/* Remaining fields are invalid when conn is NULL: */
int xact_depth; /* 0 = no xact open, 1 = main xact open, 2 =
* one level of subxact open, etc */
+ bool xact_read_only; /* xact r/o state */
bool have_prep_stmt; /* have we prepared any stmts in this xact? */
bool have_error; /* have any subxacts aborted in this xact? */
bool changing_xact_state; /* xact state change in process */
/* tracks whether any work is needed in callback functions */
static bool xact_got_connection = false;
+/*
+ * tracks the topmost read-only local transaction's nesting level determined
+ * by GetTopReadOnlyTransactionNestLevel()
+ */
+static int read_only_level = 0;
+
/* custom wait event values, retrieved from shared memory */
static uint32 pgfdw_we_cleanup_result = 0;
static uint32 pgfdw_we_connect = 0;
/* Reset all transient state fields, to be sure all are clean */
entry->xact_depth = 0;
+ entry->xact_read_only = false;
entry->have_prep_stmt = false;
entry->have_error = false;
entry->changing_xact_state = false;
* those scans. A disadvantage is that we can't provide sane emulation of
* READ COMMITTED behavior --- it would be nice if we had some other way to
* control which remote queries share a snapshot.
+ *
+ * Note also that we always start the remote transaction with the same
+ * read/write and deferrable properties as the local transaction, and start
+ * the remote subtransaction with the same read/write property as the local
+ * subtransaction.
*/
static void
begin_remote_xact(ConnCacheEntry *entry)
{
int curlevel = GetCurrentTransactionNestLevel();
- /* Start main transaction if we haven't yet */
+ /*
+ * If the current local (sub)transaction is read-only, set the topmost
+ * read-only local transaction's nesting level if we haven't yet.
+ *
+ * Note: once it's set, it's retained until the topmost read-only local
+ * transaction is committed/aborted (see pgfdw_xact_callback and
+ * pgfdw_subxact_callback).
+ */
+ if (XactReadOnly)
+ {
+ if (read_only_level == 0)
+ read_only_level = GetTopReadOnlyTransactionNestLevel();
+ Assert(read_only_level > 0);
+ }
+ else
+ Assert(read_only_level == 0);
+
+ /*
+ * Start main transaction if we haven't yet; otherwise, change the current
+ * remote (sub)transaction's read/write mode if needed.
+ */
if (entry->xact_depth <= 0)
{
- const char *sql;
+ /*
+ * This is the case when we haven't yet started a main transaction.
+ */
+ StringInfoData sql;
+ bool ro = (read_only_level == 1);
elog(DEBUG3, "starting remote transaction on connection %p",
entry->conn);
+ initStringInfo(&sql);
+ appendStringInfoString(&sql, "START TRANSACTION ISOLATION LEVEL ");
if (IsolationIsSerializable())
- sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
+ appendStringInfoString(&sql, "SERIALIZABLE");
else
- sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+ appendStringInfoString(&sql, "REPEATABLE READ");
+ if (ro)
+ appendStringInfoString(&sql, " READ ONLY");
+ if (XactDeferrable)
+ appendStringInfoString(&sql, " DEFERRABLE");
entry->changing_xact_state = true;
- do_sql_command(entry->conn, sql);
+ do_sql_command(entry->conn, sql.data);
entry->xact_depth = 1;
+ if (ro)
+ {
+ Assert(!entry->xact_read_only);
+ entry->xact_read_only = true;
+ }
entry->changing_xact_state = false;
}
+ else if (!entry->xact_read_only)
+ {
+ /*
+ * The remote (sub)transaction has been opened in read-write mode.
+ */
+ Assert(read_only_level == 0 ||
+ entry->xact_depth <= read_only_level);
+
+ /*
+ * If its nesting depth matches read_only_level, it means that the
+ * local read-write (sub)transaction that started it has changed to
+ * read-only after that; in which case change it to read-only as well.
+ * Otherwise, the local (sub)transaction is still read-write, so there
+ * is no need to do anything.
+ */
+ if (entry->xact_depth == read_only_level)
+ {
+ entry->changing_xact_state = true;
+ do_sql_command(entry->conn, "SET transaction_read_only = on");
+ entry->xact_read_only = true;
+ entry->changing_xact_state = false;
+ }
+ }
+ else
+ {
+ /*
+ * The remote (sub)transaction has been opened in read-only mode.
+ */
+ Assert(read_only_level > 0 &&
+ entry->xact_depth >= read_only_level);
+
+ /*
+ * The local read-only (sub)transaction that started it is guaranteed
+ * to be still read-only (see check_transaction_read_only), so there
+ * is no need to do anything.
+ */
+ }
/*
* If we're in a subtransaction, stack up savepoints to match our level.
