Merge DS-MRR/CPK improvements into 5.3-main

16 files changed, 2058 insertions, 272 deletions

diff --git a/sql/CMakeLists.txt b/sql/CMakeLists.txt
index 4d2088e52f0..f81afa6b27b 100755..100644
--- a/sql/CMakeLists.txt
+++ b/sql/CMakeLists.txt
@@ -59,6 +59,7 @@ SET (SQL_SOURCE
                sql_cache.cc sql_class.cc sql_client.cc sql_crypt.cc sql_crypt.h 
                sql_cursor.cc sql_db.cc sql_delete.cc sql_derived.cc sql_do.cc 
                sql_error.cc sql_handler.cc sql_help.cc sql_insert.cc
+               sql_lifo_buffer.h
                sql_join_cache.h sql_join_cache.cc
                sql_lex.cc sql_list.cc sql_load.cc sql_manager.cc
                sql_map.cc sql_parse.cc  sql_partition.cc sql_plugin.cc
diff --git a/sql/Makefile.am b/sql/Makefile.am
index 07499050146..afbef9ca197 100644
--- a/sql/Makefile.am
+++ b/sql/Makefile.am
@@ -66,6 +66,7 @@ noinst_HEADERS =	item.h item_func.h item_sum.h item_cmpfunc.h \
 			log.h log_slow.h sql_show.h rpl_rli.h rpl_mi.h \
 			sql_select.h structs.h table.h sql_udf.h hash_filo.h \
 			lex.h lex_symbol.h sql_acl.h sql_crypt.h  \
+                        sql_lifo_buffer.h \
 			sql_repl.h slave.h rpl_filter.h rpl_injector.h \
 			log_event.h rpl_record.h \
 			log_event_old.h rpl_record_old.h \
diff --git a/sql/filesort.cc b/sql/filesort.cc
index aa808a5e6b5..1ee3972c4fd 100644
--- a/sql/filesort.cc
+++ b/sql/filesort.cc
@@ -543,11 +543,6 @@ static ha_rows find_all_keys(SORTPARAM *param, SQL_SELECT *select,
 		    current_thd->variables.read_buff_size);
   }
 
-  if (quick_select)
-  {
-    if (select->quick->reset())
-      DBUG_RETURN(HA_POS_ERROR);
-  }
 
   /* Remember original bitmaps */
   save_read_set=  sort_form->read_set;
@@ -561,9 +556,19 @@ static ha_rows find_all_keys(SORTPARAM *param, SQL_SELECT *select,
   if (select && select->cond)
     select->cond->walk(&Item::register_field_in_read_map, 1,
                        (uchar*) sort_form);
+  if (select && select->pre_idx_push_select_cond)
+    select->pre_idx_push_select_cond->walk(&Item::register_field_in_read_map,
+                                           1, (uchar*) sort_form);
   sort_form->column_bitmaps_set(&sort_form->tmp_set, &sort_form->tmp_set, 
                                 &sort_form->tmp_set);
 
+
+  if (quick_select)
+  {
+    if (select->quick->reset())
+      DBUG_RETURN(HA_POS_ERROR);
+  }
+
   for (;;)
   {
     if (quick_select)
diff --git a/sql/handler.h b/sql/handler.h
index 4346ccf97cc..cf92c117935 100644
--- a/sql/handler.h
+++ b/sql/handler.h
@@ -1157,6 +1157,23 @@ typedef void *range_seq_t;
 typedef struct st_range_seq_if
 {
   /*
+    Get key information
+ 
+    SYNOPSIS
+      get_key_info()
+        init_params  The seq_init_param parameter 
+        length       OUT length of the keys in this range sequence
+        map          OUT key_part_map of the keys in this range sequence
+
+    DESCRIPTION
+      This function is set only when using HA_MRR_FIXED_KEY mode. In that mode, 
+      all ranges are single-point equality ranges that use the same set of key
+      parts. This function allows the MRR implementation to get the length of
+      a key, and which keyparts it uses.
+  */
+  void (*get_key_info)(void *init_params, uint *length, key_part_map *map);
+
+  /*
     Initialize the traversal of range sequence
     
     SYNOPSIS
@@ -1285,9 +1302,9 @@ void get_sweep_read_cost(TABLE *table, ha_rows nrows, bool interrupted,
                          COST_VECT *cost);
 
 /*
-  The below two are not used (and not handled) in this milestone of this WL
-  entry because there seems to be no use for them at this stage of
-  implementation.
+  Indicates that all scanned ranges will be singlepoint (aka equality) ranges.
+  The ranges may not use the full key but all of them will use the same number
+  of key parts.
 */
 #define HA_MRR_SINGLE_POINT 1
 #define HA_MRR_FIXED_KEY  2
@@ -1329,6 +1346,16 @@ void get_sweep_read_cost(TABLE *table, ha_rows nrows, bool interrupted,
 */
 #define HA_MRR_NO_NULL_ENDPOINTS 128
 
+/*
+  The MRR user has materialized range keys somewhere in the user's buffer.
+  This can be used for optimization of the procedure that sorts these keys
+  since in this case key values don't have to be copied into the MRR buffer.
+
+  In other words, it is guaranteed that after RANGE_SEQ_IF::next() call the 
+  pointer in range->start_key.key will point to a key value that will remain 
+  there until the end of the MRR scan.
+*/
+#define HA_MRR_MATERIALIZED_KEYS 256
 
 
 /*
@@ -1819,14 +1846,19 @@ public:
   inline int ha_index_first(uchar * buf);
   inline int ha_index_last(uchar * buf);
   inline int ha_index_next_same(uchar *buf, const uchar *key, uint keylen);
+  /*
+    TODO: should we make for those functions non-virtual ha_func_name wrappers,
+    too?
+  */
   virtual ha_rows multi_range_read_info_const(uint keyno, RANGE_SEQ_IF *seq,
                                               void *seq_init_param, 
                                               uint n_ranges, uint *bufsz,
                                               uint *flags, COST_VECT *cost);
   virtual ha_rows multi_range_read_info(uint keyno, uint n_ranges, uint keys,
-                                        uint *bufsz, uint *flags, COST_VECT *cost);
+                                        uint key_parts, uint *bufsz, 
+                                        uint *flags, COST_VECT *cost);
   virtual int multi_range_read_init(RANGE_SEQ_IF *seq, void *seq_init_param,
-                                    uint n_ranges, uint mode,
+                                    uint n_ranges, uint mode, 
                                     HANDLER_BUFFER *buf);
   virtual int multi_range_read_next(char **range_info);
   virtual int read_range_first(const key_range *start_key,
@@ -2185,7 +2217,8 @@ public:
       TRUE    if the engine supports virtual columns
   */
   virtual bool check_if_supported_virtual_columns(void) { return FALSE;}
-
+  
+  TABLE* get_table() { return table; }
 protected:
   /* deprecated, don't use in new engines */
   inline void ha_statistic_increment(ulong SSV::*offset) const { }
@@ -2378,7 +2411,6 @@ private:
   virtual int rename_partitions(const char *path)
   { return HA_ERR_WRONG_COMMAND; }
   friend class ha_partition;
-  friend class DsMrr_impl;
 public:
   /* XXX to be removed, see ha_partition::partition_ht() */
   virtual handlerton *partition_ht() const
diff --git a/sql/key.cc b/sql/key.cc
index a1793e9e5f4..1d27fdcf208 100644
--- a/sql/key.cc
+++ b/sql/key.cc
@@ -567,3 +567,54 @@ next_loop:
   } while (key_info); /* no more keys to test */
   DBUG_RETURN(0);
 }
+
+
+/*
+  Compare two key tuples.
+
+  @brief
+    Compare two key tuples, i.e. two key values in KeyTupleFormat.
+
+  @param part          KEY_PART_INFO with key description
+  @param key1          First key to compare
+  @param key2          Second key to compare 
+  @param tuple_length  Length of key1 (and key2, they are the same) in bytes.
+
+  @return
+    @retval  0  key1 == key2
+    @retval -1  key1 < key2
+    @retval +1  key1 > key2 
+*/
+
+int key_tuple_cmp(KEY_PART_INFO *part, uchar *key1, uchar *key2, 
+                  uint tuple_length)
+{
+  uchar *key1_end= key1 + tuple_length;
+  int len;
+  int res;
+  LINT_INIT(len);
+  for (;key1 < key1_end; key1 += len, key2 += len, part++)
+  {
+    len= part->store_length;
+    if (part->null_bit)
+    {
+      if (*key1) // key1 == NULL
+      {
+        if (!*key2) // key1(NULL) < key2(notNULL)
+          return -1;
+        continue;
+      }
+      else if (*key2) // key1(notNULL) > key2 (NULL)
+        return 1;
+      /* Step over the NULL bytes for key_cmp() call */
+      key1++;
+      key2++;
+      len--;
+    }
+    if ((res= part->field->key_cmp(key1, key2)))
+      return res;
+  }
+  return 0;
+}
+
+
diff --git a/sql/multi_range_read.cc b/sql/multi_range_read.cc
index 70fcbd605e6..321298fafa1 100644
--- a/sql/multi_range_read.cc
+++ b/sql/multi_range_read.cc
@@ -1,4 +1,5 @@
 #include "mysql_priv.h"
+#include <my_bit.h>
 #include "sql_select.h"
 
 /****************************************************************************
@@ -136,10 +137,16 @@ handler::multi_range_read_info_const(uint keyno, RANGE_SEQ_IF *seq,
 */
 
 ha_rows handler::multi_range_read_info(uint keyno, uint n_ranges, uint n_rows,
-                                       uint *bufsz, uint *flags, COST_VECT *cost)
+                                       uint key_parts, uint *bufsz, 
+                                       uint *flags, COST_VECT *cost)
 {
-  *bufsz= 0; /* Default implementation doesn't need a buffer */
+  /* 
+    Currently we expect this function to be called only in preparation of scan
+    with HA_MRR_SINGLE_POINT property.
+  */
+  DBUG_ASSERT(*flags | HA_MRR_SINGLE_POINT);
 
+  *bufsz= 0; /* Default implementation doesn't need a buffer */
   *flags |= HA_MRR_USE_DEFAULT_IMPL;
 
   cost->zero();
@@ -207,7 +214,6 @@ handler::multi_range_read_init(RANGE_SEQ_IF *seq_funcs, void *seq_init_param,
   DBUG_RETURN(0);
 }
 
