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From gparai <...@git.apache.org>
Subject [GitHub] drill pull request #802: DRILL-5394: Optimize query planning for MapR-DB tab...
Date Thu, 30 Mar 2017 01:21:06 GMT
Github user gparai commented on a diff in the pull request:

    https://github.com/apache/drill/pull/802#discussion_r108822233
  
    --- Diff: contrib/format-maprdb/src/main/java/org/apache/drill/exec/store/mapr/db/binary/BinaryTableGroupScan.java
---
    @@ -115,8 +112,11 @@ private void init() {
         try (Admin admin = formatPlugin.getConnection().getAdmin();
              RegionLocator locator = formatPlugin.getConnection().getRegionLocator(tableName))
{
           hTableDesc = admin.getTableDescriptor(tableName);
    -      tableStats = new MapRDBTableStats(getHBaseConf(), hbaseScanSpec.getTableName());
    -
    +      // Fetch rowCount only once and cache it in hbaseScanSpec.
    +      if (hbaseScanSpec.getRowCount() == hbaseScanSpec.ROW_COUNT_UNKNOWN) {
    +        MapRDBTableStats tableStats = new MapRDBTableStats(getHBaseConf(), hbaseScanSpec.getTableName());
    +        hbaseScanSpec.setRowCount(tableStats.getNumRows());
    --- End diff --
    
    This looks weird. We create the TableStats relying on some information from the ScanSpec
and then proceed to modify the same ScanSpec with the information retrieved from TableStats.
Please look at below comment as well regarding Spec mutability.
    
    Should we instead just overload the MapRDBTableStats constructor to allow passing numRows
- since that is what the existing constructor endup doing but makes a call to DB Client? So
instead of populating the ScanSpec we populate the tableStats using this new constructor?


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