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.

5 files changed, 23 insertions, 5 deletions

diff --git a/include/heap.h b/include/heap.h
index b734f8ae88d..f0ac527976c 100644
--- a/include/heap.h
+++ b/include/heap.h
@@ -239,8 +239,9 @@ extern int heap_disable_indexes(HP_INFO *info);
 extern int heap_enable_indexes(HP_INFO *info);
 extern int heap_indexes_are_disabled(HP_INFO *info);
 extern void heap_update_auto_increment(HP_INFO *info, const uchar *record);
-ha_rows hp_rb_records_in_range(HP_INFO *info, int inx, key_range *min_key,
-                               key_range *max_key);
+ha_rows hp_rb_records_in_range(HP_INFO *info, int inx,
+                               const key_range *min_key,
+                               const key_range *max_key);
 int hp_panic(enum ha_panic_function flag);
 int heap_rkey(HP_INFO *info, uchar *record, int inx, const uchar *key,
               key_part_map keypart_map, enum ha_rkey_function find_flag);
diff --git a/include/maria.h b/include/maria.h
index 2c711b0d31d..a4c425ced47 100644
--- a/include/maria.h
+++ b/include/maria.h
@@ -324,7 +324,9 @@ extern int maria_extra(MARIA_HA *file,
 		       enum ha_extra_function function, void *extra_arg);
 extern int maria_reset(MARIA_HA *file);
 extern ha_rows maria_records_in_range(MARIA_HA *info, int inx,
-				      key_range *min_key, key_range *max_key);
+                                      const key_range *min_key,
+                                      const key_range *max_key,
+                                      page_range *page);
 extern int maria_is_changed(MARIA_HA *info);
 extern int maria_delete_all_rows(MARIA_HA *info);
 extern uint maria_get_pointer_length(ulonglong file_length, uint def);
diff --git a/include/my_base.h b/include/my_base.h
index e73844d0937..5bc778655dc 100644
--- a/include/my_base.h
+++ b/include/my_base.h
@@ -636,6 +636,17 @@ typedef struct st_key_multi_range
 } KEY_MULTI_RANGE;
 
 
+/* Store first and last leaf page accessed by records_in_range */
+
+typedef struct st_page_range
+{
+  ulonglong first_page;
+  ulonglong last_page;
+} page_range;
+
+#define UNUSED_PAGE_NO ULONGLONG_MAX
+#define unused_page_range { UNUSED_PAGE_NO, UNUSED_PAGE_NO }
+
 /* For number of records */
 #ifdef BIG_TABLES
 #define rows2double(A)	ulonglong2double(A)
diff --git a/include/myisam.h b/include/myisam.h
index dfd5676a4d8..0942584e874 100644
--- a/include/myisam.h
+++ b/include/myisam.h
@@ -291,7 +291,9 @@ extern int mi_extra(struct st_myisam_info *file,
 		    void *extra_arg);
 extern int mi_reset(struct st_myisam_info *file);
 extern ha_rows mi_records_in_range(MI_INFO *info,int inx,
-                                   key_range *min_key, key_range *max_key);
+                                   const key_range *min_key,
+                                   const key_range *max_key,
+                                   page_range *pages);
 extern int mi_log(int activate_log);
 extern int mi_is_changed(struct st_myisam_info *info);
 extern int mi_delete_all_rows(struct st_myisam_info *info);
diff --git a/include/myisammrg.h b/include/myisammrg.h
index 76286000ff5..78e7ac00e8f 100644
--- a/include/myisammrg.h
+++ b/include/myisammrg.h
@@ -116,7 +116,9 @@ extern int myrg_extra(MYRG_INFO *file,enum ha_extra_function function,
 extern int myrg_reset(MYRG_INFO *info);
 extern void myrg_extrafunc(MYRG_INFO *info,invalidator_by_filename inv);
 extern ha_rows myrg_records_in_range(MYRG_INFO *info, int inx,
-                                     key_range *min_key, key_range *max_key);
+                                     const key_range *min_key,
+                                     const key_range *max_key,
+                                     page_range *pages);
 extern ha_rows myrg_records(MYRG_INFO *info);
 
 extern ulonglong myrg_position(MYRG_INFO *info);