Added tests if a user variable is changed in the same query.

Docs/manual.texi:
  Updated info about some common problems.
mysql-test/r/user_var.result:
  Added tests of using user variables.
mysql-test/t/user_var.test:
  Added tests of using user variables.

Docs/manual.texi

@@ -597,7 +597,7 @@ Replication in MySQL
 * Replication Options::         Replication Options in my.cnf
 * Replication SQL::             SQL Commands related to replication
 * Replication FAQ::             Frequently Asked Questions about replication
-* Troubleshooting Replication:: Troubleshooting Replication.  Troubleshooting Replication.  Troubleshooting Replication.  Troubleshooting Replication.
+* Replication Problems::        Troubleshooting Replication.
 
 Getting Maximum Performance from MySQL
 
@@ -23616,9 +23616,24 @@ Change to not use page locks at all when we are scanning tables.
 @node BDB errors,  , BDB TODO, BDB
 @subsection Errors You May Get When Using BDB Tables
 
+@itemize @bullet
+@item
+If you get the following error in the @code{hostname.err log} when
+starting @code{mysqld}:
+
+@example
+bdb:  Ignoring log file: .../log.XXXXXXXXXX: unsupported log version #}
+@end example
+it means that the new @code{BDB} version doesn't support the old log
+file format.  In this case you have to delete all @code{BDB} log BDB
+from your database directory (the files that has the format
+@code{log.XXXXXXXXXX} ) and restart @code{mysqld}.  We would also
+recommend you to do a @code{mysqldump --opt} of your old @code{BDB}
+tables, delete the old table and restore the dump.
+@item
 If you are running in not @code{auto_commit} mode and delete a table you
-are using you may get the following error messages in the @strong{MySQL}
-error file:
+are using by another thread you may get the following error messages in
+the @strong{MySQL} error file:
 
 @example
 001119 23:43:56  bdb:  Missing log fileid entry
@@ -23628,6 +23643,7 @@ error file:
 This is not fatal but we don't recommend that you delete tables if you are
 not in @code{auto_commit} mode, until this problem is fixed (the fix is
 not trivial).
+@end itemize
 
 @cindex tables, @code{GEMINI}
 @node GEMINI, INNOBASE, BDB, Table types
@@ -26676,7 +26692,7 @@ tables}.
 * Replication Options::         Replication Options in my.cnf
 * Replication SQL::             SQL Commands related to replication
 * Replication FAQ::             Frequently Asked Questions about replication
-* Troubleshooting Replication:: Troubleshooting Replication.  Troubleshooting Replication.  Troubleshooting Replication.  Troubleshooting Replication.
+* Replication Problems::	Troubleshooting Replication.
 @end menu
 
 @node Replication Intro, Replication Implementation, Replication, Replication
@@ -26884,7 +26900,7 @@ Replication will be done correctly with @code{AUTO_INCREMENT},
 @code{LAST_INSERT_ID}, and @code{TIMESTAMP} values.
 @item
 @code{RAND()} in updates does not replicate properly. Use
- @code{RAND(some_non_rand_expr)} if you are replcating updates with
+@code{RAND(some_non_rand_expr)} if you are replcating updates with
 @code{RAND()}. You can, for example, use @code{UNIX_TIMESTAMP()} for the
 argument to @code{RAND()}.
 @item
@@ -26894,6 +26910,14 @@ propagation. @code{LOAD LOCAL DATA INFILE} will be skipped.
 @item
 Update queries that use user variables are not replication-safe (yet).
 @item
+@code{FLUSH} commands are not stored in the binary log and are because
+of this not replicated to the slaves. This is not normally a problem as
+@code{FLUSH} doesn't change anything. This does however mean that if you
+update the @code{MySQL} privilege tables directly without using
+@code{GRANT} statement and you replicate the @code{MySQL} privilege
+database, you must do a @code{FLUSH PRIVILEGES} on your slaves to put
+the new privileges into effect.
+@item
 Temporary tables starting in 3.23.29 are replicated properly with the
 exception of the case when you shut down slave server ( not just slave thread),
 you have some temporary tables open, and the are used in subsequent updates.
@@ -27240,7 +27264,7 @@ last log on the list), backup all the logs you are about to delete
 
 @end multitable
 
-@node Replication FAQ, Troubleshooting Replication, Replication SQL, Replication
+@node Replication FAQ, Replication Problems, Replication SQL, Replication
 @section Replication FAQ
 
 @cindex @code{Binlog_Dump}
@@ -27493,7 +27517,7 @@ We are currently working on intergrating an automatic master election
 system into @strong{MySQL}, but until it is ready, you will have to
 create your own monitoring tools.
 
