Fix ORDER BY ... DESC optimization

7 files changed, 355 insertions, 84 deletions

diff --git a/Docs/manual.texi b/Docs/manual.texi
index 998a2e73c0f..3312803f7b6 100644
--- a/Docs/manual.texi
+++ b/Docs/manual.texi
@@ -410,6 +410,7 @@ MySQL Language Reference
 * SET OPTION::                  @code{SET OPTION} syntax
 * SET TRANSACTION::             @code{SET TRANSACTION} syntax
 * GRANT::                       @code{GRANT} and @code{REVOKE} syntax
+* HANDLER::                     @code{HANDLER} syntax
 * CREATE INDEX::                @code{CREATE INDEX} syntax
 * DROP INDEX::                  @code{DROP INDEX} syntax
 * Comments::                    Comment syntax
@@ -664,6 +665,7 @@ Replication in MySQL
 
 MySQL Full-text Search
 
+* Fulltext Search::
 * Fulltext Fine-tuning::        
 * Fulltext Features to Appear in MySQL 4.0::  
 * Fulltext TODO::               
@@ -14139,6 +14141,7 @@ to restart @code{mysqld} with @code{--skip-grant-tables} to run
 * SET OPTION::                  @code{SET OPTION} syntax
 * SET TRANSACTION::             @code{SET TRANSACTION} syntax
 * GRANT::                       @code{GRANT} and @code{REVOKE} syntax
+* HANDLER::                     @code{HANDLER} syntax
 * CREATE INDEX::                @code{CREATE INDEX} syntax
 * DROP INDEX::                  @code{DROP INDEX} syntax
 * Comments::                    Comment syntax
@@ -19410,6 +19413,8 @@ alter_specification:
   or    DROP [COLUMN] col_name
   or    DROP PRIMARY KEY
   or    DROP INDEX index_name
+  or    DISABLE KEYS
+  or    ENABLE KEYS
   or    RENAME [TO] new_tbl_name
   or    ORDER BY col
   or    table_options
@@ -19572,6 +19577,15 @@ indexes are created in a separate batch (like in @code{REPAIR}).
 This should make @code{ALTER TABLE} much faster when you have many indexes.
 
 @item
+Since @strong{MySQL 4.0} this feature could be activated explicitly.
+@code{ALTER TABLE ... DISABLE KEYS} makes @strong{MySQL} to stop updating
+non-unique indexes for @code{MyISAM} table.
+@code{ALTER TABLE ... ENABLE KEYS} then should be used to recreate missing
+indexes. As @strong{MySQL} does it with special algorithm which is much
+faster then inserting keys one by one, disabling keys could give a
+considerable speedup on bulk inserts.
+
+@item
 @findex mysql_info()
 With the C API function @code{mysql_info()}, you can find out how many
 records were copied, and (when @code{IGNORE} is used) how many records were
@@ -21880,6 +21894,9 @@ differ somewhat:
 | delayed_queue_size      | 1000                      |
 | flush                   | OFF                       |
 | flush_time              | 0                         |
+| ft_min_word_len         | 4                         |
+| ft_max_word_len         | 254                       |
+| ft_max_word_len_for_sort| 20                        |
 | have_bdb                | YES                       |
 | have_gemini             | NO                        |
 | have_innodb             | YES                       |
@@ -22063,6 +22080,31 @@ tables will be closed (to free up resources and sync things to disk). We
 only recommend this option on Win95, Win98, or on systems where you have
 very little resources.
 