*/
while (entry->xact_depth < curlevel)
{
- char sql[64];
+ StringInfoData sql;
+ bool ro = (entry->xact_depth + 1 == read_only_level);
- snprintf(sql, sizeof(sql), "SAVEPOINT s%d", entry->xact_depth + 1);
+ initStringInfo(&sql);
+ appendStringInfo(&sql, "SAVEPOINT s%d", entry->xact_depth + 1);
+ if (ro)
+ appendStringInfoString(&sql, "; SET transaction_read_only = on");
entry->changing_xact_state = true;
- do_sql_command(entry->conn, sql);
+ do_sql_command(entry->conn, sql.data);
entry->xact_depth++;
+ if (ro)
+ {
+ Assert(!entry->xact_read_only);
+ entry->xact_read_only = true;
+ }
entry->changing_xact_state = false;
}
}
/* Also reset cursor numbering for next transaction */
cursor_number = 0;
+
+ /* Likewise for read_only_level */
+ read_only_level = 0;
}
/*
false);
}
}
+
+ /* If in read_only_level, reset it */
+ if (curlevel == read_only_level)
+ read_only_level = 0;
}
/*
/* Reset state to show we're out of a transaction */
entry->xact_depth = 0;
+ /* Reset xact r/o state */
+ entry->xact_read_only = false;
+
/*
* If the connection isn't in a good idle state, it is marked as
* invalid or keep_connections option of its server is disabled, then
{
/* Reset state to show we're out of a subtransaction */
entry->xact_depth--;
+
+ /* If in read_only_level, reset xact r/o state */
+ if (entry->xact_depth + 1 == read_only_level)
+ entry->xact_read_only = false;
}
}
DROP FOREIGN TABLE remote_application_name;
DROP VIEW my_application_name;
-- ===================================================================
+-- test read-only and/or deferrable transactions
+-- ===================================================================
+CREATE TABLE loct (f1 int, f2 text);
+CREATE FUNCTION locf() RETURNS SETOF loct LANGUAGE SQL AS
+ 'UPDATE public.loct SET f2 = f2 || f2 RETURNING *';
+CREATE VIEW locv AS SELECT t.* FROM locf() t;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'locv');
+CREATE FOREIGN TABLE remt2 (f1 int, f2 text)
+ SERVER loopback2 OPTIONS (table_name 'locv');
+INSERT INTO loct VALUES (1, 'foo'), (2, 'bar');
+START TRANSACTION READ ONLY;
+SAVEPOINT s;
+SELECT * FROM remt; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SELECT * FROM remt; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK;
+START TRANSACTION;
+SAVEPOINT s;
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK;
+START TRANSACTION;
+SAVEPOINT s;
+SELECT * FROM remt; -- should work
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SELECT * FROM remt; -- should work
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK;
+-- Exercise abort code paths in pgfdw_xact_callback/pgfdw_subxact_callback
+-- in situations where multiple connections are involved
+START TRANSACTION;
+SAVEPOINT s;
+SELECT * FROM remt; -- should work
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+SET transaction_read_only = on;
+SELECT * FROM remt2; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SELECT * FROM remt; -- should work
+ f1 | f2
+----+--------
+ 1 | foofoo
+ 2 | barbar
+(2 rows)
+
+SET transaction_read_only = on;
+SELECT * FROM remt2; -- should fail
+ERROR: cannot execute UPDATE in a read-only transaction
+CONTEXT: SQL function "locf" statement 1
+remote SQL command: SELECT f1, f2 FROM public.locv
+ROLLBACK;
+DROP FOREIGN TABLE remt;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'loct');
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY;
+SELECT * FROM remt;
+ f1 | f2
+----+-----
+ 1 | foo
+ 2 | bar
+(2 rows)
+
+COMMIT;
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE DEFERRABLE;
+SELECT * FROM remt;
+ f1 | f2
+----+-----
+ 1 | foo
+ 2 | bar
+(2 rows)
+
+COMMIT;
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE;
+SELECT * FROM remt;
+ f1 | f2
+----+-----
+ 1 | foo
+ 2 | bar
+(2 rows)
+
+COMMIT;
+-- Clean up
+DROP FOREIGN TABLE remt;
+DROP FOREIGN TABLE remt2;
+DROP VIEW locv;
+DROP FUNCTION locf();
+DROP TABLE loct;
+-- ===================================================================
-- test parallel commit and parallel abort
-- ===================================================================
ALTER SERVER loopback OPTIONS (ADD parallel_commit 'true');
DROP FOREIGN TABLE remote_application_name;
DROP VIEW my_application_name;
+-- ===================================================================
+-- test read-only and/or deferrable transactions
+-- ===================================================================
