Revert pg_wal_replay_wait() stored procedure

This commit reverts 3c5db1d6b0, and subsequent improvements and fixes
including 8036d73ae3, 867d396ccd, 3ac3ec580c, 0868d7ae70, 85b98b8d5a,
2520226c95, 014f9f34d2, e658038772, e1555645d7, 5035172e4a, 6cfebfe88b,
73da6b8d1b, and e546989a26.

The reason for reverting is a set of remaining issues.  Most notably, the
stored procedure appears to need more effort than the utility statement
to turn the backend into a "snapshot-less" state.  This makes an approach
to use stored procedures questionable.

Catversion is bumped.

Discussion: https://postgr.es/m/Zyhj2anOPRKtb0xW%40paquier.xyz

1 files changed, 1 insertions, 115 deletions

diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index bca1d395683..b0c6d7c6875 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -22,19 +22,17 @@
 #include "access/xlog_internal.h"
 #include "access/xlogbackup.h"
 #include "access/xlogrecovery.h"
-#include "access/xlogwait.h"
 #include "catalog/pg_type.h"
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "replication/walreceiver.h"
 #include "storage/fd.h"
-#include "storage/proc.h"
+#include "storage/latch.h"
 #include "storage/standby.h"
 #include "utils/builtins.h"
 #include "utils/memutils.h"
 #include "utils/pg_lsn.h"
-#include "utils/snapmgr.h"
 #include "utils/timestamp.h"
 
 /*
@@ -750,115 +748,3 @@ pg_promote(PG_FUNCTION_ARGS)
 						   wait_seconds)));
 	PG_RETURN_BOOL(false);
 }
-
-static WaitLSNResult lastWaitLSNResult = WAIT_LSN_RESULT_SUCCESS;
-
-/*
- * Waits until recovery replays the target LSN with optional timeout.  Unless
- * 'no_error' provided throws an error on failure
- */
-Datum
-pg_wal_replay_wait(PG_FUNCTION_ARGS)
-{
-	XLogRecPtr	target_lsn = PG_GETARG_LSN(0);
-	int64		timeout = PG_GETARG_INT64(1);
-	bool		no_error = PG_GETARG_BOOL(2);
-
-	if (timeout < 0)
-		ereport(ERROR,
-				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
-				 errmsg("\"timeout\" must not be negative")));
-
-	/*
-	 * We are going to wait for the LSN replay.  We should first care that we
-	 * don't hold a snapshot and correspondingly our MyProc->xmin is invalid.
-	 * Otherwise, our snapshot could prevent the replay of WAL records
-	 * implying a kind of self-deadlock.  This is the reason why
-	 * pg_wal_replay_wait() is a procedure, not a function.
-	 *
-	 * At first, we should check there is no active snapshot.  According to
-	 * PlannedStmtRequiresSnapshot(), even in an atomic context, CallStmt is
-	 * processed with a snapshot.  Thankfully, we can pop this snapshot,
-	 * because PortalRunUtility() can tolerate this.
-	 */
-	if (ActiveSnapshotSet())
-		PopActiveSnapshot();
-
-	/*
-	 * At second, invalidate a catalog snapshot if any.  And we should be done
-	 * with the preparation.
-	 */
-	InvalidateCatalogSnapshot();
-
-	/* Give up if there is still an active or registered snapshot. */
-	if (GetOldestSnapshot())
-		ereport(ERROR,
-				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-				 errmsg("pg_wal_replay_wait() must be only called without an active or registered snapshot"),
-				 errdetail("Make sure pg_wal_replay_wait() isn't called within a transaction with an isolation level higher than READ COMMITTED, another procedure, or a function.")));
-
-	/*
-	 * As the result we should hold no snapshot, and correspondingly our xmin
-	 * should be unset.
-	 */
-	Assert(MyProc->xmin == InvalidTransactionId);
-
-	lastWaitLSNResult = WaitForLSNReplay(target_lsn, timeout);
-
-	if (no_error)
-		PG_RETURN_VOID();
-
-	/*
-	 * Process the result of WaitForLSNReplay().  Throw appropriate error if
-	 * needed.
-	 */
-	switch (lastWaitLSNResult)
-	{
-		case WAIT_LSN_RESULT_SUCCESS:
-			/* Nothing to do on success */
-			break;
-
-		case WAIT_LSN_RESULT_TIMEOUT:
-			ereport(ERROR,
-					(errcode(ERRCODE_QUERY_CANCELED),
-					 errmsg("timed out while waiting for target LSN %X/%X to be replayed; current replay LSN %X/%X",
-							LSN_FORMAT_ARGS(target_lsn),
-							LSN_FORMAT_ARGS(GetXLogReplayRecPtr(NULL)))));
-			break;
-
-		case WAIT_LSN_RESULT_NOT_IN_RECOVERY:
-			ereport(ERROR,
-					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-					 errmsg("recovery is not in progress"),
-					 errdetail("Recovery ended before replaying target LSN %X/%X; last replay LSN %X/%X.",
-							   LSN_FORMAT_ARGS(target_lsn),
-							   LSN_FORMAT_ARGS(GetXLogReplayRecPtr(NULL)))));
-			break;
-	}
-
-	PG_RETURN_VOID();
-}
-
-Datum
-pg_wal_replay_wait_status(PG_FUNCTION_ARGS)
-{
-	const char *result_string = "";
-
-	/* Process the result of WaitForLSNReplay(). */
-	switch (lastWaitLSNResult)
-	{
-		case WAIT_LSN_RESULT_SUCCESS:
-			result_string = "success";
-			break;
-
-		case WAIT_LSN_RESULT_TIMEOUT:
-			result_string = "timeout";
-			break;
-
-		case WAIT_LSN_RESULT_NOT_IN_RECOVERY:
-			result_string = "not in recovery";
-			break;
-	}
-
-	PG_RETURN_TEXT_P(cstring_to_text(result_string));
-}