How to limit result set size for arbitrary query in Ingres?

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小蘑菇
小蘑菇 2021-01-19 14:55

In Oracle, the number of rows returned in an arbitrary query can be limited by filtering on the \"virtual\" rownum column. Consider the following example, which

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  •  忘掉有多难
    2021-01-19 15:49

    select * from myTable limit 10 does not work.

    Have discovered one possible solution:

        TIDs are "tuple identifiers" or row addresses.  The TID contains the
        page number and the index of the offset to the row relative to the
        page boundary.  TIDs are presently implemented as 4-byte integers.
        The TID uniquely identifies each row in a table.  Every row has a
        TID.  The high-order 23 bits of the TID are the page number of the page
        in which the row occurs.  The TID can be addressed in SQL by the name 
        `tid.'
    

    So you can limit the number of rows coming back using something like:

    select * from SomeTable where tid < 2048

    The method is somewhat inexact in the number of rows it returns. It's fine for my requirement though because I just want to limit rows coming back from a very large result set to speed up testing.

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