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    set_result_set_limit changes number of records retrieved

    • Article Type: General
    • Product: Aleph
    • Product Version: 18

    Description:
    We have discovered that in v.16 and above, after setting the set_result_set_limit environment variable in www_server.conf to 3000 from the default 1000 value, we noticed that result counts went down for some searches. Our understanding is that set_result_set_limit impacts the number of records which can be displayed but not the number retrieved.

    For example, the command mode search "GPO=042" reports 7947 records retrieved when set_result_set_limit is 1000, but only 2963 when set_result_set_limit is 3000. We believe the former number is correct, based on running similar searches in our previous version system. What is going on?

    We want to use 3000 for set_result_set_limit because, based on extensive testing, it was determined to be a good compromise value balancing performance characteristics with allowing users to display up to 1000 records in most cases.

    Resolution:
    The thought that stands behind it was that when doing a search the number of results can be greater than a "result set limit"; in this case the original "number of hits" will be displayed. But in a case where the number of the results is less than the "result set limit" the "number of hits" will be set to the real number of results that will actually be displayed.

    In the case of a union catalog there are 3 types of results numbers:
    "number of hits" is the entire results including duplicates
    number of results after filtering out duplicates
    number of results that will actually be displayed

    Here are two examples to illustrate how this works:
    Take a search where:
    the "number of hits" is 7000,
    the number of results after de-duplication is 2900

    If "result set limit" is set to 1000, the figure that will display as "number of results" will be 7000.

    If "result set limit" is set to 3000 (i.e. more than 2900), the "number of results" will be set to 2900.


    • Article last edited: 10/8/2013