Don't count NULL values in cardinalty for MyISAM tables.

Free row buffer cache after each query for MyISAM tables.
Added table join option FORCE INDEX
Fixed core dump bug when connecting with hostname that could not be resolved.


include/my_base.h:
  Don't count NULL values in cardinalty
myisam/mi_check.c:
  Don't count NULL values in cardinalty
myisam/mi_extra.c:
  Free row buffer cache after each query
myisam/mi_open.c:
  Avoid realloc if cache size doesn't change
myisam/mi_search.c:
  Don't count NULL values in cardinalty
myisam/myisamdef.h:
  Change buffer length from uint to uint32 to make it more portable/predictable
mysql-test/r/myisam.result:
  Test case for cardinality with NULL keys and FORCE INDEX
mysql-test/t/myisam.test:
  Test case for cardinality with NULL keys and FORCE INDEX
sql/lex.h:
  Added table join option FORCE INDEX
sql/mysql_priv.h:
  Added table join option FORCE INDEX
sql/opt_range.cc:
  Added table join option FORCE INDEX
sql/sql_base.cc:
  Added table join option FORCE INDEX
sql/sql_lex.h:
  Added table join option FORCE INDEX
sql/sql_parse.cc:
  Added table join option FORCE INDEX
  Don't use strlen() on hostname without first checking if it's not NULL
sql/sql_select.cc:
  Added table join option FORCE INDEX
sql/sql_yacc.yy:
  Added table join option FORCE INDEX
sql/table.h:
  Added table join option FORCE INDEX

1 files changed, 37 insertions, 10 deletions

diff --git a/myisam/mi_search.c b/myisam/mi_search.c
index d57fd1bb5b2..41d53e76241 100644
--- a/myisam/mi_search.c
+++ b/myisam/mi_search.c
@@ -260,9 +260,11 @@ int _mi_prefix_search(MI_INFO *info, register MI_KEYDEF *keyinfo, uchar *page,
                       uchar *key, uint key_len, uint nextflag, uchar **ret_pos,
                       uchar *buff, my_bool *last_key)
 {
-  /* my_flag is raw comparison result to be changed according to
-     SEARCH_NO_FIND,SEARCH_LAST and HA_REVERSE_SORT flags.
-     flag is the value returned by _mi_key_cmp and as treated as final */
+  /*
+    my_flag is raw comparison result to be changed according to
+    SEARCH_NO_FIND,SEARCH_LAST and HA_REVERSE_SORT flags.
+    flag is the value returned by _mi_key_cmp and as treated as final
+  */
   int flag=0, my_flag=-1;
   uint nod_flag, length, len, matched, cmplen, kseg_len;
   uint prefix_len,suffix_len;
@@ -695,13 +697,29 @@ static int compare_bin(uchar *a, uint a_length, uchar *b, uint b_length,
 }
 
 
-        /*
-        ** Compare two keys
-        ** Returns <0, 0, >0 acording to which is bigger
-        ** Key_length specifies length of key to use.  Number-keys can't
-        ** be splited
-        ** If flag <> SEARCH_FIND compare also position
-        */
+/*
+  Compare two keys
+
+  SYNOPSIS
+    _mi_key_cmp()
+    keyseg	Key segments of key to compare
+    a		First key to compare, in format from _mi_pack_key()
+		This is normally key specified by user
+    b		Second key to compare.  This is always from a row
+    key_length	Length of key to compare.  This can be shorter than
+		a to just compare sub keys
+    next_flag	How keys should be compared
+		If bit SEARCH_FIND is not set the keys includes the row
+		position and this should also be compared
+
+  NOTES
+    Number-keys can't be splited
+  
+  RETURN VALUES
+    <0	If a < b
+    0	If a == b
+    >0	If a > b
+*/
 
 #define FCMP(A,B) ((int) (A) - (int) (B))
 
@@ -738,6 +756,15 @@ int _mi_key_cmp(register MI_KEYSEG *keyseg, register uchar *a,
       {
         if (nextflag == (SEARCH_FIND | SEARCH_UPDATE))
           nextflag=SEARCH_SAME;                 /* Allow duplicate keys */
+	else if (nextflag & SEARCH_NULL_ARE_NOT_EQUAL)
+	{
+	  /*
+	    This is only used from mi_check() to calculate cardinality.
+	    It can't be used when searching for a key as this would cause
+	    compare of (a,b) and (b,a) to return the same value.
+	  */
+	  return -1;
+	}
         next_key_length=key_length;
         continue;                               /* To next key part */
       }