Bug#8306 - TRUNCATE leads to index corruption

Added a check, if the table, which we are going to create, is open.
This can happen if a MERGE mapped table is TRUNCATEd.

1 files changed, 15 insertions, 0 deletions

diff --git a/myisam/mi_create.c b/myisam/mi_create.c
index f99a2c655d2..da3330627a7 100644
--- a/myisam/mi_create.c
+++ b/myisam/mi_create.c
@@ -533,6 +533,21 @@ int mi_create(const char *name,uint keys,MI_KEYDEF *keydefs,
     create_flag=MY_DELETE_OLD;
   }
 
+  /*
+    If a MRG_MyISAM table is in use, the mapped MyISAM tables are open,
+    but no entry is made in the table cache for them.
+    A TRUNCATE command checks for the table in the cache only and could
+    be fooled to believe, the table is not open.
+    Pull the emergency brake in this situation. (Bug #8306)
+  */
+  if (test_if_reopen(filename))
+  {
+    my_printf_error(0, "MyISAM table '%s' is in use "
+                    "(most likely by a MERGE table). Try FLUSH TABLES.",
+                    MYF(0), name + dirname_length(name));
+    goto err;
+  }
+
   if ((file= my_create_with_symlink(linkname_ptr,
 				    filename,
 				    0, O_RDWR | O_TRUNC,