-@node Troubleshooting Replication,  , Replication FAQ, Replication
+@node Replication Problems,  , Replication FAQ, Replication
 @section Troubleshooting Replication
 
 If you have followed the instructions, and your replication setup is not

mysql-test/r/user_var.result

@@ -6,3 +6,11 @@ i
 i	@vv1:=if(sv1.i,1,0)	@vv2:=if(sv2.i,1,0)	@vv3:=if(sv3.i,1,0)	@vv1+@vv2+@vv3
 1	1	0	1	2
 2	1	0	0	1
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ref	i	i	4	const	1	where used
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ALL	NULL	NULL	NULL	NULL	3	where used
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	index	NULL	i	4	NULL	3	where used; Using index
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ref	i	i	4	const	1	where used

mysql-test/t/user_var.test

@@ -12,4 +12,8 @@ create table t2 (i int not null, unique (i));
 insert into t2 select distinct i from t1;
 select * from t2; 
 select distinct t2.i,@vv1:=if(sv1.i,1,0),@vv2:=if(sv2.i,1,0),@vv3:=if(sv3.i,1,0), @vv1+@vv2+@vv3 from t2 left join t1 as sv1 on sv1.i=t2.i and sv1.v=1 left join t1 as sv2 on sv2.i=t2.i and sv2.v=2 left join t1 as sv3 on sv3.i=t2.i and sv3.v=3;
+explain select * from t1 where i=@vv1;
+explain select * from t1 where @vv1:=@vv1+1 and i=@vv1;
+explain select @vv1:=i from t1 where i=@vv1;
+explain select * from t1 where i=@vv1;
 drop table t1,t2;

sql/item_func.cc

@@ -1606,6 +1606,7 @@ static user_var_entry *get_variable(HASH *hash, LEX_STRING &name,
     entry->name.length=name.length;
     entry->value=0;
     entry->length=0;
+    entry->update_query_id=0;
     entry->type=STRING_RESULT;
     memcpy(entry->name.str, name.str, name.length+1);
     if (hash_insert(hash,(byte*) entry))
@@ -1625,6 +1626,7 @@ bool Item_func_set_user_var::fix_fields(THD *thd,TABLE_LIST *tables)
   if (Item_func::fix_fields(thd,tables) ||
       !(entry= get_variable(&thd->user_vars, name, 1)))
     return 1;
+  entry->update_query_id=thd->query_id;
   return 0;
 }
 
@@ -1809,10 +1811,12 @@ longlong Item_func_get_user_var::val_int()
 
 void Item_func_get_user_var::fix_length_and_dec()
 {
+  THD *thd=current_thd;
   maybe_null=1;
   decimals=NOT_FIXED_DEC;
   max_length=MAX_BLOB_WIDTH;
-  entry= get_variable(&current_thd->user_vars, name, 0);
+  if ((entry= get_variable(&thd->user_vars, name, 0)))
+    const_var_flag= thd->query_id != entry->update_query_id;
 }
 
 

sql/item_func.h

@@ -825,9 +825,11 @@ class Item_func_get_user_var :public Item_func
 {
   LEX_STRING name;
   user_var_entry *entry;
+  bool const_var_flag;
 
 public:
-  Item_func_get_user_var(LEX_STRING a): Item_func(), name(a) {}
+  Item_func_get_user_var(LEX_STRING a):
+    Item_func(), name(a), const_var_flag(1) {}
   user_var_entry *get_entry();
   double val();
   longlong val_int();
@@ -835,8 +837,9 @@ class Item_func_get_user_var :public Item_func
   void fix_length_and_dec();
   enum Item_result result_type() const;
   const char *func_name() const { return "get_user_var"; }
-  bool const_item() const { return 0; }
-  table_map used_tables() const { return RAND_TABLE_BIT; }
+  bool const_item() const { return const_var_flag; }
+  table_map used_tables() const
+  { return const_var_flag ? 0 : RAND_TABLE_BIT; }
 };
 
 class Item_func_inet_aton : public Item_int_func

sql/sql_class.h

@@ -550,7 +550,7 @@ class user_var_entry
  public:
   LEX_STRING name;
   char *value;
-  ulong length;
+  ulong length, update_query_id;
   Item_result type;
 };