-
 /**
   Get next record in MRR scan
 
@@ -277,7 +283,455 @@ scan_it_again:
 }
 
 /****************************************************************************
- * DS-MRR implementation 
+ * Mrr_*_reader classes (building blocks for DS-MRR)
+ ***************************************************************************/
+
+int Mrr_simple_index_reader::init(handler *h_arg, RANGE_SEQ_IF *seq_funcs, 
+                                  void *seq_init_param, uint n_ranges,
+                                  uint mode,  Key_parameters *key_par_arg,
+                                  Lifo_buffer *key_buffer_arg,
+                                  Buffer_manager *buf_manager_arg)
+{
+  HANDLER_BUFFER no_buffer = {NULL, NULL, NULL};
+  file= h_arg;
+  return file->handler::multi_range_read_init(seq_funcs, seq_init_param,
+                                              n_ranges, mode, &no_buffer);
+}
+
+
+int Mrr_simple_index_reader::get_next(char **range_info)
+{
+  int res;
+  while (!(res= file->handler::multi_range_read_next(range_info)))
+  {
+    KEY_MULTI_RANGE *curr_range= &file->handler::mrr_cur_range;
+    if (!file->mrr_funcs.skip_index_tuple ||
+        !file->mrr_funcs.skip_index_tuple(file->mrr_iter, curr_range->ptr))
+      break;
+  }
+  return res;
+}
+
+
+/**
+  @brief Get next index record
+
+  @param range_info  OUT identifier of range that the returned record belongs to
+  
+  @note
+    We actually iterate over nested sequences:
+    - an ordered sequence of groups of identical keys
+      - each key group has key value, which has multiple matching records 
+        - thus, each record matches all members of the key group
+
+  @retval 0                   OK, next record was successfully read
+  @retval HA_ERR_END_OF_FILE  End of records
+  @retval Other               Some other error
+*/
+
+int Mrr_ordered_index_reader::get_next(char **range_info)
+{
+  int res;
+  DBUG_ENTER("Mrr_ordered_index_reader::get_next");
+  
+  for(;;)
+  {
+    if (!scanning_key_val_iter)
+    {
+      while ((res= kv_it.init(this)))
+      {
+        if ((res != HA_ERR_KEY_NOT_FOUND && res != HA_ERR_END_OF_FILE))
+          DBUG_RETURN(res); /* Some fatal error */
+        
+        if (key_buffer->is_empty())
+        {
+          DBUG_RETURN(HA_ERR_END_OF_FILE);
+        }
+      }
+      scanning_key_val_iter= TRUE;
+    }
+
+    if ((res= kv_it.get_next()))
+    {
+      scanning_key_val_iter= FALSE;
+      if ((res != HA_ERR_KEY_NOT_FOUND && res != HA_ERR_END_OF_FILE))
+        DBUG_RETURN(res);
+      kv_it.move_to_next_key_value();
+      continue;
+    }
+    char *range_info;
+    memcpy(&range_info, cur_range_info, sizeof(char*));
+    if (!skip_index_tuple(range_info) &&
+        !skip_record(range_info, NULL))
+    {
+      break;
+    }
+    /* Go get another (record, range_id) combination */
+  } /* while */
+
+  memcpy(range_info, cur_range_info, sizeof(void*));
+  DBUG_RETURN(0);
+}
+
+void Mrr_ordered_index_reader::set_temp_space(uchar *space)
+{
+  //saved_key_tuple= space;
+  saved_rowid= space;
+  have_saved_rowid= FALSE;
+}
+
+void Mrr_ordered_index_reader::interrupt_read()
+{
+  /*
+  key_copy(saved_key_tuple, file->get_table()->record[0], 
+           &file->get_table()->key_info[file->active_index],
+           keypar.key_tuple_length);
+  */
+  /* Save the last rowid */
+  memcpy(saved_rowid, file->ref, file->ref_length);
+  have_saved_rowid= TRUE;
+}
+
+void Mrr_ordered_index_reader::position()
+{
+  if (have_saved_rowid)
+    memcpy(file->ref, saved_rowid, file->ref_length);
+  else
+    Mrr_index_reader::position();
+}
+
+void Mrr_ordered_index_reader::resume_read()
+{
+  /*
+  key_restore(file->get_table()->record[0], saved_key_tuple, 
+              &file->get_table()->key_info[file->active_index],
+              keypar.key_tuple_length);
+  */
+}
+
+
+/**
+  Fill the buffer with (lookup_tuple, range_id) pairs and sort
+*/
+
+int Mrr_ordered_index_reader::refill_buffer(bool initial)
+{
+  KEY_MULTI_RANGE cur_range;
+  uchar **range_info_ptr= (uchar**)&cur_range.ptr;
+  uchar *key_ptr;
+  DBUG_ENTER("Mrr_ordered_index_reader::refill_buffer");
+
+  DBUG_ASSERT(key_buffer->is_empty());
+
+  if (source_exhausted)
+    DBUG_RETURN(HA_ERR_END_OF_FILE);
+
+  //if (know_key_tuple_params)
+  {
+    buf_manager->reset_buffer_sizes(buf_manager->arg);
+    key_buffer->reset();
+    key_buffer->setup_writing(&key_ptr, keypar.key_size_in_keybuf,
+                              is_mrr_assoc? (uchar**)&range_info_ptr : NULL,
+                              sizeof(uchar*));
+  }
+
+  while (key_buffer->can_write() && 
+         !(source_exhausted= (bool)mrr_funcs.next(mrr_iter, &cur_range)))
+  {
+    DBUG_ASSERT(cur_range.range_flag & EQ_RANGE);
+
+    /* Put key, or {key, range_id} pair into the buffer */
+    key_ptr= (keypar.use_key_pointers)? (uchar*)&cur_range.start_key.key : 
+                                        (uchar*)cur_range.start_key.key;
+
+    key_buffer->write();
+  }
+  
+  /* Force get_next() to start with kv_it.init() call: */
+  scanning_key_val_iter= FALSE;
+
+  if (source_exhausted && key_buffer->is_empty())
+    DBUG_RETURN(HA_ERR_END_OF_FILE);
+
+  key_buffer->sort((key_buffer->type() == Lifo_buffer::FORWARD)? 
+                     (qsort2_cmp)Mrr_ordered_index_reader::compare_keys_reverse : 
+                     (qsort2_cmp)Mrr_ordered_index_reader::compare_keys, 
+                   this);
+  DBUG_RETURN(0);
+}
+
+
+int Mrr_ordered_index_reader::init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
+                                   void *seq_init_param, uint n_ranges,
+                                   uint mode, Key_parameters *key_par_arg,
+                                   Lifo_buffer *key_buffer_arg,
+                                   Buffer_manager *buf_manager_arg)
+{
+  file= h_arg;
+  key_buffer= key_buffer_arg;
+  buf_manager= buf_manager_arg;
+  keypar= *key_par_arg;
+
+  KEY *key_info= &file->get_table()->key_info[file->active_index];
+  keypar.index_ranges_unique= test(key_info->flags & HA_NOSAME && 
+                                   key_info->key_parts == 
+                                   my_count_bits(keypar.key_tuple_map));
+
+  mrr_iter= seq_funcs->init(seq_init_param, n_ranges, mode);
+  is_mrr_assoc=    !test(mode & HA_MRR_NO_ASSOCIATION);
+  mrr_funcs= *seq_funcs;
+  source_exhausted= FALSE;
+  /*
+    Short: don't do identical key handling when we have a pushed index
+    condition.
+
+    Long: In order to check pushed index condition, we need to have both 
+    index tuple table->record[0] and range_id.
+    
+    Key_value_records_iterator has special handling for case when we have
+    multiple (key_value, range_id) pairs with the same key_value. In that 
+    case it will make an index lookup only for the first such element, 
+    for subsequent elements it will only return the new range_id.
+
+    The problem here is that file->table->record[0] is shared with the part
+    that does full record retrieval with rnd_pos() calls, and if we have the
+    following scenario:
+
+     1. We scan ranges {(key_value, range_id1), (key_value, range_id2)}
+     2. Iterator makes a lookup with key_value, produces the (index_tuple,
+        range_id1) pair. Index tuple is read into table->record[0], which
+        allows us to check index condition.
+     3. At this point, we figure that key buffer is full, so we sort it,
+        and return control to Mrr_ordered_rndpos_reader.
+     3.1 Mrr_ordered_rndpos_reader gets rowids and makes rnd_pos() calls, which
+         puts some arbitrary data into table->record[0] in the process.
+     3.2 We ask the iterator for the next (rowid, range_id) pair. The iterator
+         puts in range_id2, and that shuld be sufficient (this is identical key
+         handling at work)
+         However, index tuple in table->record[0] has been destroyed and we 
+         can't check index conditon for (index_tuple, range_id2) now.
+
+    TODO: It is possible to support identical key handling and index condition
+    pushdown, working together (one possible solution is to save/restore the 
+    contents of table->record[0]). We will probably implement that.
+
+  */
+  disallow_identical_key_handling= test(mrr_funcs.skip_index_tuple);
+  /*bzero(saved_key_tuple, keypar.key_tuple_length);*/
+  have_saved_rowid= FALSE;
+  return 0;
+}
+
+
+static int rowid_cmp_reverse(void *file, uchar *a, uchar *b)
+{
+  return - ((handler*)file)->cmp_ref(a, b);
+}
+
+
+int Mrr_ordered_rndpos_reader::init(handler *h_arg, 
+                                    Mrr_index_reader *index_reader_arg,
+                                    uint mode,
+                                    Lifo_buffer *buf)
+{
+  file= h_arg;
+  index_reader= index_reader_arg;
+  rowid_buffer= buf;
+  is_mrr_assoc= !test(mode & HA_MRR_NO_ASSOCIATION);
+  index_reader_exhausted= FALSE;
+  index_reader_needs_refill= TRUE;
+  return 0;
+}
+
+
+/**
+  DS-MRR: Fill and sort the rowid buffer
+
+  Scan the MRR ranges and collect ROWIDs (or {ROWID, range_id} pairs) into 
+  buffer. When the buffer is full or scan is completed, sort the buffer by 
+  rowid and return.
+
+  When this function returns, either rowid buffer is not empty, or the source
+  of lookup keys (i.e. ranges) is exhaused.
+  
+  @retval 0      OK, the next portion of rowids is in the buffer,
+                 properly ordered
+  @retval other  Error
+*/
+
+int Mrr_ordered_rndpos_reader::refill_buffer(bool initial)
+{
+  int res;
+  DBUG_ENTER("Mrr_ordered_rndpos_reader::refill_buffer");
+
+  if (index_reader_exhausted)
+    DBUG_RETURN(HA_ERR_END_OF_FILE);
+
+  while (initial || index_reader_needs_refill || 
+         (res= refill_from_index_reader()) == HA_ERR_END_OF_FILE)
+  {
+    if ((res= index_reader->refill_buffer(initial)))
+    {
+      if (res == HA_ERR_END_OF_FILE)
+        index_reader_exhausted= TRUE;
+      break;
+    }
+    initial= FALSE;
+    index_reader_needs_refill= FALSE;
+  }
+  DBUG_RETURN(res);
+}
+
+
+void Mrr_index_reader::position()
+{
+  file->position(file->get_table()->record[0]);
+}
+
+
+/* 
+  @brief Try to refill the rowid buffer without calling
+  index_reader->refill_buffer(). 
+*/
+
+int Mrr_ordered_rndpos_reader::refill_from_index_reader()
+{
+  char *range_info;
+  uchar **range_info_ptr= (uchar**)&range_info;
+  int res;
+  DBUG_ENTER("Mrr_ordered_rndpos_reader::refill_from_index_reader");
+
+  DBUG_ASSERT(rowid_buffer->is_empty());
+  index_rowid= index_reader->get_rowid_ptr();
+  rowid_buffer->reset();
+  rowid_buffer->setup_writing(&index_rowid, file->ref_length,
+                              is_mrr_assoc? (uchar**)&range_info_ptr: NULL,
+                              sizeof(void*));
+
+  last_identical_rowid= NULL;
+
+  index_reader->resume_read();
+  while (rowid_buffer->can_write())
+  {
+    res= index_reader->get_next(&range_info);
+
+    if (res)
+    {
+      if (res != HA_ERR_END_OF_FILE)
+        DBUG_RETURN(res);
+      index_reader_needs_refill=TRUE;
+      break;
+    }
+
+    index_reader->position();
+
+    /* Put rowid, or {rowid, range_id} pair into the buffer */
+    rowid_buffer->write();
+  }
+   
+  index_reader->interrupt_read();
+  /* Sort the buffer contents by rowid */
+  rowid_buffer->sort((qsort2_cmp)rowid_cmp_reverse, (void*)file);
+
+  rowid_buffer->setup_reading(&rowid, file->ref_length,
+                              is_mrr_assoc? (uchar**)&rowids_range_id: NULL,
+                              sizeof(void*));
+  DBUG_RETURN(rowid_buffer->is_empty()? HA_ERR_END_OF_FILE : 0);
+}
+
+
+/*
+  Get the next {record, range_id} using ordered array of rowid+range_id pairs
+
+  @note
+    Since we have sorted rowids, we try not to make multiple rnd_pos() calls
+    with the same rowid value.
+*/
+
+int Mrr_ordered_rndpos_reader::get_next(char **range_info)
+{
+  int res;
+  
+  /* 
+    First, check if rowid buffer has elements with the same rowid value as
+    the previous.
+  */
+  while (last_identical_rowid)
+  {
+    /*
+      Current record (the one we've returned in previous call) was obtained
+      from a rowid that matched multiple range_ids. Return this record again,
+      with next matching range_id.
+    */
+    (void)rowid_buffer->read();
+
+    if (rowid == last_identical_rowid)
+      last_identical_rowid= NULL; /* reached the last of identical rowids */
+
+    if (!is_mrr_assoc)
+      return 0;
+
+    memcpy(range_info, rowids_range_id, sizeof(uchar*));
+    if (!index_reader->skip_record((char*)*range_info, rowid))
+      return 0;
+  }
+  
+  /* 
+     Ok, last_identical_rowid==NULL, it's time to read next different rowid
+     value and get record for it.
+  */
+  for(;;)
+  {
+    /* Return eof if there are no rowids in the buffer after re-fill attempt */
+    if (rowid_buffer->read())
+      return HA_ERR_END_OF_FILE;
+
+    if (is_mrr_assoc)
+    {
+      memcpy(range_info, rowids_range_id, sizeof(uchar*));
+
+      if (index_reader->skip_record(*range_info, rowid))
+        continue;
+    }
+
+    res= file->ha_rnd_pos(file->get_table()->record[0], rowid);
+
+    if (res == HA_ERR_RECORD_DELETED)
+    {
+      /* not likely to get this code with current storage engines, but still */
+      continue;
+    }
+
+    if (res)
+      return res; /* Some fatal error */
+
+    break; /* Got another record */
+  }
+
+  /* 
+    Check if subsequent buffer elements have the same rowid value as this
+    one. If yes, remember this fact so that we don't make any more rnd_pos()
+    calls with this value.
+  */
+  uchar *cur_rowid= rowid;
+  /* 
+    Note: this implies that SQL layer doesn't touch table->record[0]
+    between calls.
+  */
+  Lifo_buffer_iterator it;
+  it.init(rowid_buffer);
+  while (!it.read()) // reads to (rowid, ...)
+  {
+    if (file->cmp_ref(rowid, cur_rowid))
+      break;
+    last_identical_rowid= rowid;
+  }
+  return 0;
+}
+
+
+/****************************************************************************
+ * Top-level DS-MRR implementation functions (the ones called by storage engine)
  ***************************************************************************/
 
 /**
@@ -286,7 +740,7 @@ scan_it_again:
   Initialize and start the MRR scan. Depending on the mode parameter, this
   may use default or DS-MRR implementation.
 
