Add caching for functions that check the backend type

src/backend/distributed/commands/call.c

@@ -17,6 +17,7 @@
 
 #include "catalog/pg_proc.h"
 #include "commands/defrem.h"
+#include "distributed/backend_data.h"
 #include "distributed/citus_ruleutils.h"
 #include "distributed/colocation_utils.h"
 #include "distributed/commands.h"

src/backend/distributed/commands/utility_hook.c

@@ -42,6 +42,7 @@
 #include "commands/defrem.h"
 #include "commands/tablecmds.h"
 #include "distributed/adaptive_executor.h"
+#include "distributed/backend_data.h"
 #include "distributed/colocation_utils.h"
 #include "distributed/commands.h"
 #include "distributed/commands/multi_copy.h"

src/backend/distributed/connection/connection_management.c

@@ -1466,40 +1466,6 @@ ShouldShutdownConnection(MultiConnection *connection, const int cachedConnection
 }
 
 
-/*
- * IsRebalancerInitiatedBackend returns true if we are in a backend that citus
- * rebalancer initiated.
- */
-bool
-IsRebalancerInternalBackend(void)
-{
-	return application_name && strcmp(application_name, CITUS_REBALANCER_NAME) == 0;
-}
-
-
-/*
- * IsCitusRunCommandBackend returns true if we are in a backend that one of
- * the run_command_on_* functions initiated.
- */
-bool
-IsCitusRunCommandBackend(void)
-{
-	return application_name &&
-		   strcmp(application_name, CITUS_RUN_COMMAND_APPLICATION_NAME) == 0;
-}
-
-
-/*
- * IsCitusInitiatedRemoteBackend returns true if we are in a backend that citus
- * initiated via remote connection.
- */
-bool
-IsCitusInternalBackend(void)
-{
-	return ExtractGlobalPID(application_name) != INVALID_CITUS_INTERNAL_BACKEND_GPID;
-}
-
-
 /*
  * ResetConnection preserves the given connection for later usage by
  * resetting its states.

src/backend/distributed/executor/multi_executor.c

@@ -18,6 +18,7 @@
 #include "catalog/dependency.h"
 #include "catalog/pg_class.h"
 #include "catalog/namespace.h"
+#include "distributed/backend_data.h"
 #include "distributed/citus_custom_scan.h"
 #include "distributed/commands/multi_copy.h"
 #include "distributed/commands/utility_hook.h"

src/backend/distributed/planner/function_call_delegation.c

@@ -17,6 +17,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
+#include "distributed/backend_data.h"
 #include "distributed/metadata_utility.h"
 #include "distributed/citus_ruleutils.h"
 #include "distributed/colocation_utils.h"

src/backend/distributed/shared_library_init.c

@@ -2081,6 +2081,7 @@ static void
 ApplicationNameAssignHook(const char *newval, void *extra)
 {
 	ResetHideShardsDecision();
+	ResetCitusBackendType();
 	OldApplicationNameAssignHook(newval, extra);
 }
 

src/backend/distributed/transaction/backend_data.c

@@ -78,6 +78,19 @@ typedef struct BackendManagementShmemData
 	BackendData backends[FLEXIBLE_ARRAY_MEMBER];
 } BackendManagementShmemData;
 
+/*
+ * CitusBackendType reflects what type of backend we are in. This
+ * can change depending on the application_name.
+ */
+typedef enum CitusBackendType
+{
+	CITUS_BACKEND_NOT_ASSIGNED,
+	CITUS_INTERNAL_BACKEND,
+	CITUS_REBALANCER_BACKEND,
+	CITUS_RUN_COMMAND_BACKEND,
+	EXTERNAL_CLIENT_BACKEND
+} CitusBackendType;
+
 
 static void StoreAllActiveTransactions(Tuplestorestate *tupleStore, TupleDesc
 									   tupleDescriptor);
@@ -88,10 +101,12 @@ static uint64 GenerateGlobalPID(void);
 static shmem_startup_hook_type prev_shmem_startup_hook = NULL;
 static BackendManagementShmemData *backendManagementShmemData = NULL;
 static BackendData *MyBackendData = NULL;
+static CitusBackendType CurrentBackendType = CITUS_BACKEND_NOT_ASSIGNED;
 
 
 static void BackendManagementShmemInit(void);
 static size_t BackendManagementShmemSize(void);
+static void DetermineCitusBackendType(void);
 