+CREATE TABLE loct (f1 int, f2 text);
+CREATE FUNCTION locf() RETURNS SETOF loct LANGUAGE SQL AS
+ 'UPDATE public.loct SET f2 = f2 || f2 RETURNING *';
+CREATE VIEW locv AS SELECT t.* FROM locf() t;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'locv');
+CREATE FOREIGN TABLE remt2 (f1 int, f2 text)
+ SERVER loopback2 OPTIONS (table_name 'locv');
+INSERT INTO loct VALUES (1, 'foo'), (2, 'bar');
+
+START TRANSACTION READ ONLY;
+SAVEPOINT s;
+SELECT * FROM remt; -- should fail
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SELECT * FROM remt; -- should fail
+ROLLBACK;
+
+START TRANSACTION;
+SAVEPOINT s;
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ROLLBACK;
+
+START TRANSACTION;
+SAVEPOINT s;
+SELECT * FROM remt; -- should work
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SELECT * FROM remt; -- should work
+SET transaction_read_only = on;
+SELECT * FROM remt; -- should fail
+ROLLBACK;
+
+-- Exercise abort code paths in pgfdw_xact_callback/pgfdw_subxact_callback
+-- in situations where multiple connections are involved
+START TRANSACTION;
+SAVEPOINT s;
+SELECT * FROM remt; -- should work
+SET transaction_read_only = on;
+SELECT * FROM remt2; -- should fail
+ROLLBACK TO s;
+RELEASE SAVEPOINT s;
+SELECT * FROM remt; -- should work
+SET transaction_read_only = on;
+SELECT * FROM remt2; -- should fail
+ROLLBACK;
+
+DROP FOREIGN TABLE remt;
+CREATE FOREIGN TABLE remt (f1 int, f2 text)
+ SERVER loopback OPTIONS (table_name 'loct');
+
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY;
+SELECT * FROM remt;
+COMMIT;
+
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE DEFERRABLE;
+SELECT * FROM remt;
+COMMIT;
+
+START TRANSACTION ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE;
+SELECT * FROM remt;
+COMMIT;
+
+-- Clean up
+DROP FOREIGN TABLE remt;
+DROP FOREIGN TABLE remt2;
+DROP VIEW locv;
+DROP FUNCTION locf();
+DROP TABLE loct;
+
-- ===================================================================
-- test parallel commit and parallel abort
-- ===================================================================
<productname>PostgreSQL</productname> release might modify these rules.
</para>
+ <para>
+ The remote transaction is opened in the same read/write mode as the local
+ transaction: if the local transaction is <literal>READ ONLY</literal>,
+ the remote transaction is opened in <literal>READ ONLY</literal> mode,
+ otherwise it is opened in <literal>READ WRITE</literal> mode.
+ (This rule is also applied to remote and local subtransactions.)
+ Note that this does not prevent login triggers executed on the remote
+ server from writing.
+ </para>
+
+ <para>
+ The remote transaction is also opened in the same deferrable mode as the
+ local transaction: if the local transaction is <literal>DEFERRABLE</literal>,
+ the remote transaction is opened in <literal>DEFERRABLE</literal> mode,
+ otherwise it is opened in <literal>NOT DEFERRABLE</literal> mode.
+ </para>
+
<para>
Note that it is currently not supported by
<filename>postgres_fdw</filename> to prepare the remote transaction for
return CurrentTransactionState->startedInRecovery;
}
+/*
+ * GetTopReadOnlyTransactionNestLevel
+ *
+ * Note: this will return zero when not inside any transaction or when neither
+ * a top-level transaction nor subtransactions are read-only, one when the
+ * top-level transaction is read-only, two when one level of subtransaction is
+ * read-only, etc.
+ *
+ * Note: subtransactions of the topmost read-only transaction are also
+ * read-only, because they inherit read-only mode from the transaction, and
+ * thus can't change to read-write mode (see check_transaction_read_only).
+ */
+int
+GetTopReadOnlyTransactionNestLevel(void)
+{
+ TransactionState s = CurrentTransactionState;
+
+ if (!XactReadOnly)
+ return 0;
+ while (s->nestingLevel > 1)
+ {
+ if (!s->prevXactReadOnly)
+ return s->nestingLevel;
+ s = s->parent;
+ }
+ return s->nestingLevel;
+}
+
/*
* EnterParallelMode
*/
extern void SetCurrentStatementStartTimestamp(void);
extern int GetCurrentTransactionNestLevel(void);
extern bool TransactionIdIsCurrentTransactionId(TransactionId xid);
+extern int GetTopReadOnlyTransactionNestLevel(void);
extern void CommandCounterIncrement(void);
extern void ForceSyncCommit(void);
extern void StartTransactionCommand(void);
projects / thirdparty / postgresql.git / commitdiff