+@item @code{ft_min_word_len}
+The minimum length of the word to be included in a @code{FULLTEXT} index.
+@strong{Note: @code{FULLTEXT} index have to be rebuilt (e.g. with
+@code{OPTIMIZE TABLE}) after changing this variable.}
+
+@item @code{ft_max_word_len}
+The maximum length of the word to be included in a @code{FULLTEXT} index.
+@strong{Note: @code{FULLTEXT} index have to be rebuilt after changing
+this variable.}
+
+@item @code{ft_max_word_len_sort}
+The maximum length of the word in a @code{FULLTEXT} index
+to be used in fast index recreation method in
+@code{REPAIR}, @code{CREATE INDEX}, @code{OPTIMIZE TABLE}, or
+@code{ALTER TABLE}.  Longer words are inserted the slow way.
+The rule of the thumb is as follows: with @code{ft_max_word_len_sort}
+increasing, @strong{MySQL} will create bigger temporary files
+(thus slowing the process down, due to disk I/O), and will put
+fewer keys in one sort block (againg, decreasing the efficiency).
+When @code{ft_max_word_len_sort} is too small, instead,
+@strong{MySQL} will insert a lot of words into index the slow way -
+but short words will be inserted very fast. It applies only to
+index recreation during @code{REPAIR}, @code{CREATE INDEX},
+@code{OPTIMIZE TABLE}, or @code{ALTER TABLE}.
+
 @item @code{have_bdb}
 @code{YES} if @code{mysqld} supports Berkeley DB tables. @code{DISABLED}
 if @code{--skip-bdb} is used.
@@ -23156,7 +23198,7 @@ You can set the default isolation level for @code{mysqld} with
 
 @findex GRANT
 @findex REVOKE
-@node GRANT, CREATE INDEX, SET TRANSACTION, Reference
+@node GRANT, HANDLER, SET TRANSACTION, Reference
 @section @code{GRANT} and @code{REVOKE} Syntax
 
 @example
@@ -23386,11 +23428,52 @@ dropped only with explicit @code{REVOKE} commands or by manipulating the
 @strong{MySQL} grant tables.
 @end itemize
 
+@findex HANDLER
+@node HANDLER, CREATE INDEX, GRANT, Reference
+@section @code{HANDLER} Syntax
+
+@example
+HANDLER table OPEN [ AS alias ]
+HANDLER table READ index @{ = | >= | <= | < @} (value1, value2, ... )  [ WHERE ... ] [LIMIT ... ]
+HANDLER table READ index @{ FIRST | NEXT | PREV | LAST @} [ WHERE ... ] [LIMIT ... ]
+HANDLER table READ @{ FIRST | NEXT @}  [ WHERE ... ] [LIMIT ... ]
+HANDLER table CLOSE
+@end example
+
+The @code{HANDLER} statement provides direct access to @strong{MySQL} table
+interface, bypassing SQL optimizer. Thus, it is faster then SELECT.
+
+The first form of @code{HANDLER} statement opens a table, making
+in accessible via the following @code{HANDLER ... READ} routines.
+
+The second form fetches one (or, specified by @code{LIMIT} clause) row
+where the index specified complies to the condition and @code{WHERE}
+condition is met. If the index consists of several parts (spans over
+several columns) the values are specified in comma-separated list,
+providing values only for few first columns is possible.
+
+The third form fetches one (or, specified by @code{LIMIT} clause) row
+from the table in index order, matching @code{WHERE} condition.
+
+The fourth form (without index specification) fetches one (or, specified
+by @code{LIMIT} clause) row from the table in natural row order (as stored
+in data file) matching @code{WHERE} condition. It is faster than
+@code{HANDLER table READ index} when full table scan is desired.
+
+The last form closes the table, opened with @code{HANDLER ... OPEN}.
+
+@code{HANDLER} is somewhat low-level statement, for example it does not
+provide consistency. That is @code{HANDLER ... OPEN} does @strong{not}
+takes a snapshot of the table, and does @strong{not} locks the table. The
+above means,  that after @code{HANDLER ... OPEN} table data can be
+modified (by this or other thread) and these modifications may appear only
+partially in @code{HANDLER ... NEXT} or @code{HANDLER ... PREV} scans.
+
 @cindex indexes
 @cindex indexes, multi-part
 @cindex multi-part index
 @findex CREATE INDEX
-@node CREATE INDEX, DROP INDEX, GRANT, Reference
+@node CREATE INDEX, DROP INDEX, HANDLER, Reference
 @section @code{CREATE INDEX} Syntax
 
 @example
@@ -30809,13 +30892,10 @@ unless you know what you are doing!
 @itemize
 
 @item
-Minimal length of word to be indexed is defined in
-@code{myisam/ftdefs.h} file by the line
-@example
-#define MIN_WORD_LEN 4
-@end example
-Change it to the value you prefer, recompile @strong{MySQL}, and rebuild
-your @code{FULLTEXT} indexes.
+Minimal length of word to be indexed is defined by @strong{MySQL}
+variable @code{ft_min_word_length}. @xref{SHOW VARIABLES}.
+Change it to the value you prefer, and rebuild
+your @code{FULLTEXT} indexes (e.g. with @code{OPTIMIZE TABLE}).
 
