Introduce replication slots.

Replication slots are a crash-safe data structure which can be created
on either a master or a standby to prevent premature removal of
write-ahead log segments needed by a standby, as well as (with
hot_standby_feedback=on) pruning of tuples whose removal would cause
replication conflicts.  Slots have some advantages over existing
techniques, as explained in the documentation.

In a few places, we refer to the type of replication slots introduced
by this patch as "physical" slots, because forthcoming patches for
logical decoding will also have slots, but with somewhat different
properties.

Andres Freund and Robert Haas

1 files changed, 10 insertions, 3 deletions

diff --git a/src/backend/replication/walreceiverfuncs.c b/src/backend/replication/walreceiverfuncs.c
index cc96d7c2f8a..acadec57f5a 100644
--- a/src/backend/replication/walreceiverfuncs.c
+++ b/src/backend/replication/walreceiverfuncs.c
@@ -219,11 +219,13 @@ ShutdownWalRcv(void)
 /*
  * Request postmaster to start walreceiver.
  *
- * recptr indicates the position where streaming should begin, and conninfo
- * is a libpq connection string to use.
+ * recptr indicates the position where streaming should begin, conninfo
+ * is a libpq connection string to use, and slotname is, optionally, the name
+ * of a replication slot to acquire.
  */
 void
-RequestXLogStreaming(TimeLineID tli, XLogRecPtr recptr, const char *conninfo)
+RequestXLogStreaming(TimeLineID tli, XLogRecPtr recptr, const char *conninfo,
+					 const char *slotname)
 {
 	/* use volatile pointer to prevent code rearrangement */
 	volatile WalRcvData *walrcv = WalRcv;
@@ -250,6 +252,11 @@ RequestXLogStreaming(TimeLineID tli, XLogRecPtr recptr, const char *conninfo)
 	else
 		walrcv->conninfo[0] = '\0';
 
+	if (slotname != NULL)
+		strlcpy((char *) walrcv->slotname, slotname, NAMEDATALEN);
+	else
+		walrcv->slotname[0] = '\0';
+
 	if (walrcv->walRcvState == WALRCV_STOPPED)
 	{
 		launch = true;