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Jun 8, 2025
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[pull] master from postgres:master #950

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99 changes: 8 additions & 91 deletions contrib/postgres_fdw/connection.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,6 @@ typedef struct ConnCacheEntry
/* 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 */
Expand All @@ -85,12 +84,6 @@ static unsigned int prep_stmt_number = 0;
/* tracks whether any work is needed in callback functions */
static bool xact_got_connection = false;

/*
* tracks the nesting level of the topmost read-only transaction determined
* by GetTopReadOnlyTransactionNestLevel()
*/
static int top_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;
Expand Down Expand Up @@ -379,7 +372,6 @@ make_new_connection(ConnCacheEntry *entry, UserMapping *user)

/* 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;
Expand Down Expand Up @@ -851,81 +843,29 @@ do_sql_command_end(PGconn *conn, const char *sql, bool consume_input)
* 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();

/*
* Set the nesting level of the topmost read-only transaction if the
* current transaction is read-only and we haven't yet. Once it's set,
* it's retained until that transaction is committed/aborted, and then
* reset (see pgfdw_xact_callback and pgfdw_subxact_callback).
*/
if (XactReadOnly)
{
if (top_read_only_level == 0)
top_read_only_level = GetTopReadOnlyTransactionNestLevel();
Assert(top_read_only_level > 0);
}
else
Assert(top_read_only_level == 0);

/*
* Start main transaction if we haven't yet; otherwise, change the
* already-started remote transaction/subtransaction to read-only if the
* local transaction/subtransaction have been done so after starting them
* and we haven't yet.
*/
/* Start main transaction if we haven't yet */
if (entry->xact_depth <= 0)
{
StringInfoData sql;
bool ro = (top_read_only_level == 1);
const char *sql;

elog(DEBUG3, "starting remote transaction on connection %p",
entry->conn);

initStringInfo(&sql);
appendStringInfoString(&sql, "START TRANSACTION ISOLATION LEVEL ");
if (IsolationIsSerializable())
appendStringInfoString(&sql, "SERIALIZABLE");
sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
else
appendStringInfoString(&sql, "REPEATABLE READ");
if (ro)
appendStringInfoString(&sql, " READ ONLY");
if (XactDeferrable)
appendStringInfoString(&sql, " DEFERRABLE");
sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
entry->changing_xact_state = true;
do_sql_command(entry->conn, sql.data);
do_sql_command(entry->conn, sql);
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)
{
Assert(top_read_only_level == 0 ||
entry->xact_depth <= top_read_only_level);
if (entry->xact_depth == top_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
Assert(top_read_only_level > 0 &&
entry->xact_depth >= top_read_only_level);

/*
* If we're in a subtransaction, stack up savepoints to match our level.
Expand All @@ -934,21 +874,12 @@ begin_remote_xact(ConnCacheEntry *entry)
*/
while (entry->xact_depth < curlevel)
{
StringInfoData sql;
bool ro = (entry->xact_depth + 1 == top_read_only_level);
char sql[64];

initStringInfo(&sql);
appendStringInfo(&sql, "SAVEPOINT s%d", entry->xact_depth + 1);
if (ro)
appendStringInfoString(&sql, "; SET transaction_read_only = on");
snprintf(sql, sizeof(sql), "SAVEPOINT s%d", entry->xact_depth + 1);
entry->changing_xact_state = true;
do_sql_command(entry->conn, sql.data);
do_sql_command(entry->conn, sql);
entry->xact_depth++;
if (ro)
{
Assert(!entry->xact_read_only);
entry->xact_read_only = true;
}
entry->changing_xact_state = false;
}
}
Expand Down Expand Up @@ -1243,9 +1174,6 @@ pgfdw_xact_callback(XactEvent event, void *arg)

/* Also reset cursor numbering for next transaction */
cursor_number = 0;

/* Likewise for top_read_only_level */
top_read_only_level = 0;
}

/*
Expand Down Expand Up @@ -1344,10 +1272,6 @@ pgfdw_subxact_callback(SubXactEvent event, SubTransactionId mySubid,
false);
}
}

/* If in the topmost read-only transaction, reset top_read_only_level */
if (curlevel == top_read_only_level)
top_read_only_level = 0;
}

/*
Expand Down Expand Up @@ -1450,9 +1374,6 @@ pgfdw_reset_xact_state(ConnCacheEntry *entry, bool toplevel)
/* 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
Expand All @@ -1473,10 +1394,6 @@ pgfdw_reset_xact_state(ConnCacheEntry *entry, bool toplevel)
{
/* Reset state to show we're out of a subtransaction */
entry->xact_depth--;

/* If in the topmost read-only transaction, reset xact r/o state */
if (entry->xact_depth + 1 == top_read_only_level)
entry->xact_read_only = false;
}
}

Expand Down
134 changes: 0 additions & 134 deletions contrib/postgres_fdw/expected/postgres_fdw.out
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Original file line number Diff line number Diff line change
Expand Up @@ -12384,140 +12384,6 @@ SELECT count(*) FROM remote_application_name
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;
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');
Expand Down
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