[jira] [Created] (PHOENIX-1940) Push expected List ordinal in KeyValueColumnExpression

["James Taylor (JIRA)" <ji...@apache.org>]

James Taylor created PHOENIX-1940:
-------------------------------------

             Summary: Push expected List<Cell> ordinal in KeyValueColumnExpression
                 Key: PHOENIX-1940
                 URL: https://issues.apache.org/jira/browse/PHOENIX-1940
             Project: Phoenix
          Issue Type: Bug
            Reporter: James Taylor


Looks like quite a bit of time is spent in the binary search done to get the latest Cell value when we're evaluating expressions on the server side (up to 60% is spent in KeyValueUtil.getColumnLatest()). Since we know the set of column qualifiers being projected into the scan, we could push the expected position (assuming all columns have values). If the Cell is not in that position, we could fall back to a binary search.

Further enhancements could be to: allow a not null constraint on KeyValue columns and either a) require all non null values to be provided on an UPSERT, or b) do a check and put to enforce it (for transactional tables this could be enforced).

Additionally, the table could declare that dynamic columns are not allowed. If both of the above are true, when we'd be guaranteed to be able to positionally access the List<Cell> that we get back from an HBase Scanner.

One further enhancement would be to collect a set of all ColumnExpression instances on the server side for all expressions sent over. Then, we'd bind them once, outside of the general expression evaluation for each row. An example of where this would save time would be in evaluating the following TPCH-Q1 aggregate query:

{code}
SELECT
    l_returnflag,
    l_linestatus,
    sum(l_quantity) as sum_qty,
    sum(l_extendedprice) as sum_base_price,
    sum(l_extendedprice * (1 - l_discount)) as sum_disc_price,
    sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge,
    avg(l_quantity) as avg_qty,
    avg(l_extendedprice) as avg_price,
    avg(l_discount) as avg_disc,
    count(*) as count_order
FROM
    lineitem
WHERE
    l_shipdate <= date '1998-12-01' - interval '90' day
GROUP BY
    l_returnflag,
    l_linestatus
ORDER BY
    l_returnflag,
    l_linestatus;
{code}
During aggregation, the KeyValueColumnExpression for l_extendedprice would be evaluated four times, once per occurrence in different SELECT expressions.



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