BUG#707925: Wrong result with join_cache_level=6 optimizer_use_mrr = force (incremental, BKA join)

- The problem was that Mrr_ordered_index_reader's interrupt_read() and resume_read() would 
  save and restore 1) index tuple  2) the rowid (as bytes returned by handler->position()).  Clustered 
  primary key columns were not saved/restored. 
  They are not explicitly present in the index tuple (i.e. table->key_info[secondary_key].key_parts 
  doesn't list them), but they are actually there, in particular 
  table->field[clustered_primary_key_member].part_of_key(secondary_key) == 1. Index condition pushdown
  code [correctly] uses the latter as inidication that pushed index condition can refer to clustered PK
  members. 

  The fix was to make interrupt_read()/resume_read() to save/restore clustered primary key members as well,
  so that we get correct values for them when evaluating pushed index condition.
[3rd attempt: remove the debugging aids, fix comments in testcase]

mysql-test/r/innodb_mrr.result

@@ -736,3 +736,32 @@ SELECT * FROM t1 WHERE c2 <=> NULL ORDER BY c2 LIMIT 2;
 c1	c2	c3
 08:29:45	NULL	2009-02-01
 drop table `t1`;
+#
+# BUG#707925: Wrong result with join_cache_level=6 optimizer_use_mrr =
+#   force (incremental, BKA join)
+#
+set @_save_join_cache_level= @@join_cache_level;
+set join_cache_level = 6;
+CREATE TABLE t1 ( 
+f1 int(11), f2 int(11), f3 varchar(1), f4 varchar(1), 
+PRIMARY KEY (f1), 
+KEY (f3), 
+KEY (f2)
+) ENGINE=InnoDB;
+INSERT INTO t1 VALUES ('11','8','f','f'),('12','5','v','v'),('13','8','s','s'),
+('14','8','a','a'),('15','6','p','p'),('16','7','z','z'),('17','2','a','a'),
+('18','5','h','h'),('19','7','h','h'),('20','2','v','v'),('21','9','v','v'),
+('22','142','b','b'),('23','3','y','y'),('24','0','v','v'),('25','3','m','m'),
+('26','5','z','z'),('27','9','n','n'),('28','1','d','d'),('29','107','a','a');
+select count(*) from (
+SELECT alias1.f2 
+FROM 
+t1 AS alias1 JOIN ( 
+t1 AS alias2 FORCE KEY (f3) JOIN 
+t1 AS alias3 FORCE KEY (f2) ON alias3.f2 = alias2.f2 AND alias3.f4 = alias2.f3 
+) ON alias3.f1 <= alias2.f1
+) X;
+count(*)
+361
+set join_cache_level=@_save_join_cache_level;
+drop table t1;

mysql-test/t/innodb_mrr.test

@@ -426,3 +426,32 @@ SELECT * FROM t1 WHERE c2 <=> NULL ORDER BY c2 LIMIT 2;
 SELECT * FROM t1 WHERE c2 <=> NULL ORDER BY c2 LIMIT 2;
 drop table `t1`;
 
+--echo #
+--echo # BUG#707925: Wrong result with join_cache_level=6 optimizer_use_mrr =
+--echo #   force (incremental, BKA join)
+--echo #
+set @_save_join_cache_level= @@join_cache_level;
+set join_cache_level = 6;
+CREATE TABLE t1 ( 
+  f1 int(11), f2 int(11), f3 varchar(1), f4 varchar(1), 
+  PRIMARY KEY (f1), 
+  KEY (f3), 
+  KEY (f2)
+) ENGINE=InnoDB;
+INSERT INTO t1 VALUES ('11','8','f','f'),('12','5','v','v'),('13','8','s','s'),
+('14','8','a','a'),('15','6','p','p'),('16','7','z','z'),('17','2','a','a'),
+('18','5','h','h'),('19','7','h','h'),('20','2','v','v'),('21','9','v','v'),
+('22','142','b','b'),('23','3','y','y'),('24','0','v','v'),('25','3','m','m'),
+('26','5','z','z'),('27','9','n','n'),('28','1','d','d'),('29','107','a','a');
+
+select count(*) from (
+  SELECT alias1.f2 
+  FROM 
+    t1 AS alias1 JOIN ( 
+      t1 AS alias2 FORCE KEY (f3) JOIN 
+      t1 AS alias3 FORCE KEY (f2) ON alias3.f2 = alias2.f2 AND alias3.f4 = alias2.f3 
+    ) ON alias3.f1 <= alias2.f1
+) X;
+
+set join_cache_level=@_save_join_cache_level;
+drop table t1;

sql/multi_range_read.cc

@@ -387,15 +387,25 @@ int Mrr_ordered_index_reader::get_next(char **range_info)
 
 bool Mrr_ordered_index_reader::set_interruption_temp_buffer(uint rowid_length,
                                                             uint key_len, 
+                                                            uint saved_pk_len,
                                                             uchar **space_start,
                                                             uchar *space_end)
 {
-  if (space_end - *space_start <= (ptrdiff_t)(rowid_length + key_len))
+  if (space_end - *space_start <= (ptrdiff_t)(rowid_length + key_len + saved_pk_len))
     return TRUE;
   support_scan_interruptions= TRUE; 
   
   saved_rowid= *space_start;
   *space_start += rowid_length;
+  
+  if (saved_pk_len)
+  {
+    saved_primary_key= *space_start;
+    *space_start += saved_pk_len;
+  }
+  else
+    saved_primary_key= NULL;
+
   saved_key_tuple= *space_start;
   *space_start += key_len;
 
