Limit and offset

  1.  
    1. rishav
      Aug 4, 2008
      rishav says:

      I figured enough that you can use "limit" reserved to get the first few results of a query,

       say for some query

         "limit" : 5

       this fetches the first five , 

      how do I fetch the next 5

      2. crism Metaweb Staff
        Aug 4, 2008
        crism says:
        You use cursors. Ask for cursor:null in your first query. It will come back with a token filled in; pass that back to get the next set of results and a new cursor.
      3. maccaday
        Sep 11, 2008
        maccaday says:

        Can you explain this a little further, please?  I tried the query :

         {
          "cursor" : null,
          "limit" : 5,
          "name" : null,
          "type" : "/music/artist"
        }

         

        and I got an error saying that cursor was a reserved word.

         

        Thanks

      4. maccaday
        Sep 11, 2008
        maccaday says:
        Wouldn't using the 'offset' reserved word be a more elegant (and intuitive for those with experience in databases) method of implementing this?
      5. crism Metaweb Staff
        Sep 11, 2008
        crism says:

        Sorry; the cursor needs to go in the query envelope, not the query itself. See §4.7 of the API doc:

        {

          "cursor":null,

          "query" : {

            "limit" : 5,

            "name" : null,

            "type" : "/music/artist"

          }

        }

        The cursor is not the same as offset; we don’t currently have arbitrary offset support. The cursor must be sent back to the server to get the next page of results; a query can’t yet skip forward an arbitrary number of results.

      6. marco79
        Apr 22, 2009
        marco79 says:

        Hi,

        I'd like to use the cursors to paginate my result but I haven't found any good documentation/example about how to use them... The parameter I need are the convential 'page' and 'per_page',

        for 'per_page' parameter I'm using use 'limit',

        How can I use the cursor to fetch the right offset of result?

      7. skud Metaweb Staff
        Apr 22, 2009
        skud says:

        Marco: paginated results is a future feature which a lot of people have been asking for.  I believe it requires changes to our underlying graph database (we do not use an RDBMS, it's something completely different).  When it's done and released, you can bet we'll be publicising the fact broadly, so stay tuned.  For now, cursors are the only way to handle this.

      8. marco79
        Apr 23, 2009
        marco79 says:

        Thanks Skud for your fast replay!

        Could you please show me an example or give me a link to a tutorial about how to handle this using cursors?

        thanks!

      9. willmoffat Metaweb Staff
        Apr 23, 2009
        willmoffat says:

        Hi Macro79, recently our graph database got support for pages.

        You just need to use the 'page' and 'limit' keywords in your mql query, here's the first page:

        http://api.freebase.com/api/service/mqlread?query={"page":0,"query":[{"name":null,"type":"/music/artist","limit":5}]}

        The new Query Editor supports pages in the 'envelope' options: http://www.freebase.com/app/queryeditor

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