Rails: has_many issue

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

  1. treefrog

    treefrog Guest

    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

    Best regards,

    treefrog, Feb 6, 2006
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  2. Eric Hodel

    Eric Hodel Guest

    Eric Hodel, Feb 6, 2006
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