Remove code duplication for permission checks with replication slots

Two functions, both named check_permissions(), used the same checks to
verify if a user had required privileges to work on replication slots.
This commit removes the duplication, and moves the function doing the
checks to slot.c to be centralized.

Author: Bharath Rupireddy
Reviewed-by: Nathan Bossart, Euler Taveira
Discussion: https://postgr.es/m/CALj2ACUPpVw1u7sQocFVWrSs0n10pt_G_4NPZKSxXK6cW1dErw@mail.gmail.com

src/backend/replication/logical/logicalfuncs.c

@@ -95,15 +95,6 @@ LogicalOutputWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xi
 	p->returned_rows++;
 }
 
-static void
-check_permissions(void)
-{
-	if (!superuser() && !has_rolreplication(GetUserId()))
-		ereport(ERROR,
-				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 errmsg("must be superuser or replication role to use replication slots")));
-}
-
 /*
  * Helper function for the various SQL callable logical decoding functions.
  */
@@ -124,7 +115,7 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 	List	   *options = NIL;
 	DecodingOutputState *p;
 
-	check_permissions();
+	CheckSlotPermissions();
 
 	CheckLogicalDecodingRequirements();
 

src/backend/replication/slot.c

@@ -1059,6 +1059,18 @@ CheckSlotRequirements(void)
 				 errmsg("replication slots can only be used if wal_level >= replica")));
 }
 
+/*
+ * Check whether the user has privilege to use replication slots.
+ */
+void
+CheckSlotPermissions(void)
+{
+	if (!superuser() && !has_rolreplication(GetUserId()))
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser or replication role to use replication slots")));
+}
+
 /*
  * Reserve WAL for the currently active slot.
  *

src/backend/replication/slotfuncs.c

@@ -25,15 +25,6 @@
 #include "utils/pg_lsn.h"
 #include "utils/resowner.h"
 
-static void
-check_permissions(void)
-{
-	if (!superuser() && !has_rolreplication(GetUserId()))
-		ereport(ERROR,
-				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 errmsg("must be superuser or replication role to use replication slots")));
-}
-
 /*
  * Helper function for creating a new physical replication slot with
  * given arguments. Note that this function doesn't release the created
@@ -85,7 +76,7 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 		elog(ERROR, "return type must be a row type");
 
-	check_permissions();
+	CheckSlotPermissions();
 
 	CheckSlotRequirements();
 
@@ -188,7 +179,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 		elog(ERROR, "return type must be a row type");
 
-	check_permissions();
+	CheckSlotPermissions();
 
 	CheckLogicalDecodingRequirements();
 
@@ -224,7 +215,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
 {
 	Name		name = PG_GETARG_NAME(0);
 
-	check_permissions();
+	CheckSlotPermissions();
 
 	CheckSlotRequirements();
 
@@ -619,7 +610,7 @@ pg_replication_slot_advance(PG_FUNCTION_ARGS)
 
 	Assert(!MyReplicationSlot);
 
-	check_permissions();
+	CheckSlotPermissions();
 
 	if (XLogRecPtrIsInvalid(moveto))
 		ereport(ERROR,
@@ -718,7 +709,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 		elog(ERROR, "return type must be a row type");
 
-	check_permissions();
+	CheckSlotPermissions();
 
 	if (logical_slot)
 		CheckLogicalDecodingRequirements();

src/include/replication/slot.h

@@ -222,5 +222,6 @@ extern void StartupReplicationSlots(void);
 extern void CheckPointReplicationSlots(void);
 
 extern void CheckSlotRequirements(void);
+extern void CheckSlotPermissions(void);
 
 #endif							/* SLOT_H */