 @item
 The stopword list is defined in @code{myisam/ft_static.c}
@@ -30881,9 +30961,6 @@ index operations (querying/dumping/statistics).
 @itemize @bullet
 @item Make all operations with @code{FULLTEXT} index @strong{faster}.
 @item Support for braces @code{()} in boolean full-text search.
-@item Phrase search, proximity operators
-@item Boolean search can work without @code{FULLTEXT} index
-(yes, @strong{very} slow).
 @item Support for "always-index words". They could be any strings
 the user wants to treat as words, examples are "C++", "AS/400", "TCP/IP", etc.
 @item Support for full-text search in @code{MERGE} tables.
@@ -32543,8 +32620,12 @@ Execute a @code{FLUSH TABLES} statement or the shell command @code{mysqladmin
 flush-tables}.
 @end enumerate
 
-This procedure will be built into @code{LOAD DATA INFILE} in some future
-version of @strong{MySQL}.
+Since @strong{MySQL 4.0} you can also use
+@code{ALTER TABLE tbl_name DISABLE KEYS} instead of
+@code{myisamchk --keys-used=0 -rq /path/to/db/tbl_name} and
+@code{ALTER TABLE tbl_name ENABLE KEYS} instead of
+@code{myisamchk -r -q /path/to/db/tbl_name}. This way you can also skip
+@code{FLUSH TABLES} steps.
 @item
 You can speed up insertions by locking your tables:
 
@@ -46004,6 +46085,8 @@ Responsible for @strong{MySQL} configure.
 Full-text search.
 @item
 Added keys to the @code{MERGE} library.
+@item
+@code{HANDLER} command.
 @end itemize
 
 @item Jeremy Cole
@@ -46344,6 +46427,11 @@ Our TODO section contains what we plan to have in 4.0. @xref{TODO MySQL 4.0}.
 
