diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c index a1404cb6bb1..ee0b4acf0ba 100644 --- a/contrib/postgres_fdw/connection.c +++ b/contrib/postgres_fdw/connection.c @@ -80,6 +80,8 @@ static bool xact_got_connection = false; * SQL functions */ PG_FUNCTION_INFO_V1(postgres_fdw_get_connections); +PG_FUNCTION_INFO_V1(postgres_fdw_disconnect); +PG_FUNCTION_INFO_V1(postgres_fdw_disconnect_all); /* prototypes of private functions */ static void make_new_connection(ConnCacheEntry *entry, UserMapping *user); @@ -102,6 +104,7 @@ static bool pgfdw_exec_cleanup_query(PGconn *conn, const char *query, static bool pgfdw_get_cleanup_result(PGconn *conn, TimestampTz endtime, PGresult **result); static bool UserMappingPasswordRequired(UserMapping *user); +static bool disconnect_cached_connections(Oid serverid); /* * Get a PGconn which can be used to execute queries on the remote PostgreSQL @@ -1428,8 +1431,8 @@ postgres_fdw_get_connections(PG_FUNCTION_ARGS) * Even though the server is dropped in the current transaction, the * cache can still have associated active connection entry, say we * call such connections dangling. Since we can not fetch the server - * name from system catalogs for dangling connections, instead we - * show NULL value for server name in output. + * name from system catalogs for dangling connections, instead we show + * NULL value for server name in output. * * We could have done better by storing the server name in the cache * entry instead of server oid so that it could be used in the output. @@ -1447,7 +1450,7 @@ postgres_fdw_get_connections(PG_FUNCTION_ARGS) /* * If the server has been dropped in the current explicit * transaction, then this entry would have been invalidated in - * pgfdw_inval_callback at the end of drop sever command. Note + * pgfdw_inval_callback at the end of drop server command. Note * that this connection would not have been closed in * pgfdw_inval_callback because it is still being used in the * current explicit transaction. So, assert that here. @@ -1470,3 +1473,129 @@ postgres_fdw_get_connections(PG_FUNCTION_ARGS) PG_RETURN_VOID(); } + +/* + * Disconnect the specified cached connections. + * + * This function discards the open connections that are established by + * postgres_fdw from the local session to the foreign server with + * the given name. Note that there can be multiple connections to + * the given server using different user mappings. If the connections + * are used in the current local transaction, they are not disconnected + * and warning messages are reported. This function returns true + * if it disconnects at least one connection, otherwise false. If no + * foreign server with the given name is found, an error is reported. + */ +Datum +postgres_fdw_disconnect(PG_FUNCTION_ARGS) +{ + ForeignServer *server; + char *servername; + + servername = text_to_cstring(PG_GETARG_TEXT_PP(0)); + server = GetForeignServerByName(servername, false); + + PG_RETURN_BOOL(disconnect_cached_connections(server->serverid)); +} + +/* + * Disconnect all the cached connections. + * + * This function discards all the open connections that are established by + * postgres_fdw from the local session to the foreign servers. + * If the connections are used in the current local transaction, they are + * not disconnected and warning messages are reported. This function + * returns true if it disconnects at least one connection, otherwise false. + */ +Datum +postgres_fdw_disconnect_all(PG_FUNCTION_ARGS) +{ + PG_RETURN_BOOL(disconnect_cached_connections(InvalidOid)); +} + +/* + * Workhorse to disconnect cached connections. + * + * This function scans all the connection cache entries and disconnects + * the open connections whose foreign server OID matches with + * the specified one. If InvalidOid is specified, it disconnects all + * the cached connections. + * + * This function emits a warning for each connection that's used in + * the current transaction and doesn't close it. It returns true if + * it disconnects at least one connection, otherwise false. + * + * Note that this function disconnects even the connections that are + * established by other users in the same local session using different + * user mappings. This leads even non-superuser to be able to close + * the connections established by superusers in the same local session. + * + * XXX As of now we don't see any security risk doing this. But we should + * set some restrictions on that, for example, prevent non-superuser + * from closing the connections established by superusers even + * in the same session? + */ +static bool +disconnect_cached_connections(Oid serverid) +{ + HASH_SEQ_STATUS scan; + ConnCacheEntry *entry; + bool all = !OidIsValid(serverid); + bool result = false; + + /* + * Connection cache hashtable has not been initialized yet in this + * session, so return false. + */ + if (!ConnectionHash) + return false; + + hash_seq_init(&scan, ConnectionHash); + while ((entry = (ConnCacheEntry *) hash_seq_search(&scan))) + { + /* Ignore cache entry if no open connection right now. */ + if (!entry->conn) + continue; + + if (all || entry->serverid == serverid) + { + /* + * Emit a warning because the connection to close is used in the + * current transaction and cannot be disconnected right now. + */ + if (entry->xact_depth > 0) + { + ForeignServer *server; + + server = GetForeignServerExtended(entry->serverid, + FSV_MISSING_OK); + + if (!server) + { + /* + * If the foreign server was dropped while its connection + * was used in the current transaction, the connection + * must have been marked as invalid by + * pgfdw_inval_callback at the end of DROP SERVER command. + */ + Assert(entry->invalidated); + + ereport(WARNING, + (errmsg("cannot close dropped server connection because it is still in use"))); + } + else + ereport(WARNING, + (errmsg("cannot close connection for server \"%s\" because it is still in use", + server->servername))); + } + else + { + elog(DEBUG3, "discarding connection %p", entry->conn); + disconnect_pg_server(entry); + result = true; + } + } + } + + return result; +} diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index b4a04d2c143..e33c92d7f1c 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -17,7 +17,10 @@ DO $d$ OPTIONS (dbname '$$||current_database()||$$', port '$$||current_setting('port')||$$' )$$; - + EXECUTE $$CREATE SERVER loopback4 FOREIGN DATA WRAPPER postgres_fdw + OPTIONS (dbname '$$||current_database()||$$', + port '$$||current_setting('port')||$$' + )$$; END; $d$; CREATE USER MAPPING FOR public SERVER testserver1 @@ -25,6 +28,7 @@ CREATE USER MAPPING FOR public SERVER testserver1 CREATE USER MAPPING FOR CURRENT_USER SERVER loopback; CREATE USER MAPPING FOR CURRENT_USER SERVER loopback2; CREATE USER MAPPING FOR public SERVER loopback3; +CREATE USER MAPPING FOR public SERVER loopback4; -- =================================================================== -- create objects used through FDW loopback server -- =================================================================== @@ -140,6 +144,11 @@ CREATE FOREIGN TABLE ft7 ( c2 int NOT NULL, c3 text ) SERVER loopback3 OPTIONS (schema_name 'S 1', table_name 'T 4'); +CREATE FOREIGN TABLE ft8 ( + c1 int NOT NULL, + c2 int NOT NULL, + c3 text +) SERVER loopback4 OPTIONS (schema_name 'S 1', table_name 'T 4'); -- =================================================================== -- tests for validator -- =================================================================== @@ -211,7 +220,8 @@ ALTER FOREIGN TABLE ft2 ALTER COLUMN c1 OPTIONS (column_name 'C 1'); public | ft5 | loopback | (schema_name 'S 1', table_name 'T 4') | public | ft6 | loopback2 | (schema_name 'S 1', table_name 'T 4') | public | ft7 | loopback3 | (schema_name 'S 1', table_name 'T 4') | -(6 rows) + public | ft8 | loopback4 | (schema_name 'S 1', table_name 'T 4') | +(7 rows) -- Test that alteration of server options causes reconnection -- Remote's errors might be non-English, so hide them to ensure stable results @@ -9053,9 +9063,9 @@ ERROR: 08006 COMMIT; -- Clean up DROP PROCEDURE terminate_backend_and_wait(text); --- =================================================================== --- test connection invalidation cases --- =================================================================== +-- ============================================================================= +-- test connection invalidation cases and postgres_fdw_get_connections function +-- ============================================================================= -- This test case is for closing the connection in pgfdw_xact_callback BEGIN; -- List all the existing cached connections. Only loopback2 should be output. @@ -9118,6 +9128,194 @@ SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; loopback2 | t (1 row) +-- ======================================================================= +-- test postgres_fdw_disconnect and postgres_fdw_disconnect_all functions +-- ======================================================================= +-- Return true as all cached connections are closed. +SELECT postgres_fdw_disconnect_all(); + postgres_fdw_disconnect_all +----------------------------- + t +(1 row) + +-- Ensure to cache loopback connection. +SELECT 1 FROM ft1 LIMIT 1; + ?column? +---------- + 1 +(1 row) + +BEGIN; +-- Ensure to cache loopback2 connection. +SELECT 1 FROM ft6 LIMIT 1; + ?column? +---------- + 1 +(1 