Github user paul-guo- commented on a diff in the pull request:

    https://github.com/apache/incubator-hawq/pull/1243#discussion_r118222465
  
    --- Diff: src/backend/executor/nodeMaterial.c ---
    @@ -759,3 +764,30 @@ ExecEagerFreeMaterial(MaterialState *node)
        }
     }
     
    +
    +/*
    + * mkLockFileForWriter
    + * 
    + * Create a unique lock file for writer. Then use flock's unblock way to 
lock the lock file.
    + * We can make sure the lock file will be locked forerver until the writer 
process has quit.
    + */
    +void mkLockFileForWriter(int size, int share_id, char * name)
    +{
    +   char *lock_file;
    +   int lock;
    +
    +   lock_file = (char *)palloc0(sizeof(char) * MAXPGPATH);
    +   generate_lock_file_name(lock_file, size, share_id, name);
    +   elog(DEBUG3, "The lock file for writer in SISC is %s", lock_file);
    +   sisc_writer_lock_fd = open(lock_file, O_CREAT, S_IRWXU);
    +   if(sisc_writer_lock_fd < 0)
    +   {
    +           elog(ERROR, "Could not create lock file %s for writer in SISC. 
The error number is %d", lock_file, errno);
    +   }
    +   lock = flock(sisc_writer_lock_fd, LOCK_EX | LOCK_NB);
    +   if(lock == -1)
    +           elog(DEBUG3, "Could not lock lock file  \"%s\" for writer in 
SISC : %m. The error number is %d", lock_file, errno);
    +   else if(lock == 0)
    +           elog(DEBUG3, "Successfully locked lock file  \"%s\" for writer 
in SISC: %m.The error number is %d", lock_file, errno);
    +   pfree(lock_file);
    --- End diff --
    
    ditto.


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