database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-13 07:41:39 +03:00
Code Activity

postgres_fdw: Add option to control whether to keep connections open.

Browse Source 
This commit adds a new option keep_connections that controls
whether postgres_fdw keeps the connections to the foreign server open
so that the subsequent queries can re-use them. This option can only be
specified for a foreign server. The default is on. If set to off,
all connections to the foreign server will be discarded
at the end of transaction. Closed connections will be re-established
when they are necessary by future queries using a foreign table.

This option is useful, for example, when users want to prevent
the connections from eating up the foreign servers connections
capacity.

Author: Bharath Rupireddy
Reviewed-by: Alexey Kondratov, Vignesh C, Fujii Masao
Discussion: https://postgr.es/m/CALj2ACVvrp5=AVp2PupEm+nAC8S4buqR3fJMmaCoc7ftT0aD2A@mail.gmail.com
This commit is contained in:
Fujii Masao
2021-04-02 19:45:42 +09:00
parent 9c5f67fd62
commit b1be3074ac
5 changed files with 101 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
contrib/postgres_fdw/connection.c
View File

@ -59,6 +59,8 @@ typedef struct ConnCacheEntry
bool have_error; /* have any subxacts aborted in this xact? */
bool changing_xact_state; /* xact state change in process */
bool invalidated; /* true if reconnect is pending */
bool keep_connections; /* setting value of keep_connections
* server option */
Oid serverid; /* foreign server OID used to get server name */
uint32 server_hashvalue; /* hash value of foreign server OID */
uint32 mapping_hashvalue; /* hash value of user mapping OID */
@ -286,6 +288,7 @@ static void
make_new_connection(ConnCacheEntry *entry, UserMapping *user)
{
ForeignServer *server = GetForeignServer(user->serverid);
ListCell *lc;
Assert(entry->conn == NULL);
@ -304,6 +307,26 @@ make_new_connection(ConnCacheEntry *entry, UserMapping *user)
ObjectIdGetDatum(user->umid));
memset(&entry->state, 0, sizeof(entry->state));
/*
* Determine whether to keep the connection that we're about to make here
* open even after the transaction using it ends, so that the subsequent
* transactions can re-use it.
*
* It's enough to determine this only when making new connection because
* all the connections to the foreign server whose keep_connections option
* is changed will be closed and re-made later.
*
* By default, all the connections to any foreign servers are kept open.
*/
entry->keep_connections = true;
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "keep_connections") == 0)
entry->keep_connections = defGetBoolean(def);
}
/* Now try to make the connection */
entry->conn = connect_pg_server(server, user);
@ -970,14 +993,16 @@ pgfdw_xact_callback(XactEvent event, void *arg)
entry->xact_depth = 0;
/*
* If the connection isn't in a good idle state or it is marked as
* invalid, then discard it to recover. Next GetConnection will open a
* new connection.
* 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
* discard it to recover. Next GetConnection will open a new
* connection.
*/
if (PQstatus(entry->conn) != CONNECTION_OK ||
PQtransactionStatus(entry->conn) != PQTRANS_IDLE ||
entry->changing_xact_state ||
entry->invalidated)
entry->invalidated ||
!entry->keep_connections)
{
elog(DEBUG3, "discarding connection %p", entry->conn);
disconnect_pg_server(entry);