1 files changed, 129 insertions, 0 deletions
diff --git a/sql/filesort_utils.h b/sql/filesort_utils.h
new file mode 100644
index 00000000000..00fa6f2566b
--- /dev/null
+++ b/sql/filesort_utils.h
@@ -0,0 +1,129 @@
+/* Copyright (c) 2010, 2012 Oracle and/or its affiliates. All rights reserved.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+#ifndef FILESORT_UTILS_INCLUDED
+#define FILESORT_UTILS_INCLUDED
+
+#include "my_global.h"
+#include "my_base.h"
+#include "sql_array.h"
+
+class Sort_param;
+/*
+  Calculate cost of merge sort
+
+    @param num_rows            Total number of rows.
+    @param num_keys_per_buffer Number of keys per buffer.
+    @param elem_size           Size of each element.
+
+    Calculates cost of merge sort by simulating call to merge_many_buff().
+
+  @retval
+    Computed cost of merge sort in disk seeks.
+
+  @note
+    Declared here in order to be able to unit test it,
+    since library dependencies have not been sorted out yet.
+
+    See also comments get_merge_many_buffs_cost().
+*/
+
+double get_merge_many_buffs_cost_fast(ha_rows num_rows,
+                                      ha_rows num_keys_per_buffer,
+                                      uint    elem_size);
+
+
+/**
+  A wrapper class around the buffer used by filesort().
+  The buffer is a contiguous chunk of memory,
+  where the first part is <num_records> pointers to the actual data.
+
+  We wrap the buffer in order to be able to do lazy initialization of the
+  pointers: the buffer is often much larger than what we actually need.
+
+  The buffer must be kept available for multiple executions of the
+  same sort operation, so we have explicit allocate and free functions,
+  rather than doing alloc/free in CTOR/DTOR.
+*/
+class Filesort_buffer
+{
+public:
+  Filesort_buffer() :
+    m_idx_array(), m_record_length(0), m_start_of_data(NULL)
+  {}
+
+  /** Sort me... */
+  void sort_buffer(const Sort_param *param, uint count);
+
+  /// Initializes a record pointer.
+  uchar *get_record_buffer(uint idx)
+  {
+    m_idx_array[idx]= m_start_of_data + (idx * m_record_length);
+    return m_idx_array[idx];
+  }
+
+  /// Initializes all the record pointers.
+  void init_record_pointers()
+  {
+    for (uint ix= 0; ix < m_idx_array.size(); ++ix)
+      (void) get_record_buffer(ix);
+  }
+
+  /// Returns total size: pointer array + record buffers.
+  size_t sort_buffer_size() const
+  {
+    return m_idx_array.size() * (m_record_length + sizeof(uchar*));
+  }
+
+  /// Allocates the buffer, but does *not* initialize pointers.
+  uchar **alloc_sort_buffer(uint num_records, uint record_length);
+
+
+  /// Check  <num_records, record_length> for the buffer
+  bool check_sort_buffer_properties(uint num_records,  uint record_length)
+  {
+    return (static_cast<uint>(m_idx_array.size()) == num_records &&
+            m_record_length == record_length);
+  }
+
+  /// Frees the buffer.
+  void free_sort_buffer();
+
+  /// Getter, for calling routines which still use the uchar** interface.
+  uchar **get_sort_keys() { return m_idx_array.array(); }
+
+  /**
+    We need an assignment operator, see filesort().
+    This happens to have the same semantics as the one that would be
+    generated by the compiler. We still implement it here, to show shallow
+    assignment explicitly: we have two objects sharing the same array.
+  */
+  Filesort_buffer &operator=(const Filesort_buffer &rhs)
+  {
+    m_idx_array= rhs.m_idx_array;
+    m_record_length= rhs.m_record_length;
+    m_start_of_data= rhs.m_start_of_data;
+    return *this;
+  }
+
+private:
+  typedef Bounds_checked_array<uchar*> Idx_array;
+
+  Idx_array  m_idx_array;
+  uint       m_record_length;
+  uchar     *m_start_of_data;
+};
+
+#endif  // FILESORT_UTILS_INCLUDED