Rails: has_many issue

Discussion in 'Ruby' started by treefrog, Feb 6, 2006.

  1. treefrog

    treefrog Guest

    Hi,
    I'm trying to work out how to tackle a particular problem in rails.

    I have some data. A lot of data (well not NSA style a lot of data, but
    a lot for me: 1Gb at the moment, more to come).

    I'm building a ruby application to process and view this data, and have
    been working round using rails as a front end - do the heavy lifting
    using some maths libraries, then use rails to display results, etc.

    The problem that I have is as follows: The natural organisation is that
    the data consists of DataSets, each DataSet is a group of related time
    series (Series), and each series consists fo a set of observations,
    each Observation having a set of parameters.

    So far, so good. The logical layout of the data is something like

    DataSet has_many Series
    Series has_many Observation

    The problem is that I need to be able to do processing of the data
    offline at a later point, and one of the thngs I am doing is developing
    new ways of dealing with the data. So I need to apply a transformation
    to each Observation. The transformed data hasn't lost anything, and it
    still comes in Series which belong to a dataset.

    One option would be

    DataSet has_many Series
    DataSet has many TransformedSeries
    Series has_many Observation
    TransformedSeries has many TransformedObservation

    but the problem is that every time I add a new transformation, I need
    to change my DB schema, etc, and add new code in to DataSet - which I
    personally believe is quite ugly!

    What I would really like is for the Series to have a field
    (series_type) which contains the name of the table to look up the
    Observation in. So, depending on the value in the series_type field,
    Series would perform has_many operations using the Observation table or
    the TransformedObservation table (or whatever other table).

    Is there any easy way to achieve this without directly hacking
    has_many?

    Best regards,

    Treefrog
     
    treefrog, Feb 6, 2006
    #1
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  2. treefrog

    Eric Hodel Guest

    Eric Hodel, Feb 6, 2006
    #2
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