@@ -406,18 +416,26 @@ bool Mrr_ordered_index_reader::set_interruption_temp_buffer(uint rowid_length,
 void Mrr_ordered_index_reader::set_no_interruption_temp_buffer()
 {
   support_scan_interruptions= FALSE;
-  saved_key_tuple= saved_rowid= NULL; /* safety */
+  saved_key_tuple= saved_rowid= saved_primary_key= NULL; /* safety */
   have_saved_rowid= FALSE;
 }
 
 void Mrr_ordered_index_reader::interrupt_read()
 {
   DBUG_ASSERT(support_scan_interruptions);
+  TABLE *table= file->get_table();
   /* Save the current key value */
-  key_copy(saved_key_tuple, file->get_table()->record[0], 
-           &file->get_table()->key_info[file->active_index],
+  key_copy(saved_key_tuple, table->record[0],
+           &table->key_info[file->active_index],
            keypar.key_tuple_length);
   
+  if (saved_primary_key)
+  {
+    key_copy(saved_primary_key, table->record[0], 
+             &table->key_info[table->s->primary_key],
+             table->key_info[table->s->primary_key].key_length);
+  }
+
   /* Save the last rowid */
   memcpy(saved_rowid, file->ref, file->ref_length);
   have_saved_rowid= TRUE;
@@ -433,9 +451,16 @@ void Mrr_ordered_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],
+  TABLE *table= file->get_table();
+  key_restore(table->record[0], saved_key_tuple, 
+              &table->key_info[file->active_index],
               keypar.key_tuple_length);
+  if (saved_primary_key)
+  {
+    key_restore(table->record[0], saved_primary_key, 
+                &table->key_info[table->s->primary_key],
+                table->key_info[table->s->primary_key].key_length);
+  }
 }
 
 
@@ -819,9 +844,17 @@ int DsMrr_impl::dsmrr_init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
     /* Ordered index reader needs some space to store an index tuple */
     if (strategy != index_strategy)
     {
+      uint saved_pk_length=0;
+      if (h_idx->primary_key_is_clustered())
+      {
+        uint pk= h_idx->get_table()->s->primary_key;
+        saved_pk_length= h_idx->get_table()->key_info[pk].key_length;
+      }
+
       if (reader_factory.ordered_index_reader.
             set_interruption_temp_buffer(primary_file->ref_length,
                                          keypar.key_tuple_length,
+                                         saved_pk_length,
                                          &full_buf, full_buf_end))
         goto use_default_impl;
     }

sql/multi_range_read.h

@@ -272,6 +272,7 @@ public:
   }
   
   bool set_interruption_temp_buffer(uint rowid_length, uint key_len, 
+                                    uint saved_pk_len,
                                     uchar **space_start, uchar *space_end);
   void set_no_interruption_temp_buffer();
 
@@ -301,19 +302,27 @@ private:
   /* TRUE == reached eof when enumerating ranges */
   bool source_exhausted;
    
-  bool support_scan_interruptions;
   /* 
-    Space where we save the rowid of the last record we've returned. This is
-    needed for the cases where index scan is interrupted by some other activity
-    that destroys contents in file->record[0] (which some storage engines use
-    to store the last rowid value)
+    Following members are for interrupt_read()/resume_read(). The idea is that 
+    in some cases index scan that is done by this object is interrupted by
+    rnd_pos() calls made by Mrr_ordered_rndpos_reader. The problem is that
+    we're sharing handler->record[0] with that object, and it destroys its
+    contents.
+    We need to save/restore our current
+    - index tuple (for pushed index condition checks)
+    - clustered primary key values (again, for pushed index condition checks)
+    - rowid of the last record we've retrieved (in case this rowid matches
+      multiple ranges and we'll need to return it again)
   */ 
+  bool support_scan_interruptions;
+  /* Space where we save the rowid of the last record we've returned */
   uchar *saved_rowid;
   
   /* TRUE <=> saved_rowid has the last saved rowid */
   bool have_saved_rowid;
   
-  uchar *saved_key_tuple;
+  uchar *saved_key_tuple; /* Saved current key tuple */
+  uchar *saved_primary_key; /* Saved current primary key tuple */
 
   static int compare_keys(void* arg, uchar* key1, uchar* key2);
   static int compare_keys_reverse(void* arg, uchar* key1, uchar* key2);