Remove logical_read_local_xlog_page

It devolved into a content-less wrapper over read_local_xlog_page, with
nothing to add, plus it's easily confused with walsender's
logical_read_xlog_page.  There doesn't seem to be any reason for it to
stay.

src/include/replication/logicalfuncs.h becomes empty, so remove it too.
The prototypes it initially had were absorbed by generated fmgrprotos.h.

Discussion: https://postgr.es/m/20191115214102.GA15616@alvherre.pgsql

src/backend/replication/logical/logicalfuncs.c

@@ -28,7 +28,6 @@
 #include "nodes/makefuncs.h"
 #include "replication/decode.h"
 #include "replication/logical.h"
-#include "replication/logicalfuncs.h"
 #include "replication/message.h"
 #include "storage/fd.h"
 #include "utils/array.h"
@@ -105,14 +104,6 @@ check_permissions(void)
 				 errmsg("must be superuser or replication role to use replication slots")));
 }
 
-int
-logical_read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
-							 int reqLen, XLogRecPtr targetRecPtr, char *cur_page)
-{
-	return read_local_xlog_page(state, targetPagePtr, reqLen,
-								targetRecPtr, cur_page);
-}
-
 /*
  * Helper function for the various SQL callable logical decoding functions.
  */
@@ -242,7 +233,7 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 		ctx = CreateDecodingContext(InvalidXLogRecPtr,
 									options,
 									false,
-									logical_read_local_xlog_page,
+									read_local_xlog_page,
 									LogicalOutputPrepareWrite,
 									LogicalOutputWrite, NULL);
 

src/backend/replication/slotfuncs.c

@@ -14,11 +14,11 @@
 
 #include "access/htup_details.h"
 #include "access/xlog_internal.h"
+#include "access/xlogutils.h"
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "replication/decode.h"
 #include "replication/logical.h"
-#include "replication/logicalfuncs.h"
 #include "replication/slot.h"
 #include "utils/builtins.h"
 #include "utils/inval.h"
@@ -152,7 +152,7 @@ create_logical_replication_slot(char *name, char *plugin,
 	ctx = CreateInitDecodingContext(plugin, NIL,
 									false,	/* just catalogs is OK */
 									restart_lsn,
-									logical_read_local_xlog_page, NULL, NULL,
+									read_local_xlog_page, NULL, NULL,
 									NULL);
 
 	/*
@@ -424,7 +424,7 @@ pg_logical_replication_slot_advance(XLogRecPtr moveto)
 		ctx = CreateDecodingContext(InvalidXLogRecPtr,
 									NIL,
 									true,	/* fast_forward */
-									logical_read_local_xlog_page,
+									read_local_xlog_page,
 									NULL, NULL, NULL);
 
 		/*

src/backend/replication/walsender.c

@@ -70,7 +70,6 @@
 #include "replication/basebackup.h"
 #include "replication/decode.h"
 #include "replication/logical.h"
-#include "replication/logicalfuncs.h"
 #include "replication/slot.h"
 #include "replication/snapbuild.h"
 #include "replication/syncrep.h"
@@ -759,7 +758,7 @@ StartReplication(StartReplicationCmd *cmd)
 /*
  * read_page callback for logical decoding contexts, as a walsender process.
  *
- * Inside the walsender we can do better than logical_read_local_xlog_page,
+ * Inside the walsender we can do better than read_local_xlog_page,
  * which has to do a plain sleep/busy loop, because the walsender's latch gets
  * set every time WAL is flushed.
  */

src/include/replication/logicalfuncs.h

-/*-------------------------------------------------------------------------
- * logicalfuncs.h
- *	   PostgreSQL WAL to logical transformation support functions
- *
- * Copyright (c) 2012-2020, PostgreSQL Global Development Group
- *
- *-------------------------------------------------------------------------
- */
-#ifndef LOGICALFUNCS_H
-#define LOGICALFUNCS_H
-
-#include "replication/logical.h"
-
-extern int	logical_read_local_xlog_page(XLogReaderState *state,
-										 XLogRecPtr targetPagePtr,
-										 int reqLen, XLogRecPtr targetRecPtr,
-										 char *cur_page);
-
-#endif