Implementation of WL#1824 "Add replication of character set variables in 4.1",

by binlogging some SET ONE_SHOT CHARACTER_SETetc,
which will be enough until we have it more compact and more complete in 5.0. With the present patch,
replication will work ok between 4.1.3 master and slaves, as long as:
- master and slave have the same GLOBAL.COLLATION_SERVER
- COLLATION_DATABASE and CHARACTER_SET_DATABASE are not used
- application does not use the fact that table is created with charset of the USEd db (BUG#2326).
all of which are not too hard to fulfill. 
ONE_SHOT is reserved for internal use of mysqlbinlog|mysql and works only for charsets,
so we give error if used for non-charset vars.
Fix for BUG#3875 "mysqlbinlog produces wrong ouput  if query uses
 variables containing quotes" and BUG#3943 "Queries with non-ASCII literals are not replicated
 properly after SET NAMES".
Detecting that master and slave have different global charsets or server ids.


mysql-test/r/rpl_server_id1.result:
  it's normal to not run as I have added a test to compare server ids of master and slave
  at startup and stop if equal (unless --replicate-same-server-id)
mysql-test/r/rpl_user_variables.result:
  result update (as we now print charset of user var).
mysql-test/r/user_var.result:
  result update
mysql-test/t/rpl_server_id1.test:
  no need to select as slave is not running
mysql-test/t/user_var.test:
  testing if the content of user vars is escaped when mysqlbinlog prints them,
  and if the name is backquoted.
sql/lex.h:
  new keyword ONE_SHOT
sql/log.cc:
  when writing to the binlog, before writing the actual statement, write some SET ONE_SHOT CHARACTER_SET_CLIENT etc
  for the slave to know the charset variables (which are important as they affect the inserted data).
sql/log_event.cc:
  print charset and collation of user var in mysqlbinlog and SHOW BINLOG EVENTS.
  escape the content of the var. Backquote its name.
  Will ask Bar to check that using my_charset_bin for escaping is ok.
sql/set_var.cc:
  understand SET CHARACTER_SET_CLIENT=10 (don't require a string, accept a number).
  Refuse changing of GLOBAL CHARACTER_SET_SERVER/COLLATION_SERVER if binlog or slave,
  as it will make the master or slave make wrong assumptions.
  A function to catch SET ONE_SHOT on non-charset variables (which is forbidden)
sql/set_var.h:
  no_support_one_shot to know if the var supports ONE_SHOT (only charset vars do, soon timezones).
  Accept int arg in SET CHARACTER_SET_etc
sql/slave.cc:
  when I/O slave thread starts, verify that master's and slave charsets match.
  And by the way verify that server ids are different.
  Don't fail if UNIX_TIMESTAMP() can't be done on master (very old master), that's
  not fatal.
sql/sql_class.cc:
  one_shot
sql/sql_class.h:
  one_shot
sql/sql_lex.h:
  one_shot
sql/sql_parse.cc:
  when SET ONE_SHOT is used, verify that it's only used for charset/collation vars;
  otherwise refuse.
sql/sql_yacc.yy:
  ONE_SHOT keyword in SET

1 files changed, 60 insertions, 23 deletions

diff --git a/sql/slave.cc b/sql/slave.cc
index fa17a192b12..f88d828df1d 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -72,7 +72,7 @@ static int safe_sleep(THD* thd, int sec, CHECK_KILLED_FUNC thread_killed,
 static int request_table_dump(MYSQL* mysql, const char* db, const char* table);
 static int create_table_from_dump(THD* thd, MYSQL *mysql, const char* db,
 				  const char* table_name, bool overwrite);
-static int check_master_version_and_clock(MYSQL* mysql, MASTER_INFO* mi);
+static int get_master_version_and_clock(MYSQL* mysql, MASTER_INFO* mi);
 
 
 /*
@@ -1187,38 +1187,75 @@ slaves can't replicate a 5.0 or newer master.";
     break;
   }
 
