bk commit into 5.1 tree (ingo:1.2195) BUG#18775

[ingo]

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ChangeSet
  1.2195 06/06/16 09:02:03 ingo@stripped +1 -0
  Bug#18775 - Temporary table from alter table visible to other threads
  
  The intermediate (not temporary) files of the new table
  during ALTER TABLE was visible for SHOW TABLES. These
  intermediate files are copies of the original table with
  the changes done by ALTER TABLE. After all the data is
  copied over from the original table, these files are renamed 
  to the original tables file names. So they are not temporary 
  files. They persist after ALTER TABLE, but just with another 
  name.
  
  Normal GRANT checking takes place for the intermediate table.
  Everyone who can see the original table (and hence the final
  table) can also see the intermediate table. But noone else.
  
  In 5.0 the intermediate files are invisible for SHOW TABLES
  because all file names beginning with "#sql" were suppressed.
  In 5.1 temporary files are created in TMPDIR, so that they
  don't appear in the database directories. Also in 5.1 a
  translation between table names and file names is done. The
  tmp_file_prefix on file level is now "@0023sql".
  
  The suppression of files starting with tmp_file_prefix is
  still in place, but still only files beginning with "#sql"
  were suppressed.
  
  I do now translate tmp_file_prefix from table name to file
  name before comparing it with the files in a directory.
  This suppresses the intermediate files again.
  
  No test case. The test case looks so that a reasonable big
  table is altered while a second thread runs SHOW TABLES.
  This in itself would be possible to do, but on slow machines
  it would add too much time to the test suite, while on fast
  machines the ALTER TABLE might have finished before SHOW
  TABLES looks at the directory. Even if there might be a good
  balance for todays machines, one day the test would become
  void as the intermediate table would not be seen even with
  the bug in place. I added a test script to the bug report.
  It can easily be changed so that it uses a table size that
  is appropriate for the test machine.

  sql/sql_show.cc
    1.348 06/06/16 09:01:57 ingo@stripped +4 -1
    Bug#18775 - Temporary table from alter table visible to other threads
    Translating tmp_file_prefix to filename before comparison.

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	ingo
# Host:	chilla.local
# Root:	/home/mydev/mysql-5.1-bug18775

--- 1.347/sql/sql_show.cc	2006-06-06 13:48:09 +02:00
+++ 1.348/sql/sql_show.cc	2006-06-16 09:01:57 +02:00
@@ -438,6 +438,7 @@ mysql_find_files(THD *thd,List<char> *fi
   uint col_access=thd->col_access;
 #endif
   TABLE_LIST table_list;
+  char tbbuff[FN_REFLEN];
   DBUG_ENTER("mysql_find_files");
 
   if (wild && !wild[0])
@@ -454,6 +455,8 @@ mysql_find_files(THD *thd,List<char> *fi
     DBUG_RETURN(-1);
   }
 
+  VOID(tablename_to_filename(tmp_file_prefix, tbbuff, sizeof(tbbuff)));
+
   for (i=0 ; i < (uint) dirp->number_off_files  ; i++)
   {
     char uname[NAME_LEN*3+1];                   /* Unencoded name */
@@ -491,7 +494,7 @@ mysql_find_files(THD *thd,List<char> *fi
     {
         // Return only .frm files which aren't temp files.
       if (my_strcasecmp(system_charset_info, ext=fn_rext(file->name),reg_ext) ||
-          is_prefix(file->name,tmp_file_prefix))
+          is_prefix(file->name,tbbuff))
         continue;
       *ext=0;
       VOID(filename_to_tablename(file->name, uname, sizeof(uname)));