 @itemize @bullet
 @item
+Added @code{ALTER TABLE table_name DISABLE KEYS} and
+      @code{ALTER TABLE table_name ENABLE KEYS} commands.
+@item
+@code{LOAD DATA FROM MASTER} "auto-magically" sets up a slave.
+@item
 Renamed @code{safe_mysqld} to @code{mysqld_safe}.
 @item
 Allow one to use @code{IN} instead of @code{FROM} in @code{SHOW} commands.
@@ -46471,6 +46559,9 @@ not yet 100% confident in this code.
 @appendixsubsec Changes in release 3.23.40
 @itemize @bullet
 @item
+Added option @code{--warnings} to @code{mysqld}. Now @code{mysqld}
+only prints the error @code{Aborted connection} if this option is used.
+@item
 Fixed parser to allow floats of type @code{1.0e1} (no sign after @code{e}).
 @item
 Option @code{--force} to @code{myisamchk} now also updates states.
@@ -51899,6 +51990,8 @@ Multiple result sets.
 Change the protocol to allow binary transfer of values. To do this
 efficiently, we need to add an API to allow binding of variables.
 @item
+Add @code{PREPARE} of statements and sending of parameters to @code{mysqld}.
+@item
 Make it possible to specify @code{long_query_time} with a granularity
 in microseconds.
 @item
diff --git a/mysql-test/r/order_by.result b/mysql-test/r/order_by.result
index 5c9e20c35a3..a47fc950f0e 100644
--- a/mysql-test/r/order_by.result
+++ b/mysql-test/r/order_by.result
@@ -112,58 +112,118 @@ member_id	nickname	voornaam
 1		
 2		
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	index	NULL	a	20	NULL	10	Using index
+t1	range	a	a	20	NULL	2	where used; Using index
 a	b	c
-1	NULL	NULL
 1	NULL	b
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	range	a	a	4	NULL	10	where used; Using index
+a	b	c
+2	3	c
+2	2	b
+2	2	a
+2	1	b
+2	1	a
+1	3	b
+1	1	b
+1	1	b
+1	1	NULL
+1	NULL	b
+1	NULL	NULL
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ref	a	a	4	const	5	where used; Using index; Using filesort
+a	b	c
+1	3	b
 1	1	NULL
 1	1	b
 1	1	b
-2	0	a
-2	0	b
+1	NULL	NULL
+1	NULL	b
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ref	a	a	9	const,const	2	where used; Using index; Using filesort
+a	b	c
+1	NULL	NULL
+1	NULL	b
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	range	a	a	9	NULL	8	where used; Using index; Using filesort
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	range	a	a	9	NULL	5	where used; Using index
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ref	a	a	9	const,const	1	where used; Using index; Using filesort
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	range	a	a	9	NULL	6	where used; Using index
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	range	a	a	9	NULL	5	where used; Using index
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	range	a	a	9	NULL	2	where used; Using index; Using filesort
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	index	NULL	a	18	NULL	11	Using index
+a	b	c
+1	0	
+1	0	b
+1	1	
+1	1	b
+1	1	b
+1	3	b
 2	1	a
 2	1	b
-2	1	c
+2	2	a
+2	2	b
+2	3	c
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	index	NULL	a	20	NULL	10	Using index
+t1	index	NULL	a	18	NULL	11	Using index
 a	b	c
-2	1	c
+2	3	c
+2	2	b
+2	2	a
 2	1	b
 2	1	a
-2	0	b
-2	0	a
+1	3	b
 1	1	b
 1	1	b
-1	1	NULL
-1	NULL	b
-1	NULL	NULL
+1	1	
+1	0	b
+1	0	
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	range	a	a	20	NULL	2	where used; Using index
+t1	range	a	a	18	NULL	3	where used; Using index
 a	b	c
 1	1	b
 1	1	b
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	range	a	a	4	NULL	5	where used; Using index
+t1	range	a	a	4	NULL	6	where used; Using index
 a	b	c
 1	1	b
 1	1	b
-1	1	NULL
+1	1	
+1	0	b
+1	0	
+count(*)
+9
+a	b	c
+2	3	c
+2	2	b
+2	2	a
+2	1	b
+2	1	a
+1	3	b
+1	1	b
+1	1	b
+1	1	
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	range	a	a	9	NULL	7	where used; Using index
+t1	range	a	a	8	NULL	10	where used; Using index
 a	b	c
-2	1	c
 2	1	b
 2	1	a
-2	0	b
-2	0	a
 1	1	b
 1	1	b
-1	1	NULL
+1	1	
+1	0	b
+1	0	
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t1	range	a	a	4	NULL	4	where used; Using index
+t1	range	a	a	4	NULL	5	where used; Using index
 a	b	c
+1	3	b
 1	1	b
 1	1	b
-1	1	NULL
-1	NULL	b
-1	NULL	NULL
+1	1	
+1	0	b
+1	0	
diff --git a/mysql-test/t/order_by.test b/mysql-test/t/order_by.test
index 7d1c6346aa1..08d26413761 100644
--- a/mysql-test/t/order_by.test
+++ b/mysql-test/t/order_by.test
@@ -168,8 +168,8 @@ drop table t1,t2,t3;
 
 #bug reported by Wouter de Jong
 
-drop table if exists members;
-CREATE TABLE members (
+drop table if exists t1;
+CREATE TABLE t1 (
   member_id int(11) NOT NULL auto_increment,
   inschrijf_datum varchar(20) NOT NULL default '',
   lastchange_datum varchar(20) NOT NULL default '',
@@ -200,24 +200,51 @@ CREATE TABLE members (
   PRIMARY KEY  (member_id)
 ) TYPE=MyISAM PACK_KEYS=1;
 
-insert into members (member_id) values (1),(2),(3);
-select member_id, nickname, voornaam FROM members
+insert into t1 (member_id) values (1),(2),(3);
+select member_id, nickname, voornaam FROM t1
 ORDER by lastchange_datum DESC LIMIT 2;
-drop table members;
+drop table t1;
 
