MDEV-7084: innodb index stats inadequate using constant innodb_stats_sample_pages

Use traditional statistics estimation by default (innodb-stats-traditional=true).
There could be performance regression for customers if there is a lot of
open table operations.

storage/innobase/handler/ha_innodb.cc

@@ -11746,8 +11746,8 @@ static MYSQL_SYSVAR_ULONGLONG(stats_modified_counter, srv_stats_modified_counter
 
 static MYSQL_SYSVAR_BOOL(stats_traditional, srv_stats_sample_traditional,
   PLUGIN_VAR_RQCMDARG,
-  "Enable traditional statistic calculation based on number of configured pages (default false)",
-  NULL, NULL, FALSE);
+  "Enable traditional statistic calculation based on number of configured pages (default true)",
+  NULL, NULL, TRUE);
 
 static MYSQL_SYSVAR_BOOL(adaptive_hash_index, btr_search_enabled,
   PLUGIN_VAR_OPCMDARG,

storage/innobase/srv/srv0srv.c

@@ -754,8 +754,8 @@ static ulint	srv_meter_foreground[SRV_MASTER + 1];
 UNIV_INTERN unsigned long long srv_stats_modified_counter = 0;
 
 /* Enable traditional statistic calculation based on number of configured
-pages default false. */
-UNIV_INTERN my_bool	srv_stats_sample_traditional = FALSE;
+pages default true. */
+UNIV_INTERN my_bool	srv_stats_sample_traditional = TRUE;
 
 /* The following values give info about the activity going on in
 the database. They are protected by the server mutex. The arrays

storage/xtradb/handler/ha_innodb.cc

@@ -13114,8 +13114,8 @@ static MYSQL_SYSVAR_ULONGLONG(stats_modified_counter, srv_stats_modified_counter
 
 static MYSQL_SYSVAR_BOOL(stats_traditional, srv_stats_sample_traditional,
   PLUGIN_VAR_RQCMDARG,
-  "Enable traditional statistic calculation based on number of configured pages (default false)",
-  NULL, NULL, FALSE);
+  "Enable traditional statistic calculation based on number of configured pages (default true)",
+  NULL, NULL, TRUE);
 
 static MYSQL_SYSVAR_ULINT(stats_auto_update, srv_stats_auto_update,
   PLUGIN_VAR_RQCMDARG,

storage/xtradb/srv/srv0srv.c

@@ -416,8 +416,8 @@ UNIV_INTERN ulong	srv_sys_stats_root_page = 0;
 UNIV_INTERN unsigned long long srv_stats_modified_counter = 0;
 
 /* Enable traditional statistic calculation based on number of configured
-pages default false. */
-UNIV_INTERN my_bool	srv_stats_sample_traditional = FALSE;
+pages default true. */
+UNIV_INTERN my_bool	srv_stats_sample_traditional = TRUE;
 
 UNIV_INTERN ibool	srv_use_doublewrite_buf	= TRUE;
 UNIV_INTERN ibool       srv_use_atomic_writes = FALSE;