vrozov commented on a change in pull request #1298: DRILL-5796: Filter pruning
for multi rowgroup parquet file
URL: https://github.com/apache/drill/pull/1298#discussion_r202733948
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/stat/ParquetIsPredicate.java
##########
@@ -62,50 +62,51 @@ private ParquetIsPredicate(LogicalExpression expr,
BiPredicate<Statistics<C>, Ra
return visitor.visitUnknown(this, value);
}
- @Override
- public boolean canDrop(RangeExprEvaluator<C> evaluator) {
+ /**
+ * Apply the filter condition against the meta of the rowgroup.
+ */
+ public RowsMatch matches(RangeExprEvaluator<C> evaluator) {
Statistics<C> exprStat = expr.accept(evaluator, null);
- if (isNullOrEmpty(exprStat)) {
- return false;
- }
+ return isNullOrEmpty(exprStat) ? RowsMatch.SOME :
predicate.apply(exprStat, evaluator);
+ }
- return predicate.test(exprStat, evaluator);
+ /**
+ * After the applying of the filter against the statistics of the rowgroup,
if the result is RowsMatch.ALL,
+ * then we still must know if the rowgroup contains some null values,
because it can change the filter result.
+ * If it contains some null values, then we change the RowsMatch.ALL into
RowsMatch.SOME, which sya that maybe
+ * some values (the null ones) should be disgarded.
+ */
+ private static RowsMatch checkNull(Statistics exprStat) {
+ return hasNoNulls(exprStat) ? RowsMatch.ALL : RowsMatch.SOME;
}
/**
* IS NULL predicate.
*/
private static <C extends Comparable<C>> LogicalExpression
createIsNullPredicate(LogicalExpression expr) {
return new ParquetIsPredicate<C>(expr,
- //if there are no nulls -> canDrop
- (exprStat, evaluator) -> hasNoNulls(exprStat)) {
- private final boolean isArray = isArray(expr);
-
- private boolean isArray(LogicalExpression expression) {
- if (expression instanceof TypedFieldExpr) {
- TypedFieldExpr typedFieldExpr = (TypedFieldExpr) expression;
- SchemaPath schemaPath = typedFieldExpr.getPath();
- return schemaPath.isArray();
- }
- return false;
- }
-
- @Override
- public boolean canDrop(RangeExprEvaluator<C> evaluator) {
+ (exprStat, evaluator) -> {
// for arrays we are not able to define exact number of nulls
// [1,2,3] vs [1,2] -> in second case 3 is absent and thus it's null
but statistics shows no nulls
- return !isArray && super.canDrop(evaluator);
- }
- };
+ if (expr instanceof TypedFieldExpr) {
+ TypedFieldExpr typedFieldExpr = (TypedFieldExpr) expr;
+ if (typedFieldExpr.getPath().isArray()) {
+ return RowsMatch.SOME;
+ }
+ }
+ if (hasNoNulls(exprStat)) {
Review comment:
@arina-ielchiieva `num_nulls` must be -1 even for older files as well,
otherwise, it is a bug in parquet library or drill that sets `num_nulls`
incorrectly. If you have a concrete example where parquet library sets
`num_nulls` to 0 where it should be -1, it is necessary to file JIRA for
parquet. If drill sets `num_nulls` incorrectly while evaluating expressions or
reading old parquet files, the bug needs to be fixed in drill. In the example
you provided, should not statistics be empty (with `num_nulls` set to -1)?
AFAIK, it is not valid to use `hasNonNullValue()` in place for nulls check
as min/max may not be defined when all values are nulls or when a comparator is
not defined for a data type.
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