-  @param h               Table handler to be used
+  @param h_arg           Table handler to be used
   @param key             Index to be used
   @param seq_funcs       Interval sequence enumeration functions
   @param seq_init_param  Interval sequence enumeration parameter
@@ -302,279 +756,563 @@ int DsMrr_impl::dsmrr_init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
                            void *seq_init_param, uint n_ranges, uint mode,
                            HANDLER_BUFFER *buf)
 {
-  uint elem_size;
-  Item *pushed_cond= NULL;
-  handler *new_h2= 0;
+  THD *thd= current_thd;
+  int res;
+  Key_parameters keypar;
+  uint key_buff_elem_size;
+  handler *h_idx;
+  Mrr_ordered_rndpos_reader *disk_strategy= NULL;
+  bool do_sort_keys= FALSE;
   DBUG_ENTER("DsMrr_impl::dsmrr_init");
 
   /*
     index_merge may invoke a scan on an object for which dsmrr_info[_const]
     has not been called, so set the owner handler here as well.
   */
-  h= h_arg;
-  if (mode & HA_MRR_USE_DEFAULT_IMPL || mode & HA_MRR_SORTED)
+  primary_file= h_arg;
+  is_mrr_assoc=    !test(mode & HA_MRR_NO_ASSOCIATION);
+
+  strategy_exhausted= FALSE;
+  
+  /* By default, have do-nothing buffer manager */
+  buf_manager.arg= this;
+  buf_manager.reset_buffer_sizes= do_nothing;
+  buf_manager.redistribute_buffer_space= do_nothing;
+
+  if (mode & (HA_MRR_USE_DEFAULT_IMPL | HA_MRR_SORTED))
+    goto use_default_impl;
+  
+  /*
+    Determine whether we'll need to do key sorting and/or rnd_pos() scan
+  */
+  index_strategy= NULL;
+  if ((mode & HA_MRR_SINGLE_POINT) &&
+      optimizer_flag(thd, OPTIMIZER_SWITCH_MRR_SORT_KEYS))
   {
-    use_default_impl= TRUE;
-    const int retval=
-      h->handler::multi_range_read_init(seq_funcs, seq_init_param,
-                                        n_ranges, mode, buf);
-    DBUG_RETURN(retval);
+    do_sort_keys= TRUE;
+    index_strategy= &reader_factory.ordered_index_reader;
   }
-  rowids_buf= buf->buffer;
+  else
+    index_strategy= &reader_factory.simple_index_reader;
 
-  is_mrr_assoc= !test(mode & HA_MRR_NO_ASSOCIATION);
+  strategy= index_strategy;
+  /*
+    We don't need a rowid-to-rndpos step if
+     - We're doing a scan on clustered primary key
+     - [In the future] We're doing an index_only read
+  */
+  DBUG_ASSERT(primary_file->inited == handler::INDEX || 
+              (primary_file->inited == handler::RND && 
+               secondary_file && 
+               secondary_file->inited == handler::INDEX));
+
+  h_idx= (primary_file->inited == handler::INDEX)? primary_file: secondary_file;
+  keyno= h_idx->active_index;
+
+  if (!(keyno == table->s->primary_key && h_idx->primary_key_is_clustered()))
+  {
+    strategy= disk_strategy= &reader_factory.ordered_rndpos_reader;
+  }
 
   if (is_mrr_assoc)
-    status_var_increment(table->in_use->status_var.ha_multi_range_read_init_count);
- 
-  rowids_buf_end= buf->buffer_end;
-  elem_size= h->ref_length + (int)is_mrr_assoc * sizeof(void*);
-  rowids_buf_last= rowids_buf + 
-                      ((rowids_buf_end - rowids_buf)/ elem_size)*
-                      elem_size;
-  rowids_buf_end= rowids_buf_last;
+    status_var_increment(thd->status_var.ha_multi_range_read_init_count);
 
-    /*
-    There can be two cases:
-    - This is the first call since index_init(), h2==NULL
-       Need to setup h2 then.
-    - This is not the first call, h2 is initalized and set up appropriately.
-       The caller might have called h->index_init(), need to switch h to
-       rnd_pos calls.
+  full_buf= buf->buffer;
+  full_buf_end= buf->buffer_end;
+
+  if (do_sort_keys)
+  {
+    /* Pre-calculate some parameters of key sorting */
+    keypar.use_key_pointers= test(mode & HA_MRR_MATERIALIZED_KEYS);
+    seq_funcs->get_key_info(seq_init_param, &keypar.key_tuple_length, 
+                            &keypar.key_tuple_map);
+    keypar.key_size_in_keybuf= keypar.use_key_pointers? 
+                                 sizeof(char*) : keypar.key_tuple_length;
+    key_buff_elem_size= keypar.key_size_in_keybuf + (int)is_mrr_assoc * sizeof(void*);
+    
+    /* Ordered index reader needs some space to store an index tuple */
+    if (strategy != index_strategy)
+    {
+      if (full_buf_end - full_buf <= (ptrdiff_t)primary_file->ref_length/*keypar.key_tuple_length*/)
+        goto use_default_impl;
+      reader_factory.ordered_index_reader.set_temp_space(full_buf);
+      //full_buf += keypar.key_tuple_length;
+      full_buf += primary_file->ref_length;
+    }
+  }
+
+  if (strategy == index_strategy)
+  {
+    /* 
+      Index strategy alone handles the record retrieval. Give all buffer space
+      to it. Key buffer should have forward orientation so we can return the
+      end of it.
+    */
+    key_buffer= &forward_key_buf;
+    key_buffer->set_buffer_space(full_buf, full_buf_end);
+    
+    /* Safety: specify that rowid buffer has zero size: */
+    rowid_buffer.set_buffer_space(full_buf_end, full_buf_end);
+
+    if (do_sort_keys && !key_buffer->have_space_for(key_buff_elem_size))
+      goto use_default_impl;
+
+    if ((res= index_strategy->init(primary_file, seq_funcs, seq_init_param, n_ranges,
+                                   mode, &keypar, key_buffer, &buf_manager)))
+      goto error;
+  }
+  else
+  {
+    /* We'll have both index and rndpos strategies working together */
+    if (do_sort_keys)
+    {
+      /* Both strategies will need buffer space, share the buffer */
+      if (setup_buffer_sharing(keypar.key_size_in_keybuf, keypar.key_tuple_map))
+        goto use_default_impl;
+
+      buf_manager.reset_buffer_sizes= reset_buffer_sizes;
+      buf_manager.redistribute_buffer_space= redistribute_buffer_space;
+    }
+    else
+    {
+      /* index strategy doesn't need buffer, give all space to rowids*/
+      rowid_buffer.set_buffer_space(full_buf, full_buf_end);
+      if (!rowid_buffer.have_space_for(primary_file->ref_length + 
+                                       (int)is_mrr_assoc * sizeof(char*)))
+        goto use_default_impl;
+    }
+
+    if ((res= setup_two_handlers()))
+      goto error;
+
+    if ((res= index_strategy->init(secondary_file, seq_funcs, seq_init_param,
+                                   n_ranges, mode, &keypar, key_buffer, 
+                                   &buf_manager)) || 
+        (res= disk_strategy->init(primary_file, index_strategy, mode, 
+                                  &rowid_buffer)))
+    {
+      goto error;
+    }
+  }
+
+  res= strategy->refill_buffer(TRUE);
+  if (res)
+  {
+    if (res != HA_ERR_END_OF_FILE)
+      goto error;
+    strategy_exhausted= TRUE;
+  }
+
+  /*
+    If we have scanned through all intervals in *seq, then adjust *buf to 
+    indicate that the remaining buffer space will not be used.
   */
-  if (!h2)
+//  if (dsmrr_eof) 
+//    buf->end_of_used_area= rowid_buffer.end_of_space();
+
+  
+  DBUG_RETURN(0);
+error:
+  close_second_handler();
+   /* Safety, not really needed but: */
+  strategy= NULL;
+  DBUG_RETURN(1);
+
+use_default_impl:
+  DBUG_ASSERT(primary_file->inited == handler::INDEX);
+  /* Call correct init function and assign to top level object */
+  Mrr_simple_index_reader *s= &reader_factory.simple_index_reader;
+  res= s->init(primary_file, seq_funcs, seq_init_param, n_ranges, mode, NULL, 
+               NULL, NULL);
+  strategy= s;
+  DBUG_RETURN(res);
+}
+
+
+/*
+  Whatever the current state is, make it so that we have two handler objects:
+  - primary_file       -  initialized for rnd_pos() scan
+  - secondary_file     -  initialized for scanning the index specified in
+                          this->keyno
+  RETURN 
+    0        OK
+    HA_XXX   Error code
+*/
+
+int DsMrr_impl::setup_two_handlers()
+{
+  int res;
+  THD *thd= primary_file->get_table()->in_use;
+  DBUG_ENTER("DsMrr_impl::setup_two_handlers");
+  if (!secondary_file)
   {
-    /* Create a separate handler object to do rndpos() calls. */
-    THD *thd= current_thd;
+    handler *new_h2;
+    Item *pushed_cond= NULL;
+    DBUG_ASSERT(primary_file->inited == handler::INDEX);
+    /* Create a separate handler object to do rnd_pos() calls. */
     /*
       ::clone() takes up a lot of stack, especially on 64 bit platforms.
       The constant 5 is an empiric result.
     */
     if (check_stack_overrun(thd, 5*STACK_MIN_SIZE, (uchar*) &new_h2))
       DBUG_RETURN(1);
-    DBUG_ASSERT(h->active_index != MAX_KEY);
-    uint mrr_keyno= h->active_index;
 
-    /* Create a separate handler object to do rndpos() calls. */
-    if (!(new_h2= h->clone(thd->mem_root)) || 
+    /* Create a separate handler object to do rnd_pos() calls. */
+    if (!(new_h2= primary_file->clone(thd->mem_root)) || 
         new_h2->ha_external_lock(thd, F_RDLCK))
     {
       delete new_h2;
       DBUG_RETURN(1);
     }
 
-    if (mrr_keyno == h->pushed_idx_cond_keyno)
-      pushed_cond= h->pushed_idx_cond;
-
+    if (keyno == primary_file->pushed_idx_cond_keyno)
+      pushed_cond= primary_file->pushed_idx_cond;
+    
+    Mrr_reader *save_strategy= strategy;
+    strategy= NULL;
     /*
       Caution: this call will invoke this->dsmrr_close(). Do not put the
-      created secondary table handler into this->h2 or it will delete it.
+      created secondary table handler new_h2 into this->secondary_file or it 
+      will delete it. Also, save the picked strategy
     */
-    if (h->ha_index_end())
-    {
-      h2=new_h2;
+    res= primary_file->ha_index_end();
+
+    strategy= save_strategy;
+    secondary_file= new_h2;
+
+    if (res || (res= (primary_file->ha_rnd_init(FALSE))))
       goto error;
-    }
 
-    h2= new_h2; /* Ok, now can put it into h2 */
     table->prepare_for_position();
-    h2->extra(HA_EXTRA_KEYREAD);
-  
-    if (h2->ha_index_init(mrr_keyno, FALSE))
+    secondary_file->extra(HA_EXTRA_KEYREAD);
+    secondary_file->mrr_iter= primary_file->mrr_iter;
+
+    if ((res= secondary_file->ha_index_init(keyno, FALSE)))
       goto error;
 
-    use_default_impl= FALSE;
     if (pushed_cond)
-      h2->idx_cond_push(mrr_keyno, pushed_cond);
+      secondary_file->idx_cond_push(keyno, pushed_cond);
   }
   else
   {
+    DBUG_ASSERT(secondary_file && secondary_file->inited==handler::INDEX);
     /* 
       We get here when the access alternates betwen MRR scan(s) and non-MRR
       scans.
 
-      Calling h->index_end() will invoke dsmrr_close() for this object,
-      which will delete h2. We need to keep it, so save put it away and dont
+      Calling primary_file->index_end() will invoke dsmrr_close() for this object,
+      which will delete secondary_file. We need to keep it, so put it away and dont
       let it be deleted:
     */
-    handler *save_h2= h2;
-    h2= NULL;
-    int res= (h->inited == handler::INDEX && h->ha_index_end());
-    h2= save_h2;
-    use_default_impl= FALSE;
-    if (res)
+    if (primary_file->inited == handler::INDEX)
+    {
+      handler *save_h2= secondary_file;
+      Mrr_reader *save_strategy= strategy;
+      secondary_file= NULL;
+      strategy= NULL;
+      res= primary_file->ha_index_end();
+      secondary_file= save_h2;
+      strategy= save_strategy;
+      if (res)
+        goto error;
+    }
+    if ((primary_file->inited != handler::RND) && primary_file->ha_rnd_init(FALSE))
       goto error;
   }
+  DBUG_RETURN(0);
 
-  if (h2->handler::multi_range_read_init(seq_funcs, seq_init_param, n_ranges,
-                                          mode, buf) || 
-      dsmrr_fill_buffer())
-  {
-    goto error;
-  }
-  /*
-    If the above call has scanned through all intervals in *seq, then
-    adjust *buf to indicate that the remaining buffer space will not be used.
-  */
-  if (dsmrr_eof) 
-    buf->end_of_used_area= rowids_buf_last;
+error:
+  DBUG_RETURN(res);
+}
 
-  /*
-     h->inited == INDEX may occur when 'range checked for each record' is
-     used.
-  */
-  if ((h->inited != handler::RND) && 
-      ((h->inited==handler::INDEX? h->ha_index_end(): FALSE) || 
-       (h->ha_rnd_init(FALSE))))
-      goto error;
 
-  use_default_impl= FALSE;
-  h->mrr_funcs= *seq_funcs;
-  
-  DBUG_RETURN(0);
-error:
-  h2->ha_index_or_rnd_end();
-  h2->ha_external_lock(current_thd, F_UNLCK);
-  h2->close();
-  delete h2;
-  h2= NULL;
-  DBUG_RETURN(1);
+void DsMrr_impl::close_second_handler()
+{
+  if (secondary_file)
+  {
+    secondary_file->ha_index_or_rnd_end();
+    secondary_file->ha_external_lock(current_thd, F_UNLCK);
+    secondary_file->close();
+    delete secondary_file;
+    secondary_file= NULL;
+  }
 }
 
 
 void DsMrr_impl::dsmrr_close()
 {
   DBUG_ENTER("DsMrr_impl::dsmrr_close");
-  if (h2)
+  close_second_handler();
+  strategy= NULL;
+  DBUG_VOID_RETURN;
+}
+
+
+/* 
+  my_qsort2-compatible static member function to compare key tuples 
+*/
+
+int Mrr_ordered_index_reader::compare_keys(void* arg, uchar* key1_arg, 
+                                           uchar* key2_arg)
+{
+  Mrr_ordered_index_reader *reader= (Mrr_ordered_index_reader*)arg;
+  TABLE *table= reader->file->get_table();
+  KEY_PART_INFO *part= table->key_info[reader->file->active_index].key_part;
+  uchar *key1, *key2;
+   
+  if (reader->keypar.use_key_pointers)
   {
-    h2->ha_index_or_rnd_end();
-    h2->ha_external_lock(current_thd, F_UNLCK);
-    h2->close();
-    delete h2;
-    h2= NULL;
+    /* the buffer stores pointers to keys, get to the keys */
+    memcpy(&key1, key1_arg, sizeof(char*));
+    memcpy(&key2, key2_arg, sizeof(char*));
   }
-  use_default_impl= TRUE;
-  DBUG_VOID_RETURN;
+  else
+  {
+    key1= key1_arg;
+    key2= key2_arg;
+  }
+
+  return key_tuple_cmp(part, key1, key2, reader->keypar.key_tuple_length);
 }
 
