when calling eZClusterFileHandler::delete() and the mysql db backend is in use, no files are really deleted, only their timestamps are set to a negative value.

Problems:

• there is a bug in function eZDBFileHandlerMysqlBackend->_exists(): it checks if $row[0][1] is positive, but it should check $row[1] instead

• all the file content fetching functions will happily return contents of a deleted file

• the same is true for getfilelist

• a deleted file cannot be recreated (dup val on unique index)

a possible solution would involve using the 'expired' column as a counter:

• PK is (name_hash, expired)
• every time a file is deleted, its expired column is set to max(expired)+1
• purge deletes all files where expired > 0
• most (all?) functions that operate on the rows in the db use for selecting the combination name_hash, 0 so queries are not slower
  it makes deletions a bit slower (since it has to recover last expired vals)