row) + +-- List all the existing cached connections. loopback and loopback2 should be +-- output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + server_name | valid +-------------+------- + loopback | t + loopback2 | t +(2 rows) + +-- Issue a warning and return false as loopback2 connection is still in use and +-- can not be closed. +SELECT postgres_fdw_disconnect('loopback2'); +WARNING: cannot close connection for server "loopback2" because it is still in use + postgres_fdw_disconnect +------------------------- + f +(1 row) + +-- Close loopback connection, return true and issue a warning as loopback2 +-- connection is still in use and can not be closed. +SELECT postgres_fdw_disconnect_all(); +WARNING: cannot close connection for server "loopback2" because it is still in use + postgres_fdw_disconnect_all +----------------------------- + t +(1 row) + +-- List all the existing cached connections. loopback2 should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + server_name | valid +-------------+------- + loopback2 | t +(1 row) + +-- Ensure to cache loopback connection. +SELECT 1 FROM ft1 LIMIT 1; + ?column? +---------- + 1 +(1 row) + +-- Ensure to cache loopback4 connection. +SELECT 1 FROM ft8 LIMIT 1; + ?column? +---------- + 1 +(1 row) + +-- List all the existing cached connections. loopback, loopback2, loopback4 +-- should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + server_name | valid +-------------+------- + loopback | t + loopback2 | t + loopback4 | t +(3 rows) + +DROP SERVER loopback4 CASCADE; +NOTICE: drop cascades to 2 other objects +DETAIL: drop cascades to user mapping for public on server loopback4 +drop cascades to foreign table ft8 +-- Return false as connections are still in use, warnings are issued. +SELECT postgres_fdw_disconnect_all(); +WARNING: cannot close dropped server connection because it is still in use +WARNING: cannot close connection for server "loopback" because it is still in use +WARNING: cannot close connection for server "loopback2" because it is still in use + postgres_fdw_disconnect_all +----------------------------- + f +(1 row) + +COMMIT; +-- Close loopback2 connection and return true. +SELECT postgres_fdw_disconnect('loopback2'); + postgres_fdw_disconnect +------------------------- + t +(1 row) + +-- List all the existing cached connections. loopback should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + server_name | valid +-------------+------- + loopback | t +(1 row) + +-- Return false as loopback2 connectin is closed already. +SELECT postgres_fdw_disconnect('loopback2'); + postgres_fdw_disconnect +------------------------- + f +(1 row) + +-- Return an error as there is no foreign server with given name. +SELECT postgres_fdw_disconnect('unknownserver'); +ERROR: server "unknownserver" does not exist +-- Close loopback connection and return true. +SELECT postgres_fdw_disconnect_all(); + postgres_fdw_disconnect_all +----------------------------- + t +(1 row) + +-- List all the existing cached connections. No connection exists, so NULL +-- should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + server_name | valid +-------------+------- +(0 rows) + +-- ============================================================================= +-- test case for having multiple cached connections for a foreign server +-- ============================================================================= +CREATE ROLE multi_conn_user1 SUPERUSER; +CREATE ROLE multi_conn_user2 SUPERUSER; +CREATE USER MAPPING FOR multi_conn_user1 SERVER loopback; +CREATE USER MAPPING FOR multi_conn_user2 SERVER loopback; +-- Will cache loopback connection with user mapping for multi_conn_user1 +SET ROLE multi_conn_user1; +SELECT 1 FROM ft1 LIMIT 1; + ?column? +---------- + 1 +(1 row) + +RESET ROLE; +-- Will cache loopback connection with user mapping for multi_conn_user2 +SET ROLE multi_conn_user2; +SELECT 1 FROM ft1 LIMIT 1; + ?column? +---------- + 1 +(1 row) + +RESET ROLE; +-- Should output two connections for loopback server +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + server_name | valid +-------------+------- + loopback | t + loopback | t +(2 rows) + +-- Close loopback connections and return true. +SELECT postgres_fdw_disconnect('loopback'); + postgres_fdw_disconnect +------------------------- + t +(1 row) + +-- List all the existing cached connections. No connection exists, so NULL +-- should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + server_name | valid +-------------+------- +(0 rows) + +-- Clean up +DROP USER MAPPING FOR multi_conn_user1 SERVER loopback; +DROP USER MAPPING FOR multi_conn_user2 SERVER loopback; +DROP ROLE multi_conn_user1; +DROP ROLE