 
-static int rowid_cmp(void *h, uchar *a, uchar *b)
+int Mrr_ordered_index_reader::compare_keys_reverse(void* arg, uchar* key1, 
+                                                   uchar* key2)
 {
-  return ((handler*)h)->cmp_ref(a, b);
+  return -compare_keys(arg, key1, key2);
 }
 
 
 /**
-  DS-MRR: Fill the buffer with rowids and sort it by rowid
+  Set the buffer space to be shared between rowid and key buffer
+
+  @return FALSE  ok 
+  @return TRUE   There is so little buffer space that we won't be able to use
+                 the strategy. 
+                 This happens when we don't have enough space for one rowid 
+                 element and one key element so this is mainly targeted at
+                 testing.
+*/
 
-  {This is an internal function of DiskSweep MRR implementation}
-  Scan the MRR ranges and collect ROWIDs (or {ROWID, range_id} pairs) into 
-  buffer. When the buffer is full or scan is completed, sort the buffer by 
-  rowid and return.
+bool DsMrr_impl::setup_buffer_sharing(uint key_size_in_keybuf, 
+                                      key_part_map key_tuple_map)
+{
+  long key_buff_elem_size= key_size_in_keybuf + 
+                           (int)is_mrr_assoc * sizeof(void*);
   
-  The function assumes that rowids buffer is empty when it is invoked. 
+  KEY *key_info= &primary_file->get_table()->key_info[keyno];
+  /* 
+    Ok if we got here we need to allocate one part of the buffer 
+    for keys and another part for rowids.
+  */
+  ulonglong rowid_buf_elem_size= primary_file->ref_length + 
+                                 (int)is_mrr_assoc * sizeof(char*);
   
-  @param h  Table handler
+  /*
+    Use rec_per_key statistics as a basis to find out how many rowids 
+    we'll get for each key value.
+     TODO: what should be the default value to use when there is no 
+           statistics?
+  */
+  uint parts= my_count_bits(key_tuple_map);
+  ulong rpc;
+  ulonglong rowids_size= rowid_buf_elem_size;
+  if ((rpc= key_info->rec_per_key[parts - 1]))
+    rowids_size= rowid_buf_elem_size * rpc;
+
+  double fraction_for_rowids=
+    (ulonglong2double(rowids_size) / 
+     (ulonglong2double(rowids_size) + key_buff_elem_size));
+
+  size_t bytes_for_rowids= 
+    round(fraction_for_rowids * (full_buf_end - full_buf));
+  
+  long bytes_for_keys= (full_buf_end - full_buf) - bytes_for_rowids;
 
-  @retval 0      OK, the next portion of rowids is in the buffer,
-                 properly ordered
-  @retval other  Error
-*/
+  if (bytes_for_keys < key_buff_elem_size + 1)
+  {
+    long add= key_buff_elem_size + 1 - bytes_for_keys;
+    bytes_for_keys= key_buff_elem_size + 1;
+    bytes_for_rowids -= add;
+  }
 
-int DsMrr_impl::dsmrr_fill_buffer()
+  if (bytes_for_rowids < rowid_buf_elem_size + 1)
+  {
+    long add= rowid_buf_elem_size + 1 - bytes_for_rowids;
+    bytes_for_rowids= rowid_buf_elem_size + 1;
+    bytes_for_keys -= add;
+  }
+
+  rowid_buffer_end= full_buf + bytes_for_rowids;
+  rowid_buffer.set_buffer_space(full_buf, rowid_buffer_end);
+  key_buffer= &backward_key_buf;
+  key_buffer->set_buffer_space(rowid_buffer_end, full_buf_end); 
+
+  if (!key_buffer->have_space_for(key_buff_elem_size) ||
+      !rowid_buffer.have_space_for(rowid_buf_elem_size))
+    return TRUE; /* Failed to provide minimum space for one of the buffers */
+
+  return FALSE;
+}
+
+
+void DsMrr_impl::do_nothing(void *dsmrr_arg)
 {
-  char *range_info;
-  int res;
-  DBUG_ENTER("DsMrr_impl::dsmrr_fill_buffer");
+  /* Do nothing */
+}
 
-  rowids_buf_cur= rowids_buf;
-  while ((rowids_buf_cur < rowids_buf_end) && 
-         !(res= h2->handler::multi_range_read_next(&range_info)))
-  {
-    KEY_MULTI_RANGE *curr_range= &h2->handler::mrr_cur_range;
-    if (h2->mrr_funcs.skip_index_tuple &&
-        h2->mrr_funcs.skip_index_tuple(h2->mrr_iter, curr_range->ptr))
-      continue;
-    
-    /* Put rowid, or {rowid, range_id} pair into the buffer */
-    h2->position(table->record[0]);
-    memcpy(rowids_buf_cur, h2->ref, h2->ref_length);
-    rowids_buf_cur += h2->ref_length;
 
-    if (is_mrr_assoc)
-    {
-      memcpy(rowids_buf_cur, &range_info, sizeof(void*));
-      rowids_buf_cur += sizeof(void*);
-    }
-  }
+void DsMrr_impl::reset_buffer_sizes(void *dsmrr_arg)
+{
+  DsMrr_impl *dsmrr= (DsMrr_impl*)dsmrr_arg;
+  dsmrr->rowid_buffer.set_buffer_space(dsmrr->full_buf, 
+                                       dsmrr->rowid_buffer_end);
+  dsmrr->key_buffer->set_buffer_space(dsmrr->rowid_buffer_end, 
+                                      dsmrr->full_buf_end);
+}
 
-  if (res && res != HA_ERR_END_OF_FILE)
-    DBUG_RETURN(res); 
-  dsmrr_eof= test(res == HA_ERR_END_OF_FILE);
 
-  /* Sort the buffer contents by rowid */
-  uint elem_size= h->ref_length + (int)is_mrr_assoc * sizeof(void*);
-  uint n_rowids= (rowids_buf_cur - rowids_buf) / elem_size;
-  
-  my_qsort2(rowids_buf, n_rowids, elem_size, (qsort2_cmp)rowid_cmp,
-            (void*)h);
-  rowids_buf_last= rowids_buf_cur;
-  rowids_buf_cur=  rowids_buf;
-  DBUG_RETURN(0);
+/*
+  Take unused space from the key buffer and give it to the rowid buffer
+*/
+
+void DsMrr_impl::redistribute_buffer_space(void *dsmrr_arg)
+{
+  DsMrr_impl *dsmrr= (DsMrr_impl*)dsmrr_arg;
+  uchar *unused_start, *unused_end;
+  dsmrr->key_buffer->remove_unused_space(&unused_start, &unused_end);
+  dsmrr->rowid_buffer.grow(unused_start, unused_end);
 }
 
 
-/**
-  DS-MRR implementation: multi_range_read_next() function
+/*
+  @brief Initialize the iterator
+  
+  @note
+  Initialize the iterator to produce matches for the key of the first element 
+  in owner_arg->key_buffer
+
+  @retval  0                    OK
+  @retval  HA_ERR_END_OF_FILE   Either the owner->key_buffer is empty or 
+                                no matches for the key we've tried (check
+                                key_buffer->is_empty() to tell these apart)
+  @retval  other code           Fatal error
 */
 
-int DsMrr_impl::dsmrr_next(char **range_info)
+int Key_value_records_iterator::init(Mrr_ordered_index_reader *owner_arg)
 {
   int res;
-  uchar *cur_range_info= 0;
-  uchar *rowid;
+  owner= owner_arg;
+
+  identical_key_it.init(owner->key_buffer);
+  /* Get the first pair into (cur_index_tuple, cur_range_info) */ 
+  owner->key_buffer->setup_reading(&cur_index_tuple, 
+                                   owner->keypar.key_size_in_keybuf,
+                                   owner->is_mrr_assoc? 
+                                     (uchar**)&owner->cur_range_info: NULL,
+                                   sizeof(void*));
+
+  if (identical_key_it.read())
+    return HA_ERR_END_OF_FILE;
+
+  uchar *key_in_buf= cur_index_tuple;
 
-  if (use_default_impl)
-    return h->handler::multi_range_read_next(range_info);
+  last_identical_key_ptr= cur_index_tuple;
+  if (owner->keypar.use_key_pointers)
+    memcpy(&cur_index_tuple, key_in_buf, sizeof(char*));
   
-  do
+  /* Check out how many more identical keys are following */
+  uchar *save_cur_index_tuple= cur_index_tuple;
+  while (!identical_key_it.read())
+  {
+    if (owner->disallow_identical_key_handling ||
+        Mrr_ordered_index_reader::compare_keys(owner, key_in_buf, 
+                                               cur_index_tuple))
+      break;
+    last_identical_key_ptr= cur_index_tuple;
+  }
+  identical_key_it.init(owner->key_buffer);
+  cur_index_tuple= save_cur_index_tuple;
+  res= owner->file->ha_index_read_map(owner->file->get_table()->record[0], 
+                                   cur_index_tuple, 
+                                   owner->keypar.key_tuple_map, 
+                                   HA_READ_KEY_EXACT);
+
+  if (res)
   {
-    if (rowids_buf_cur == rowids_buf_last)
+    /* Failed to find any matching records */
+    move_to_next_key_value();
+    return res;
+  }
+  owner->have_saved_rowid= FALSE;
+  get_next_row= FALSE;
+  return 0;
+}
+
+
+int Key_value_records_iterator::get_next()
+{
+  int res;
+
+  if (get_next_row)
+  {
+    if (owner->keypar.index_ranges_unique)
     {
-      if (dsmrr_eof)
-      {
-        res= HA_ERR_END_OF_FILE;
-        goto end;
-      }
-      res= dsmrr_fill_buffer();
-      if (res)
-        goto end;
+      /* We're using a full unique key, no point to call index_next_same */
+      return HA_ERR_END_OF_FILE;
     }
-   
-    /* return eof if there are no rowids in the buffer after re-fill attempt */
-    if (rowids_buf_cur == rowids_buf_last)
+    
+    handler *h= owner->file;
+    if ((res= h->ha_index_next_same(h->get_table()->record[0], 
+                                    cur_index_tuple, 
+                                    owner->keypar.key_tuple_length)))
     {
-      res= HA_ERR_END_OF_FILE;
-      goto end;
+      /* It's either HA_ERR_END_OF_FILE or some other error */
+      return res; 
     }
-    rowid= rowids_buf_cur;
+    identical_key_it.init(owner->key_buffer);
+    owner->have_saved_rowid= FALSE;
+    get_next_row= FALSE;
+  }
 
-    if (is_mrr_assoc)
-      memcpy(&cur_range_info, rowids_buf_cur + h->ref_length, sizeof(uchar**));
+  identical_key_it.read(); /* This gets us next range_id */
+  if (!last_identical_key_ptr || (cur_index_tuple == last_identical_key_ptr))
+  {
+    /* 
+      We've reached the last of the identical keys that current record is a
+      match for.  Set get_next_row=TRUE so that we read the next index record
+      on the next call to this function.
+    */
+    get_next_row= TRUE;
+  }
+  return 0;
+}
 
-    rowids_buf_cur += h->ref_length + sizeof(void*) * test(is_mrr_assoc);
-    if (h2->mrr_funcs.skip_record &&
-	h2->mrr_funcs.skip_record(h2->mrr_iter, (char *) cur_range_info, rowid))
-      continue;
-    res= h->ha_rnd_pos(table->record[0], rowid);
-    break;
-  } while (true);
- 
-  if (is_mrr_assoc)
+
+void Key_value_records_iterator::move_to_next_key_value()
+{
+  while (!owner->key_buffer->read() && 
+         (cur_index_tuple != last_identical_key_ptr)) {}
+}
+
+
+/**
+  DS-MRR implementation: multi_range_read_next() function.
+
+  Calling convention is like multi_range_read_next() has.
+*/
+
+int DsMrr_impl::dsmrr_next(char **range_info)
+{
+  int res;
+  if (strategy_exhausted)
+    return HA_ERR_END_OF_FILE;
+
+  while ((res= strategy->get_next(range_info)) == HA_ERR_END_OF_FILE)
   {
-    memcpy(range_info, rowid + h->ref_length, sizeof(void*));
+    if ((res= strategy->refill_buffer(FALSE)))
+      break; /* EOF or error */
   }
-end:
   return res;
 }
 
@@ -582,7 +1320,8 @@ end:
 /**
   DS-MRR implementation: multi_range_read_info() function
 */
-ha_rows DsMrr_impl::dsmrr_info(uint keyno, uint n_ranges, uint rows,
+ha_rows DsMrr_impl::dsmrr_info(uint keyno, uint n_ranges, uint rows, 
+                               uint key_parts,
                                uint *bufsz, uint *flags, COST_VECT *cost)
 {  
   ha_rows res;
@@ -590,8 +1329,9 @@ ha_rows DsMrr_impl::dsmrr_info(uint keyno, uint n_ranges, uint rows,
   uint def_bufsz= *bufsz;
 
