MDEV-33044 Loading time zones does not work with alter_algorithm INPLACE

$MYSQL_TZINFO_TO_SQL works by truncating tables. Truncation is an
operation that cannot be done in-place and therefore is fundamentally
incompatible with alter_algorithm='INPLACE'. As a result, we override
the default alter_algorithm setting in tztime.cc to
alter_algorithm='COPY' so that timezones can be loaded regardless
of the previously set alter_algorithm.

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/load_timezones_with_alter_algorithm_inplace.result

+set global alter_algorithm=INPLACE;
+RENAME TABLE mysql.time_zone TO mysql.time_zone_BACKUP;
+RENAME TABLE mysql.time_zone_name TO mysql.time_zone_name_BACKUP;
+RENAME TABLE mysql.time_zone_transition TO mysql.time_zone_transition_BACKUP;
+RENAME TABLE mysql.time_zone_transition_type TO mysql.time_zone_transition_type_BACKUP;
+CREATE TABLE mysql.time_zone LIKE mysql.time_zone_BACKUP;
+CREATE TABLE mysql.time_zone_name LIKE mysql.time_zone_name_BACKUP;
+CREATE TABLE mysql.time_zone_transition LIKE mysql.time_zone_transition_BACKUP;
+CREATE TABLE mysql.time_zone_transition_type LIKE mysql.time_zone_transition_type_BACKUP;
+DROP TABLE mysql.time_zone;
+DROP TABLE mysql.time_zone_name;
+DROP TABLE mysql.time_zone_transition;
+DROP TABLE mysql.time_zone_transition_type;
+RENAME TABLE mysql.time_zone_BACKUP TO mysql.time_zone;
+RENAME TABLE mysql.time_zone_name_BACKUP TO mysql.time_zone_name;
+RENAME TABLE mysql.time_zone_transition_BACKUP TO mysql.time_zone_transition;
+RENAME TABLE mysql.time_zone_transition_type_BACKUP TO mysql.time_zone_transition_type;
+set global alter_algorithm=DEFAULT;

mysql-test/main/load_timezones_with_alter_algorithm_inplace.test

+# MDEV-33044 Loading time zones does not work with alter_algorithm INPLACE
+
+set global alter_algorithm=INPLACE;
+
+# Because loading timezones alters the mysql tables,
+# this test will leave mysql in a different state than when it started.
+# Furthermore, checksums on the various mysql.timezone_x tables will fail. 
+
+# Therefore we:
+# 1. Make "backups" of the existing tables by renaming them
+# 2. Make dummy clones of the tables we just backed up
+# 3. Load timezones with alterations made to the dummy clone tables
+# 4. Drop the newly made tables with changes made to them
+# 5. Restore the backed up tables so the checksums will pass
+
+RENAME TABLE mysql.time_zone TO mysql.time_zone_BACKUP;
+RENAME TABLE mysql.time_zone_name TO mysql.time_zone_name_BACKUP;
+RENAME TABLE mysql.time_zone_transition TO mysql.time_zone_transition_BACKUP;
+RENAME TABLE mysql.time_zone_transition_type TO mysql.time_zone_transition_type_BACKUP;
+
+CREATE TABLE mysql.time_zone LIKE mysql.time_zone_BACKUP;
+CREATE TABLE mysql.time_zone_name LIKE mysql.time_zone_name_BACKUP;
+CREATE TABLE mysql.time_zone_transition LIKE mysql.time_zone_transition_BACKUP;
+CREATE TABLE mysql.time_zone_transition_type LIKE mysql.time_zone_transition_type_BACKUP;
+
+--exec $MYSQL_TZINFO_TO_SQL std_data/zoneinfo | $MYSQL mysql
+
+DROP TABLE mysql.time_zone;
+DROP TABLE mysql.time_zone_name;
+DROP TABLE mysql.time_zone_transition;
+DROP TABLE mysql.time_zone_transition_type;
+
+RENAME TABLE mysql.time_zone_BACKUP TO mysql.time_zone;
+RENAME TABLE mysql.time_zone_name_BACKUP TO mysql.time_zone_name;
+RENAME TABLE mysql.time_zone_transition_BACKUP TO mysql.time_zone_transition;
+RENAME TABLE mysql.time_zone_transition_type_BACKUP TO mysql.time_zone_transition_type;
+
+set global alter_algorithm=DEFAULT;
\ No newline at end of file

