okumin commented on a change in pull request #1531:
URL: https://github.com/apache/hive/pull/1531#discussion_r500420813



##########
File path: 
ql/src/test/results/clientpositive/llap/annotate_stats_lateral_view_join.q.out
##########
@@ -503,14 +503,14 @@ STAGE PLANS:
                             Statistics: Num rows: 1 Data size: 376 Basic 
stats: COMPLETE Column stats: COMPLETE
                             Lateral View Join Operator
                               outputColumnNames: _col0, _col1, _col5, _col6
-                              Statistics: Num rows: 0 Data size: 24 Basic 
stats: PARTIAL Column stats: NONE
+                              Statistics: Num rows: 0 Data size: 24 Basic 
stats: PARTIAL Column stats: COMPLETE

Review comment:
       With clone, the following condition is not satisfied since the basic 
stats of parent operators are PARTIAL.
   
https://github.com/apache/hive/blob/91e492de239427fc1e38e5e4350cfdce409ebb70/ql/src/java/org/apache/hadoop/hive/ql/optimizer/stats/annotation/StatsRulesProcFactory.java#L2969

##########
File path: 
ql/src/test/results/clientpositive/llap/annotate_stats_lateral_view_join.q.out
##########
@@ -503,14 +503,14 @@ STAGE PLANS:
                             Statistics: Num rows: 1 Data size: 376 Basic 
stats: COMPLETE Column stats: COMPLETE
                             Lateral View Join Operator
                               outputColumnNames: _col0, _col1, _col5, _col6
-                              Statistics: Num rows: 0 Data size: 24 Basic 
stats: PARTIAL Column stats: NONE
+                              Statistics: Num rows: 0 Data size: 24 Basic 
stats: PARTIAL Column stats: COMPLETE

Review comment:
       BTW, it would be better that the UDTF rule puts one in num rows in case 
that it becomes zero.

##########
File path: 
ql/src/java/org/apache/hadoop/hive/ql/optimizer/stats/annotation/StatsRulesProcFactory.java
##########
@@ -2921,6 +2920,97 @@ public Object process(Node nd, Stack<Node> stack, 
NodeProcessorCtx procCtx,
     }
   }
 
+  /**
+   * LateralViewJoinOperator changes the data size and column level statistics.
+   *
+   * A diagram of LATERAL VIEW.
+   *
+   *   [Lateral View Forward]
+   *          /     \
+   *    [Select]  [Select]
+   *        |        |
+   *        |     [UDTF]
+   *        \       /
+   *   [Lateral View Join]
+   *
+   * For each row of the source, the left branch just picks columns and the 
right branch processes UDTF.
+   * And then LVJ joins a row from the left branch with rows from the right 
branch.
+   * The join has one-to-many relationship since UDTF can generate multiple 
rows.
+   *
+   * This rule multiplies the stats from the left branch by T(right) / T(left) 
and sums up the both sides.
+   */
+  public static class LateralViewJoinStatsRule extends DefaultStatsRule 
implements SemanticNodeProcessor {
+    @Override
+    public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx,
+                          Object... nodeOutputs) throws SemanticException {
+      final LateralViewJoinOperator lop = (LateralViewJoinOperator) nd;
+      final AnnotateStatsProcCtx aspCtx = (AnnotateStatsProcCtx) procCtx;
+      final HiveConf conf = aspCtx.getConf();
+
+      if (!isAllParentsContainStatistics(lop)) {
+        return null;
+      }
+
+      final List<Operator<? extends OperatorDesc>> parents = 
lop.getParentOperators();
+      if (parents.size() != 2) {
+        LOG.warn("LateralViewJoinOperator should have just two parents but 
actually has "
+                + parents.size() + " parents.");
+        return null;
+      }
+
+      final Statistics selectStats = 
parents.get(LateralViewJoinOperator.SELECT_TAG).getStatistics().clone();

Review comment:
       Nothing was not unexpectedly broken. CI failed but it would not be 
related to this PR...
   - 
https://github.com/apache/hive/pull/1531/commits/91e492de239427fc1e38e5e4350cfdce409ebb70




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