gparai commented on a change in pull request #1699: DRILL-7108: Improve
selectivity estimates for (NOT)LIKE, NOT_EQUALS, IS NOT NULL predicates
URL: https://github.com/apache/drill/pull/1699#discussion_r267535338
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/cost/DrillRelMdSelectivity.java
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@@ -173,6 +177,58 @@ private double getScanSelectivityInternal(DrillTable
table, RexNode predicate, L
return (sel > 1.0) ? 1.0 : sel;
}
+ private double computeEqualsSelectivity(DrillTable table, RexNode orPred,
List<String> fieldNames) {
+ String col = getColumn(orPred, fieldNames);
+ if (col != null) {
+ if (table.getStatsTable() != null
+ && table.getStatsTable().getNdv(col) != null) {
+ return 1.00 / table.getStatsTable().getNdv(col);
+ }
+ }
+ return guessSelectivity(orPred);
+ }
+
+ private double computeIsNullSelectivity(DrillTable table, RexNode orPred,
List<String> fieldNames) {
+ String col = getColumn(orPred, fieldNames);
+ if (col != null) {
+ if (table.getStatsTable() != null
+ && table.getStatsTable().getNNRowCount(col) != null) {
+ // Cap selectivity between {1/Total_Rows, Calcite Guess}
+ return Math.min(Math.max(1.0/table.getStatsTable().getRowCount(),
Review comment:
That was just to prevent the selectivity to become 0. I vaguely remember
running into planning issues with 0 selectivity - maybe I am being paranoid. I
will remove it for now.
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