multi_conn_user2; -- =================================================================== -- batch insert -- =================================================================== diff --git a/contrib/postgres_fdw/postgres_fdw--1.0--1.1.sql b/contrib/postgres_fdw/postgres_fdw--1.0--1.1.sql index 7f85784466c..ed4ca378d4a 100644 --- a/contrib/postgres_fdw/postgres_fdw--1.0--1.1.sql +++ b/contrib/postgres_fdw/postgres_fdw--1.0--1.1.sql @@ -8,3 +8,13 @@ CREATE FUNCTION postgres_fdw_get_connections (OUT server_name text, RETURNS SETOF record AS 'MODULE_PATHNAME' LANGUAGE C STRICT PARALLEL RESTRICTED; + +CREATE FUNCTION postgres_fdw_disconnect (text) +RETURNS bool +AS 'MODULE_PATHNAME' +LANGUAGE C STRICT PARALLEL RESTRICTED; + +CREATE FUNCTION postgres_fdw_disconnect_all () +RETURNS bool +AS 'MODULE_PATHNAME' +LANGUAGE C STRICT PARALLEL RESTRICTED; diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index 28b82f5f9dc..9473ab07623 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -19,7 +19,10 @@ DO $d$ OPTIONS (dbname '$$||current_database()||$$', port '$$||current_setting('port')||$$' )$$; - + EXECUTE $$CREATE SERVER loopback4 FOREIGN DATA WRAPPER postgres_fdw + OPTIONS (dbname '$$||current_database()||$$', + port '$$||current_setting('port')||$$' + )$$; END; $d$; @@ -28,6 +31,7 @@ CREATE USER MAPPING FOR public SERVER testserver1 CREATE USER MAPPING FOR CURRENT_USER SERVER loopback; CREATE USER MAPPING FOR CURRENT_USER SERVER loopback2; CREATE USER MAPPING FOR public SERVER loopback3; +CREATE USER MAPPING FOR public SERVER loopback4; -- =================================================================== -- create objects used through FDW loopback server @@ -154,6 +158,12 @@ CREATE FOREIGN TABLE ft7 ( c3 text ) SERVER loopback3 OPTIONS (schema_name 'S 1', table_name 'T 4'); +CREATE FOREIGN TABLE ft8 ( + c1 int NOT NULL, + c2 int NOT NULL, + c3 text +) SERVER loopback4 OPTIONS (schema_name 'S 1', table_name 'T 4'); + -- =================================================================== -- tests for validator -- =================================================================== @@ -2710,9 +2720,9 @@ COMMIT; -- Clean up DROP PROCEDURE terminate_backend_and_wait(text); --- =================================================================== --- test connection invalidation cases --- =================================================================== +-- ============================================================================= +-- test connection invalidation cases and postgres_fdw_get_connections function +-- ============================================================================= -- This test case is for closing the connection in pgfdw_xact_callback BEGIN; -- List all the existing cached connections. Only loopback2 should be output. @@ -2739,6 +2749,86 @@ COMMIT; -- the above transaction. SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; +-- ======================================================================= +-- test postgres_fdw_disconnect and postgres_fdw_disconnect_all functions +-- ======================================================================= +-- Return true as all cached connections are closed. +SELECT postgres_fdw_disconnect_all(); +-- Ensure to cache loopback connection. +SELECT 1 FROM ft1 LIMIT 1; +BEGIN; +-- Ensure to cache loopback2 connection. +SELECT 1 FROM ft6 LIMIT 1; +-- List all the existing cached connections. loopback and loopback2 should be +-- output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; +-- Issue a warning and return false as loopback2 connection is still in use and +-- can not be closed. +SELECT postgres_fdw_disconnect('loopback2'); +-- Close loopback connection, return true and issue a warning as loopback2 +-- connection is still in use and can not be closed. +SELECT postgres_fdw_disconnect_all(); +-- List all the existing cached connections. loopback2 should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; +-- Ensure to cache loopback connection. +SELECT 1 FROM ft1 LIMIT 1; +-- Ensure to cache loopback4 connection. +SELECT 1 FROM ft8 LIMIT 1; +-- List all the existing cached connections. loopback, loopback2, loopback4 +-- should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; +DROP SERVER loopback4 CASCADE; +-- Return false as connections are still in use, warnings are issued. +SELECT postgres_fdw_disconnect_all(); +COMMIT; +-- Close loopback2 connection and return true. +SELECT postgres_fdw_disconnect('loopback2'); +-- List all the existing cached connections. loopback should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; +-- Return false as loopback2 connectin is closed already. +SELECT postgres_fdw_disconnect('loopback2'); +-- Return an error as there