ihuzenko commented on a change in pull request #1955: DRILL-7491: Incorrect
count() returned for complex types in parquet
URL: https://github.com/apache/drill/pull/1955#discussion_r366313821
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractGroupScanWithMetadata.java
##########
@@ -167,29 +167,43 @@ public boolean isMatchAllMetadata() {
*/
@Override
public long getColumnValueCount(SchemaPath column) {
- long tableRowCount, colNulls;
- Long nulls;
ColumnStatistics<?> columnStats =
getTableMetadata().getColumnStatistics(column);
- ColumnStatistics<?> nonInterestingColStats = null;
- if (columnStats == null) {
- nonInterestingColStats =
getNonInterestingColumnsMetadata().getColumnStatistics(column);
- }
+ ColumnStatistics<?> nonInterestingColStats = (columnStats == null)
+ ? getNonInterestingColumnsMetadata().getColumnStatistics(column) :
null;
+ long tableRowCount;
if (columnStats != null) {
tableRowCount =
TableStatisticsKind.ROW_COUNT.getValue(getTableMetadata());
} else if (nonInterestingColStats != null) {
tableRowCount =
TableStatisticsKind.ROW_COUNT.getValue(getNonInterestingColumnsMetadata());
+ columnStats = nonInterestingColStats;
+ } else if (existsNestedStatsForColumn(column, getTableMetadata())
+ || existsNestedStatsForColumn(column,
getNonInterestingColumnsMetadata())) {
+ return Statistic.NO_COLUMN_STATS;
} else {
return 0; // returns 0 if the column doesn't exist in the table.
}
- columnStats = columnStats != null ? columnStats : nonInterestingColStats;
- nulls = ColumnStatisticsKind.NULLS_COUNT.getFrom(columnStats);
- colNulls = nulls != null ? nulls : Statistic.NO_COLUMN_STATS;
+ Long nulls = ColumnStatisticsKind.NULLS_COUNT.getFrom(columnStats);
+ if (nulls == null || Statistic.NO_COLUMN_STATS == nulls ||
Statistic.NO_COLUMN_STATS == tableRowCount) {
+ return Statistic.NO_COLUMN_STATS;
+ } else {
+ return tableRowCount - nulls;
+ }
+ }
- return Statistic.NO_COLUMN_STATS == tableRowCount
- || Statistic.NO_COLUMN_STATS == colNulls
- ? Statistic.NO_COLUMN_STATS : tableRowCount - colNulls;
+ /**
+ * For complex columns, stats may be present only for nested fields. For
example, a column path is `a`,
+ * but stats present for `a`.`b`. So before making a decision that column is
absent, the case needs
+ * to be tested.
+ *
+ * @param column column path
+ * @param metadata metadata with column statistics
+ * @return whether stats exists for nested fields
+ */
+ private boolean existsNestedStatsForColumn(SchemaPath column, Metadata
metadata) {
Review comment:
No, the nested stats exists but not applicable for the parent column. As
javadoc says, the method is used only to determine whether the column is
actually absent. The current name expresses exactly what the method does.
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