Test additional speculative conflict scenarios.

Previously, the speculative insert tests did not cover the case when a
tuple t is inserted into a table with a unique index on a column but
before it can insert into the index, a concurrent transaction has
inserted a conflicting value into the index and the insertion of tuple t
must be aborted.

The basic permutation is one session successfully inserts into the table
and an associated unique index while a concurrent session successfully
inserts into the table but discovers a conflict before inserting into
the index and must abort the insertion.

Several variants on this include:
- swap which session is successful
- first session insert transaction does not commit, so second session
must wait on a transaction lock
- first session insert does not "complete", so second session must wait
on a speculative insertion lock

Also, refactor the existing TOAST table upsert test to be in the same
spec and reuse the steps.

Author: Melanie Plageman, Ashwin Agrawal, Andres Freund
Reviewed-by: Andres Freund, Taylor Vesely
Discussion: https://postgr.es/m/CAAKRu_ZRmxy_OEryfY3G8Zp01ouhgw59_-_Cm8n7LzRH5BAvng@mail.gmail.com

src/test/isolation/expected/insert-conflict-toast.out

-Parsed test spec with 3 sessions
-
-starting permutation: s2insert s3insert s1commit
-pg_advisory_xact_lock
-
-               
-step s2insert: 
-  INSERT INTO ctoast (key, val) VALUES (1, ctoast_large_val()) ON CONFLICT DO NOTHING;
- <waiting ...>
-step s3insert: 
-  INSERT INTO ctoast (key, val) VALUES (1, ctoast_large_val()) ON CONFLICT DO NOTHING;
- <waiting ...>
-step s1commit: COMMIT;
-step s2insert: <... completed>
-step s3insert: <... completed>

src/test/isolation/isolation_schedule

@@ -38,7 +38,6 @@ test: insert-conflict-do-nothing-2
 test: insert-conflict-do-update
 test: insert-conflict-do-update-2
 test: insert-conflict-do-update-3
-test: insert-conflict-toast
 test: insert-conflict-specconflict
 test: delete-abort-savept
 test: delete-abort-savept-2

src/test/isolation/specs/insert-conflict-specconflict.spec

@@ -8,24 +8,34 @@
 
 setup
 {
-     CREATE OR REPLACE FUNCTION blurt_and_lock(text) RETURNS text IMMUTABLE LANGUAGE plpgsql AS $$
+     CREATE OR REPLACE FUNCTION blurt_and_lock_123(text) RETURNS text IMMUTABLE LANGUAGE plpgsql AS $$
      BEGIN
-        RAISE NOTICE 'called for %', $1;
+        RAISE NOTICE 'blurt_and_lock_123() called for % in session %', $1, current_setting('spec.session')::int;
 
 	-- depending on lock state, wait for lock 2 or 3
         IF pg_try_advisory_xact_lock(current_setting('spec.session')::int, 1) THEN
-            RAISE NOTICE 'blocking 2';
+            RAISE NOTICE 'acquiring advisory lock on 2';
             PERFORM pg_advisory_xact_lock(current_setting('spec.session')::int, 2);
         ELSE
-            RAISE NOTICE 'blocking 3';
+            RAISE NOTICE 'acquiring advisory lock on 3';
             PERFORM pg_advisory_xact_lock(current_setting('spec.session')::int, 3);
         END IF;
     RETURN $1;
     END;$$;
 
+    CREATE OR REPLACE FUNCTION blurt_and_lock_4(text) RETURNS text IMMUTABLE LANGUAGE plpgsql AS $$
+    BEGIN
+        RAISE NOTICE 'blurt_and_lock_4() called for % in session %', $1, current_setting('spec.session')::int;
+        RAISE NOTICE 'acquiring advisory lock on 4';
+        PERFORM pg_advisory_xact_lock(current_setting('spec.session')::int, 4);
+    RETURN $1;
+    END;$$;
+
+    CREATE OR REPLACE FUNCTION ctoast_large_val() RETURNS TEXT LANGUAGE SQL AS 'select array_agg(md5(g::text))::text from generate_series(1, 256) g';
+
     CREATE TABLE upserttest(key text, data text);
 
-    CREATE UNIQUE INDEX ON upserttest((blurt_and_lock(key)));
+    CREATE UNIQUE INDEX upserttest_key_uniq_idx ON upserttest((blurt_and_lock_123(key)));
 }
 
