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CREATE TABLE toasttest(descr text, cnt int DEFAULT 0, f1 text, f2 text);
INSERT INTO toasttest(descr, f1, f2) VALUES('two-compressed', repeat('1234567890',1000), repeat('1234567890',1000));
INSERT INTO toasttest(descr, f1, f2) VALUES('two-toasted', repeat('1234567890',30000), repeat('1234567890',50000));
INSERT INTO toasttest(descr, f1, f2) VALUES('one-compressed,one-null', NULL, repeat('1234567890',1000));
INSERT INTO toasttest(descr, f1, f2) VALUES('one-toasted,one-null', NULL, repeat('1234567890',50000));
-- check whether indirect tuples works on the most basic level
SELECT descr, substring(make_tuple_indirect(toasttest)::text, 1, 200) FROM toasttest;
descr | substring
-------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
two-compressed | (two-compressed,0,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012
two-toasted | (two-toasted,0,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345
one-compressed,one-null | ("one-compressed,one-null",0,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
one-toasted,one-null | ("one-toasted,one-null",0,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
-- modification without changing varlenas
UPDATE toasttest SET cnt = cnt +1 RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,1,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012
(two-toasted,1,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345
("one-compressed,one-null",1,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",1,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
-- modification without modifying assigned value
UPDATE toasttest SET cnt = cnt +1, f1 = f1 RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,2,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012
(two-toasted,2,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345
("one-compressed,one-null",2,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",2,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
-- modification modifying, but effectively not changing
UPDATE toasttest SET cnt = cnt +1, f1 = f1||'' RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,3,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012
(two-toasted,3,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345
("one-compressed,one-null",3,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",3,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
UPDATE toasttest SET cnt = cnt +1, f1 = '-'||f1||'-' RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,4,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901
(two-toasted,4,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
("one-compressed,one-null",4,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",4,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
SELECT substring(toasttest::text, 1, 200) FROM toasttest;
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,4,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901
(two-toasted,4,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
("one-compressed,one-null",4,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",4,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
-- check we didn't screw with main/toast tuple visibility
VACUUM FREEZE toasttest;
SELECT substring(toasttest::text, 1, 200) FROM toasttest;
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,4,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901
(two-toasted,4,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
("one-compressed,one-null",4,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",4,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
-- now create a trigger that forces all Datums to be indirect ones
CREATE FUNCTION update_using_indirect()
RETURNS trigger
LANGUAGE plpgsql AS $$
BEGIN
NEW := make_tuple_indirect(NEW);
RETURN NEW;
END$$;
CREATE TRIGGER toasttest_update_indirect
BEFORE INSERT OR UPDATE
ON toasttest
FOR EACH ROW
EXECUTE PROCEDURE update_using_indirect();
-- modification without changing varlenas
UPDATE toasttest SET cnt = cnt +1 RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,5,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901
(two-toasted,5,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
("one-compressed,one-null",5,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",5,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
-- modification without modifying assigned value
UPDATE toasttest SET cnt = cnt +1, f1 = f1 RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,6,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901
(two-toasted,6,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
("one-compressed,one-null",6,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",6,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
-- modification modifying, but effectively not changing
UPDATE toasttest SET cnt = cnt +1, f1 = f1||'' RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,7,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901
(two-toasted,7,-1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234
("one-compressed,one-null",7,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",7,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
UPDATE toasttest SET cnt = cnt +1, f1 = '-'||f1||'-' RETURNING substring(toasttest::text, 1, 200);
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,8,--123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
(two-toasted,8,--123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
("one-compressed,one-null",8,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",8,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
(4 rows)
INSERT INTO toasttest(descr, f1, f2) VALUES('one-toasted,one-null, via indirect', repeat('1234567890',30000), NULL);
SELECT substring(toasttest::text, 1, 200) FROM toasttest;
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,8,--123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
(two-toasted,8,--123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
("one-compressed,one-null",8,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",8,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
("one-toasted,one-null, via indirect",0,1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
(5 rows)
-- check we didn't screw with main/toast tuple visibility
VACUUM FREEZE toasttest;
SELECT substring(toasttest::text, 1, 200) FROM toasttest;
substring
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(two-compressed,8,--123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
(two-toasted,8,--123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
("one-compressed,one-null",8,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
("one-toasted,one-null",8,,12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
("one-toasted,one-null, via indirect",0,1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
(5 rows)
DROP TABLE toasttest;
DROP FUNCTION update_using_indirect();
|
