WL#3984 (Revise locking of mysql.general_log and mysql.slow_log)

Bug#25422 (Hang with log tables)
Bug 17876 (Truncating mysql.slow_log in a SP after using cursor locks the
          thread)
Bug 23044 (Warnings on flush of a log table)
Bug 29129 (Resetting general_log while the GLOBAL READ LOCK is set causes
           a deadlock)

Prior to this fix, the server would hang when performing concurrent
ALTER TABLE or TRUNCATE TABLE statements against the LOG TABLES,
which are mysql.general_log and mysql.slow_log.

The root cause traces to the following code:
in sql_base.cc, open_table()
  if (table->in_use != thd)
  {
    /* wait_for_condition will unlock LOCK_open for us */
    wait_for_condition(thd, &LOCK_open, &COND_refresh);
  }
The problem with this code is that the current implementation of the
LOGGER creates 'fake' THD objects, like
- Log_to_csv_event_handler::general_log_thd
- Log_to_csv_event_handler::slow_log_thd
which are not associated to a real thread running in the server,
so that waiting for these non-existing threads to release table locks
cause the dead lock.

In general, the design of Log_to_csv_event_handler does not fit into the
general architecture of the server, so that the concept of general_log_thd
and slow_log_thd has to be abandoned:
- this implementation does not work with table locking
- it will not work with commands like SHOW PROCESSLIST
- having the log tables always opened does not integrate well with DDL
operations / FLUSH TABLES / SET GLOBAL READ_ONLY

With this patch, the fundamental design of the LOGGER has been changed to:
- always open and close a log table when writing a log
- remove totally the usage of fake THD objects
- clarify how locking of log tables is implemented in general.

See WL#3984 for details related to the new locking design.

Additional changes (misc bugs exposed and fixed):

1)

mysqldump which would ignore some tables in dump_all_tables_in_db(),
 but forget to ignore the same in dump_all_views_in_db().

2)

mysqldump would also issue an empty "LOCK TABLE" command when all the tables
to lock are to be ignored (numrows == 0), instead of not issuing the query.

3)

Internal errors handlers could intercept errors but not warnings
(see sql_error.cc).

4)

Implementing a nested call to open tables, for the performance schema tables,
exposed an existing bug in remove_table_from_cache(), which would perform:
  in_use->some_tables_deleted=1;
against another thread, without any consideration about thread locking.
This call inside remove_table_from_cache() was not required anyway,
since calling mysql_lock_abort() takes care of aborting -- cleanly -- threads
that might hold a lock on a table.
This line (in_use->some_tables_deleted=1) has been removed.


