EEP: XXX
Title: read/2 function for Mnesia
Version: $Revision: 14 $
Last-Modified: $Date: 2007-06-29 16:24:01 +0200 (Fri, 29 Jun 2007) $
Author: Richard A. O'Keefe <ok@cs.otago.ac.nz>
Status: Draft
Type: Standards Track
Erlang-Version: R12B-4
Content-Type: text/plain
Created: 22-Oct-2008
Post-History:



Abstract

    A convenience function mnesia:read/2 is added.



Specification

    The 'mnesia' module has read/1 and read/3
    and dirty_read/1 and dirty_read/2.
    But there is no read/2.  So we add

    read(Tab, Key) -> read(Tab, Key, read).

    The documentation is revised to match.


Motivation

    On the 22nd of October, 2008, attila.rajmund.nohl@ericsson.com
    complained that it is hard to switch between 'dirty_read' and
    'read' because the arities don't match.



Rationale

    In effect, this provides a default argument.
    With this addition, programmers can as easily switch
    between dirty_read(Tab, Key) and read(Tab, Key)
    as they can between dirty_read({Tab,Key}) and read({Tab,Key}).



Backwards Compatibility

    Nothing should break.
    Most of the work is fixing the documentation.



Reference Implementation

    (1) Add the two lines

        read(Tab, Key) ->
            read(Tab, Key, read).

        somewhere in mnesia.erl; just after read/1 would be good.

    (2) Change the documentation for dirty_read/2 from
        "This is the dirty equivalent of the
         mnesia:read/3 function."
        to
        "This is the dirty equivalent of the
         mnesia:read/2 function."
        
    (3) Add the documentation entry
        "read({Tab, Key}) -> transaction abort | RecordList 

         Invokes mnesia:read(Tab, Key, read)."
        between the entries for read/1 and read/3.



References
    
    None.



Copyright

    This document has been placed in the public domain.



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