From c40761f07cec1d34912f667caadf44fb632131ee Mon Sep 17 00:00:00 2001
From: Nitish Upreti <niupre@microsoft.com>
Date: Wed, 31 Aug 2022 10:12:30 -0700
Subject: [PATCH] Fix hang

---
 .../distributed/operations/shard_cleaner.c    | 38 ++++++++++++++-----
 .../distributed/operations/shard_split.c      |  2 +-
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/src/backend/distributed/operations/shard_cleaner.c b/src/backend/distributed/operations/shard_cleaner.c
index 9420f3f66..74724ed1a 100644
--- a/src/backend/distributed/operations/shard_cleaner.c
+++ b/src/backend/distributed/operations/shard_cleaner.c
@@ -15,12 +15,14 @@
 #include "access/genam.h"
 #include "access/xact.h"
 #include "catalog/namespace.h"
+#include "commands/dbcommands.h"
 #include "commands/sequence.h"
 #include "postmaster/postmaster.h"
 #include "nodes/makefuncs.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 
+#include "distributed/citus_safe_lib.h"
 #include "distributed/listutils.h"
 #include "distributed/coordinator_protocol.h"
 #include "distributed/metadata_cache.h"
@@ -657,17 +659,35 @@ GetNextOperationId()
 		return operationdId;
 	}
 
-	/* token location, or -1 if unknown */
-	const int location = -1;
-	RangeVar *sequenceName = makeRangeVar(PG_CATALOG,
-										  OPERATIONID_SEQUENCE_NAME,
-										  location);
+	/* Generate sequence using a subtransaction. else we can hold replication slot creation for operations */
+	StringInfo nextValueCommand = makeStringInfo();
+	appendStringInfo(nextValueCommand, "SELECT nextval(%s);", OPERATIONID_SEQUENCE_NAME);
 
-	bool missingOK = false;
-	Oid sequenceId = RangeVarGetRelid(sequenceName, NoLock, missingOK);
+	int connectionFlag = FORCE_NEW_CONNECTION;
+	MultiConnection *connection = GetNodeUserDatabaseConnection(connectionFlag,
+																LocalHostName,
+																PostPortNumber,
+																CitusExtensionOwnerName(),
+																get_database_name(
+																	MyDatabaseId));
 
-	bool checkPermissions = false;
-	operationdId = nextval_internal(sequenceId, checkPermissions);
+	PGresult *result = NULL;
+	int queryResult = ExecuteOptionalRemoteCommand(connection, nextValueCommand->data,
+												   &result);
+	if (queryResult != RESPONSE_OKAY || !IsResponseOK(result) || PQntuples(result) != 1 ||
+		PQnfields(result) != 1)
+	{
+		PQclear(result);
+		ForgetResults(connection);
+		CloseConnection(connection);
+
+		ereport(ERROR, (errcode(ERRCODE_CONNECTION_FAILURE),
+						errmsg(
+							"Could not generate next operation id while executing shard splits.")));
+	}
+
+	operationdId = SafeStringToUint64(PQgetvalue(result, 0, 0 /* nodeId column*/));
+	CloseConnection(connection);
 
 	return operationdId;
 }
diff --git a/src/backend/distributed/operations/shard_split.c b/src/backend/distributed/operations/shard_split.c
index 122af8af6..6c9bad75d 100644
--- a/src/backend/distributed/operations/shard_split.c
+++ b/src/backend/distributed/operations/shard_split.c
@@ -47,7 +47,7 @@
 #include "postmaster/postmaster.h"
 
 /* declarations for dynamic loading */
-bool DeferShardDeleteOnSplit = false;
+bool DeferShardDeleteOnSplit = true;
 
 /*
  * Entry for map that tracks ShardInterval -> Placement Node