How does Tableau run queries on Redshift? (And/or why can't Redshift display Tableau queries?)

Question

I'm kicking tires on BI tools, including, of course, Tableau. Part of my evaluation includes correlating the SQL generated by the BI tool with my actions in the tool.

Tableau has me mystified. My database has 2 billion things; however, no matter what I do in Tableau, the query Redshift reports as having been run is "Fetch 10000 in SQL_CURxyz", i.e. a cursor operation. In the screenshot below, you can see the cursor ids change, indicating new queries are being run -- but you don't see the original queries.

Is this a Redshift or Tableau quirk? Any idea how to see what's actually running under the hood? And why is Tableau always operating on 10000 records at a time?

Answer 1

•  Write this query to get all queries for currently active cursors:

SELECT

    usr.usename                                     AS username

  , min(cur.starttime)                              AS start_time

  , DATEDIFF(second, min(cur.starttime), getdate()) AS run_time

  , min(cur.row_count)                           AS row_count

  , min(cur.fetched_rows)                           AS fetched_rows

  , listagg(util_text.text)

    WITHIN GROUP (ORDER BY sequence)                AS query

FROM STV_ACTIVE_CURSORS cur

  JOIN stl_utilitytext util_text

    ON cur.pid = util_text.pid AND cur.xid = util_text.xid

  JOIN pg_user usr

    ON usr.usesysid = cur.userid

GROUP BY usr.usename, util_text.xid;

• You can also see the query behind completed cursors by joining STL_QUERY for a fetch query with STL_UTILITYTEXT on pid and xid ordered by sequence. 

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