Cassandra CQL method for paging through all rows

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心在旅途
心在旅途 2021-01-07 07:52

I want to programmatically examine all the rows in a large cassandra table, and was hoping to use CQL. I know I could do this with thrift, getting 10,000 (or so) rows at a t

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  •  灰色年华
    2021-01-07 08:26

    Turns out greater than and less than have a very non-intuitive, but useful, behavior (at least in CQL2, I haven't check CQL3 yet). It actually compares the tokens not the key values. Here is an example:

    > create table users (KEY varchar PRIMARY KEY, data varchar);
    > insert into users (KEY, 'data') values ('1', 'one');
    > insert into users (KEY, 'data') values ('2', 'two');
    > insert into users (KEY, 'data') values ('3', 'three');
    > insert into users (KEY, 'data') values ('4', 'four');
    > select * from users;
       3 | three
       2 |   two
       1 |   one
       4 |  four
    > select * from users LIMIT 1;
       3 | three
    > select * from users WHERE KEY > '3' LIMIT 1;
       2 |  two
    > select * from users WHERE KEY > '2' LIMIT 1;
       1 |  one
    > select * from users WHERE KEY > '1' LIMIT 1;
       4 | four
    

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