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  1. Phoenix
  2. PHOENIX-3439

Query using an RVC based on the base table PK is incorrectly using an index and doing a full scan instead of a point query

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 4.8.1
    • Fix Version/s: 4.9.0, 4.8.2
    • Labels:
      None

      Description

      We use Phoenix RVCs to support paginated queries. This performance of this functionality relies on Phoenix predictably generating scans against a table or index with a PK that matches the RVC specified for each page.

      What we do is that on the initial query we use PhoenixRuntime.getPkColsDataTypesForSql() to get the list of PK columns and persist that and use those to generate RVCs for paginated queries.

      We have discovered that for queries where:
      a) the user doesn't specify an ORDER BY
      b) for tables where secondary indexes are present

      Phoenix returns pk cols for the base table via getPkColsDataTypesForSql() but then subsequent queries using the RVCs to paginate execute against a secondary index doing a full scan.

      We have a table with a secondary index where this is an issue. The base table has a PK of PKCOL1, PKCOL2, PKCOL3 and
      PKCOL4. We have an immutable secondary index where the PK is PKCOL1, PKCOL3, PKCOL2, PKCOL4.

      Here's what happens:

      Here is our query we run to get the Query plan from which we generate the RVCs to be used for paging:

      EXPLAIN SELECT pkcol1, pkcol2, pkcol3, pkcol4, col1, col2
      FROM MY_TABLES."MYTABLE"
      LIMIT 501;

      I get the following explain:
      CLIENT 6-CHUNK SERIAL 1-WAY ROUND ROBIN RANGE SCAN OVER MY_TABLES.MY_TABLE ['00Dxx0000001gFA']
      SERVER 501 ROW LIMIT
      CLIENT 501 ROW LIMIT

      Therefore the columns we record for RVCs for paging are PK1, PK2, PK3, PK4 from MY_TABLES.MY_TABLE

      However when I generate the RVC query to page through the data:

      EXPLAIN SELECT pkcol1, pkcol2, pkcol3, pkcol4, col1, col2
      FROM MY_TABLES."MYTABLE"
      (pkcol1, pkcol2, pkcol3,pkcol4) > ('001','001xx000003DHml',to_date('2015-10-21 09 (tel:2015102109):50:55.0'),'017xx0000022FuI')
      LIMIT 501;

      I get the follow explain plan:
      CLIENT 24-CHUNK 7811766 ROWS 6291457403 BYTES PARALLEL 1-WAY ROUND ROBIN RANGE SCAN OVER MY_TABLES.MY_SECONDARY_INDEX ['00Dxx0000001gFA','001'] - ['00Dxx0000001gFA',*]
      SERVER FILTER BY ("PKCOL1", "PKCOL2, "PKCOL3", "PKCOL4") > (TO_CHAR('001'), TO_CHAR('001xx000003DHml'), DATE '2015-10-21 09 (tel:2015102109):50:55.000', TO_CHAR('017xx0000022FuI'))
      SERVER 501 ROW LIMIT
      CLIENT 501 ROW LIMIT

      We expected that the second query with RVCs above would execute against the base table as the base table PK is PKCOL1, PKCOL2, PKCOL3, PKCOL4 and the index PK is PKCOL1, PKCOL3, PKCOL2, PKCOL4.

        Attachments

        1. PHOENIX-3439_addendum1.patch
          9 kB
          James R. Taylor
        2. PHOENIX-3439.patch
          3 kB
          James R. Taylor

          Activity

            People

            • Assignee:
              jamestaylor James R. Taylor
              Reporter:
              jfernando_sfdc Jan Fernando
            • Votes:
              1 Vote for this issue
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              6 Start watching this issue

              Dates

              • Created:
                Updated:
                Resolved: