This commit fixes three, unfortunately related, issues:
1) Since
5db6df0c01, the introduction of DML via tableam, it was
possible to trigger "ERROR: unexpected table_lock_tuple status: 1"
when updating a row that was previously updated in the same
transaction - but only when the previously updated row was before
updated in a concurrent transaction (and READ COMMITTED was
used). The reason for that was that that case simply wasn't
expected. Fixing that lead to:
2) Even before the above commit, there were error checks (introduced
in
6868ed7491b7) preventing a row being updated by different
commands within the same statement (say in a function called by an
UPDATE) - but that check wasn't performed when the row was first
updated in a concurrent transaction - instead the second update was
silently skipped in that case. After this change we throw the same
error as we'd without the concurrent transaction.
3) The error messages (introduced in
6868ed7491b7) preventing such
updates emitted the same error message for both DELETE and
UPDATE ("tuple to be updated was already modified by an operation
triggered by the current command"). While that could be changed
separately, it made it hard to write tests that verify the correct
correct behavior of the code.
This commit changes heap's implementation of table_lock_tuple() to
return TM_SelfModified instead of TM_Invisible (previously loosely
modeled after EvalPlanQualFetch), and teaches nodeModifyTable.c to
handle that in response to table_lock_tuple() and not just in response
to table_(delete|update).
Additionally it fixes the wrong error message (see 3 above). The
comment for table_lock_tuple() is also adjusted to state that
TM_Deleted won't return information in TM_FailureData - it'll not
always be available.
This also adds tests to ensure that DELETE/UPDATE correctly error out
when affecting a row that concurrently was modified by another
transaction.
Author: Andres Freund
Reported-By: Tom Lane, when investigating a bug bug fix to another bug
by Amit Langote
Discussion: https://postgr.es/m/19321.
1554567786@sss.pgh.pa.us
if (TransactionIdIsCurrentTransactionId(priorXmax) &&
HeapTupleHeaderGetCmin(tuple->t_data) >= cid)
{
+ tmfd->xmax = priorXmax;
+ /*
+ * Cmin is the problematic value, so store that. See
+ * above.
+ */
+ tmfd->cmax = HeapTupleHeaderGetCmin(tuple->t_data);
ReleaseBuffer(buffer);
- return TM_Invisible;
+ return TM_SelfModified;
}
/*
if (tmfd.cmax != estate->es_output_cid)
ereport(ERROR,
(errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
- errmsg("tuple to be updated was already modified by an operation triggered by the current command"),
+ errmsg("tuple to be deleted was already modified by an operation triggered by the current command"),
errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
/* Else, already deleted by self; nothing to do */
else
goto ldelete;
+ case TM_SelfModified:
+ /*
+ * This can be reached when following an update
+ * chain from a tuple updated by another session,
+ * reaching a tuple that was already updated in
+ * this transaction. If previously updated by this
+ * command, ignore the delete, otherwise error
+ * out.
+ *
+ * See also TM_SelfModified response to
+ * table_delete() above.
+ */
+ if (tmfd.cmax != estate->es_output_cid)
+ ereport(ERROR,
+ (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
+ errmsg("tuple to be deleted was already modified by an operation triggered by the current command"),
+ errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
+ return NULL;
+
case TM_Deleted:
/* tuple already deleted; nothing to do */
return NULL;
* already have errored out if the first version
* is invisible.
*
- * TM_SelfModified should be impossible, as we'd
- * otherwise should have hit the TM_SelfModified
- * case in response to table_delete above.
- *
* TM_Updated should be impossible, because we're
* locking the latest version via
* TUPLE_LOCK_FLAG_FIND_LAST_VERSION.
/* tuple already deleted; nothing to do */
return NULL;
+ case TM_SelfModified:
+ /*
+ * This can be reached when following an update
+ * chain from a tuple updated by another session,
+ * reaching a tuple that was already updated in
+ * this transaction. If previously modified by
+ * this command, ignore the redundant update,
+ * otherwise error out.
+ *
+ * See also TM_SelfModified response to
+ * table_update() above.
+ */
+ if (tmfd.cmax != estate->es_output_cid)
+ ereport(ERROR,
+ (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
+ errmsg("tuple to be updated was already modified by an operation triggered by the current command"),
+ errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));
+ return NULL;
+
default:
/* see table_lock_tuple call in ExecDelete() */
elog(ERROR, "unexpected table_lock_tuple status: %u",
* TM_Deleted: lock failed because tuple deleted by other xact
* TM_WouldBlock: lock couldn't be acquired and wait_policy is skip
*
- * In the failure cases other than TM_Invisible, the routine fills *tmfd with
- * the tuple's t_ctid, t_xmax, and, if possible, t_cmax. See comments for
- * struct TM_FailureData for additional info.
+ * In the failure cases other than TM_Invisible and TM_Deleted, the routine
+ * fills *tmfd with the tuple's t_ctid, t_xmax, and, if possible, t_cmax. See
+ * comments for struct TM_FailureData for additional info.