   /* Get cost/flags/mem_usage of default MRR implementation */
-  res= h->handler::multi_range_read_info(keyno, n_ranges, rows, &def_bufsz,
-                                         &def_flags, cost);
+  res= primary_file->handler::multi_range_read_info(keyno, n_ranges, rows,
+                                                    key_parts, &def_bufsz, 
+                                                    &def_flags, cost);
   DBUG_ASSERT(!res);
 
   if ((*flags & HA_MRR_USE_DEFAULT_IMPL) || 
@@ -623,9 +1363,11 @@ ha_rows DsMrr_impl::dsmrr_info_const(uint keyno, RANGE_SEQ_IF *seq,
   uint def_flags= *flags;
   uint def_bufsz= *bufsz;
   /* Get cost/flags/mem_usage of default MRR implementation */
-  rows= h->handler::multi_range_read_info_const(keyno, seq, seq_init_param,
-                                                n_ranges, &def_bufsz, 
-                                                &def_flags, cost);
+  rows= primary_file->handler::multi_range_read_info_const(keyno, seq, 
+                                                           seq_init_param,
+                                                           n_ranges, 
+                                                           &def_bufsz, 
+                                                           &def_flags, cost);
   if (rows == HA_POS_ERROR)
   {
     /* Default implementation can't perform MRR scan => we can't either */
@@ -683,7 +1425,28 @@ bool key_uses_partial_cols(TABLE *table, uint keyno)
   return FALSE;
 }
 
-/**
+
+/*
+  Check if key/flags allow DS-MRR/CPK strategy to be used
+  
+  @param thd
+  @param keyno      Index that will be used
+  @param  mrr_flags  
+  
+  @retval TRUE   DS-MRR/CPK should be used
+  @retval FALSE  Otherwise
+*/
+
+bool DsMrr_impl::check_cpk_scan(THD *thd, uint keyno, uint mrr_flags)
+{
+  return test((mrr_flags & HA_MRR_SINGLE_POINT) &&
+              keyno == table->s->primary_key && 
+              primary_file->primary_key_is_clustered() && 
+              optimizer_flag(thd, OPTIMIZER_SWITCH_MRR_SORT_KEYS));
+}
+
+
+/*
   DS-MRR Internals: Choose between Default MRR implementation and DS-MRR
 
   Make the choice between using Default MRR implementation and DS-MRR.
@@ -706,22 +1469,26 @@ bool key_uses_partial_cols(TABLE *table, uint keyno)
   @retval FALSE  DS-MRR implementation should be used
 */
 
+
 bool DsMrr_impl::choose_mrr_impl(uint keyno, ha_rows rows, uint *flags,
                                  uint *bufsz, COST_VECT *cost)
 {
   COST_VECT dsmrr_cost;
   bool res;
   THD *thd= current_thd;
+
+  bool doing_cpk_scan= check_cpk_scan(thd, keyno, *flags); 
+  bool using_cpk= test(keyno == table->s->primary_key &&
+                       primary_file->primary_key_is_clustered());
   if (thd->variables.optimizer_use_mrr == 2 || *flags & HA_MRR_INDEX_ONLY ||
-      (keyno == table->s->primary_key && h->primary_key_is_clustered()) ||
-       key_uses_partial_cols(table, keyno))
+      (using_cpk && !doing_cpk_scan) || key_uses_partial_cols(table, keyno))
   {
     /* Use the default implementation */
     *flags |= HA_MRR_USE_DEFAULT_IMPL;
     return TRUE;
   }
-  
-  uint add_len= table->key_info[keyno].key_length + h->ref_length; 
+
+  uint add_len= table->key_info[keyno].key_length + primary_file->ref_length; 
   *bufsz -= add_len;
   if (get_disk_sweep_mrr_cost(keyno, rows, *flags, bufsz, &dsmrr_cost))
     return TRUE;
@@ -744,6 +1511,10 @@ bool DsMrr_impl::choose_mrr_impl(uint keyno, ha_rows rows, uint *flags,
     *flags &= ~HA_MRR_SORTED;          /* We will return unordered output */
     *cost= dsmrr_cost;
     res= FALSE;
+
+    if ((*flags & HA_MRR_SINGLE_POINT) && 
+         optimizer_flag(thd, OPTIMIZER_SWITCH_MRR_SORT_KEYS))
+      *flags |= HA_MRR_MATERIALIZED_KEYS;
   }
   else
   {
@@ -779,7 +1550,8 @@ bool DsMrr_impl::get_disk_sweep_mrr_cost(uint keynr, ha_rows rows, uint flags,
   uint n_full_steps;
   double index_read_cost;
 
-  elem_size= h->ref_length + sizeof(void*) * (!test(flags & HA_MRR_NO_ASSOCIATION));
+  elem_size= primary_file->ref_length + 
+             sizeof(void*) * (!test(flags & HA_MRR_NO_ASSOCIATION));
   max_buff_entries = *buffer_size / elem_size;
 
   if (!max_buff_entries)
@@ -807,7 +1579,7 @@ bool DsMrr_impl::get_disk_sweep_mrr_cost(uint keynr, ha_rows rows, uint flags,
     cost->zero();
     *buffer_size= max(*buffer_size, 
                       (size_t)(1.2*rows_in_last_step) * elem_size + 
-                      h->ref_length + table->key_info[keynr].key_length);
+                      primary_file->ref_length + table->key_info[keynr].key_length);
   }
   
   COST_VECT last_step_cost;
@@ -820,7 +1592,7 @@ bool DsMrr_impl::get_disk_sweep_mrr_cost(uint keynr, ha_rows rows, uint flags,
     cost->mem_cost= (double)rows_in_last_step * elem_size;
   
   /* Total cost of all index accesses */
-  index_read_cost= h->keyread_time(keynr, 1, rows);
+  index_read_cost= primary_file->keyread_time(keynr, 1, rows);
   cost->add_io(index_read_cost, 1 /* Random seeks */);
   return FALSE;
 }
@@ -828,17 +1600,14 @@ bool DsMrr_impl::get_disk_sweep_mrr_cost(uint keynr, ha_rows rows, uint flags,
 
 /* 
   Get cost of one sort-and-sweep step
+  
+  It consists of two parts:
+   - sort an array of #nrows ROWIDs using qsort
+   - read #nrows records from table in a sweep.
 
-  SYNOPSIS
-    get_sort_and_sweep_cost()
-      table       Table being accessed
-      nrows       Number of rows to be sorted and retrieved
-      cost   OUT  The cost
-
-  DESCRIPTION
-    Get cost of these operations:
-     - sort an array of #nrows ROWIDs using qsort
-     - read #nrows records from table in a sweep.
+  @param table       Table being accessed
+  @param nrows       Number of rows to be sorted and retrieved
+  @param cost   OUT  The cost of scan
 */
 
 static 
diff --git a/sql/multi_range_read.h b/sql/multi_range_read.h
index 90e2e4c93d6..a22ef0fef61 100644
--- a/sql/multi_range_read.h
+++ b/sql/multi_range_read.h
@@ -1,70 +1,618 @@
-/*
-  This file contains declarations for 
-   - Disk-Sweep MultiRangeRead (DS-MRR) implementation
+/**
+  @defgroup DS-MRR declarations
+  @{
 */
 
 /**
-  A Disk-Sweep MRR interface implementation
+  A Disk-Sweep implementation of MRR Interface (DS-MRR for short)
+
+  This is a "plugin"(*) for storage engines that allows to
+    1. When doing index scans, read table rows in rowid order;
+    2. when making many index lookups, do them in key order and don't
+       lookup the same key value multiple times;
+    3. Do both #1 and #2, when applicable.
+  These changes are expected to speed up query execution for disk-based 
+  storage engines running io-bound loads and "big" queries (ie. queries that
+  do joins and enumerate lots of records).
+
+  (*) - only conceptually. No dynamic loading or binary compatibility of any
+        kind.
+
+  General scheme of things:
+   
+      SQL Layer code
+       |   |   |
+       v   v   v 
+      -|---|---|---- handler->multi_range_read_XXX() function calls
+       |   |   |
+      _____________________________________
+     / DS-MRR module                       \
+     | (order/de-duplicate lookup keys,    |
+     | scan indexes in key order,          |
+     | order/de-duplicate rowids,          |
+     | retrieve full record reads in rowid |
+     | order)                              |
+     \_____________________________________/
+       |   |   |
+      -|---|---|----- handler->read_range_first()/read_range_next(), 
+       |   |   |      handler->index_read(), handler->rnd_pos() calls.
+       |   |   |
+       v   v   v
+      Storage engine internals
+
+
+  Currently DS-MRR is used by MyISAM, InnoDB/XtraDB and Maria storage engines.
+  Potentially it can be used with any table handler that has disk-based data
+  storage and has better performance when reading data in rowid order.
+*/
+
+#include "sql_lifo_buffer.h"
+
+class DsMrr_impl;
+class Mrr_ordered_index_reader;
+
+
+/* A structure with key parameters that's shared among several classes */
+class Key_parameters
+{
+public:
+  uint         key_tuple_length; /* Length of index lookup tuple, in bytes */
+  key_part_map key_tuple_map;    /* keyparts used in index lookup tuples */
+
+  /*
+    This is 
+      = key_tuple_length   if we copy keys to buffer
+      = sizeof(void*)      if we're using pointers to materialized keys.
+  */
+  uint key_size_in_keybuf;
+
+  /* TRUE <=> don't copy key values, use pointers to them instead.  */
+  bool use_key_pointers;
 
-  This implementation makes range (and, in the future, 'ref') scans to read
-  table rows in disk sweeps. 
+  /* TRUE <=> We can get at most one index tuple for a lookup key */
+  bool index_ranges_unique;
+};
+
+
+/**
+  A class to enumerate (record, range_id) pairs that match given key value.
   
-  Currently it is used by MyISAM and InnoDB. Potentially it can be used with
-  any table handler that has non-clustered indexes and on-disk rows.
+  @note
+
+  The idea is that we have a Lifo_buffer which holds (key, range_id) pairs
+  ordered by key value. From the front of the buffer we see
+
+    (key_val1, range_id1), (key_val1, range_id2) ... (key_val2, range_idN)
+
+  we take the first elements that have the same key value (key_val1 in the
+  example above), and make lookup into the table.  The table will have 
+  multiple matches for key_val1:
+ 
+                  == Table Index ==
+                   ...
+     key_val1 ->  key_val1, index_tuple1
+                  key_val1, index_tuple2
+                   ...
+                  key_val1, index_tupleN
+                   ...
+  
+  Our goal is to produce all possible combinations, i.e. we need:
+  
+    {(key_val1, index_tuple1), range_id1}
+    {(key_val1, index_tuple1), range_id2}
+       ...           ...               |
+    {(key_val1, index_tuple1), range_idN},
+                  
+    {(key_val1, index_tuple2), range_id1}
+    {(key_val1, index_tuple2), range_id2}
+        ...          ...               |
+    {(key_val1, index_tuple2), range_idN},
+
+        ...          ...          ...                          
+
+    {(key_val1, index_tupleK), range_idN}
 */
 
-class DsMrr_impl
+class Key_value_records_iterator
 {
+  /* Use this to get table handler, key buffer and other parameters */
+  Mrr_ordered_index_reader *owner;
+
+  /* Iterator to get (key, range_id) pairs from */
+  Lifo_buffer_iterator identical_key_it;
+  
+  /* 
+    Last of the identical key values (when we get this pointer from
+    identical_key_it, it will be time to stop).
+  */
+  uchar *last_identical_key_ptr;
+
+  /*
+    FALSE <=> we're right after the init() call, the record has been already
+    read with owner->file->index_read_map() call
+  */
+  bool get_next_row;
+  
+  uchar *cur_index_tuple; /* key_buffer.read() reads to here */
 public:
-  typedef void (handler::*range_check_toggle_func_t)(bool on);
+  int init(Mrr_ordered_index_reader *owner_arg);
+  int get_next();
+  void move_to_next_key_value();
+};
 
-  DsMrr_impl()
-    : h2(NULL) {};
+
+/*
+  Buffer manager interface. Mrr_reader objects use it to inqure DsMrr_impl
+  to manage buffer space for them.
+*/
+typedef struct st_buffer_manager
+{
+public:
+  /* Opaque value to be passed as the first argument to all member functions */
+  void *arg;
   
