DS-MRR improvements:

- address the review feedback (class/var renames)
- fix wrong test result (bug in buffer refill logic)

sql/multi_range_read.cc

@@ -623,21 +623,26 @@ int Mrr_ordered_rndpos_reader::get_next(char **range_info)
 
   while (1)
   {
-    if (rowid_buffer->is_empty())
+    if (rowid_buffer->is_empty()) /* We're out of rowids */
     {
-      /*
-        We're out of rowids. If there are still some sorted keys, use up them
-        first (that is, don't call re-fill for keys when we still have some).
-      */
+      /* First, finish off the sorted keys we have */ 
       if (!index_reader->eof())
       {
         if ((res= refill_buffer()))
           return res; /* for fatal errors */
       }
-      else
+
+      if (rowid_buffer->is_empty())
       {
-        //TODO: here: redistribute the buffer space, then refill the index
-        //reader, then refill us.
+        /*
+          Ok neither index_reader nor us have any records. Refill index
+          reader, then refill us.
+        */
+        // TODO: if key buffer is empty, too, redistribute the buffer space.
+  
+        if ((res= index_reader->refill_buffer()) ||
+            (res= refill_buffer()))
+          return res;
       }
     }
    
@@ -871,7 +876,7 @@ int DsMrr_impl::setup_two_handlers()
     if (keyno == h->pushed_idx_cond_keyno)
       pushed_cond= h->pushed_idx_cond;
     
-    Mrr_strategy *save_strategy= strategy;
+    Mrr_reader *save_strategy= strategy;
     strategy= NULL;
     /*
       Caution: this call will invoke this->dsmrr_close(). Do not put the
@@ -910,7 +915,7 @@ int DsMrr_impl::setup_two_handlers()
     if (h->inited == handler::INDEX)
     {
       handler *save_h2= h2;
-      Mrr_strategy *save_strategy= strategy;
+      Mrr_reader *save_strategy= strategy;
       h2= NULL;
       strategy= NULL;
       res= h->ha_index_end();
@@ -919,7 +924,7 @@ int DsMrr_impl::setup_two_handlers()
       if (res)
         goto error;
     }
-    if ((h->inited == handler::RND) && h->ha_rnd_init(FALSE))
+    if ((h->inited != handler::RND) && h->ha_rnd_init(FALSE))
       goto error;
   }
   DBUG_RETURN(0);

sql/multi_range_read.h

@@ -130,18 +130,18 @@ class Buffer_manager
   been reached and get_next() must not be called anymore.
 */
 
-class Mrr_strategy 
+class Mrr_reader 
 {
 public:
   virtual int get_next(char **range_info) = 0;
   virtual int refill_buffer()=0;
   
-  virtual ~Mrr_strategy() {};
+  virtual ~Mrr_reader() {}; /* just to remove compiler warning */
 };
 
 
 /* A common base for strategies that do index scans and produce index tuples */
-class Mrr_index_reader : public Mrr_strategy
+class Mrr_index_reader : public Mrr_reader
 {
 public:
   handler *h;
@@ -241,7 +241,7 @@ class Mrr_ordered_index_reader : public Mrr_index_reader
 
 /* MRR strategy that fetches rowids */
 
-class Mrr_ordered_rndpos_reader : public Mrr_strategy 
+class Mrr_ordered_rndpos_reader : public Mrr_reader 
 {
 public:
   int init(handler *h, Mrr_index_reader *index_reader, uint mode,
@@ -271,7 +271,7 @@ class Mrr_ordered_rndpos_reader : public Mrr_strategy
   uchar *rowids_range_id;
 };
 
-class Mrr_strategy_factory
+class Mrr_reader_factory
 {
 public:
   Mrr_ordered_rndpos_reader ordered_rndpos_reader;
@@ -458,8 +458,8 @@ class DsMrr_impl : public Buffer_manager
   /* TRUE <=> sort rowids and use rnd_pos() to get and return full records */
   //bool do_rndpos_scan;
 
-  Mrr_strategy_factory strategy_factory;
-  Mrr_strategy *strategy;
+  Mrr_reader_factory strategy_factory;
+  Mrr_reader *strategy;
   Mrr_index_reader *index_strategy;
 
   /* The whole buffer space that we're using */