*/
static inline TM_Result
table_lock_tuple(Relation rel, ItemPointer tid, Snapshot snapshot,
checking 1050
savings 600
+starting permutation: wx1 updwcte c1 c2 read
+step wx1: UPDATE accounts SET balance = balance - 200 WHERE accountid = 'checking' RETURNING balance;
+balance
+
+400
+step updwcte: WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *) UPDATE accounts a SET balance = doup.balance + 100 FROM doup RETURNING *; <waiting ...>
+step c1: COMMIT;
+step updwcte: <... completed>
+accountid balance accountid balance
+
+savings 1600 checking 1500
+step c2: COMMIT;
+step read: SELECT * FROM accounts ORDER BY accountid;
+accountid balance
+
+checking 1500
+savings 1600
+
+starting permutation: wx1 updwctefail c1 c2 read
+step wx1: UPDATE accounts SET balance = balance - 200 WHERE accountid = 'checking' RETURNING balance;
+balance
+
+400
+step updwctefail: WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *, update_checking(999)) UPDATE accounts a SET balance = doup.balance + 100 FROM doup RETURNING *; <waiting ...>
+step c1: COMMIT;
+step updwctefail: <... completed>
+error in steps c1 updwctefail: ERROR: tuple to be updated was already modified by an operation triggered by the current command
+step c2: COMMIT;
+step read: SELECT * FROM accounts ORDER BY accountid;
+accountid balance
+
+checking 400
+savings 600
+
+starting permutation: wx1 delwcte c1 c2 read
+step wx1: UPDATE accounts SET balance = balance - 200 WHERE accountid = 'checking' RETURNING balance;
+balance
+
+400
+step delwcte: WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *) DELETE FROM accounts a USING doup RETURNING *; <waiting ...>
+step c1: COMMIT;
+step delwcte: <... completed>
+accountid balance accountid balance
+
+savings 600 checking 1500
+step c2: COMMIT;
+step read: SELECT * FROM accounts ORDER BY accountid;
+accountid balance
+
+checking 1500
+
+starting permutation: wx1 delwctefail c1 c2 read
+step wx1: UPDATE accounts SET balance = balance - 200 WHERE accountid = 'checking' RETURNING balance;
+balance
+
+400
+step delwctefail: WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *, update_checking(999)) DELETE FROM accounts a USING doup RETURNING *; <waiting ...>
+step c1: COMMIT;
+step delwctefail: <... completed>
+error in steps c1 delwctefail: ERROR: tuple to be deleted was already modified by an operation triggered by the current command
+step c2: COMMIT;
+step read: SELECT * FROM accounts ORDER BY accountid;
+accountid balance
+
+checking 400
+savings 600
+
starting permutation: upsert1 upsert2 c1 c2 read
step upsert1:
WITH upsert AS
CREATE TABLE accounts (accountid text PRIMARY KEY, balance numeric not null);
INSERT INTO accounts VALUES ('checking', 600), ('savings', 600);
+ CREATE FUNCTION update_checking(int) RETURNS bool LANGUAGE sql AS $$
+ UPDATE accounts SET balance = balance + 1 WHERE accountid = 'checking'; SELECT true;$$;
+
CREATE TABLE accounts_ext (accountid text PRIMARY KEY, balance numeric not null, other text);
INSERT INTO accounts_ext VALUES ('checking', 600, 'other'), ('savings', 700, null);
ALTER TABLE accounts_ext ADD COLUMN newcol int DEFAULT 42;
teardown
{
DROP TABLE accounts;
+ DROP FUNCTION update_checking(int);
DROP TABLE accounts_ext;
DROP TABLE p CASCADE;
DROP TABLE table_a, table_b, jointest;
}
step "wrtwcte" { UPDATE table_a SET value = 'tableAValue2' WHERE id = 1; }
step "wrjt" { UPDATE jointest SET data = 42 WHERE id = 7; }
+
+# Use writable CTEs to create self-updated rows, that then are
+# (updated|deleted). The *fail versions of the tests additionally
+# perform an update, via a function, in a different command, to test
+# behaviour relating to that.
+step "updwcte" { WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *) UPDATE accounts a SET balance = doup.balance + 100 FROM doup RETURNING *; }
+step "updwctefail" { WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *, update_checking(999)) UPDATE accounts a SET balance = doup.balance + 100 FROM doup RETURNING *; }
+step "delwcte" { WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *) DELETE FROM accounts a USING doup RETURNING *; }
+step "delwctefail" { WITH doup AS (UPDATE accounts SET balance = balance + 1100 WHERE accountid = 'checking' RETURNING *, update_checking(999)) DELETE FROM accounts a USING doup RETURNING *; }
+
step "c2" { COMMIT; }
step "r2" { ROLLBACK; }
permutation "d1" "wx2" "c1" "c2" "read"
permutation "d1" "wx2" "r1" "c2" "read"
+# test that an update to a self-modified row is ignored when
+# previously updated by the same cid
+permutation "wx1" "updwcte" "c1" "c2" "read"
+# test that an update to a self-modified row throws error when
+# previously updated by a different cid
+permutation "wx1" "updwctefail" "c1" "c2" "read"
+# test that a delete to a self-modified row is ignored when
+# previously updated by the same cid
+permutation "wx1" "delwcte" "c1" "c2" "read"
+# test that a delete to a self-modified row throws error when
+# previously updated by a different cid
+permutation "wx1" "delwctefail" "c1" "c2" "read"
+
permutation "upsert1" "upsert2" "c1" "c2" "read"
permutation "readp1" "writep1" "readp2" "c1" "c2"
permutation "writep2" "returningp1" "c1" "c2"
(1 row)
delete from parent where aid = 1; -- should fail
-ERROR: tuple to be updated was already modified by an operation triggered by the current command
+ERROR: tuple to be deleted was already modified by an operation triggered by the current command
HINT: Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.
select * from parent; select * from child;
aid | val1 | val2 | val3 | val4 | bcnt
projects / postgresql / commitdiff