   /*
-    The "owner" handler object (the one that calls dsmrr_XXX functions.
-    It is used to retrieve full table rows by calling rnd_pos().
+    This is called when we've freed more space from the rowid buffer. The
+    callee will get the unused space from the rowid buffer and give it to the
+    key buffer.
+  */
+  void (*redistribute_buffer_space)(void *arg);
+
+  /* 
+    This is called when both key and rowid buffers are empty, and so it's time 
+    to reset them to their original size (They've lost their original size,
+    because we were dynamically growing rowid buffer and shrinking key buffer).
   */
-  handler *h;
-  TABLE *table; /* Always equal to h->table */
+  void (*reset_buffer_sizes)(void *arg);
+
+} Buffer_manager;
+
+
+/* 
+  Mrr_reader - DS-MRR execution strategy abstraction
+
+  A reader produces ([index]_record, range_info) pairs, and requires periodic
+  refill operations.
+
+  - one starts using the reader by calling reader->get_next(),
+  - when a get_next() call returns HA_ERR_END_OF_FILE, one must call 
+    refill_buffer() before they can make more get_next() calls.
+  - when refill_buffer() returns HA_ERR_END_OF_FILE, this means the real
+    end of stream and get_next() should not be called anymore.
+
+  Both functions can return other error codes, these mean unrecoverable errors
+  after which one cannot continue.
+*/
+
+class Mrr_reader 
+{
+public:
+  virtual int get_next(char **range_info) = 0;
+  virtual int refill_buffer(bool initial) = 0;
+  virtual ~Mrr_reader() {}; /* just to remove compiler warning */
+};
+
+
+/* 
+  A common base for readers that do index scans and produce index tuples 
+*/
+
+class Mrr_index_reader : public Mrr_reader
+{
+protected:
+  handler *file; /* Handler object to use */
+public:
+  virtual int init(handler *h_arg, RANGE_SEQ_IF *seq_funcs, 
+                   void *seq_init_param, uint n_ranges,
+                   uint mode, Key_parameters *key_par, 
+                   Lifo_buffer *key_buffer, 
+                   Buffer_manager *buf_manager_arg) = 0;
+
+  /* Get pointer to place where every get_next() call will put rowid */
+  virtual uchar *get_rowid_ptr() = 0;
+  /* Get the rowid (call this after get_next() call) */
+  virtual void position();
+  virtual bool skip_record(char *range_id, uchar *rowid) = 0;
+
+  virtual void interrupt_read() {}
+  virtual void resume_read() {}
+};
+
+
+/*
+  A "bypass" index reader that just does and index scan. The index scan is done 
+  by calling default MRR implementation (i.e.  handler::multi_range_read_XXX())
+  functions.
+*/
+
+class Mrr_simple_index_reader : public Mrr_index_reader
+{
+public:
+  int init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
+           void *seq_init_param, uint n_ranges,
+           uint mode, Key_parameters *key_par,
+           Lifo_buffer *key_buffer,
+           Buffer_manager *buf_manager_arg);
+  int get_next(char **range_info);
+  int refill_buffer(bool initial) { return initial? 0: HA_ERR_END_OF_FILE; }
+  uchar *get_rowid_ptr() { return file->ref; }
+  bool skip_record(char *range_id, uchar *rowid)
+  {
+    return (file->mrr_funcs.skip_record &&
+            file->mrr_funcs.skip_record(file->mrr_iter, range_id, rowid));
+  }
+};
+
+
+/* 
+  A reader that sorts the key values before it makes the index lookups.
+*/
+
+class Mrr_ordered_index_reader : public Mrr_index_reader
+{
+public:
+  int init(handler *h_arg, RANGE_SEQ_IF *seq_funcs, 
+           void *seq_init_param, uint n_ranges,
+           uint mode, Key_parameters *key_par,
+           Lifo_buffer *key_buffer,
+           Buffer_manager *buf_manager_arg);
+  int get_next(char **range_info);
+  int refill_buffer(bool initial);
+  uchar *get_rowid_ptr() { return file->ref; }
+  
+  bool skip_record(char *range_info, uchar *rowid)
+  {
+    return (mrr_funcs.skip_record &&
+            mrr_funcs.skip_record(mrr_iter, range_info, rowid));
+  }
+
+  bool skip_index_tuple(char *range_info)
+  {
+    return (mrr_funcs.skip_index_tuple &&
+            mrr_funcs.skip_index_tuple(mrr_iter, range_info));
+  }
+
+  void set_temp_space(uchar *space);
+  void interrupt_read();
+  void resume_read();
+  void position();
 private:
-  /* Secondary handler object.  It is used for scanning the index */
-  handler *h2;
+  Key_value_records_iterator kv_it;
 
-  /* Buffer to store rowids, or (rowid, range_id) pairs */
-  uchar *rowids_buf;
-  uchar *rowids_buf_cur;   /* Current position when reading/writing */
-  uchar *rowids_buf_last;  /* When reading: end of used buffer space */
-  uchar *rowids_buf_end;   /* End of the buffer */
+  bool scanning_key_val_iter;
+  
+  /* Key_value_records_iterator::read() will place range_info here */
+  char *cur_range_info;
 
-  bool dsmrr_eof; /* TRUE <=> We have reached EOF when reading index tuples */
+  /* Buffer to store (key, range_id) pairs */
+  Lifo_buffer *key_buffer;
+  
+  /* This manages key buffer allocation and sizing for us */
+  Buffer_manager *buf_manager;
 
-  /* TRUE <=> need range association, buffer holds {rowid, range_id} pairs */
+  Key_parameters  keypar; /* index scan and lookup tuple parameters */
+
+  /* TRUE <=> need range association, buffers hold {rowid, range_id} pairs */
   bool is_mrr_assoc;
+  
+  /*
+    TRUE <=> Don't do optimizations for identical key value (see comment in
+    Mrr_ordered_index_reader::init for details)
+  */
+  bool disallow_identical_key_handling;
+  
+  /* Range sequence iteration members */
+  RANGE_SEQ_IF mrr_funcs;
+  range_seq_t mrr_iter;
+  
+  /* TRUE == reached eof when enumerating ranges */
+  bool source_exhausted;
+  
+  /* TODO */
+  /*uchar *saved_key_tuple;*/
+  uchar *saved_rowid;
+  bool have_saved_rowid;
+
+  static int compare_keys(void* arg, uchar* key1, uchar* key2);
+  static int compare_keys_reverse(void* arg, uchar* key1, uchar* key2);
+  
+  friend class Key_value_records_iterator; 
+  friend class DsMrr_impl;
+  friend class Mrr_ordered_rndpos_reader;
+};
+
 
-  bool use_default_impl; /* TRUE <=> shortcut all calls to default MRR impl */
+/* 
+  A reader that gets rowids from an Mrr_index_reader, and then sorts them 
+  before getting full records with handler->rndpos() calls.
+*/
+
+class Mrr_ordered_rndpos_reader : public Mrr_reader 
+{
 public:
+  int init(handler *file, Mrr_index_reader *index_reader, uint mode,
+           Lifo_buffer *buf);
+  int get_next(char **range_info);
+  int refill_buffer(bool initial);
+private:
+  handler *file; /* Handler to use */
+  
+  /* This what we get (rowid, range_info) pairs from */
+  Mrr_index_reader *index_reader;
+
+  /* index_reader->get_next() puts rowid here */
+  uchar *index_rowid;
+  
+  /* TRUE <=> index_reader->refill_buffer() call has returned EOF */
+  bool index_reader_exhausted;
+  
+  bool index_reader_needs_refill;
+  /* TRUE <=> need range association, buffers hold {rowid, range_id} pairs */
+  bool is_mrr_assoc;
+  
+  /* 
+    When reading from ordered rowid buffer: the rowid element of the last
+    buffer element that has rowid identical to this one.
+  */
+  uchar *last_identical_rowid;
+
+  /* Buffer to store (rowid, range_id) pairs */
+  Lifo_buffer *rowid_buffer;
+  
+  /* rowid_buffer.read() will set the following:  */
+  uchar *rowid;
+  uchar *rowids_range_id;
+
+  int refill_from_index_reader();
+};
+
+
+/*
+  A primitive "factory" of various Mrr_*_reader classes (the point is to 
+  get various kinds of readers without having to allocate them on the heap)
+*/
+
+class Mrr_reader_factory
+{
+public:
+  Mrr_ordered_rndpos_reader ordered_rndpos_reader;
+  Mrr_ordered_index_reader  ordered_index_reader;
+  Mrr_simple_index_reader   simple_index_reader;
+};
+
+
+/*
+  DS-MRR implementation for one table. Create/use one object of this class for
+  each ha_{myisam/innobase/etc} object. That object will be further referred to
+  as "the handler"
+
+  DsMrr_impl supports has the following execution strategies:
+
+  - Bypass DS-MRR, pass all calls to default MRR implementation, which is 
+    an MRR-to-non-MRR call converter.
+  - Key-Ordered Retrieval
+  - Rowid-Ordered Retrieval
+
+  DsMrr_impl will use one of the above strategies, or a combination of them, 
+  according to the following diagram:
+
+         (mrr function calls)
+                |
+                +----------------->-----------------+
+                |                                   |
+     ___________v______________      _______________v________________
+    / default: use lookup keys \    / KEY-ORDERED RETRIEVAL:         \
+    | (or ranges) in whatever  |    | sort lookup keys and then make | 
+    | order they are supplied  |    | index lookups in index order   |
+    \__________________________/    \________________________________/
+              | |  |                           |    |
+      +---<---+ |  +--------------->-----------|----+
+      |         |                              |    |
+      |         |              +---------------+    |
+      |   ______v___ ______    |     _______________v_______________
+      |  / default: read   \   |    / ROWID-ORDERED RETRIEVAL:      \
+      |  | table records   |   |    | Before reading table records, |
+      v  | in random order |   v    | sort their rowids and then    |
+      |  \_________________/   |    | read them in rowid order      |
+      |         |              |    \_______________________________/
+      |         |              |                    |
+      |         |              |                    |
+      +-->---+  |  +----<------+-----------<--------+
+             |  |  |                                
+             v  v  v
+      (table records and range_ids)
+
+  The choice of strategy depends on MRR scan properties, table properties
+  (whether we're scanning clustered primary key), and @@optimizer_switch
+  settings.
+  
+  Key-Ordered Retrieval
+  ---------------------
+  The idea is: if MRR scan is essentially a series of lookups on 
+   
+    tbl.key=value1 OR tbl.key=value2 OR ... OR tbl.key=valueN
+  
+  then it makes sense to collect and order the set of lookup values, i.e.
+   
+     sort(value1, value2, .. valueN)
+
+  and then do index lookups in index order. This results in fewer index page
+  fetch operations, and we also can avoid making multiple index lookups for the
+  same value. That is, if value1=valueN we can easily discover that after
+  sorting and make one index lookup for them instead of two.
+
+  Rowid-Ordered Retrieval
+  -----------------------
+  If we do a regular index scan or a series of index lookups, we'll be hitting
+  table records at random. For disk-based engines, this is much slower than 
+  reading the same records in disk order. We assume that disk ordering of
+  rows is the same as ordering of their rowids (which is provided by 
+  handler::cmp_ref())
+  In order to retrieve records in different order, we must separate index
+  scanning and record fetching, that is, MRR scan uses the following steps:
+
+    1. Scan the index (and only index, that is, with HA_EXTRA_KEYREAD on) and 
+        fill a buffer with {rowid, range_id} pairs
+    2. Sort the buffer by rowid value
+    3. for each {rowid, range_id} pair in the buffer
+         get record by rowid and return the {record, range_id} pair
+    4. Repeat the above steps until we've exhausted the list of ranges we're
+       scanning.
+
+  Buffer space management considerations
+  --------------------------------------
+  With regards to buffer/memory management, MRR interface specifies that 
+   - SQL layer provides multi_range_read_init() with buffer of certain size.
+   - MRR implementation may use (i.e. have at its disposal till the end of 
+     the MRR scan) all of the buffer, or return the unused end of the buffer 
+     to SQL layer.
+
+  DS-MRR needs buffer in order to accumulate and sort rowids and/or keys. When
+  we need to accumulate/sort only keys (or only rowids), it is fairly trivial.
+
+  When we need to accumulate/sort both keys and rowids, efficient buffer use
+  gets complicated. We need to:
+   - First, accumulate keys and sort them
+   - Then use the keys (smaller values go first) to obtain rowids. A key is not
+     needed after we've got matching rowids for it.
+   - Make sure that rowids are accumulated at the front of the buffer, so that we
+     can return the end part of the buffer to SQL layer, should there be too
+     few rowid values to occupy the buffer.
+
+  All of these goals are achieved by using the following scheme:
+
+     |                    |   We get an empty buffer from SQL layer.   
+
+     |                  *-|    
+     |               *----|   First, we fill the buffer with keys. Key_buffer
+     |            *-------|   part grows from end of the buffer space to start
+     |         *----------|   (In this picture, the buffer is big enough to
+     |      *-------------|    accomodate all keys and even have some space left)
+
+     |      *=============|   We want to do key-ordered index scan, so we sort
+                              the keys
+
+     |-x      *===========|   Then we use the keys get rowids. Rowids are 
+     |----x      *========|   stored from start of buffer space towards the end.
+     |--------x     *=====|   The part of the buffer occupied with keys
+     |------------x   *===|   gradually frees up space for rowids. In this
+     |--------------x   *=|   picture we run out of keys before we've ran out
+     |----------------x   |   of buffer space (it can be other way as well).
+
+     |================x   |   Then we sort the rowids.
+                     
+     |                |~~~|   The unused part of the buffer is at the end, so
+                              we can return it to the SQL layer.
+
+     |================*       Sorted rowids are then used to read table records 
+                              in disk order
+
+*/
+
+class DsMrr_impl
+{
+public:
+  typedef void (handler::*range_check_toggle_func_t)(bool on);
+
+  DsMrr_impl()
+    : secondary_file(NULL) {};
+  
   void init(handler *h_arg, TABLE *table_arg)
   {
-    h= h_arg; 
+    primary_file= h_arg; 
     table= table_arg;
   }
-  int dsmrr_init(handler *h, RANGE_SEQ_IF *seq_funcs, void *seq_init_param, 
-                 uint n_ranges, uint mode, HANDLER_BUFFER *buf);
+  int dsmrr_init(handler *h_arg, RANGE_SEQ_IF *seq_funcs, 
+                 void *seq_init_param, uint n_ranges, uint mode, 
+                 HANDLER_BUFFER *buf);
   void dsmrr_close();
-  int dsmrr_fill_buffer();
   int dsmrr_next(char **range_info);
 