 
 PG_FUNCTION_INFO_V1(assign_distributed_transaction_id);
@@ -1278,3 +1293,87 @@ DecrementExternalClientBackendCounter(void)
 {
 	pg_atomic_sub_fetch_u32(&backendManagementShmemData->externalClientBackendCounter, 1);
 }
+
+
+/*
+ * ResetCitusBackendType resets the backend type cache.
+ */
+void
+ResetCitusBackendType(void)
+{
+	CurrentBackendType = CITUS_BACKEND_NOT_ASSIGNED;
+}
+
+
+/*
+ * IsRebalancerInitiatedBackend returns true if we are in a backend that citus
+ * rebalancer initiated.
+ */
+bool
+IsRebalancerInternalBackend(void)
+{
+	if (CurrentBackendType == CITUS_BACKEND_NOT_ASSIGNED)
+	{
+		DetermineCitusBackendType();
+	}
+
+	return CurrentBackendType == CITUS_REBALANCER_BACKEND;
+}
+
+
+/*
+ * IsCitusInitiatedRemoteBackend returns true if we are in a backend that citus
+ * initiated via remote connection.
+ */
+bool
+IsCitusInternalBackend(void)
+{
+	if (CurrentBackendType == CITUS_BACKEND_NOT_ASSIGNED)
+	{
+		DetermineCitusBackendType();
+	}
+
+	return CurrentBackendType == CITUS_INTERNAL_BACKEND;
+}
+
+
+/*
+ * IsCitusRunCommandBackend returns true if we are in a backend that one of
+ * the run_command_on_* functions initiated.
+ */
+bool
+IsCitusRunCommandBackend(void)
+{
+	if (CurrentBackendType == CITUS_BACKEND_NOT_ASSIGNED)
+	{
+		DetermineCitusBackendType();
+	}
+
+	return CurrentBackendType == CITUS_RUN_COMMAND_BACKEND;
+}
+
+
+/*
+ * DetermineCitusBackendType determines the type of backend based on the application_name.
+ */
+static void
+DetermineCitusBackendType(void)
+{
+	if (ExtractGlobalPID(application_name) != INVALID_CITUS_INTERNAL_BACKEND_GPID)
+	{
+		CurrentBackendType = CITUS_INTERNAL_BACKEND;
+	}
+	else if (application_name && strcmp(application_name, CITUS_REBALANCER_NAME) == 0)
+	{
+		CurrentBackendType = CITUS_REBALANCER_BACKEND;
+	}
+	else if (application_name &&
+			 strcmp(application_name, CITUS_RUN_COMMAND_APPLICATION_NAME) == 0)
+	{
+		CurrentBackendType = CITUS_RUN_COMMAND_BACKEND;
+	}
+	else
+	{
+		CurrentBackendType = EXTERNAL_CLIENT_BACKEND;
+	}
+}

src/backend/distributed/worker/worker_shard_visibility.c

@@ -14,6 +14,7 @@
 #include "catalog/namespace.h"
 #include "catalog/pg_class.h"
 #include "catalog/pg_type.h"
+#include "distributed/backend_data.h"
 #include "distributed/metadata_cache.h"
 #include "distributed/coordinator_protocol.h"
 #include "distributed/listutils.h"

src/include/distributed/backend_data.h

@@ -69,6 +69,10 @@ extern LocalTransactionId GetMyProcLocalTransactionId(void);
 extern int GetExternalClientBackendCount(void);
 extern uint32 IncrementExternalClientBackendCounter(void);
 extern void DecrementExternalClientBackendCounter(void);
+extern bool IsCitusInternalBackend(void);
+extern bool IsRebalancerInternalBackend(void);
+extern bool IsCitusRunCommandBackend(void);
+extern void ResetCitusBackendType(void);
 
 #define INVALID_CITUS_INTERNAL_BACKEND_GPID 0
 #define GLOBAL_PID_NODE_ID_FOR_NODES_NOT_IN_METADATA 99999999

src/include/distributed/connection_management.h

@@ -288,9 +288,6 @@ extern void FinishConnectionListEstablishment(List *multiConnectionList);
 extern void FinishConnectionEstablishment(MultiConnection *connection);
 extern void ClaimConnectionExclusively(MultiConnection *connection);
 extern void UnclaimConnection(MultiConnection *connection);
-extern bool IsCitusInternalBackend(void);
-extern bool IsRebalancerInternalBackend(void);
-extern bool IsCitusRunCommandBackend(void);
 extern void MarkConnectionConnected(MultiConnection *connection);
 
 /* waiteventset utilities */