1 files changed, 76 insertions, 0 deletions
diff --git a/myisammrg/myrg_rprev.c b/myisammrg/myrg_rprev.c
new file mode 100644
index 00000000000..3ee0894b42c
--- /dev/null
+++ b/myisammrg/myrg_rprev.c
@@ -0,0 +1,76 @@
+/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
+
+   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; either version 2 of the License, or
+   (at your option) any later version.
+
+   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
+
+#include "mymrgdef.h"
+
+	/*
+	   Read previous row with the same key as previous read
+	*/
+
+int myrg_rprev(MYRG_INFO *info, byte *buf, int inx)
+{
+  MYRG_TABLE *table;
+  MI_INFO *mi;
+  uchar *key_buff;
+  uint pack_key_length;
+  int err;
+
+  /* at first, do rnext for the table found before */
+  err=mi_rprev(info->current_table->table,NULL,inx);
+  if (err == HA_ERR_END_OF_FILE)
+  {
+    queue_remove(&(info->by_key),0);
+    if (!info->by_key.elements)
+      return HA_ERR_END_OF_FILE;
+  }
+  else if (err)
+    return err;
+  else
+  {
+    /* Found here, adding to queue */
+    queue_top(&(info->by_key))=(byte *)(info->current_table);
+    queue_replaced(&(info->by_key));
+  }
+
+  /* next, let's finish myrg_rkey's initial scan */
+  table=info->last_used_table+1;
+  if (table < info->end_table)
+  {
+    mi=info->last_used_table->table;
+    key_buff=mi->lastkey+mi->s->base.max_key_length;
+    pack_key_length=mi->last_rkey_length;
+    for (; table < info->end_table ; table++)
+    {
+      mi=table->table;
+      err=_mi_rkey(mi,NULL,inx,key_buff,pack_key_length,HA_READ_KEY_OR_PREV,FALSE);
+      info->last_used_table=table;
+
+      if (err == HA_ERR_KEY_NOT_FOUND)
+        continue;
+      if (err)
+        return err;
+
+      /* Found here, adding to queue */
+      queue_insert(&(info->by_key),(byte *)table);
+    }
+  }
+
+  /* now, mymerge's read_prev is as simple as one queue_top */
+  mi=(info->current_table=(MYRG_TABLE *)queue_top(&(info->by_key)))->table;
+  return mi_rrnd(mi,buf,mi->lastpos);
+}
+
+