-  ha_rows dsmrr_info(uint keyno, uint n_ranges, uint keys, uint *bufsz,
-                     uint *flags, COST_VECT *cost);
+  ha_rows dsmrr_info(uint keyno, uint n_ranges, uint keys, uint key_parts, 
+                     uint *bufsz, uint *flags, COST_VECT *cost);
 
   ha_rows dsmrr_info_const(uint keyno, RANGE_SEQ_IF *seq, 
                             void *seq_init_param, uint n_ranges, uint *bufsz,
                             uint *flags, COST_VECT *cost);
 private:
+  /* Buffer to store (key, range_id) pairs */
+  Lifo_buffer *key_buffer;
+
+  /*
+    The "owner" handler object (the one that is expected to "own" this object
+    and call its functions).
+  */
+  handler *primary_file;
+  TABLE *table; /* Always equal to primary_file->table */
+
+  /*
+    Secondary handler object. (created when needed, we need it when we need 
+    to run both index scan and rnd_pos() scan at the same time)
+  */
+  handler *secondary_file;
+  
+  uint keyno; /* index we're running the scan on */
+  /* TRUE <=> need range association, buffers hold {rowid, range_id} pairs */
+  bool is_mrr_assoc;
+
+  Mrr_reader_factory reader_factory;
+
+  Mrr_reader *strategy;
+  bool strategy_exhausted;
+
+  Mrr_index_reader *index_strategy;
+
+  /* The whole buffer space that we're using */
+  uchar *full_buf;
+  uchar *full_buf_end;
+  
+  /* 
+    When using both rowid and key buffers: the boundary between key and rowid
+    parts of the buffer. This is the "original" value, actual memory ranges 
+    used by key and rowid parts may be different because of dynamic space 
+    reallocation between them.
+  */
+  uchar *rowid_buffer_end;
+ 
+  /*
+    One of the following two is used for key buffer: forward is used when 
+    we only need key buffer, backward is used when we need both key and rowid
+    buffers.
+  */
+  Forward_lifo_buffer forward_key_buf;
+  Backward_lifo_buffer backward_key_buf;
+
+  /*
+    Buffer to store (rowid, range_id) pairs, or just rowids if 
+    is_mrr_assoc==FALSE
+  */
+  Forward_lifo_buffer rowid_buffer;
+  
   bool choose_mrr_impl(uint keyno, ha_rows rows, uint *flags, uint *bufsz, 
                        COST_VECT *cost);
   bool get_disk_sweep_mrr_cost(uint keynr, ha_rows rows, uint flags, 
                                uint *buffer_size, COST_VECT *cost);
+  bool check_cpk_scan(THD *thd, uint keyno, uint mrr_flags);
+
+  bool setup_buffer_sharing(uint key_size_in_keybuf, key_part_map key_tuple_map);
+
+  /* Buffer_manager and its member functions */
+  Buffer_manager buf_manager;
+  static void redistribute_buffer_space(void *dsmrr_arg);
+  static void reset_buffer_sizes(void *dsmrr_arg);
+  static void do_nothing(void *dsmrr_arg);
+
+  Lifo_buffer* get_key_buffer() { return key_buffer; }
+
+  friend class Key_value_records_iterator;
+  friend class Mrr_ordered_index_reader;
+  friend class Mrr_ordered_rndpos_reader;
+
+  int  setup_two_handlers();
+  void close_second_handler();
 };
 
+/**
+  @} (end of group DS-MRR declarations)
+*/
+
diff --git a/sql/mysql_priv.h b/sql/mysql_priv.h
index 666882d6890..122baf47bac 100644
--- a/sql/mysql_priv.h
+++ b/sql/mysql_priv.h
@@ -570,17 +570,18 @@ protected:
 #define OPTIMIZER_SWITCH_PARTIAL_MATCH_ROWID_MERGE 512
 #define OPTIMIZER_SWITCH_PARTIAL_MATCH_TABLE_SCAN 1024
 #define OPTIMIZER_SWITCH_SUBQUERY_CACHE (1<<11)
-#define OPTIMIZER_SWITCH_OUTER_JOIN_WITH_CACHE (1<<12)
-#define OPTIMIZER_SWITCH_SEMIJOIN_WITH_CACHE (1<<13)
-#define OPTIMIZER_SWITCH_JOIN_CACHE_INCREMENTAL (1<<14)
-#define OPTIMIZER_SWITCH_JOIN_CACHE_HASHED (1<<15)
-#define OPTIMIZER_SWITCH_JOIN_CACHE_BKA (1<<16)
+#define OPTIMIZER_SWITCH_MRR_SORT_KEYS (1<<12)
+#define OPTIMIZER_SWITCH_OUTER_JOIN_WITH_CACHE (1<<13)
+#define OPTIMIZER_SWITCH_SEMIJOIN_WITH_CACHE (1<<14)
+#define OPTIMIZER_SWITCH_JOIN_CACHE_INCREMENTAL (1<<15)
+#define OPTIMIZER_SWITCH_JOIN_CACHE_HASHED (1<<16)
+#define OPTIMIZER_SWITCH_JOIN_CACHE_BKA (1<<17)
 
 #ifdef DBUG_OFF
-#  define OPTIMIZER_SWITCH_LAST (1<<17)
-#else
-#  define OPTIMIZER_SWITCH_TABLE_ELIMINATION (1<<17)
 #  define OPTIMIZER_SWITCH_LAST (1<<18)
+#else
+#  define OPTIMIZER_SWITCH_TABLE_ELIMINATION (1<<18)
+#  define OPTIMIZER_SWITCH_LAST (1<<19)
 #endif
 
 #ifdef DBUG_OFF 
@@ -596,6 +597,8 @@ protected:
                                     OPTIMIZER_SWITCH_SEMIJOIN | \
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_ROWID_MERGE|\
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_TABLE_SCAN|\
+                                    OPTIMIZER_SWITCH_SUBQUERY_CACHE|\
+                                    OPTIMIZER_SWITCH_MRR_SORT_KEYS|\
                                     OPTIMIZER_SWITCH_SUBQUERY_CACHE | \
                                     OPTIMIZER_SWITCH_JOIN_CACHE_INCREMENTAL | \
                                     OPTIMIZER_SWITCH_JOIN_CACHE_HASHED | \
@@ -613,7 +616,8 @@ protected:
                                     OPTIMIZER_SWITCH_SEMIJOIN | \
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_ROWID_MERGE|\
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_TABLE_SCAN|\
-                                    OPTIMIZER_SWITCH_SUBQUERY_CACHE | \
+                                    OPTIMIZER_SWITCH_SUBQUERY_CACHE|\
+                                    OPTIMIZER_SWITCH_MRR_SORT_KEYS|\
                                     OPTIMIZER_SWITCH_JOIN_CACHE_INCREMENTAL | \
                                     OPTIMIZER_SWITCH_JOIN_CACHE_HASHED | \
                                     OPTIMIZER_SWITCH_JOIN_CACHE_BKA)
@@ -1880,6 +1884,7 @@ void key_unpack(String *to,TABLE *form,uint index);
 bool is_key_used(TABLE *table, uint idx, const MY_BITMAP *fields);
 int key_cmp(KEY_PART_INFO *key_part, const uchar *key, uint key_length);
 extern "C" int key_rec_cmp(void *key_info, uchar *a, uchar *b);
+int key_tuple_cmp(KEY_PART_INFO *part, uchar *key1, uchar *key2, uint tuple_length);
 
 bool init_errmessage(void);
 #endif /* MYSQL_SERVER */
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index b9faf09f4f4..d7a457c6921 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -345,6 +345,7 @@ static const char *optimizer_switch_names[]=
   "partial_match_rowid_merge",
   "partial_match_table_scan",
   "subquery_cache",
+  "mrr_sort_keys",
   "outer_join_with_cache",
   "semijoin_with_cache",
   "join_cache_incremental",
@@ -371,6 +372,7 @@ static const unsigned int optimizer_switch_names_len[]=
   sizeof("partial_match_rowid_merge") - 1,
   sizeof("partial_match_table_scan") - 1,
   sizeof("subquery_cache") - 1,
+  sizeof("mrr_sort_keys") - 1,
   sizeof("outer_join_with_cache") - 1,
   sizeof("semijoin_with_cache") - 1,
   sizeof("join_cache_incremental") - 1,
@@ -475,6 +477,7 @@ static const char *optimizer_switch_str="index_merge=on,index_merge_union=on,"
                                         "partial_match_rowid_merge=on,"
                                         "partial_match_table_scan=on,"
                                         "subquery_cache=on,"
+                                        "mrr_sort_keys=on,"
                                         "join_cache_incremental=on,"
                                         "join_cache_hashed=on,"
                                         "join_cache_bka=on"
diff --git a/sql/opt_index_cond_pushdown.cc b/sql/opt_index_cond_pushdown.cc
index 71eadfb45cf..6f0210a3d21 100644
--- a/sql/opt_index_cond_pushdown.cc
+++ b/sql/opt_index_cond_pushdown.cc
@@ -381,6 +381,7 @@ void push_index_cond(JOIN_TAB *tab, uint keyno, bool other_tbls_ok,
                                  QT_ORDINARY););
 
         tab->select->cond= tab->select_cond;
+        tab->select->pre_idx_push_select_cond= tab->pre_idx_push_select_cond;
       }
     }
   }
diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index 9e903d3121b..9d89911eec3 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -1119,7 +1119,7 @@ SQL_SELECT *make_select(TABLE *head, table_map const_tables,
 }
 
 
-SQL_SELECT::SQL_SELECT() :quick(0),cond(0),free_cond(0)
+SQL_SELECT::SQL_SELECT() :quick(0),cond(0),pre_idx_push_select_cond(NULL),free_cond(0)
 {
   quick_keys.clear_all(); needed_reg.clear_all();
   my_b_clear(&file);
@@ -7459,7 +7459,7 @@ ha_rows check_quick_select(PARAM *param, uint idx, bool index_only,
                            uint *mrr_flags, uint *bufsize, COST_VECT *cost)
 {
   SEL_ARG_RANGE_SEQ seq;
-  RANGE_SEQ_IF seq_if = {sel_arg_range_seq_init, sel_arg_range_seq_next, 0, 0};
+  RANGE_SEQ_IF seq_if = {NULL, sel_arg_range_seq_init, sel_arg_range_seq_next, 0, 0};
   handler *file= param->table->file;
   ha_rows rows;
   uint keynr= param->real_keynr[idx];
@@ -8016,6 +8016,7 @@ QUICK_RANGE_SELECT *get_quick_select_for_ref(THD *thd, TABLE *table,
 
   quick->mrr_buf_size= thd->variables.mrr_buff_size;
   if (table->file->multi_range_read_info(quick->index, 1, (uint)records,
+                                         ~0, 
                                          &quick->mrr_buf_size,
                                          &quick->mrr_flags, &cost))
     goto err;
@@ -8420,7 +8421,7 @@ int QUICK_RANGE_SELECT::reset()
   if (!mrr_buf_desc)
     empty_buf.buffer= empty_buf.buffer_end= empty_buf.end_of_used_area= NULL;
  
-  RANGE_SEQ_IF seq_funcs= {quick_range_seq_init, quick_range_seq_next, 0, 0};
+  RANGE_SEQ_IF seq_funcs= {NULL, quick_range_seq_init, quick_range_seq_next, 0, 0};
   error= file->multi_range_read_init(&seq_funcs, (void*)this, ranges.elements,
                                      mrr_flags, mrr_buf_desc? mrr_buf_desc: 
                                                               &empty_buf);
diff --git a/sql/opt_range.h b/sql/opt_range.h
index 7b74ea30c80..4761d95d0ca 100644
--- a/sql/opt_range.h
+++ b/sql/opt_range.h
@@ -826,6 +826,13 @@ class SQL_SELECT :public Sql_alloc {
  public:
   QUICK_SELECT_I *quick;	// If quick-select used
   COND		*cond;		// where condition
+
+  /*
+    When using Index Condition Pushdown: condition that we've had before
+    extracting and pushing index condition.
+    In other cases, NULL.
+  */
+  Item *pre_idx_push_select_cond;
   TABLE	*head;
   IO_CACHE file;		// Positions to used records
   ha_rows records;		// Records in use if read from file
diff --git a/sql/sql_join_cache.cc b/sql/sql_join_cache.cc
index c0e68c6090f..240e18ed913 100644
--- a/sql/sql_join_cache.cc
+++ b/sql/sql_join_cache.cc
@@ -2136,7 +2136,7 @@ enum_nested_loop_state JOIN_CACHE::join_matching_records(bool skip_last)
 
   /* Prepare to retrieve all records of the joined table */
   if ((error= join_tab_scan->open())) 
-    goto finish;
+    goto finish; /* psergey-note: if this returns error, we will assert in net_send_statement() */
 
   while (!(error= join_tab_scan->next()))   
   {
@@ -2627,6 +2627,7 @@ int JOIN_CACHE_HASHED::realloc_buffer()
   return rc;   	
 }
 
+
 /*
   Get maximum size of the additional space per record used for record keys
 
@@ -3596,6 +3597,16 @@ int JOIN_TAB_SCAN_MRR::next()
 }
 
 
+static 
+void bka_range_seq_key_info(void *init_params, uint *length, 
+                            key_part_map *map)
+{
+  TABLE_REF *ref= &(((JOIN_CACHE*)init_params)->join_tab->ref);
+  *length= ref->key_length;
+  *map= (key_part_map(1) << ref->key_parts) - 1;
+}
+
+
 /*
   Initialize retrieval of range sequence for BKA join algorithm
     
@@ -3872,9 +3883,11 @@ void JOIN_CACHE_BKA::read_next_candidate_for_match(uchar *rec_ptr)
 
 int JOIN_CACHE_BKA::init()
 {
+  int res;
   bool check_only_first_match= join_tab->check_only_first_match();
 
