in reply to data bulk query, sorting and paging

It all depends on how your data looks like, especially how big the datasets are. If they are rather small (like, a few hundred entries) it makes sense to put that functionality into your provider. If not...

Databases can sort and page, so for larger data sets it makes sense to move that functionality down to the individual provider classes, and provide a generic replacement for those providers that don't support it natively. You can do the sorting with built-in sort function, and the paging with Data::Pager.

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  • Comment on Re: data bulk query, sorting and paging

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Re^2: data bulk query, sorting and paging
by Anonymous Monk on Nov 30, 2009 at 18:01 UTC
    Datasets may be in the thousands, or millon rows...

    The problem I have with delegating sorting and querying to providers is that paging gets really tricky. 

    my @rows;
for my $provider( qw/Provider1 Provider2 Provider3/ ) {
   push @rows, $provider->search( 
        query=>..., sort=>..., 
        page=>1, rows=>10 
    );
}
# now I may end up with 30 rows for page 1
# but the client grid expects 10, so let's cut it down...
@rows = @rows [ 0..9  ];

    [download]

    So, ideally, the "collection manager object" should work with this algorithm:

    1. Ask each provider to search for a certain query and sort
    2. Ask for a row from each provider starting at a given page
    3. Is the page complete? Then call any external filters callbacks.
    4. External filters dropped rows? Then keep fetching until page is complete again.
    5. Sort the combined rows
    6. Return resulting array, but keep track of the current paging state

    --Miguel

    Code tags added by GrandFather

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