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https://issues.apache.org/jira/browse/DRILL-7119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16810357#comment-16810357
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ASF GitHub Bot commented on DRILL-7119:
---------------------------------------
gparai commented on pull request #1733: DRILL-7119: Compute range predicate
selectivity using histograms.
URL: https://github.com/apache/drill/pull/1733#discussion_r272391854
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/NumericEquiDepthHistogram.java
##########
@@ -69,27 +79,177 @@ public void setNumRowsPerBucket(long numRows) {
}
@Override
- public Double estimatedSelectivity(RexNode filter) {
+ public Double estimatedSelectivity(final RexNode filter) {
if (numRowsPerBucket >= 0) {
- return 1.0;
- } else {
- return null;
+ // at a minimum, the histogram should have a start and end point of 1
bucket, so at least 2 entries
+ Preconditions.checkArgument(buckets.length >= 2, "Histogram has invalid
number of entries");
+ final int first = 0;
+ final int last = buckets.length - 1;
+
+ // number of buckets is 1 less than the total # entries in the buckets
array since last
+ // entry is the end point of the last bucket
+ final int numBuckets = buckets.length - 1;
+ final long totalRows = numBuckets * numRowsPerBucket;
+ if (filter instanceof RexCall) {
+ // get the operator
+ SqlOperator op = ((RexCall) filter).getOperator();
+ if (op.getKind() == SqlKind.GREATER_THAN ||
+ op.getKind() == SqlKind.GREATER_THAN_OR_EQUAL) {
+ Double value = getLiteralValue(filter);
+ if (value != null) {
+
+ // *** Handle the boundary conditions first ***
+
+ // if value is less than or equal to the first bucket's start
point then all rows qualify
+ int result = value.compareTo(buckets[first]);
+ if (result <= 0) {
+ return LARGE_SELECTIVITY;
+ }
+ // if value is greater than the end point of the last bucket, then
none of the rows qualify
+ result = value.compareTo(buckets[last]);
+ if (result > 0) {
+ return SMALL_SELECTIVITY;
Review comment:
For posterity, please add an explanation for SMALL_SELECTIVITY > 0 and the
meaning of buckets[n], if not added elsewhere.
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> Modify selectivity calculations to use histograms
> -------------------------------------------------
>
> Key: DRILL-7119
> URL: https://issues.apache.org/jira/browse/DRILL-7119
> Project: Apache Drill
> Issue Type: Sub-task
> Components: Query Planning & Optimization
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Priority: Major
> Fix For: 1.16.0
>
>
> (Please see parent JIRA for the design document)
> Once the t-digest based histogram is created, we need to read it back and
> modify the selectivity calculations such that they use the histogram buckets
> for range conditions.
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