sql/handler.cc:
  Moved logic for system / log tables in the SQL layer.
sql/handler.h:
  Moved logic for system / log tables in the SQL layer.
sql/lock.cc:
  Revised locking of log tables
sql/log.cc:
  Major cleanup: changed how log tables are locked / written to.
sql/log.h:
  Major cleanup: changed how log tables are locked / written to.
sql/mysql_priv.h:
  performance schema helpers
sql/slave.cc:
  open_ltable() lock flags
sql/sp.cc:
  open_ltable() lock flags
sql/sql_acl.cc:
  open_ltable() lock flags
sql/sql_class.h:
  performance schema helpers
sql/sql_delete.cc:
  log tables cleanup in TRUNCATE
sql/sql_error.cc:
  Internal handlers can also intercept warnings
sql/sql_insert.cc:
  open_ltable() lock flags
sql/sql_parse.cc:
  performance schema helpers
sql/sql_plugin.cc:
  open_ltable() lock flags
sql/sql_rename.cc:
  log tables cleanup in RENAME
sql/sql_servers.cc:
  open_ltable() lock flags
sql/sql_show.cc:
  Move INFORMATION_SCHEMA_NAME to table.cc
sql/sql_table.cc:
  log tables cleanup (admin operations, ALTER TABLE)
sql/sql_udf.cc:
  open_ltable() lock flags
sql/table.cc:
  Implemented TABLE_CATEGORY.
sql/share/errmsg.txt:
  Changed the wording and name of ER_CANT_READ_LOCK_LOG_TABLE
sql/table.h:
  Implemented TABLE_CATEGORY.
storage/csv/ha_tina.cc:
  Moved logic for system / log tables in the SQL layer.
storage/csv/ha_tina.h:
  Moved logic for system / log tables in the SQL layer.
storage/myisam/ha_myisam.cc:
  Moved logic for system / log tables in the SQL layer.
storage/myisam/ha_myisam.h:
  Moved logic for system / log tables in the SQL layer.
client/mysqldump.c:
  Don't lock tables in the ignore list.
  Don't issue empty LOCK TABLES queries.
sql/sql_base.cc:
  log tables cleanup
  performance schema helpers
mysql-test/r/ps.result:
  Adjust test results
mysql-test/r/show_check.result:
  Adjust test results
mysql-test/r/status.result:
  Adjust test results
mysql-test/t/log_state.test:
  Added tests for Bug#29129
mysql-test/t/ps.test:
  Make the test output deterministic
mysql-test/t/show_check.test:
  Make the test output deterministic
mysql-test/r/log_state.result:
  Changed the default location of the log output to LOG_FILE,
  for backward compatibility with MySQL 5.0
  ---
  Adjust test results
mysql-test/r/log_tables.result:
  cleanup for -ps-protocol
mysql-test/t/log_tables.test:
  cleanup for -ps-protocol
sql/set_var.cc:
  Changed the default location of the log output to LOG_FILE,
  for backward compatibility with MySQL 5.0
  ---
  log tables cleanup

client/mysqldump.c

@@ -3726,11 +3726,12 @@ static int dump_all_tables_in_db(char *database)
   {
     DYNAMIC_STRING query;
     init_dynamic_string_checked(&query, "LOCK TABLES ", 256, 1024);
-    for (numrows= 0 ; (table= getTableName(1)) ; numrows++)
+    for (numrows= 0 ; (table= getTableName(1)) ; )
     {
       char *end= strmov(afterdot, table);
       if (include_table(hash_key,end - hash_key))
       {
+        numrows++;
         dynstr_append_checked(&query, quote_name(table, table_buff, 1));
         dynstr_append_checked(&query, " READ /*!32311 LOCAL */,");
       }
@@ -3804,6 +3805,11 @@ static my_bool dump_all_views_in_db(char *database)
   char *table;
   uint numrows;
   char table_buff[NAME_LEN*2+3];
+  char hash_key[2*NAME_LEN+2];  /* "db.tablename" */
+  char *afterdot;
+
+  afterdot= strmov(hash_key, database);
+  *afterdot++= '.';
 
   if (init_dumping(database, init_dumping_views))
     return 1;
@@ -3813,10 +3819,15 @@ static my_bool dump_all_views_in_db(char *database)
   {
     DYNAMIC_STRING query;
     init_dynamic_string_checked(&query, "LOCK TABLES ", 256, 1024);
-    for (numrows= 0 ; (table= getTableName(1)); numrows++)
+    for (numrows= 0 ; (table= getTableName(1)); )
     {
-      dynstr_append_checked(&query, quote_name(table, table_buff, 1));
-      dynstr_append_checked(&query, " READ /*!32311 LOCAL */,");
+      char *end= strmov(afterdot, table);
+      if (include_table(hash_key,end - hash_key))
+      {
+        numrows++;
+        dynstr_append_checked(&query, quote_name(table, table_buff, 1));
+        dynstr_append_checked(&query, " READ /*!32311 LOCAL */,");
+      }
     }
     if (numrows && mysql_real_query(mysql, query.str, query.length-1))
       DB_error(mysql, "when using LOCK TABLES");
@@ -3830,7 +3841,11 @@ static my_bool dump_all_views_in_db(char *database)
            /* We shall continue here, if --force was given */
   }
   while ((table= getTableName(0)))
-     get_view_structure(table, database);
+  {
+    char *end= strmov(afterdot, table);
+    if (include_table(hash_key, end - hash_key))
+      get_view_structure(table, database);
+  }
   if (opt_xml)
   {
     fputs("</database>\n", md_result_file);