Added page_range to records_in_range() to improve range statistics

Prototype change:
-  virtual ha_rows records_in_range(uint inx, key_range *min_key,
-                                   key_range *max_key)
+  virtual ha_rows records_in_range(uint inx, const key_range *min_key,
+                                   const key_range *max_key,
+                                   page_range *res)

The handler can ignore the page_range parameter. In the case the handler
updates the parameter, the optimizer can deduce the following:
- If previous range's last key is on the same block as next range's first
  key
- If the current key range is in one block
- We can also assume that the first and last block read are cached!
  This can be used for a better calculation of IO seeks when we
  estimate the cost of a range index scan.

The parameter is fully implemented for MyISAM, Aria and InnoDB.
A separate patch will update handler::multi_range_read_info_const() to
take the benefits of this change and also remove the double
records_in_range() calls that are not anymore needed.

2 files changed, 6 insertions, 3 deletions

diff --git a/storage/oqgraph/ha_oqgraph.cc b/storage/oqgraph/ha_oqgraph.cc
index d84a59474f6..20a3732ce95 100644
--- a/storage/oqgraph/ha_oqgraph.cc
+++ b/storage/oqgraph/ha_oqgraph.cc
@@ -1185,8 +1185,10 @@ int ha_oqgraph::rename_table(const char *, const char *)
 }
 
 
-ha_rows ha_oqgraph::records_in_range(uint inx, key_range *min_key,
-                                  key_range *max_key)
+ha_rows ha_oqgraph::records_in_range(uint inx,
+                                     const key_range *min_key,
+                                     const key_range *max_key,
+                                     page_range *pages)
 {
   if (graph->get_thd() != current_thd) {
     DBUG_PRINT( "oq-debug", ("g->table->in_use: 0x%lx <-- current_thd 0x%lx", (long) graph->get_thd(), (long) current_thd));
diff --git a/storage/oqgraph/ha_oqgraph.h b/storage/oqgraph/ha_oqgraph.h
index 0c0af6def97..c8e175df616 100644
--- a/storage/oqgraph/ha_oqgraph.h
+++ b/storage/oqgraph/ha_oqgraph.h
@@ -99,7 +99,8 @@ public:
   int extra(enum ha_extra_function operation);
   int external_lock(THD *thd, int lock_type);
   int delete_all_rows(void);
-  ha_rows records_in_range(uint inx, key_range *min_key, key_range *max_key);
+  ha_rows records_in_range(uint inx, const key_range *min_key,
+                           const key_range *max_key, page_range *pages);
   int delete_table(const char *from);
   int rename_table(const char * from, const char * to);
   int create(const char *name, TABLE *form, HA_CREATE_INFO *create_info);