Backport into MariaDB-5.2 the following:

WL#2474 "Multi Range Read: Change the default MRR implementation to implement new MRR interface"
WL#2475 "Batched range read functions for MyISAM/InnoDb"
        "Index condition pushdown for MyISAM/InnoDB"
Igor's fix from sp1r-igor@olga.mysql.com-20080330055902-07614:
  There could be observed the following problems:
  1. EXPLAIN did not mention pushdown conditions from on expressions in the 
  'extra' column.  As a result if a query had no where conditions pushed 
  down to a table, but had on conditions pushed to this table the 'extra' 
  column in the EXPLAIN for the table missed 'using where'.
  2. Conditions for ref access were not eliminated from on expressions 
  though such conditions were eliminated from the where condition.

1 files changed, 46 insertions, 11 deletions

diff --git a/storage/myisam/mi_key.c b/storage/myisam/mi_key.c
index 94f3f34ec58..aab5797a03b 100644
--- a/storage/myisam/mi_key.c
+++ b/storage/myisam/mi_key.c
@@ -31,7 +31,8 @@
               set_if_smaller(char_length,length);                           \
             } while(0)
 
-static int _mi_put_key_in_record(MI_INFO *info,uint keynr,uchar *record);
+static int _mi_put_key_in_record(MI_INFO *info,uint keynr,
+                                 my_bool unpack_blobs, uchar *record);
 
 /*
   Make a intern key from a record
@@ -312,6 +313,9 @@ uint _mi_pack_key(register MI_INFO *info, uint keynr, uchar *key, uchar *old,
     _mi_put_key_in_record()
     info		MyISAM handler
     keynr		Key number that was used
+    unpack_blobs        TRUE  <=> Unpack blob columns
+                        FALSE <=> Skip them. This is used by index condition 
+                                  pushdown check function
     record 		Store key here
 
     Last read key is in info->lastkey
@@ -325,7 +329,7 @@ uint _mi_pack_key(register MI_INFO *info, uint keynr, uchar *key, uchar *old,
 */
 
 static int _mi_put_key_in_record(register MI_INFO *info, uint keynr,
-				 uchar *record)
+                                 my_bool unpack_blobs, uchar *record)
 {
   reg2 uchar *key;
   uchar *pos,*key_end;
@@ -418,16 +422,19 @@ static int _mi_put_key_in_record(register MI_INFO *info, uint keynr,
       if (length > keyseg->length || key+length > key_end)
 	goto err;
 #endif
-      memcpy(record+keyseg->start+keyseg->bit_start,
-	     (char*) &blob_ptr,sizeof(char*));
-      memcpy(blob_ptr,key,length);
-      blob_ptr+=length;
+      if (unpack_blobs)
+      {
+        memcpy(record+keyseg->start+keyseg->bit_start,
+               (char*) &blob_ptr,sizeof(char*));
+        memcpy(blob_ptr,key,length);
+        blob_ptr+=length;
 
-      /* The above changed info->lastkey2. Inform mi_rnext_same(). */
-      info->update&= ~HA_STATE_RNEXT_SAME;
+        /* The above changed info->lastkey2. Inform mi_rnext_same(). */
+        info->update&= ~HA_STATE_RNEXT_SAME;
 
-      _mi_store_blob_length(record+keyseg->start,
-			    (uint) keyseg->bit_start,length);
+        _mi_store_blob_length(record+keyseg->start,
+                              (uint) keyseg->bit_start,length);
+      }
       key+=length;
     }
     else if (keyseg->flag & HA_SWAP_KEY)
@@ -471,7 +478,7 @@ int _mi_read_key_record(MI_INFO *info, my_off_t filepos, uchar *buf)
   {
     if (info->lastinx >= 0)
     {				/* Read only key */
-      if (_mi_put_key_in_record(info,(uint) info->lastinx,buf))
+      if (_mi_put_key_in_record(info,(uint) info->lastinx, TRUE, buf))
       {
         mi_print_error(info->s, HA_ERR_CRASHED);
 	my_errno=HA_ERR_CRASHED;
@@ -487,6 +494,34 @@ int _mi_read_key_record(MI_INFO *info, my_off_t filepos, uchar *buf)
 
 
 /*
+  Save current key tuple to record and call index condition check function
+
+  SYNOPSIS
+    mi_check_index_cond()
+      info    MyISAM handler
+      keynr   Index we're running a scan on
+      record  Record buffer to use (it is assumed that index check function 
+              will look for column values there)
+
+  RETURN
+    -1  Error 
+    0   Index condition is not satisfied, continue scanning
+    1   Index condition is satisfied
+    2   Index condition is not satisfied, end the scan. 
+*/
+
+int mi_check_index_cond(register MI_INFO *info, uint keynr, uchar *record)
+{
+  if (_mi_put_key_in_record(info, keynr, FALSE, record))
+  {
+    mi_print_error(info->s, HA_ERR_CRASHED);
+    my_errno=HA_ERR_CRASHED;
+    return -1;
+  }
+  return info->index_cond_func(info->index_cond_func_arg);
+}
+
+/*
   Retrieve auto_increment info
 
   SYNOPSIS