-  MYSQL_RES *master_clock_res;
-  MYSQL_ROW master_clock_row;
-  time_t slave_clock;
-
-  if (mysql_real_query(mysql, "SELECT UNIX_TIMESTAMP()", 23))
-    errmsg= "\"SELECT UNIX_TIMESTAMP()\" failed on master"; 
-  else if (!(master_clock_res= mysql_store_result(mysql)))
+  /*
+    Compare the master and slave's clock. Do not die if master's clock is
+    unavailable (very old master not supporting UNIX_TIMESTAMP()?).
+  */
+  MYSQL_RES *master_res= 0;
+  MYSQL_ROW master_row;
+  
+  if (!mysql_real_query(mysql, "SELECT UNIX_TIMESTAMP()", 23) &&
+      (master_res= mysql_store_result(mysql)) &&
+      (master_row= mysql_fetch_row(master_res)))
   {
-    errmsg= "Could not read the result of \"SELECT UNIX_TIMESTAMP()\" on \
-master"; 
+    mi->clock_diff_with_master= 
+      (long) (time((time_t*) 0) - strtoul(master_row[0], 0, 10));
   }
-  else 
+  else
   {
-    if (!(master_clock_row= mysql_fetch_row(master_clock_res)))
-      errmsg= "Could not read a row from the result of \"SELECT \
-UNIX_TIMESTAMP()\" on master"; 
-    else
-    {
-      slave_clock= time((time_t*) 0);
-      mi->clock_diff_with_master= (long) (slave_clock -
-                                          strtoul(master_clock_row[0], 0, 10));
-      DBUG_PRINT("info",("slave_clock=%lu, master_clock=%s",
-                         slave_clock, master_clock_row[0]));
-    }
-  mysql_free_result(master_clock_res);
+    mi->clock_diff_with_master= 0; /* The "most sensible" value */
+    sql_print_error("Warning: \"SELECT UNIX_TIMESTAMP()\" failed on master, \
+do not trust column Seconds_Behind_Master of SHOW SLAVE STATUS");
+  }
+  if (master_res)
+    mysql_free_result(master_res);      
+ 
+  /*
+    Check that the master's server id and ours are different. Because if they
+    are equal (which can result from a simple copy of master's datadir to slave,
+    thus copying some my.cnf), replication will work but all events will be
+    skipped.
+    Do not die if SHOW VARIABLES LIKE 'SERVER_ID' fails on master (very old
+    master?).
+    Note: we could have put a @@SERVER_ID in the previous SELECT
+    UNIX_TIMESTAMP() instead, but this would not have worked on 3.23 masters.
+  */
+  if (!mysql_real_query(mysql, "SHOW VARIABLES LIKE 'SERVER_ID'", 31) &&
+      (master_res= mysql_store_result(mysql)))
+  {
+    if ((master_row= mysql_fetch_row(master_res)) &&
+        (::server_id == strtoul(master_row[1], 0, 10)) &&
+        !replicate_same_server_id)
+      errmsg= "The slave I/O thread stops because master and slave have equal \
+MySQL server ids; these ids must be different for replication to work (or \
+the --replicate-same-server-id option must be used on slave but this does \
+not always make sense; please check the manual before using it).";
+    mysql_free_result(master_res);
+  }
+
+  /*
+    Check that the master's global character_set_server and ours are the same.
+    Not fatal if query fails (old master?).
+  */
+  if (!mysql_real_query(mysql, "SELECT @@GLOBAL.COLLATION_SERVER", 32) &&
+      (master_res= mysql_store_result(mysql)))
+  {
+    if ((master_row= mysql_fetch_row(master_res)) &&
+        strcmp(master_row[0], global_system_variables.collation_server->name))
+      errmsg= "The slave I/O thread stops because master and slave have \
+different values for the COLLATION_SERVER global variable. The values must \
+be equal for replication to work";
+    mysql_free_result(master_res);
   }
 
+  /* Add a timezones check here */
+
   if (errmsg)
   {
     sql_print_error(errmsg);
     return 1;
   }
+
   return 0;
 }