DS-MRR/CPK improvements: correct buffer exhaustion handling

sql/multi_range_read.cc

@@ -484,7 +484,7 @@ int Mrr_ordered_index_reader::refill_buffer()
   scanning_key_val_iter= FALSE;
   index_scan_eof= FALSE; 
 
-  DBUG_RETURN(0);
+  DBUG_RETURN((no_more_keys && key_buffer->is_empty())? HA_ERR_END_OF_FILE:0);
 }
 
 
@@ -522,7 +522,10 @@ int Mrr_ordered_rndpos_reader::init(handler *h_arg,
   //if (!(mode & HA_MRR_NO_ASSOCIATION))
   //  rowid_buff_elem_size += sizeof(char*);
   
-  return index_reader->refill_buffer();
+  int res= index_reader->refill_buffer();
+  if (res && res!=HA_ERR_END_OF_FILE)
+    return res;
+  return 0;
 }
 
 
@@ -561,7 +564,7 @@ int Mrr_ordered_rndpos_reader::refill_buffer()
   last_identical_rowid= NULL;
 
   if (index_reader->eof())
-    DBUG_RETURN(0);
+    DBUG_RETURN(HA_ERR_END_OF_FILE);
 
   while (rowid_buffer->can_write())
   {
@@ -586,7 +589,7 @@ int Mrr_ordered_rndpos_reader::refill_buffer()
   rowid_buffer->setup_reading(&rowid, h->ref_length,
                               is_mrr_assoc? (uchar**)&rowids_range_id: NULL,
                               sizeof(void*));
-  DBUG_RETURN(0);
+  DBUG_RETURN((rowid_buffer->is_empty() && res) ? HA_ERR_END_OF_FILE : 0);
 }
 
 
@@ -632,8 +635,9 @@ int Mrr_ordered_rndpos_reader::get_next(char **range_info)
       /* First, finish off the sorted keys we have */ 
       if (!index_reader->eof())
       {
-        if ((res= refill_buffer()))
-          return res; /* for fatal errors */
+        res= refill_buffer();
+        if (res && res != HA_ERR_END_OF_FILE)
+          return res;
       }
 
       if (rowid_buffer->is_empty())
@@ -822,7 +826,8 @@ int DsMrr_impl::dsmrr_init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
     }
   }
   
-  if (strategy->refill_buffer())
+  res= strategy->refill_buffer();
+  if (res && res != HA_ERR_END_OF_FILE)
     goto error;
 
   /*

sql/multi_range_read.h

@@ -126,8 +126,16 @@ class Buffer_manager
   index tuple or a table record.
 
   Getting HA_ERR_END_OF_FILE from get_next() means that the source should be
-  re-filled. if eof() returns true after refill attempt, then the end of 
+  re-filled. 
+  
+  Was:
+  if eof() returns true after refill attempt, then the end of 
   stream has been reached and get_next() must not be called anymore.
+
+  Now:
+  if refill_buffer() returns HA_ERR_END_OF_FILE that means the stream is 
+  really exhausted.
+
 */
 
 class Mrr_reader 
@@ -168,7 +176,7 @@ class Mrr_simple_index_reader : public Mrr_index_reader
            void *seq_init_param, uint n_ranges,
            uint mode, Buffer_manager *buf_manager_arg);
   int get_next(char **range_info);
-  int refill_buffer() { return 0; }
+  int refill_buffer() { return HA_ERR_END_OF_FILE; }
   bool eof() { return test(res); }
   uchar *get_rowid_ptr() { return h->ref; }
   bool skip_record(char *range_id, uchar *rowid)