mysql-test/main/mysql_tzinfo_to_sql_symlink.result

@@ -20,12 +20,16 @@ ALTER TABLE time_zone ENGINE=InnoDB;
 ALTER TABLE time_zone_name ENGINE=InnoDB;
 ALTER TABLE time_zone_transition ENGINE=InnoDB;
 ALTER TABLE time_zone_transition_type ENGINE=InnoDB;
+SET @old_alter_alg=@@SESSION.alter_algorithm;
+SET session alter_algorithm='COPY';
 TRUNCATE TABLE time_zone;
 TRUNCATE TABLE time_zone_name;
 TRUNCATE TABLE time_zone_transition;
 TRUNCATE TABLE time_zone_transition_type;
 START TRANSACTION;
 ELSE
+SET @old_alter_alg=@@SESSION.alter_algorithm;
+SET session alter_algorithm='COPY';
 TRUNCATE TABLE time_zone;
 TRUNCATE TABLE time_zone_name;
 TRUNCATE TABLE time_zone_transition;
@@ -62,6 +66,7 @@ ALTER TABLE time_zone_transition ENGINE=Aria, ORDER BY Time_zone_id, Transition_
 ALTER TABLE time_zone_transition_type ENGINE=Aria, ORDER BY Time_zone_id, Transition_type_id;
 END IF|
 \d ;
+SET session alter_algorithm=@old_alter_alg;
 SELECT COUNT(*) FROM time_zone;
 COUNT(*)
 0
@@ -85,12 +90,16 @@ ALTER TABLE time_zone ENGINE=InnoDB;
 ALTER TABLE time_zone_name ENGINE=InnoDB;
 ALTER TABLE time_zone_transition ENGINE=InnoDB;
 ALTER TABLE time_zone_transition_type ENGINE=InnoDB;
+SET @old_alter_alg=@@SESSION.alter_algorithm;
+SET session alter_algorithm='COPY';
 TRUNCATE TABLE time_zone;
 TRUNCATE TABLE time_zone_name;
 TRUNCATE TABLE time_zone_transition;
 TRUNCATE TABLE time_zone_transition_type;
 START TRANSACTION;
 ELSE
+SET @old_alter_alg=@@SESSION.alter_algorithm;
+SET session alter_algorithm='COPY';
 TRUNCATE TABLE time_zone;
 TRUNCATE TABLE time_zone_name;
 TRUNCATE TABLE time_zone_transition;
@@ -124,6 +133,7 @@ ALTER TABLE time_zone_transition ENGINE=Aria, ORDER BY Time_zone_id, Transition_
 ALTER TABLE time_zone_transition_type ENGINE=Aria, ORDER BY Time_zone_id, Transition_type_id;
 END IF|
 \d ;
+SET session alter_algorithm=@old_alter_alg;
 SELECT COUNT(*) FROM time_zone;
 COUNT(*)
 2
@@ -145,6 +155,8 @@ COUNT(*)
 set @prep1=if((select count(*) from information_schema.global_variables where variable_name='wsrep_on' and variable_value='ON'), 'SET SESSION WSREP_ON=OFF', 'do 0');
 SET SESSION SQL_LOG_BIN=0;
 execute immediate @prep1;
+SET @old_alter_alg=@@SESSION.alter_algorithm;
+SET session alter_algorithm='COPY';
 TRUNCATE TABLE time_zone;
 TRUNCATE TABLE time_zone_name;
 TRUNCATE TABLE time_zone_transition;
@@ -172,6 +184,7 @@ UNLOCK TABLES;
 COMMIT;
 ALTER TABLE time_zone_transition ORDER BY Time_zone_id, Transition_time;
 ALTER TABLE time_zone_transition_type ORDER BY Time_zone_id, Transition_type_id;
+SET session alter_algorithm=@old_alter_alg;
 SELECT COUNT(*) FROM time_zone;
 COUNT(*)
 2
@@ -432,12 +445,16 @@ ALTER TABLE time_zone ENGINE=InnoDB;
 ALTER TABLE time_zone_name ENGINE=InnoDB;
 ALTER TABLE time_zone_transition ENGINE=InnoDB;
 ALTER TABLE time_zone_transition_type ENGINE=InnoDB;
+SET @old_alter_alg=@@SESSION.alter_algorithm;
+SET session alter_algorithm='COPY';
 TRUNCATE TABLE time_zone;
 TRUNCATE TABLE time_zone_name;
 TRUNCATE TABLE time_zone_transition;
 TRUNCATE TABLE time_zone_transition_type;
 START TRANSACTION;
 ELSE
+SET @old_alter_alg=@@SESSION.alter_algorithm;
+SET session alter_algorithm='COPY';
 TRUNCATE TABLE time_zone;
 TRUNCATE TABLE time_zone_name;
 TRUNCATE TABLE time_zone_transition;
@@ -457,6 +474,7 @@ ALTER TABLE time_zone_transition ENGINE=Aria, ORDER BY Time_zone_id, Transition_
 ALTER TABLE time_zone_transition_type ENGINE=Aria, ORDER BY Time_zone_id, Transition_type_id;
 END IF|
 \d ;
+SET session alter_algorithm=@old_alter_alg;
 DROP TABLE time_zone;
 DROP TABLE time_zone_name;
 DROP TABLE time_zone_transition;

sql/tztime.cc

@@ -2718,6 +2718,8 @@ static const char *lock_tables=
   "  time_zone_transition WRITE,\n"
   "  time_zone_transition_type WRITE;\n";
 static const char *trunc_tables_const=
+  "SET @old_alter_alg=@@SESSION.alter_algorithm;\n"
+  "SET session alter_algorithm='COPY';\n"
   "TRUNCATE TABLE time_zone;\n"
   "TRUNCATE TABLE time_zone_name;\n"
   "TRUNCATE TABLE time_zone_transition;\n"
@@ -2833,6 +2835,9 @@ main(int argc, char **argv)
       "END IF|\n"
       "\\d ;\n");
 
+  if (argc == 1 && !opt_leap)
+    printf("SET session alter_algorithm=@old_alter_alg;\n");
+  
   free_allocated_data();
   my_end(0);
   return 0;