+#
+# Test optimization of ORDER BY DESC
+#
 
 create table t1 (a int not null, b int, c varchar(10), key (a, b, c));
-insert into t1 values (1, NULL, NULL), (1, NULL, 'b'), (1, 1, NULL), (1, 1, 'b'), (1, 1, 'b'), (2, 0, 'a'), (2, 0, 'b'), (2, 1, 'a'), (2, 1, 'b'), (2, 1, 'c');
+insert into t1 values (1, NULL, NULL), (1, NULL, 'b'), (1, 1, NULL), (1, 1, 'b'), (1, 1, 'b'), (2, 1, 'a'), (2, 1, 'b'), (2, 2, 'a'), (2, 2, 'b'), (2, 3, 'c'),(1,3,'b');
+
+explain select * from t1 where (a = 1 and b is null and c = 'b') or (a > 2) order by a desc;
+select * from t1 where (a = 1 and b is null and c = 'b') or (a > 2) order by a desc;
+explain select * from t1 where a >= 1 and a < 3 order by a desc;
+select * from t1 where a >= 1 and a < 3 order by a desc;
+explain select * from t1 where a = 1 order by a desc, b desc;
+select * from t1 where a = 1 order by a desc, b desc;
+explain select * from t1 where a = 1 and b is null order by a desc, b desc;
+select * from t1 where a = 1 and b is null order by a desc, b desc;
+explain select * from t1 where a >= 1 and a < 3 and b >0 order by a desc,b desc;
+explain select * from t1 where a = 2 and b >0 order by a desc,b desc;
+explain select * from t1 where a = 2 and b is null order by a desc,b desc;
+explain select * from t1 where a = 2 and (b is null or b > 0) order by a
+desc,b desc;
+explain select * from t1 where a = 2 and b > 0 order by a desc,b desc;
+explain select * from t1 where a = 2 and b < 2 order by a desc,b desc;
+
+#
+# Test things when we don't have NULL keys
+#
+
+alter table t1 modify b int not null, modify c varchar(10) not null;
 explain select * from t1 order by a, b, c;
 select * from t1 order by a, b, c;
 explain select * from t1 order by a desc, b desc, c desc;
 select * from t1 order by a desc, b desc, c desc;
 # test multiple ranges, NO_MAX_RANGE and EQ_RANGE
-explain select * from t1 where (a = 1 and b is null and c = 'b') or (a > 2) order by a desc;
+explain select * from t1 where (a = 1 and b = 1 and c = 'b') or (a > 2) order by a desc;
 select * from t1 where (a = 1 and b = 1 and c = 'b') or (a > 2) order by a desc;
 # test NEAR_MAX, NO_MIN_RANGE
 explain select * from t1 where a < 2 and b <= 1 order by a desc, b desc;
 select * from t1 where a < 2 and b <= 1 order by a desc, b desc;
+select count(*) from t1 where a < 5 and b > 0;
+select * from t1 where a < 5 and b > 0 order by a desc,b desc;
 # test HA_READ_AFTER_KEY (at the end of the file), NEAR_MIN
 explain select * from t1 where a between 1 and 3 and b <= 1 order by a desc, b desc;
 select * from t1 where a between 1 and 3 and b <= 1 order by a desc, b desc;
@@ -226,4 +253,4 @@ explain select * from t1 where a between 0 and 1 order by a desc, b desc;
 select * from t1 where a between 0 and 1 order by a desc, b desc;
 drop table t1;
 
-/* vim:set ft=sql sw=2 noet: */
+
diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index cd7c8196c4d..0b3ac27d1f6 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -382,7 +382,7 @@ SQL_SELECT::~SQL_SELECT()
 #undef index					// Fix for Unixware 7
 
 QUICK_SELECT::QUICK_SELECT(TABLE *table,uint key_nr,bool no_alloc)
-  :error(0),index(key_nr),max_used_key_length(0),head(table),
+  :dont_free(0),error(0),index(key_nr),max_used_key_length(0),head(table),
    it(ranges),range(0)
 {
   if (!no_alloc)
@@ -399,8 +399,11 @@ QUICK_SELECT::QUICK_SELECT(TABLE *table,uint key_nr,bool no_alloc)
 
