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# Test SKIP LOCKED with an updated tuple chain.
setup
{
CREATE TABLE foo (
id int PRIMARY KEY,
data text NOT NULL
);
INSERT INTO foo VALUES (1, 'x'), (2, 'x');
}
teardown
{
DROP TABLE foo;
}
session s1
setup { BEGIN; }
step s1a { SELECT * FROM foo WHERE pg_advisory_lock(0) IS NOT NULL ORDER BY id LIMIT 1 FOR UPDATE SKIP LOCKED; }
step s1b { COMMIT; }
session s2
step s2a { SELECT pg_advisory_lock(0); }
step s2b { UPDATE foo SET data = data WHERE id = 1; }
step s2c { BEGIN; }
step s2d { UPDATE foo SET data = data WHERE id = 1; }
step s2e { SELECT pg_advisory_unlock(0); }
step s2f { COMMIT; }
# s1 takes a snapshot but then waits on an advisory lock, then s2
# updates the row in one transaction, then again in another without
# committing, before allowing s1 to proceed to try to lock a row;
# because it has a snapshot that sees the older version, we reach the
# waiting code in EvalPlanQualFetch which skips rows when in SKIP
# LOCKED mode, so s1 sees the second row
permutation s2a s1a s2b s2c s2d s2e s1b s2f
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