 teardown
@@ -37,6 +47,7 @@ session "controller"
 setup
 {
     SET default_transaction_isolation = 'read committed';
+    SET application_name = 'isolation/insert-conflict-specconflict-controller';
 }
 step "controller_locks" {SELECT pg_advisory_lock(sess, lock), sess, lock FROM generate_series(1, 2) a(sess), generate_series(1,3) b(lock);}
 step "controller_unlock_1_1" { SELECT pg_advisory_unlock(1, 1); }
@@ -45,16 +56,29 @@ step "controller_unlock_1_2" { SELECT pg_advisory_unlock(1, 2); }
 step "controller_unlock_2_2" { SELECT pg_advisory_unlock(2, 2); }
 step "controller_unlock_1_3" { SELECT pg_advisory_unlock(1, 3); }
 step "controller_unlock_2_3" { SELECT pg_advisory_unlock(2, 3); }
+step "controller_lock_2_4" { SELECT pg_advisory_lock(2, 4); }
+step "controller_unlock_2_4" { SELECT pg_advisory_unlock(2, 4); }
 step "controller_show" {SELECT * FROM upserttest; }
+step "controller_show_count" {SELECT COUNT(*) FROM upserttest; }
+step "controller_print_speculative_locks" {
+    SELECT pa.application_name, locktype, mode, granted
+    FROM pg_locks pl JOIN pg_stat_activity pa USING (pid)
+    WHERE locktype IN ('speculative token', 'transactionid') AND pa.datname = current_database()
+    ORDER BY 1, 2, 3, 4;
+}
 
 session "s1"
 setup
 {
     SET default_transaction_isolation = 'read committed';
     SET spec.session = 1;
+    SET application_name = 'isolation/insert-conflict-specconflict-s1';
 }
 step "s1_begin"  { BEGIN; }
-step "s1_upsert" { INSERT INTO upserttest(key, data) VALUES('k1', 'inserted s1') ON CONFLICT (blurt_and_lock(key)) DO UPDATE SET data = upserttest.data || ' with conflict update s1'; }
+step "s1_create_non_unique_index" { CREATE INDEX upserttest_key_idx ON upserttest((blurt_and_lock_4(key))); }
+step "s1_confirm_index_order" { SELECT 'upserttest_key_uniq_idx'::regclass::int8 < 'upserttest_key_idx'::regclass::int8; }
+step "s1_upsert" { INSERT INTO upserttest(key, data) VALUES('k1', 'inserted s1') ON CONFLICT (blurt_and_lock_123(key)) DO UPDATE SET data = upserttest.data || ' with conflict update s1'; }
+step "s1_insert_toast" { INSERT INTO upserttest VALUES('k2', ctoast_large_val()) ON CONFLICT DO NOTHING; }
 step "s1_commit"  { COMMIT; }
 
 session "s2"
@@ -62,16 +86,18 @@ setup
 {
     SET default_transaction_isolation = 'read committed';
     SET spec.session = 2;
+    SET application_name = 'isolation/insert-conflict-specconflict-s2';
 }
 step "s2_begin"  { BEGIN; }
-step "s2_upsert" { INSERT INTO upserttest(key, data) VALUES('k1', 'inserted s2') ON CONFLICT (blurt_and_lock(key)) DO UPDATE SET data = upserttest.data || ' with conflict update s2'; }
+step "s2_upsert" { INSERT INTO upserttest(key, data) VALUES('k1', 'inserted s2') ON CONFLICT (blurt_and_lock_123(key)) DO UPDATE SET data = upserttest.data || ' with conflict update s2'; }
+step "s2_insert_toast" { INSERT INTO upserttest VALUES('k2', ctoast_large_val()) ON CONFLICT DO NOTHING; }
 step "s2_commit"  { COMMIT; }
 
 # Test that speculative locks are correctly acquired and released, s2
 # inserts, s1 updates.
 permutation
    # acquire a number of locks, to control execution flow - the
-   # blurt_and_lock function acquires advisory locks that allow us to
+   # blurt_and_lock_123 function acquires advisory locks that allow us to
    # continue after a) the optimistic conflict probe b) after the
    # insertion of the speculative tuple.
    "controller_locks"
@@ -92,11 +118,11 @@ permutation
    # This should now show a successful UPSERT
    "controller_show"
 
-# Test that speculative locks are correctly acquired and released, s2
-# inserts, s1 updates.
+# Test that speculative locks are correctly acquired and released, s1
+# inserts, s2 updates.
 permutation
    # acquire a number of locks, to control execution flow - the
-   # blurt_and_lock function acquires advisory locks that allow us to
+   # blurt_and_lock_123 function acquires advisory locks that allow us to
    # continue after a) the optimistic conflict probe b) after the
    # insertion of the speculative tuple.
    "controller_locks"
@@ -117,12 +143,37 @@ permutation
    # This should now show a successful UPSERT
    "controller_show"
 
