Merge pull request #9014 from amosbird/joingetfix2

Fix joinGet with nullable return types.

dbms/src/Functions/FunctionJoinGet.h

@@ -17,6 +17,10 @@ public:
 
     static constexpr auto name = "joinGet";
 
+    bool useDefaultImplementationForNulls() const override { return false; }
+    bool useDefaultImplementationForConstants() const override { return true; }
+    bool useDefaultImplementationForLowCardinalityColumns() const override { return true; }
+
     void execute(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override;
 
     String getName() const override { return name; }
@@ -72,6 +76,9 @@ public:
     FunctionBaseImplPtr build(const ColumnsWithTypeAndName & arguments, const DataTypePtr &) const override;
     DataTypePtr getReturnType(const ColumnsWithTypeAndName & arguments) const override;
 
+    bool useDefaultImplementationForNulls() const override { return false; }
+    bool useDefaultImplementationForLowCardinalityColumns() const override { return true; }
+
     bool isVariadic() const override { return true; }
     size_t getNumberOfArguments() const override { return 0; }
 

dbms/tests/queries/0_stateless/01080_join_get_null.reference

+2	2

dbms/tests/queries/0_stateless/01080_join_get_null.sql

+DROP TABLE IF EXISTS test_joinGet;
+DROP TABLE IF EXISTS test_join_joinGet;
+
+CREATE TABLE test_joinGet(id Int32, user_id Nullable(Int32)) Engine = Memory();
+CREATE TABLE test_join_joinGet(user_id Int32, name String) Engine = Join(ANY, LEFT, user_id);
+
+INSERT INTO test_join_joinGet VALUES (2, 'a'), (6, 'b'), (10, 'c');
+
+SELECT 2 id, toNullable(toInt32(2)) user_id WHERE joinGet(test_join_joinGet, 'name', user_id) != '';
+
+DROP TABLE test_joinGet;
+DROP TABLE test_join_joinGet;