okumin commented on a change in pull request #1531:
URL: https://github.com/apache/hive/pull/1531#discussion_r501691897
##########
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();
+ final Statistics udtfStats =
parents.get(LateralViewJoinOperator.UDTF_TAG).getStatistics();
+
+ final double factor = (double) udtfStats.getNumRows() / (double)
selectStats.getNumRows();
Review comment:
Added steps to check both numbers and ensure at least one record on
stats.
https://github.com/apache/hive/pull/1531/commits/50396346eaed5d6bab4ff87dd079918a769a7ebd
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