is no foreign server with given name. +SELECT postgres_fdw_disconnect('unknownserver'); +-- Close loopback connection and return true. +SELECT postgres_fdw_disconnect_all(); +-- List all the existing cached connections. No connection exists, so NULL +-- should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + +-- ============================================================================= +-- test case for having multiple cached connections for a foreign server +-- ============================================================================= +CREATE ROLE multi_conn_user1 SUPERUSER; +CREATE ROLE multi_conn_user2 SUPERUSER; +CREATE USER MAPPING FOR multi_conn_user1 SERVER loopback; +CREATE USER MAPPING FOR multi_conn_user2 SERVER loopback; + +-- Will cache loopback connection with user mapping for multi_conn_user1 +SET ROLE multi_conn_user1; +SELECT 1 FROM ft1 LIMIT 1; +RESET ROLE; + +-- Will cache loopback connection with user mapping for multi_conn_user2 +SET ROLE multi_conn_user2; +SELECT 1 FROM ft1 LIMIT 1; +RESET ROLE; + +-- Should output two connections for loopback server +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + +-- Close loopback connections and return true. +SELECT postgres_fdw_disconnect('loopback'); + +-- List all the existing cached connections. No connection exists, so NULL +-- should be output. +SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + +-- Clean up +DROP USER MAPPING FOR multi_conn_user1 SERVER loopback; +DROP USER MAPPING FOR multi_conn_user2 SERVER loopback; +DROP ROLE multi_conn_user1; +DROP ROLE multi_conn_user2; + -- =================================================================== -- batch insert -- =================================================================== diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml index fb4c22ac69f..8d6abd4c548 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -512,7 +512,7 @@ OPTIONS (ADD password_required 'false'); the end of that transaction. true is returned otherwise. If there are no open connections, no record is returned. Example usage of the function: - + postgres=# SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; server_name | valid -------------+------- @@ -522,6 +522,51 @@ postgres=# SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; + + + postgres_fdw_disconnect(server_name text) returns boolean + + + This function discards the open connections that are established by + postgres_fdw from the local session to + the foreign server with the given name. Note that there can be + multiple connections to the given server using different user mappings. + If the connections are used in the current local transaction, + they are not disconnected and warning messages are reported. + This function returns true if it disconnects + at least one connection, otherwise false. + If no foreign server with the given name is found, an error is reported. + Example usage of the function: + +postgres=# SELECT postgres_fdw_disconnect('loopback1'); + postgres_fdw_disconnect +------------------------- + t + + + + + + + postgres_fdw_disconnect_all() returns boolean + + + This function discards all the open connections that are established by + postgres_fdw from the local session to + the foreign servers. If the connections are used in the current local + transaction, they are not disconnected and warning messages are reported. + This function returns true if it disconnects + at least one connection, otherwise false. + Example usage of the function: + +postgres=# SELECT postgres_fdw_disconnect_all(); + postgres_fdw_disconnect_all +----------------------------- + t + + + + @@ -537,6 +582,26 @@ postgres=# SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; multiple user identities (user mappings) are used to access the foreign server, a connection is established for each user mapping. + + + When changing the definition of or removing a foreign server or + a user mapping, the corresponding connections are closed. + But note that if the connections are used in the current local transaction + at that moment, they are kept until the end of the transaction. + Closed connections will be established again when they are necessary + by subsequent queries using a foreign table. + + + + Once a connection to a foreign server has been established, + it's usually kept until the local or the corresponding remote + session exits. To disconnect a connection explicitly, + postgres_fdw_disconnect and + postgres_fdw_disconnect_all functions + need to be used. For example, these are useful when closing + the connections that are no longer necessary and then preventing them + from consuming the foreign server connections capacity too much. +