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From: jinfengni <git@git.apache.org>
To: dev@drill.apache.org
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References: <git-pr-519-drill@git.apache.org>
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Subject: [GitHub] drill pull request #519: DRILL-4530: Optimize partition pruning with metadat...
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Message-Id: <20160617200754.A9980E049D@git1-us-west.apache.org>
Date: Fri, 17 Jun 2016 20:07:54 +0000 (UTC)
archived-at: Fri, 17 Jun 2016 20:08:01 -0000

Github user jinfengni commented on a diff in the pull request:

    https://github.com/apache/drill/pull/519#discussion_r67567993
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/partition/PruneScanRule.java ---
    @@ -269,13 +283,54 @@ protected void doOnMatch(RelOptRuleCall call, Filter filterRel, Project projectR
             int recordCount = 0;
             int qualifiedCount = 0;
     
    -        // Inner loop: within each batch iterate over the PartitionLocations
    -        for(PartitionLocation part: partitions){
    -          if(!output.getAccessor().isNull(recordCount) && output.getAccessor().get(recordCount) == 1){
    -            newPartitions.add(part);
    -            qualifiedCount++;
    +        if (checkForSingle &&
    +            partitions.get(0).isCompositePartition() /* apply single partition check only for composite partitions */) {
    +          // Inner loop: within each batch iterate over the PartitionLocations
    +          for (PartitionLocation part : partitions) {
    +            assert part.isCompositePartition();
    +            if(!output.getAccessor().isNull(recordCount) && output.getAccessor().get(recordCount) == 1) {
    +              newPartitions.add(part);
    +              if (isSinglePartition) { // only need to do this if we are already single partition
    +                // compose the array of partition values for the directories that are referenced by filter:
    +                // e.g suppose the dir hierarchy is year/quarter/month and the query is:
    +                //     SELECT * FROM T WHERE dir0=2015 AND dir1 = 'Q1',
    +                // then for 2015/Q1/Feb, this will have ['2015', 'Q1', null]
    +                // Note that we are not using the PartitionLocation here but composing a different list because
    +                // we are only interested in the directory columns that are referenced in the filter condition. not
    +                // the SELECT list or other parts of the query.
    +                Pair<String[], Integer> p = composePartition(referencedDirsBitSet, partitionMap, vectors, recordCount);
    +                String[] parts = p.getLeft();
    +                int tmpIndex = p.getRight();
    +                if (spInfo == null) {
    +                  spInfo = parts;
    +                  maxIndex = tmpIndex;
    +                } else if (maxIndex != tmpIndex) {
    +                  isSinglePartition = false;
    +                  break;
    +                } else {
    +                  // we only want to compare until the maxIndex inclusive since subsequent values would be null
    +                  for (int j = 0; j <= maxIndex; j++) {
    +                    if (spInfo[j] == null // prefixes should be non-null
    --- End diff --
    
    Form Line 305-306, spInfo and maxIndex are in sync. Why will we have spInfo[j] == null, when j <= maxIndex? I thought maxIndex is obtained such that element in spInfo is not null.


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