MDEV-24920: Merge "old" SQL variable to "old_mode" sql variablebb-10.7-MDEV-24920

Analysis: There are 2 server variables- "old_mode" and "old". "old" is no
longer needed as "old_mode" has replaced it (however still used in some places
 in the code). "old_mode" and "old" has same purpose- emulate behavior from
previous MariaDB versions. So they can be merged to avoid confusion.
Fix: Deprecate "old" variable and create another mode for @@old_mode to mimic
behavior of previous "old" variable. Create specific modes for specifix task
that --old sql variable was doing earlier and use the new modes instead.

7 files changed, 42 insertions, 9 deletions

diff --git a/sql/handler.cc b/sql/handler.cc
index 9c4c6287950..aea8f38d71a 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -5783,7 +5783,8 @@ int handler::calculate_checksum()
     {
       Field *f= table->field[i];
 
-      if (! thd->variables.old_mode && f->is_real_null(0))
+      if (! (thd->variables.old_behavior & OLD_MODE_CHECKSUM_SLOW_NULLS) &&
+            f->is_real_null(0))
       {
         flush_checksum(&row_crc, &checksum_start, &checksum_length);
         continue;
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index e7e5af8a2c8..f6c6c1effd7 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -8471,6 +8471,14 @@ static int get_options(int *argc_ptr, char ***argv_ptr)
     between options, setting of multiple variables, etc.
     Do them here.
   */
+
+  if (global_system_variables.old_mode)
+  {
+    global_system_variables.old_behavior|= (OLD_MODE_NO_PROGRESS_INFO |
+                                           OLD_MODE_INDEX_HINT_MASK_JOIN |
+                                           OLD_MODE_CHECKSUM_SLOW_NULLS);
+  }
+
   if (global_system_variables.net_buffer_length > 
       global_system_variables.max_allowed_packet)
   {
diff --git a/sql/sql_class.h b/sql/sql_class.h
index df9d89b5aff..ab3f3b3af4b 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -191,6 +191,8 @@ enum enum_binlog_row_image {
 #define OLD_MODE_NO_PROGRESS_INFO			(1 << 1)
 #define OLD_MODE_ZERO_DATE_TIME_CAST                    (1 << 2)
 #define OLD_MODE_UTF8_IS_UTF8MB3      (1 << 3)
+#define OLD_MODE_INDEX_HINT_MASK_JOIN          (1 << 4)
+#define OLD_MODE_CHECKSUM_SLOW_NULLS    (1 << 5)
 
 extern char internal_table_name[2];
 extern char empty_c_string[1];
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index d01f84fe7d1..a4e7c69d089 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -2918,8 +2918,7 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
                        Item_empty_string(thd, "Info", arg.max_query_length),
                        mem_root);
   field->set_maybe_null();;
-  if (!thd->variables.old_mode &&
-      !(thd->variables.old_behavior & OLD_MODE_NO_PROGRESS_INFO))
+  if (!(thd->variables.old_behavior & OLD_MODE_NO_PROGRESS_INFO))
   {
     field_list.push_back(field= new (mem_root)
                          Item_float(thd, "Progress", 0.0, 3, 7),
@@ -2961,8 +2960,7 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
                       thd_info->query_string.charset());
     else
       protocol->store_null();
-    if (!thd->variables.old_mode &&
-        !(thd->variables.old_behavior & OLD_MODE_NO_PROGRESS_INFO))
+    if (!(thd->variables.old_behavior & OLD_MODE_NO_PROGRESS_INFO))
       protocol->store_double(thd_info->progress, 3);
     if (protocol->write())
       break; /* purecov: inspected */
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index a9ad8b7720d..331dea5acd5 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -11487,8 +11487,10 @@ bool mysql_checksum_table(THD *thd, TABLE_LIST *tables,
     {
       /* Call ->checksum() if the table checksum matches 'old_mode' settings */
       if (!(check_opt->flags & T_EXTEND) &&
-          (((t->file->ha_table_flags() & HA_HAS_OLD_CHECKSUM) && thd->variables.old_mode) ||
-           ((t->file->ha_table_flags() & HA_HAS_NEW_CHECKSUM) && !thd->variables.old_mode)))
+          (((t->file->ha_table_flags() & HA_HAS_OLD_CHECKSUM) &&
+           (thd->variables.old_behavior & OLD_MODE_CHECKSUM_SLOW_NULLS)) ||
+           ((t->file->ha_table_flags() & HA_HAS_NEW_CHECKSUM) &&
+           !(thd->variables.old_behavior & OLD_MODE_CHECKSUM_SLOW_NULLS))))
       {
         if (t->file->info(HA_STATUS_VARIABLE) || t->file->stats.checksum_null)
           protocol->store_null();
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 8ebefbb3d82..d605c4e89b4 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -11769,7 +11769,8 @@ opt_outer:
 index_hint_clause:
           /* empty */
           {
-            $$= thd->variables.old_mode ?  INDEX_HINT_MASK_JOIN : INDEX_HINT_MASK_ALL; 
+            $$= (thd->variables.old_behavior & OLD_MODE_INDEX_HINT_MASK_JOIN) ?
+                INDEX_HINT_MASK_JOIN : INDEX_HINT_MASK_ALL;
           }
         | FOR_SYM JOIN_SYM      { $$= INDEX_HINT_MASK_JOIN;  }
         | FOR_SYM ORDER_SYM BY  { $$= INDEX_HINT_MASK_ORDER; }
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index 7127cbc00f6..a7f27930123 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -2648,9 +2648,28 @@ static Sys_var_ulong Sys_net_retry_count(
        BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
        ON_UPDATE(fix_net_retry_count));
 
+static bool set_old_mode (sys_var *self, THD *thd, enum_var_type type)
+{
+  if (thd->variables.old_mode)
+  {
+    thd->variables.old_behavior|= (OLD_MODE_NO_PROGRESS_INFO |
+                                   OLD_MODE_INDEX_HINT_MASK_JOIN |
+                                   OLD_MODE_CHECKSUM_SLOW_NULLS);
+  }
+  else
+  {
+    thd->variables.old_behavior&= ~(OLD_MODE_NO_PROGRESS_INFO|
+                                    OLD_MODE_INDEX_HINT_MASK_JOIN |
+                                    OLD_MODE_CHECKSUM_SLOW_NULLS);
+  }
+
+  return false;
+}
+
 static Sys_var_mybool Sys_old_mode(
        "old", "Use compatible behavior from previous MariaDB version. See also --old-mode",
-       SESSION_VAR(old_mode), CMD_LINE(OPT_ARG), DEFAULT(FALSE));
+       SESSION_VAR(old_mode), CMD_LINE(OPT_ARG), DEFAULT(FALSE), 0, NOT_IN_BINLOG, ON_CHECK(0),
+       ON_UPDATE(set_old_mode), DEPRECATED("'@@old_mode'"));
 
 static const char *alter_algorithm_modes[]= {"DEFAULT", "COPY", "INPLACE",
 "NOCOPY", "INSTANT", NULL};
@@ -3751,6 +3770,8 @@ static const char *old_mode_names[]=
   "NO_PROGRESS_INFO",
   "ZERO_DATE_TIME_CAST",
   "UTF8_IS_UTF8MB3",
+  "INDEX_HINT_MASK_JOIN",
+  "CHECKSUM_SLOW_NULLS",
   0
 };