MDEV-28782: modify mariadb-tzinfo-to-sql to set 'wsrep*' variables...

MDEV-28782: modify mariadb-tzinfo-to-sql to set 'wsrep*' variables appropriately in cases where Galera is not compiled in

In 3b662c6e, it was discovered that the
values of the 'wsrep_is_on' and 'wsrep_cannot_replicate_tz' variables need
to be overridden for embedded builds to pass

However, there are other build configurations where these variables also
have NULL values.  The mariadb-tzinfo-to-sql script (implemented in
sql/tztime.cc) can be slightly modified to set its 'wsrep_is_on' and
'wsrep_cannot_replicate_tz' variables more predictably in all such cases,
thus allowing the mysql_tzinfo_to_sql_symlink.test test to pass without
any special-casing for particular build types.

See comments:

- https://github.com/MariaDB/server/commit/3b662c6ebd26b54ce534d9e7451cdc31e6c0046c#r78994411
- https://jira.mariadb.org/browse/MDEV-28782?focusedCommentId=230038&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-230038

All new code of the whole pull request, including one or several files that
are either new files or modified ones, are contributed under the BSD-new
license.  I am contributing on behalf of my employer Amazon Web Services,
Inc.

mysql-test/main/mysql_tzinfo_to_sql_symlink.test

@@ -3,8 +3,6 @@
 --source include/not_windows.inc
 --source include/no_protocol.inc
 
-let $is_embedded=`select version() like '%embedded%'`;
-
 CREATE TABLE time_zone LIKE mysql.time_zone;
 CREATE TABLE time_zone_name LIKE mysql.time_zone_name;
 CREATE TABLE time_zone_transition LIKE mysql.time_zone_transition;
@@ -63,9 +61,6 @@ SELECT COUNT(*) FROM time_zone_transition;
 SELECT COUNT(*) FROM time_zone_transition_type;
 SELECT COUNT(*) FROM time_zone_leap_second;
 
-if ($is_embedded) {
---replace_column 1 0 2 0
-}
 SELECT @wsrep_is_on,  @wsrep_cannot_replicate_tz, @save_wsrep_on, @save_sql_log_bin, @@SQL_LOG_BIN;
 SELECT g.VARIABLE_NAME, g.VARIABLE_VALUE - b.VARIABLE_VALUE AS diff
   FROM information_schema.global_status g
@@ -100,9 +95,6 @@ SELECT COUNT(*) FROM time_zone_transition;
 SELECT COUNT(*) FROM time_zone_transition_type;
 SELECT COUNT(*) FROM time_zone_leap_second;
 
-if ($is_embedded) {
---replace_column 1 0 2 0
-}
 SELECT @wsrep_is_on,  @wsrep_cannot_replicate_tz, @save_wsrep_on, @save_sql_log_bin, @@SQL_LOG_BIN;
 SELECT g.VARIABLE_NAME, g.VARIABLE_VALUE - b.VARIABLE_VALUE AS diff
   FROM information_schema.global_status g
@@ -135,9 +127,6 @@ SELECT COUNT(*) FROM time_zone_transition;
 SELECT COUNT(*) FROM time_zone_transition_type;
 SELECT COUNT(*) FROM time_zone_leap_second;
 
-if ($is_embedded) {
---replace_column 1 0 2 0
-}
 SELECT @wsrep_is_on,  @wsrep_cannot_replicate_tz, @save_wsrep_on, @save_sql_log_bin, @@SQL_LOG_BIN;
 SELECT g.VARIABLE_NAME, g.VARIABLE_VALUE - b.VARIABLE_VALUE AS diff
   FROM information_schema.global_status g
@@ -170,9 +159,6 @@ SELECT COUNT(*) FROM time_zone_transition;
 SELECT COUNT(*) FROM time_zone_transition_type;
 SELECT COUNT(*) FROM time_zone_leap_second;
 
-if ($is_embedded) {
---replace_column 1 0 2 0
-}
 SELECT @wsrep_is_on,  @wsrep_cannot_replicate_tz, @save_wsrep_on, @save_sql_log_bin, @@SQL_LOG_BIN;
 SELECT g.VARIABLE_NAME, g.VARIABLE_VALUE - b.VARIABLE_VALUE AS diff
   FROM information_schema.global_status g
@@ -205,9 +191,6 @@ SELECT COUNT(*) FROM time_zone_transition;
 SELECT COUNT(*) FROM time_zone_transition_type;
 SELECT COUNT(*) FROM time_zone_leap_second;
 
-if ($is_embedded) {
---replace_column 1 0 2 0
-}
 SELECT @wsrep_is_on,  @wsrep_cannot_replicate_tz, @save_wsrep_on, @save_sql_log_bin, @@SQL_LOG_BIN;
 SELECT g.VARIABLE_NAME, g.VARIABLE_VALUE - b.VARIABLE_VALUE AS diff
   FROM information_schema.global_status g

sql/tztime.cc

@@ -2725,11 +2725,20 @@ static const char *trunc_tables_const=
   "TRUNCATE TABLE time_zone_name;\n"
   "TRUNCATE TABLE time_zone_transition;\n"
   "TRUNCATE TABLE time_zone_transition_type;\n";
+
+/*
+   These queries need to return FALSE/0 when the 'wsrep*' variables do not
+   exist at all.
+   Moving the WHERE clause into the sum(...) seems like the obvious solution
+   here, but it does not work in bootstrap mode (see MDEV-28782 and
+   0e4cf497ca11a7298e2bd896cb594bd52085a1d4).
+   Thus we use coalesce(..., 0) instead,
+*/
 static const char *wsrep_is_on=
-  "select sum(SESSION_VALUE='ON')"
+  "select coalesce(sum(SESSION_VALUE='ON'), 0)"
   " from information_schema.SYSTEM_VARIABLES WHERE VARIABLE_NAME='wsrep_on'";
 static const char *wsrep_cannot_replicate_tz=
-  "select sum(GLOBAL_VALUE NOT LIKE @replicate_opt)"
+  "select coalesce(sum(GLOBAL_VALUE NOT LIKE @replicate_opt), 0)"
   " from information_schema.SYSTEM_VARIABLES WHERE VARIABLE_NAME='wsrep_mode'";
 
 int
@@ -2770,7 +2779,7 @@ main(int argc, char **argv)
          " ORDER BY OPTION DESC;\n");
   printf("set @wsrep_cannot_replicate_tz=@wsrep_is_on AND (%s);\n", wsrep_cannot_replicate_tz);
   if (opt_skip_write_binlog)
-    /* If turn off session wsrep if we cannot replicate using galera.
+    /* We turn off session wsrep if we cannot replicate using galera.
        Disable sql_log_bin as the name implies. */
     printf("execute immediate if(@wsrep_is_on, 'SET @save_wsrep_on=@@WSREP_ON, WSREP_ON=OFF', 'do 0');\n"
            "SET @save_sql_log_bin=@@SQL_LOG_BIN;\n"