Check if AND/OR expression can be NULL

Better fix for ALTER TABLE on BDB tables
(Both of the above fixes are already in 4.0)

Docs/manual.texi

@@ -46929,6 +46929,10 @@ not yet 100% confident in this code.
 @appendixsubsec Changes in release 3.23.53
 @itemize @bullet
 @item
+Changed @code{AND/OR} to report that they can return NULL. This fixes a
+small problem in @code{GROUP BY} on @code{AND/OR} expression that return
+@code{NULL}.
+@item
 Fixed a @code{BDB}-related @code{ALTER TABLE} bug with dropping a column
 and shutting down immediately thereafter.
 @item

sql/item_cmpfunc.cc

@@ -1097,6 +1097,8 @@ Item_cond::fix_fields(THD *thd,TABLE_LIST *tables)
     used_tables_cache|=item->used_tables();
     with_sum_func= with_sum_func || item->with_sum_func;
     const_item_cache&=item->const_item();
+    if (item->maybe_null)
+      maybe_null=1;
   }
   if (thd)
     thd->cond_count+=list.elements;

sql/sql_table.cc

@@ -19,6 +19,9 @@
 
 #include "mysql_priv.h"
 #include <hash.h>
+#ifdef HAVE_BERKELEY_DB
+#include <ha_berkeley.h>
+#endif
 #include <myisam.h>
 
 #ifdef __WIN__
@@ -1675,11 +1678,18 @@ int mysql_alter_table(THD *thd,char *new_db, char *new_name,
   VOID(pthread_cond_broadcast(&COND_refresh));
   VOID(pthread_mutex_unlock(&LOCK_open));
 #ifdef HAVE_BERKELEY_DB
-  extern bool berkeley_flush_logs(void);
   if (old_db_type == DB_TYPE_BERKELEY_DB)
   {
-    (void)berkeley_flush_logs();
-    table=open_ltable(thd,table_list,TL_READ);
+    (void) berkeley_flush_logs();
+    /*
+      For the alter table to be properly flushed to the logs, we
+      have to open the new table.  If not, we get a problem on server
+      shutdown.
+    */
+    if (!open_tables(thd, table_list))		// Should always succeed
+    {
+      close_thread_table(thd, &table_list->table);
+    }
   }
 #endif