointer with the value saved uncompressed in the secondary TOAST relation. There was zero coverage for this code path. This commit adds a test able to exercise it, relying on two external attributes, one with a low toast_tuple_target, so as it is possible to trigger the threshold for the insertion of short varlenas into the TOAST relation. Author: Nikhil Kumar Veldanda Co-authored-by: Michael Paquier Discussion: https://postgr.es/m/aJAl7-NvIk0kZByz@paquier.xyz --- diff --git a/src/test/regress/expected/strings.out b/src/test/regress/expected/strings.out index 1bfd33de3f3..ba302da51e7 100644 --- a/src/test/regress/expected/strings.out +++ b/src/test/regress/expected/strings.out @@ -2090,6 +2090,40 @@ SELECT c FROM toasttest; x (1 row) +DROP TABLE toasttest; +-- test with short varlenas (up to 126 data bytes reduced to a 1-byte header) +-- being toasted. +CREATE TABLE toasttest (f1 text, f2 text); +ALTER TABLE toasttest SET (toast_tuple_target = 128); +ALTER TABLE toasttest ALTER COLUMN f1 SET STORAGE EXTERNAL; +ALTER TABLE toasttest ALTER COLUMN f2 SET STORAGE EXTERNAL; +-- Here, the first value is a varlena large enough to make it toasted and +-- stored uncompressed. The second value is a short varlena, toasted +-- and stored uncompressed. +INSERT INTO toasttest values(repeat('1234', 1000), repeat('5678', 30)); +SELECT reltoastrelid::regclass AS reltoastname FROM pg_class + WHERE oid = 'toasttest'::regclass \gset +-- There should be two values inserted in the toast relation. +SELECT count(*) FROM :reltoastname WHERE chunk_seq = 0; + count +------- + 2 +(1 row) + +SELECT substr(f1, 5, 10) AS f1_data, substr(f2, 5, 10) AS f2_data + FROM toasttest; + f1_data | f2_data +------------+------------ + 1234123412 | 5678567856 +(1 row) + +SELECT pg_column_compression(f1) AS f1_comp, pg_column_compression(f2) AS f2_comp + FROM toasttest; + f1_comp | f2_comp +---------+--------- + | +(1 row) + DROP TABLE toasttest; -- -- test length diff --git a/src/test/regress/sql/strings.sql b/src/test/regress/sql/strings.sql index 92c445c2439..b94004cc08c 100644 --- a/src/test/regress/sql/strings.sql +++ b/src/test/regress/sql/strings.sql @@ -650,6 +650,26 @@ SELECT length(c), c::text FROM toasttest; SELECT c FROM toasttest; DROP TABLE toasttest; +-- test with short varlenas (up to 126 data bytes reduced to a 1-byte header) +-- being toasted. +CREATE TABLE toasttest (f1 text, f2 text); +ALTER TABLE toasttest SET (toast_tuple_target = 128); +ALTER TABLE toasttest ALTER COLUMN f1 SET STORAGE EXTERNAL; +ALTER TABLE toasttest ALTER COLUMN f2 SET STORAGE EXTERNAL; +-- Here, the first value is a varlena large enough to make it toasted and +-- stored uncompressed. The second value is a short varlena, toasted +-- and stored uncompressed. +INSERT INTO toasttest values(repeat('1234', 1000), repeat('5678', 30)); +SELECT reltoastrelid::regclass AS reltoastname FROM pg_class + WHERE oid = 'toasttest'::regclass \gset +-- There should be two values inserted in the toast relation. +SELECT count(*) FROM :reltoastname WHERE chunk_seq = 0; +SELECT substr(f1, 5, 10) AS f1_data, substr(f2, 5, 10) AS f2_data + FROM toasttest; +SELECT pg_column_compression(f1) AS f1_comp, pg_column_compression(f2) AS f2_comp + FROM toasttest; +DROP TABLE toasttest; + -- -- test length --