From 2de6eaf8380a5d184db595fb5382fc031a440821 Mon Sep 17 00:00:00 2001
From: vdimir <vdimir@clickhouse.com>
Date: Tue, 15 Feb 2022 11:11:59 +0000
Subject: [PATCH] Fix LowCardinality using key for join_use_nulls in pipeline

---
 src/Interpreters/HashJoin.cpp    | 10 +++++-----
 src/Interpreters/join_common.cpp |  8 ++++++++
 src/Interpreters/join_common.h   |  1 +
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/Interpreters/HashJoin.cpp b/src/Interpreters/HashJoin.cpp
index 8268dc20b01..feb5ecd4261 100644
--- a/src/Interpreters/HashJoin.cpp
+++ b/src/Interpreters/HashJoin.cpp
@@ -1524,13 +1524,13 @@ void HashJoin::joinBlockImpl(
                     continue;
 
                 const auto & col = block.getByName(left_name);
-                bool is_nullable = nullable_right_side || right_key.type->isNullable();
+                bool is_nullable = JoinCommon::isNullable(right_key.type);
                 auto right_col_name = getTableJoin().renamedRightColumnName(right_key.name);
                 ColumnWithTypeAndName right_col(col.column, col.type, right_col_name);
                 if (right_col.type->lowCardinality() != right_key.type->lowCardinality())
                     JoinCommon::changeLowCardinalityInplace(right_col);
                 right_col = correctNullability(std::move(right_col), is_nullable);
-                block.insert(right_col);
+                block.insert(std::move(right_col));
             }
         }
     }
@@ -1556,7 +1556,7 @@ void HashJoin::joinBlockImpl(
                     continue;
 
                 const auto & col = block.getByName(left_name);
-                bool is_nullable = nullable_right_side || right_key.type->isNullable();
+                bool is_nullable = JoinCommon::isNullable(right_key.type);
 
                 ColumnPtr thin_column = filterWithBlanks(col.column, filter);
 
@@ -1564,7 +1564,7 @@ void HashJoin::joinBlockImpl(
                 if (right_col.type->lowCardinality() != right_key.type->lowCardinality())
                     JoinCommon::changeLowCardinalityInplace(right_col);
                 right_col = correctNullability(std::move(right_col), is_nullable, null_map_filter);
-                block.insert(right_col);
+                block.insert(std::move(right_col));
 
                 if constexpr (jf.need_replication)
                     right_keys_to_replicate.push_back(block.getPositionByName(right_key.name));
@@ -2088,7 +2088,7 @@ void HashJoin::reuseJoinedData(const HashJoin & join)
 
 const ColumnWithTypeAndName & HashJoin::rightAsofKeyColumn() const
 {
-    /// It should be nullable if nullable_right_side is true
+    /// It should be nullable when right side is nullable
     return savedBlockSample().getByName(table_join->getOnlyClause().key_names_right.back());
 }
 
diff --git a/src/Interpreters/join_common.cpp b/src/Interpreters/join_common.cpp
index ca6d3124934..60f67c8a9d1 100644
--- a/src/Interpreters/join_common.cpp
+++ b/src/Interpreters/join_common.cpp
@@ -115,6 +115,14 @@ bool canBecomeNullable(const DataTypePtr & type)
     return can_be_inside;
 }
 
+bool isNullable(const DataTypePtr & type)
+{
+    bool is_nullable = type->isNullable();
+    if (const auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(type.get()))
+        is_nullable |= low_cardinality_type->getDictionaryType()->isNullable();
+    return is_nullable;
+}
+
 /// Add nullability to type.
 /// Note: LowCardinality(T) transformed to LowCardinality(Nullable(T))
 DataTypePtr convertTypeToNullable(const DataTypePtr & type)
diff --git a/src/Interpreters/join_common.h b/src/Interpreters/join_common.h
index 3e5a22f33bf..38b431db3e0 100644
--- a/src/Interpreters/join_common.h
+++ b/src/Interpreters/join_common.h
@@ -59,6 +59,7 @@ private:
 };
 
 
+bool isNullable(const DataTypePtr & type);
 bool canBecomeNullable(const DataTypePtr & type);
 DataTypePtr convertTypeToNullable(const DataTypePtr & type);
 void convertColumnToNullable(ColumnWithTypeAndName & column);