amansinha100 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_r266517952
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/cost/DrillRelMdSelectivity.java
##########
@@ -137,34 +138,33 @@ private double getScanSelectivityInternal(DrillTable
table, RexNode predicate, L
for (RexNode pred : RelOptUtil.conjunctions(predicate)) {
double orSel = 0;
for (RexNode orPred : RelOptUtil.disjunctions(pred)) {
- //CALCITE guess
- Double guess = RelMdUtil.guessSelectivity(pred);
+
if (orPred.isA(SqlKind.EQUALS)) {
+ orSel += computeEqualsSelectivity(table, orPred, fieldNames);
+ } else if (orPred.isA(SqlKind.NOT_EQUALS)) {
+ orSel += 1.0 - computeEqualsSelectivity(table, orPred, fieldNames);
+ } else if (orPred.isA(SqlKind.LIKE)) {
+ // LIKE selectivity is 5% more than a similar equality predicate,
capped at CALCITE guess
+ orSel += Math.min(computeEqualsSelectivity(table, orPred,
fieldNames) + LIKE_PREDICATE_SELECTIVITY,
+ RelMdUtil.guessSelectivity(orPred));
+ } else if (orPred.isA(SqlKind.NOT)) {
if (orPred instanceof RexCall) {
- int colIdx = -1;
- RexInputRef op = findRexInputRef(orPred);
- if (op != null) {
- colIdx = op.hashCode();
- }
- if (colIdx != -1 && colIdx < fieldNames.size()) {
- String col = fieldNames.get(colIdx);
- if (table.getStatsTable() != null
- && table.getStatsTable().getNdv(col) != null) {
- orSel += 1.00 / table.getStatsTable().getNdv(col);
- } else {
- orSel += guess;
- }
+ // LIKE selectivity is 5% more than a similar equality predicate,
capped at CALCITE guess
+ RexNode childOp = ((RexCall) orPred).getOperands().get(0);
+ if (childOp.isA(SqlKind.LIKE)) {
+ orSel += 1.0 - Math.min(computeEqualsSelectivity(table, childOp,
fieldNames) + LIKE_PREDICATE_SELECTIVITY,
+ RelMdUtil.guessSelectivity(childOp));
} else {
- orSel += guess;
- if (logger.isDebugEnabled()) {
- logger.warn(String.format("No input reference $[%s] found for
predicate [%s]",
- Integer.toString(colIdx), orPred.toString()));
- }
+ orSel += 1.0 - RelMdUtil.guessSelectivity(orPred);
}
}
+ } else if (orPred.isA(SqlKind.IS_NULL)) {
+ orSel += computeNullSelectivity(table, orPred, fieldNames);
+ } else if (orPred.isA(SqlKind.IS_NOT_NULL)) {
+ orSel += 1.0 - computeNullSelectivity(table, orPred, fieldNames);
Review comment:
If we already have a NN row count, the IS_NOT_NULL selectivity could be
simplified to NNRowCount/TotalRowCount. Why do we need to do the (1 -
NullSelectivity) ? If we don't have the NN row count for any reason, then we
are anyway defaulting to the Calcite guess.
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