-  RANGE_SEQ_IF rs_funcs= { bka_range_seq_init, 
+  RANGE_SEQ_IF rs_funcs= { bka_range_seq_key_info,
+                           bka_range_seq_init, 
                            bka_range_seq_next,
                            check_only_first_match ?
                              bka_range_seq_skip_record : 0,
@@ -3882,11 +3895,18 @@ int JOIN_CACHE_BKA::init()
 
   DBUG_ENTER("JOIN_CACHE_BKA::init");
 
-  if (!(join_tab_scan= new JOIN_TAB_SCAN_MRR(join, join_tab, 
-                                             mrr_mode, rs_funcs)))
+  JOIN_TAB_SCAN_MRR *jsm;
+  if (!(join_tab_scan= jsm= new JOIN_TAB_SCAN_MRR(join, join_tab, 
+                                                  mrr_mode, rs_funcs)))
     DBUG_RETURN(1);
 
-  DBUG_RETURN(JOIN_CACHE::init());
+  if ((res= JOIN_CACHE::init()))
+    DBUG_RETURN(res);
+
+  if (use_emb_key)
+    jsm->mrr_mode |= HA_MRR_MATERIALIZED_KEYS;
+
+  DBUG_RETURN(0);
 }
 
 
@@ -4256,7 +4276,8 @@ int JOIN_CACHE_BKAH::init()
 
   no_association= test(mrr_mode & HA_MRR_NO_ASSOCIATION);
 
-  RANGE_SEQ_IF rs_funcs= { bkah_range_seq_init,
+  RANGE_SEQ_IF rs_funcs= { bka_range_seq_key_info,
+                           bkah_range_seq_init,
                            bkah_range_seq_next,
                            check_only_first_match && !no_association ?
                              bkah_range_seq_skip_record : 0,
diff --git a/sql/sql_join_cache.h b/sql/sql_join_cache.h
index ea84a50c885..fccd32e1319 100644
--- a/sql/sql_join_cache.h
+++ b/sql/sql_join_cache.h
@@ -1195,6 +1195,7 @@ public:
  
   int next();
 
+  friend class JOIN_CACHE_BKA; /* it needs to add an mrr_mode flag after JOIN_CACHE::init() call */
 };
 
 /*
diff --git a/sql/sql_lifo_buffer.h b/sql/sql_lifo_buffer.h
new file mode 100644
index 00000000000..f85bc1e6c41
--- /dev/null
+++ b/sql/sql_lifo_buffer.h
@@ -0,0 +1,340 @@
+/**
+  @defgroup Bi-directional LIFO buffers used by DS-MRR implementation
+  @{
+*/
+
+class Forward_lifo_buffer;
+class Backward_lifo_buffer;
+
+
+/*
+  A base class for in-memory buffer used by DS-MRR implementation. Common
+  properties:
+  - The buffer is last-in-first-out, i.e. elements that are written last are
+    read first.
+  - The buffer contains fixed-size elements. The elements are either atomic
+    byte sequences or pairs of them.
+  - The buffer resides in the memory provided by the user. It is possible to
+     = dynamically (ie. between write operations) add ajacent memory space to
+       the buffer
+     = dynamically remove unused space from the buffer.
+    The intent of this is to allow to have two buffers on adjacent memory
+    space, one is being read from (and so its space shrinks), while the other 
+    is being written to (and so it needs more and more space).
+
+  There are two concrete classes, Forward_lifo_buffer and Backward_lifo_buffer.
+*/
+
+class Lifo_buffer 
+{
+protected:
+  /**
+    Pointers to data to be written. write() call will assume that 
+    (*write_ptr1) points to size1 bytes of data to be written.
+    If write_ptr2 != NULL then the buffer stores pairs, and (*write_ptr2) 
+    points to size2 bytes of data that form the second component.
+  */
+  uchar **write_ptr1;
+  size_t size1;
+  uchar **write_ptr2;
+  size_t size2;
+
+  /**
+    read() will do reading by storing pointer to read data into *read_ptr1 (if
+    the buffer stores atomic elements), or into {*read_ptr1, *read_ptr2} (if
+    the buffer stores pairs).
+  */
+  uchar **read_ptr1;
+  uchar **read_ptr2;
+
+  uchar *start; /**< points to start of buffer space */
+  uchar *end;   /**< points to just beyond the end of buffer space */
+public:
+
+  enum enum_direction {
+    BACKWARD=-1, /**< buffer is filled/read from bigger to smaller memory addresses */
+    FORWARD=1  /**< buffer is filled/read from smaller to bigger memory addresses */
+  };
+
+  virtual enum_direction type() = 0;
+
+  /* Buffer space control functions */
+
+  /** Let the buffer store data in the given space. */
+  void set_buffer_space(uchar *start_arg, uchar *end_arg) 
+  {
+    start= start_arg;
+    end= end_arg;
+    TRASH(start, end - start);
+    reset();
+  }
+  
+  /** 
+    Specify where write() should get the source data from, as well as source
+    data size.
+  */
+  void setup_writing(uchar **data1, size_t len1, uchar **data2, size_t len2)
+  {
+    write_ptr1= data1;
+    size1= len1;
+    write_ptr2= data2;
+    size2= len2;
+  }
+
+  /** 
+    Specify where read() should store pointers to read data, as well as read
+    data size. The sizes must match those passed to setup_writing().
+  */
+  void setup_reading(uchar **data1, size_t len1, uchar **data2, size_t len2)
+  {
+    read_ptr1= data1;
+    DBUG_ASSERT(len1 == size1);
+    read_ptr2= data2;
+    DBUG_ASSERT(len2 == size2);
+  }
+  
+  bool can_write()
+  {
+    return have_space_for(size1 + (write_ptr2 ? size2 : 0));
+  }
+  virtual void write() = 0;
+
+  bool is_empty() { return used_size() == 0; }
+  virtual bool read() = 0;
+  
+  void sort(qsort2_cmp cmp_func, void *cmp_func_arg)
+  {
+    uint elem_size= size1 + (write_ptr2 ? size2 : 0);
+    uint n_elements= used_size() / elem_size;
+    my_qsort2(used_area(), n_elements, elem_size, cmp_func, cmp_func_arg);
+  }
+
+  virtual void reset() = 0;
+  virtual uchar *end_of_space() = 0;
+protected:
+  virtual size_t used_size() = 0;
+  
+  /* To be used only by iterator class: */
+  virtual uchar *get_pos()= 0;
+  virtual bool read(uchar **position)= 0;
+  friend class Lifo_buffer_iterator;
+public:
+  virtual bool have_space_for(size_t bytes) = 0;
+
+  virtual void remove_unused_space(uchar **unused_start, uchar **unused_end)=0;
+  virtual uchar *used_area() = 0; 
+  virtual ~Lifo_buffer() {};
+};
+
+
+/**
+  Forward LIFO buffer
+
+  The buffer that is being written to from start to end and read in the
+  reverse.  'pos' points to just beyond the end of used space.
+
+  It is possible to grow/shink the buffer at the end bound
+
+     used space      unused space  
+   *==============*-----------------*
+   ^              ^                 ^
+   |              |                 +--- end
+   |              +---- pos              
+   +--- start           
+*/
+
+class Forward_lifo_buffer: public Lifo_buffer
+{
+  uchar *pos;
+public:
+  enum_direction type() { return FORWARD; }
+  size_t used_size()
+  {
+    return (size_t)(pos - start);
+  }
+  void reset()
+  {
+    pos= start;
+  }
+  uchar *end_of_space() { return pos; }
+  bool have_space_for(size_t bytes)
+  {
+    return (pos + bytes < end);
+  }
+
+  void write()
+  {
+    write_bytes(*write_ptr1, size1);
+    if (write_ptr2)
+      write_bytes(*write_ptr2, size2);
+  }
+  void write_bytes(const uchar *data, size_t bytes)
+  {
+    DBUG_ASSERT(have_space_for(bytes));
+    memcpy(pos, data, bytes);
+    pos += bytes;
+  }
+  bool have_data(uchar *position, size_t bytes)
+  {
+    return ((position - start) >= (ptrdiff_t)bytes);
+  }
+  uchar *read_bytes(uchar **position, size_t bytes)
+  {
+    DBUG_ASSERT(have_data(*position, bytes));
+    *position= (*position) - bytes;
+    return *position;
+  }
+  bool read() { return read(&pos); }
+  bool read(uchar **position)
+  {
+    if (!have_data(*position, size1 + (read_ptr2 ? size2 : 0)))
+      return TRUE;
+    if (read_ptr2)
+      *read_ptr2= read_bytes(position, size2);
+    *read_ptr1= read_bytes(position, size1);
+    return FALSE;
+  }
+  void remove_unused_space(uchar **unused_start, uchar **unused_end)
+  {
+    DBUG_ASSERT(0); /* Don't need this yet */
+  }
+  /**
+    Add more space to the buffer. The caller is responsible that the space
+    being added is adjacent to the end of the buffer.
+
+    @param unused_start Start of space
+    @param unused_end   End of space
+  */
+  void grow(uchar *unused_start, uchar *unused_end)
+  {
+    DBUG_ASSERT(unused_end >= unused_start);
+    DBUG_ASSERT(end == unused_start);
+    TRASH(unused_start, unused_end - unused_start);
+    end= unused_end;
+  }
+  /* Return pointer to start of the memory area that is occupied by the data */
+  uchar *used_area() { return start; }
+  friend class Lifo_buffer_iterator;
+  uchar *get_pos() { return pos; }
+};
+
+
+
+/**
+  Backward LIFO buffer
+
+  The buffer that is being written to from start to end and read in the
+  reverse.  'pos' points to the start of used space.
+
+  It is possible to grow/shink the buffer at the start.
+
+     unused space      used space  
+   *--------------*=================*
+   ^              ^                 ^
+   |              |                 +--- end
+   |              +---- pos              
+   +--- start           
+*/
+class Backward_lifo_buffer: public Lifo_buffer
+{
+  uchar *pos;
+public:
+  enum_direction type() { return BACKWARD; }
+ 
+  size_t used_size()
+  {
+    return (size_t)(end - pos);
+  }
+  void reset()
+  {
+    pos= end;
+  }
+  uchar *end_of_space() { return end; }
+  bool have_space_for(size_t bytes)
+  {
+    return (pos - bytes >= start);
+  }
+  void write()
+  {
+    if (write_ptr2)
+      write_bytes(*write_ptr2, size2);
+    write_bytes(*write_ptr1, size1);
+  }
+  void write_bytes(const uchar *data, size_t bytes)
+  {
+    DBUG_ASSERT(have_space_for(bytes));
+    pos -= bytes;
+    memcpy(pos, data, bytes);
+  }
+  bool read()
+  {
+    return read(&pos);
+  }
+  bool read(uchar **position)
+  {
+    if (!have_data(*position, size1 + (read_ptr2 ? size2 : 0)))
+      return TRUE;
+    *read_ptr1= read_bytes(position, size1);
+    if (read_ptr2)
+      *read_ptr2= read_bytes(position, size2);
+    return FALSE;
+  }
+  bool have_data(uchar *position, size_t bytes)
+  {
+    return ((end - position) >= (ptrdiff_t)bytes);
+  }
+  uchar *read_bytes(uchar **position, size_t bytes)
+  {
+    DBUG_ASSERT(have_data(*position, bytes));
+    uchar *ret= *position;
+    *position= *position + bytes;
+    return ret;
+  }
+  /**
+    Stop using/return the unused part of the space
+    @param unused_start  OUT Start of the unused space
+    @param unused_end    OUT End of the unused space
+  */
+  void remove_unused_space(uchar **unused_start, uchar **unused_end)
+  {
+    *unused_start= start;
+    *unused_end= pos;
+    start= pos;
+  }
+  void grow(uchar *unused_start, uchar *unused_end)
+  {
+    DBUG_ASSERT(0); /* Not used for backward buffers */
+  }
+  /* Return pointer to start of the memory area that is occupied by the data */
+  uchar *used_area() { return pos; }
+  friend class Lifo_buffer_iterator;
+  uchar *get_pos() { return pos; }
+};
+
+
+
+/** Iterator to walk over contents of the buffer without reading it. */
+class Lifo_buffer_iterator
+{
+  uchar *pos;
+  Lifo_buffer *buf;
+public:
+  void init(Lifo_buffer *buf_arg)
+  {
+    buf= buf_arg;
+    pos= buf->get_pos();
+  }
+  /*
+    Read the next value. The calling convention is the same as buf->read()
+    has.
+
+    @retval FALSE - ok
+    @retval TRUE  - EOF, reached the end of the buffer
+  */
+  bool read() 
+  {
+    return buf->read(&pos);
+  }
+};
+
+
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 2228d725c98..efd58c5bea4 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -7749,11 +7749,11 @@ uint check_join_cache_usage(JOIN_TAB *tab,
   case JT_EQ_REF:
     if (cache_level <=2 || (no_hashed_cache && no_bka_cache))
       goto no_join_cache;
-
-    flags= HA_MRR_NO_NULL_ENDPOINTS;
+    flags= HA_MRR_NO_NULL_ENDPOINTS | HA_MRR_SINGLE_POINT;
     if (tab->table->covering_keys.is_set(tab->ref.key))
       flags|= HA_MRR_INDEX_ONLY;
     rows= tab->table->file->multi_range_read_info(tab->ref.key, 10, 20,
+                                                  tab->ref.key_parts,
                                                   &bufsz, &flags, &cost);
 
     if ((cache_level <=4 && !no_hashed_cache) || no_bka_cache ||