 QUICK_SELECT::~QUICK_SELECT()
 {
-  file->index_end();
-  free_root(&alloc,MYF(0));
+  if (!dont_free)
+  {
+    file->index_end();
+    free_root(&alloc,MYF(0));
+  }
 }
 
 int QUICK_SELECT::init()
@@ -2516,6 +2519,7 @@ int QUICK_SELECT::cmp_next(QUICK_RANGE *range)
   return (range->flag & NEAR_MAX) ? 1 : 0;		// Exact match
 }
 
+
 /*
  * This is a hack: we inherit from QUICK_SELECT so that we can use the
  * get_next() interface, but we have to hold a pointer to the original
@@ -2525,29 +2529,44 @@ int QUICK_SELECT::cmp_next(QUICK_RANGE *range)
  * which handle the ranges and implement the get_next() function.  But
  * for now, this seems to work right at least.
  */
-QUICK_SELECT_DESC::QUICK_SELECT_DESC(QUICK_SELECT *q)
-  : QUICK_SELECT(*q), quick(q), rev_it(rev_ranges)
+
+QUICK_SELECT_DESC::QUICK_SELECT_DESC(QUICK_SELECT *q, uint used_key_parts)
+  : QUICK_SELECT(*q), rev_it(rev_ranges)
 {
   bool not_read_after_key = file->option_flag() & HA_NOT_READ_AFTER_KEY;
   for (QUICK_RANGE *r = it++; r; r = it++)
   {
     rev_ranges.push_front(r);
-    if (not_read_after_key && range_reads_after_key(r))
+    if (not_read_after_key && range_reads_after_key(r) ||
+	test_if_null_range(r,used_key_parts))
     {
+      it.rewind();				// Reset range
       error = HA_ERR_UNSUPPORTED;
-      break;
+      dont_free=1;				// Don't free memory from 'q'
+      return;
     }
   }
+  /* Remove EQ_RANGE flag for keys that are not using the full key */
+  for (QUICK_RANGE *r = rev_it++; r; r = rev_it++)
+  {
+    if ((r->flag & EQ_RANGE) &&
+	head->key_info[index].key_length != r->max_length)
+      r->flag&= ~EQ_RANGE;
+  }
+  rev_it.rewind();
+  q->dont_free=1;				// Don't free shared mem
+  delete q;
 }
 
+
 int QUICK_SELECT_DESC::get_next()
 {
   DBUG_ENTER("QUICK_SELECT_DESC::get_next");
 
   /* The max key is handled as follows:
    *   - if there is NO_MAX_RANGE, start at the end and move backwards
-   *   - if it is an EQ_RANGE and max key covers the entire key, go directly
-   *     to the key and read through it (sorting backwards is
+   *   - if it is an EQ_RANGE, which means that max key covers the entire
+   *     key, go directly to the key and read through it (sorting backwards is
    *     same as sorting forwards)
    *   - if it is NEAR_MAX, go to the key or next, step back once, and
    *     move backwards
@@ -2560,9 +2579,9 @@ int QUICK_SELECT_DESC::get_next()
     int result;
     if (range)
     {						// Already read through key
-      result = ((range->flag & EQ_RANGE) ?
-		file->index_next_same(record, (byte*) range->min_key,
-				      range->min_length) :
+      result = ((range->flag & EQ_RANGE)
+		? file->index_next_same(record, (byte*) range->min_key,
+					range->min_length) :
 		file->index_prev(record));
       if (!result)
       {
@@ -2587,8 +2606,7 @@ int QUICK_SELECT_DESC::get_next()
       continue;
     }
 
-    if (range->flag & EQ_RANGE &&
-	head->key_info[index].key_length == range->max_length)
+    if (range->flag & EQ_RANGE)
     {
       result = file->index_read(record, (byte*) range->max_key,
 				range->max_length, HA_READ_KEY_EXACT);
@@ -2598,9 +2616,10 @@ int QUICK_SELECT_DESC::get_next()
       dbug_assert(range->flag & NEAR_MAX || range_reads_after_key(range));
       /* Note: even if max_key is only a prefix, HA_READ_AFTER_KEY will
        * do the right thing - go past all keys which match the prefix */
-      file->index_read(record, (byte*) range->max_key, range->max_length,
-		       ((range->flag & NEAR_MAX) ?
-			HA_READ_KEY_OR_PREV : HA_READ_AFTER_KEY));
+      result=file->index_read(record, (byte*) range->max_key,
+			      range->max_length,
+			      ((range->flag & NEAR_MAX) ?
+			       HA_READ_KEY_EXACT : HA_READ_AFTER_KEY));
       result = file->index_prev(record);
     }
     if (result)
@@ -2629,7 +2648,7 @@ int QUICK_SELECT_DESC::cmp_prev(QUICK_RANGE *range)
   if (range->flag & NO_MIN_RANGE)
     return (0);					/* key can't be to small */
 
