dvjyothsna commented on a change in pull request #1771: DRILL-7199: Optimize
population of metadata for non-interesting columns
URL: https://github.com/apache/drill/pull/1771#discussion_r280169434
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File path:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractGroupScanWithMetadata.java
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@@ -146,15 +148,23 @@ public boolean isMatchAllMetadata() {
*/
@Override
public long getColumnValueCount(SchemaPath column) {
- long tableRowCount = (long)
TableStatisticsKind.ROW_COUNT.getValue(getTableMetadata());
+ long tableRowCount, colNulls;
+ Long nulls;
ColumnStatistics columnStats =
getTableMetadata().getColumnStatistics(column);
- long colNulls;
+ ColumnStatistics nonInterestingColStats =
getNonInterestingColumnsMetadata().getColumnStatistics(column);
+
if (columnStats != null) {
- Long nulls = (Long)
columnStats.getStatistic(ColumnStatisticsKind.NULLS_COUNT);
- colNulls = nulls != null ? nulls : GroupScan.NO_COLUMN_STATS;
+ tableRowCount = (long)
TableStatisticsKind.ROW_COUNT.getValue(getTableMetadata());
+ } else if (nonInterestingColStats != null) {
Review comment:
Yes, tablemetadata holds only the interesting column stats. ColumnStats will
be non-null only for the interesting columns. There are three scenarios here:
- Column is interesting. Then the columnStats is not null and it has the
correct row count.
- Column is non-interesting. Then the columnStats will be null and
nonInterestingColStats is not null and the row count is marked as unknown.
- Column doesn't exist in the table. So both columnStats and
nonInterestingColStats will be null. Since the column doesn't exist, the row
count is set to 0.
Here we know that a column will only belong to one of the above cases. Thats
the reason there is an else-if instead of if.
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