+# Test that speculatively inserted toast rows do not cause conflicts.
+# s1 inserts successfully, s2 does not.
+permutation
+   # acquire a number of locks, to control execution flow - the
+   # blurt_and_lock_123 function acquires advisory locks that allow us to
+   # continue after a) the optimistic conflict probe b) after the
+   # insertion of the speculative tuple.
+   "controller_locks"
+   "controller_show"
+   "s1_insert_toast" "s2_insert_toast"
+   "controller_show"
+   # Switch both sessions to wait on the other lock next time (the speculative insertion)
+   "controller_unlock_1_1" "controller_unlock_2_1"
+   # Allow both sessions to continue
+   "controller_unlock_1_3" "controller_unlock_2_3"
+   "controller_show"
+   # Allow the first session to finish insertion
+   "controller_unlock_1_2"
+   # This should now show that 1 additional tuple was inserted successfully
+   "controller_show_count"
+   # Allow the second session to finish insertion and kill the speculatively inserted tuple
+   "controller_unlock_2_2"
+   # This should show the same number of tuples as before s2 inserted
+   "controller_show_count"
+
 # Test that speculative locks are correctly acquired and released, s2
 # inserts, s1 updates.  With the added complication that transactions
 # don't immediately commit.
 permutation
    # acquire a number of locks, to control execution flow - the
-   # blurt_and_lock function acquires advisory locks that allow us to
+   # blurt_and_lock_123 function acquires advisory locks that allow us to
    # continue after a) the optimistic conflict probe b) after the
    # insertion of the speculative tuple.
    "controller_locks"
@@ -147,3 +198,58 @@ permutation
    "controller_show"
    "s2_commit"
    "controller_show"
+
+# Test that speculative wait is performed if a session sees a speculatively
+# inserted tuple. A speculatively inserted tuple is one which has been inserted
+# both into the table and the unique index but has yet to *complete* the
+# speculative insertion
+permutation
+   # acquire a number of advisory locks to control execution flow - the
+   # blurt_and_lock_123 function acquires advisory locks that allow us to
+   # continue after a) the optimistic conflict probe and b) after the
+   # insertion of the speculative tuple.
+   # blurt_and_lock_4 acquires an advisory lock which allows us to pause
+   # execution c) before completing the speculative insertion
+
+   # create the second index here to avoid affecting the other
+   # permutations.
+   "s1_create_non_unique_index"
+   # confirm that the insertion into the unique index will happen first
+   "s1_confirm_index_order"
+   "controller_locks"
+   "controller_show"
+   "s2_begin"
+   # Both sessions wait on advisory locks
+   "s1_upsert" "s2_upsert"
+   "controller_show"
+   # Switch both sessions to wait on the other lock next time (the speculative insertion)
+   "controller_unlock_1_1" "controller_unlock_2_1"
+   # Allow both sessions to do the optimistic conflict probe and do the
+   # speculative insertion into the table
+   # They will then be waiting on another advisory lock when they attempt to
+   # update the index
+   "controller_unlock_1_3" "controller_unlock_2_3"
+   "controller_show"
+   # take lock to block second session after inserting in unique index but
+   # before completing the speculative insert
+   "controller_lock_2_4"
+   # Allow the second session to move forward
+   "controller_unlock_2_2"
+   # This should still not show a successful insertion
+   "controller_show"
+   # Allow the first session to continue, it should perform speculative wait
+   "controller_unlock_1_2"
+   # Should report s1 is waiting on speculative lock
+   "controller_print_speculative_locks"
+   # Allow s2 to insert into the non-unique index and complete s1 will
+   # no longer wait on speculative lock, but proceed to wait on the
+   # transaction to finish.
+   "controller_unlock_2_4"
+   # Should report that s1 is now waiting for s1 to commit
+   "controller_print_speculative_locks"
+   # Once s2 commits, s1 is finally free to continue to update
+   "s2_commit"
+   # This should now show a successful UPSERT
+   "controller_show"
+   # Ensure no unexpected locks survive
+   "controller_print_speculative_locks"

src/test/isolation/specs/insert-conflict-toast.spec

-# INSERT...ON CONFLICT test on table with TOAST
-#
-# This test verifies that speculatively inserted toast rows do not
-# cause conflicts. It does so by using expression index over a
-# function which acquires an advisory lock, triggering two index
-# insertions to happen almost at the same time. This is not guaranteed
-# to lead to a failed speculative insertion, but makes one quite
-# likely.
-
-setup
-{
-  CREATE TABLE ctoast (key int primary key, val text);
-  CREATE OR REPLACE FUNCTION ctoast_lock_func(int) RETURNS INT IMMUTABLE LANGUAGE SQL AS 'select pg_advisory_xact_lock_shared(1); select $1;';
-  CREATE OR REPLACE FUNCTION ctoast_large_val() RETURNS TEXT LANGUAGE SQL AS 'select array_agg(md5(g::text))::text from generate_series(1, 256) g';
-  CREATE UNIQUE INDEX ctoast_lock_idx ON ctoast (ctoast_lock_func(key));
-}
-
-teardown
-{
-  DROP TABLE ctoast;
-  DROP FUNCTION ctoast_lock_func(int);
-  DROP FUNCTION ctoast_large_val();
-}
-
-session "s1"
-setup
-{
-  BEGIN ISOLATION LEVEL READ COMMITTED;
-  SELECT pg_advisory_xact_lock(1);
-}
-step "s1commit" { COMMIT; }
-
-session "s2"
-setup
-{
-  SET default_transaction_isolation = 'read committed';
-}
-step "s2insert" {
-  INSERT INTO ctoast (key, val) VALUES (1, ctoast_large_val()) ON CONFLICT DO NOTHING;
-}
-
-session "s3"
-setup
-{
-  SET default_transaction_isolation = 'read committed';
-}
-step "s3insert" {
-  INSERT INTO ctoast (key, val) VALUES (1, ctoast_large_val()) ON CONFLICT DO NOTHING;
-}
-
-permutation "s2insert" "s3insert" "s1commit"