Introduce logical decoding.

This feature, building on previous commits, allows the write-ahead log
stream to be decoded into a series of logical changes; that is,
inserts, updates, and deletes and the transactions which contain them.
It is capable of handling decoding even across changes to the schema
of the effected tables.  The output format is controlled by a
so-called "output plugin"; an example is included.  To make use of
this in a real replication system, the output plugin will need to be
modified to produce output in the format appropriate to that system,
and to perform filtering.

Currently, information can be extracted from the logical decoding
system only via SQL; future commits will add the ability to stream
changes via walsender.

Andres Freund, with review and other contributions from many other
people, including Álvaro Herrera, Abhijit Menon-Sen, Peter Gheogegan,
Kevin Grittner, Robert Haas, Heikki Linnakangas, Fujii Masao, Abhijit
Menon-Sen, Michael Paquier, Simon Riggs, Craig Ringer, and Steve
Singer.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index d1a58a3661b..d0b4103a09e 100644
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -15,6 +15,7 @@
 #define PROCARRAY_H
 
 #include "storage/standby.h"
+#include "utils/relcache.h"
 #include "utils/snapshot.h"
 
 
@@ -50,8 +51,9 @@ extern RunningTransactions GetRunningTransactionData(void);
 
 extern bool TransactionIdIsInProgress(TransactionId xid);
 extern bool TransactionIdIsActive(TransactionId xid);
-extern TransactionId GetOldestXmin(bool allDbs, bool ignoreVacuum);
+extern TransactionId GetOldestXmin(Relation rel, bool ignoreVacuum);
 extern TransactionId GetOldestActiveTransactionId(void);
+extern TransactionId GetOldestSafeDecodingTransactionId(void);
 
 extern VirtualTransactionId *GetVirtualXIDsDelayingChkpt(int *nvxids);
 extern bool HaveVirtualXIDsDelayingChkpt(VirtualTransactionId *vxids, int nvxids);
@@ -77,6 +79,10 @@ extern void XidCacheRemoveRunningXids(TransactionId xid,
 						  int nxids, const TransactionId *xids,
 						  TransactionId latestXid);
 
-extern void ProcArraySetReplicationSlotXmin(TransactionId xmin);
+extern void ProcArraySetReplicationSlotXmin(TransactionId xmin,
+							TransactionId catalog_xmin, bool already_locked);
+
+extern void ProcArrayGetReplicationSlotXmin(TransactionId *xmin,
+											TransactionId *catalog_xmin);
 
 #endif   /* PROCARRAY_H */