-  KEY_PART *key_part = quick->key_parts;
+  KEY_PART *key_part = key_parts;
   for (char *key = range->min_key, *end = key + range->min_length;
        key < end;
        key += key_part++->part_length)
@@ -2659,15 +2678,64 @@ int QUICK_SELECT_DESC::cmp_prev(QUICK_RANGE *range)
 
 /*
  * True if this range will require using HA_READ_AFTER_KEY
+   See comment in get_next() about this
  */
+
 bool QUICK_SELECT_DESC::range_reads_after_key(QUICK_RANGE *range)
 {
-  // See comment in get_next()
-  return range->flag & (NO_MAX_RANGE | NEAR_MAX) ? 1 :
-    (range->flag & EQ_RANGE &&
-     head->key_info[index].key_length == range->max_length) ? 0 : 1;
+  return ((range->flag & (NO_MAX_RANGE | NEAR_MAX)) ||
+	  !(range->flag & EQ_RANGE) ||
+	  head->key_info[index].key_length != range->max_length) ? 1 : 0;
 }
 
+/* True if we are reading over a key that may have a NULL value */
+
+bool QUICK_SELECT_DESC::test_if_null_range(QUICK_RANGE *range,
+					   uint used_key_parts)
+{
+  uint offset,end;
+  KEY_PART *key_part = key_parts,
+           *key_part_end= key_part+used_key_parts;
+
+  for (offset= 0,  end = min(range->min_length, range->max_length) ;
+       offset < end && key_part != key_part_end ;
+       offset += key_part++->part_length)
+  {
+    uint null_length=test(key_part->null_bit);
+    if (!memcmp((char*) range->min_key+offset, (char*) range->max_key+offset,
+		key_part->part_length + null_length))
+    {
+      offset+=null_length;
+      continue;
+    }
+    if (null_length && range->min_key[offset])
+      return 1;				// min_key is null and max_key isn't
+    // Range doesn't cover NULL. This is ok if there is no more null parts
+    break;
+  }
+  /*
+    If the next min_range is > NULL, then we can use this, even if
+    it's a NULL key
+    Example:  SELECT * FROM t1 WHERE a = 2 AND b >0 ORDER BY a DESC,b DESC;
+
+  */
+  if (key_part != key_part_end && key_part->null_bit)
+  {
+    if (offset >= range->min_length || range->min_key[offset])
+      return 1;					// Could be null
+    key_part++;
+  }
+  /*
+    If any of the key parts used in the ORDER BY could be NULL, we can't
+    use the key to sort the data.
+  */
+  for (; key_part != key_part_end ; key_part++)
+    if (key_part->null_bit)
+      return 1;					// Covers null part
+  return 0;
+}
+
+
 /*****************************************************************************
 ** Print a quick range for debugging
 ** TODO:
diff --git a/sql/opt_range.h b/sql/opt_range.h
index 0c8dcf7fed3..50215b94be0 100644
--- a/sql/opt_range.h
+++ b/sql/opt_range.h
@@ -54,9 +54,10 @@ class QUICK_RANGE :public Sql_alloc {
     {}
 };
 
+
 class QUICK_SELECT {
 public:
-  bool next;
+  bool next,dont_free;
   int error;
   uint index,max_used_key_length;
   TABLE *head;
@@ -80,16 +81,17 @@ public:
   bool unique_key_range();
 };
 
