[GitHub] [druid] cryptoe commented on a change in pull request #12139: Limit the subquery results by memory usage (estimated)

[GitBox <gi...@apache.org>]

cryptoe commented on a change in pull request #12139:
URL: https://github.com/apache/druid/pull/12139#discussion_r783645116



##########
File path: server/src/main/java/org/apache/druid/server/ClientQuerySegmentWalker.java
##########
@@ -592,6 +642,48 @@ private DataSource insertSubqueryIds(
     return InlineDataSource.fromIterable(resultList, signature);
   }
 
+  private static long estimateResultRowSize(Object[] row, RowSignature rowSignature)
+  {
+    int estimate = 0;
+    if (row == null) {
+      return 0;
+    }
+    estimate += 24; // Add memory overhead for the row array
+    for (int i = 0; i < rowSignature.size(); ++i) {
+      Optional<ColumnType> maybeColumnType = rowSignature.getColumnType(i);
+      if (!maybeColumnType.isPresent()) {
+        // This shouldn't be encountered
+        continue;
+      }
+      ColumnType columnType = maybeColumnType.get();
+      if (columnType.equals(ColumnType.LONG)) {
+        estimate += Long.BYTES;
+      } else if (columnType.equals(ColumnType.FLOAT)) {
+        estimate += Float.BYTES;
+      } else if (columnType.equals(ColumnType.DOUBLE)) {
+        estimate += Double.BYTES;
+      } else if (columnType.equals(ColumnType.STRING)
+                 || columnType.equals(ColumnType.STRING_ARRAY)
+                 || columnType.equals(ColumnType.LONG_ARRAY)
+                 || columnType.equals(ColumnType.DOUBLE_ARRAY)) {
+        if (row[i] instanceof String) {
+          estimate += 28 + 16 + 2 * (((String) row[i]).length());
+        } else if (row[i] instanceof Long) {
+          estimate += Long.BYTES;
+        } else if (row[i] instanceof Double) {
+          estimate += Double.BYTES;
+        } else if (row[i] instanceof Float) {
+          estimate += Float.BYTES;
+        } else {
+          estimate += 0;

Review comment:
       We might want to call out that we do a conservative/underestimate in case of unknown col's somewhere in the property documentation.




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