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From "Jiarong Wei (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CALCITE-1429) Error of deciding pagingIdentifiers in select query for Druid
Date Tue, 11 Oct 2016 14:38:22 GMT
Jiarong Wei created CALCITE-1429:
------------------------------------

             Summary: Error of deciding pagingIdentifiers in select query for Druid
                 Key: CALCITE-1429
                 URL: https://issues.apache.org/jira/browse/CALCITE-1429
             Project: Calcite
          Issue Type: Bug
          Components: druid
            Reporter: Jiarong Wei
            Assignee: Julian Hyde


As mentioned in [Druid documentation|http://druid.io/docs/0.9.1.1/querying/select-query.html],
{quote}
Note that in the second query, an offset is specified and that it is 1 greater than the largest
offset found in the initial results. To return the next "page", this offset must be incremented
by 1 (should be decremented by 1 for descending query), with each new query, but with option
{{fromNext}} enabled, this operation is not needed. When an empty results set is received,
the very last page has been returned.
{quote}
I think Druid adapter [presumes|https://github.com/apache/calcite/blob/master/druid/src/main/java/org/apache/calcite/adapter/druid/DruidQuery.java#L935]
this feature is turned on but it's not set in [code|https://github.com/apache/calcite/blob/master/druid/src/main/java/org/apache/calcite/adapter/druid/DruidQuery.java#L627].

Also, {{previousOffset}} may not be reasonable, see [DruidQuery|https://github.com/apache/calcite/blob/master/druid/src/main/java/org/apache/calcite/adapter/druid/DruidQuery.java#L940].
I think whether we have already fetched all data is decided by the next request. If we don't
have any data returned on next request, that means fetching is done.



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