+
 class QUICK_SELECT_DESC: public QUICK_SELECT
 {
 public:
-  QUICK_SELECT_DESC(QUICK_SELECT *q);
+  QUICK_SELECT_DESC(QUICK_SELECT *q, uint used_key_parts);
   int get_next();
 private:
   int cmp_prev(QUICK_RANGE *range);
   bool range_reads_after_key(QUICK_RANGE *range);
-
-  QUICK_SELECT *quick;
+  bool test_if_null_range(QUICK_RANGE *range, uint used_key_parts);
+  void reset(void) { next=0; rev_it.rewind(); }
   List<QUICK_RANGE> rev_ranges;
   List_iterator<QUICK_RANGE> rev_it;
 };
diff --git a/sql/sql_delete.cc b/sql/sql_delete.cc
index b690ef4b327..d69d1cf9cfd 100644
--- a/sql/sql_delete.cc
+++ b/sql/sql_delete.cc
@@ -290,11 +290,7 @@ int mysql_delete(THD *thd,
 ** delete multiple tables from join 
 ***************************************************************************/
 
-#ifndef DBUG_OFF
-#define MEM_STRIP_BUF_SIZE 2048
-#else
-#define MEM_STRIP_BUF_SIZE sortbuffer_size
-#endif
+#define MEM_STRIP_BUF_SIZE sortbuff_size
 
 #ifndef SINISAS_STRIP
 int refposcmp2(void* arg, const void *a,const void *b)
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 6a5d3fede15..5cdc1104a46 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -5153,9 +5153,11 @@ part_of_refkey(TABLE *table,Field *field)
 ** Returns: 1 if key is ok.
 **	    0 if key can't be used
 **	    -1 if reverse key can be used
+**          used_key_parts is set to key parts used if length != 0
 *****************************************************************************/
 
-static int test_if_order_by_key(ORDER *order, TABLE *table, uint idx)
+static int test_if_order_by_key(ORDER *order, TABLE *table, uint idx,
+				uint *used_key_parts)
 {
   KEY_PART_INFO *key_part,*key_part_end;
   key_part=table->key_info[idx].key_part;
@@ -5187,6 +5189,7 @@ static int test_if_order_by_key(ORDER *order, TABLE *table, uint idx)
     reverse=flag;				// Remember if reverse
     key_part++;
   }
+  *used_key_parts= (uint) (key_part - table->key_info[idx].key_part);
   return reverse;
 }
 
@@ -5249,16 +5252,37 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
   if (ref_key >= 0)
   {
     int order_direction;
+    uint used_key_parts;
     /* Check if we get the rows in requested sorted order by using the key */
     if ((usable_keys & ((key_map) 1 << ref_key)) &&
-	(order_direction = test_if_order_by_key(order,table,ref_key)))
+	(order_direction = test_if_order_by_key(order,table,ref_key,
+						&used_key_parts)))
     {
-      if (order_direction == -1 && select && select->quick)
+      if (order_direction == -1)
       {
-	// ORDER BY ref_key DESC
-	select->quick = new QUICK_SELECT_DESC(select->quick);
-	if (select->quick->error)
+	if (select && select->quick)
+	{
+	  // ORDER BY ref_key DESC
+	  QUICK_SELECT_DESC *tmp=new QUICK_SELECT_DESC(select->quick,
+						       used_key_parts);
+	  if (!tmp || tmp->error)
+	  {
+	    delete tmp;
+	    DBUG_RETURN(0);		// Reverse sort not supported
+	  }
+	  select->quick=tmp;
+	  DBUG_RETURN(1);
+	}
+	if (tab->ref.key_parts < used_key_parts)
+	{
+	  /*
+	    SELECT * FROM t1 WHERE a=1 ORDER BY a DESC,b DESC
+	    TODO:
+	    Add a new traversal function to read last matching row and
+	    traverse backwards.
+	  */
 	  DBUG_RETURN(0);
+	}
       }
       DBUG_RETURN(1);			/* No need to sort */
     }
@@ -5280,10 +5304,11 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
 
     for (nr=0; keys ; keys>>=1, nr++)
     {
+      uint not_used;
       if (keys & 1)
       {
 	int flag;
-	if ((flag=test_if_order_by_key(order,table,nr)))
+	if ((flag=test_if_order_by_key(order, table, nr, &not_used)))
 	{
 	  if (!no_changes)
 	  {