Remove MLOG_COMP_REC_SEC_DELETE_MARK.

The InnoDB redo log record type MLOG_COMP_REC_SEC_DELETE_MARK has
been unused for a long time, and it has never been written after
WL#8845 introduced the redo log format identifier in MySQL 5.7.9
or MariaDB Server 10.2.2. Thus, removing the record type does not
constitute any functional change.

storage/innobase/include/mtr0types.h

 /*****************************************************************************
 
 Copyright (c) 1995, 2015, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation
+Copyright (c) 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -168,11 +168,6 @@ enum mlog_id_t {
 	/** mark compact clustered index record deleted */
 	MLOG_COMP_REC_CLUST_DELETE_MARK = 39,
 
-	/** mark compact secondary index record deleted; this log
-	record type is redundant, as MLOG_REC_SEC_DELETE_MARK is
-	independent of the record format. */
-	MLOG_COMP_REC_SEC_DELETE_MARK = 40,
-
 	/** update of a compact record, preserves record field sizes */
 	MLOG_COMP_REC_UPDATE_IN_PLACE = 41,
 

storage/innobase/log/log0recv.cc

@@ -2,7 +2,7 @@
 
 Copyright (c) 1997, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
-Copyright (c) 2013, 2017, MariaDB Corporation. All Rights Reserved.
+Copyright (c) 2013, 2017, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -1331,17 +1331,6 @@ recv_parse_or_apply_log_rec_body(
 				ptr, end_ptr, page, page_zip, index);
 		}
 		break;
-	case MLOG_COMP_REC_SEC_DELETE_MARK:
-		ut_ad(!page || fil_page_type_is_index(page_type));
-		/* This log record type is obsolete, but we process it for
-		backward compatibility with MySQL 5.0.3 and 5.0.4. */
-		ut_a(!page || page_is_comp(page));
-		ut_a(!page_zip);
-		ptr = mlog_parse_index(ptr, end_ptr, TRUE, &index);
-		if (!ptr) {
-			break;
-		}
-		/* Fall through */
 	case MLOG_REC_SEC_DELETE_MARK:
 		ut_ad(!page || fil_page_type_is_index(page_type));
 		ptr = btr_cur_parse_del_mark_set_sec_rec(ptr, end_ptr,
@@ -3701,9 +3690,6 @@ get_mlog_string(mlog_id_t type)
 	case MLOG_COMP_REC_CLUST_DELETE_MARK:
 		return("MLOG_COMP_REC_CLUST_DELETE_MARK");
 
-	case MLOG_COMP_REC_SEC_DELETE_MARK:
-		return("MLOG_COMP_REC_SEC_DELETE_MARK");
-
 	case MLOG_COMP_REC_UPDATE_IN_PLACE:
 		return("MLOG_COMP_REC_UPDATE_IN_PLACE");