Do not move to prewhere in select with joins

src/Interpreters/InterpreterSelectQuery.cpp

@@ -560,7 +560,10 @@ InterpreterSelectQuery::InterpreterSelectQuery(
             view = nullptr;
         }
 
-        if (try_move_to_prewhere && storage && storage->canMoveConditionsToPrewhere() && query.where() && !query.prewhere())
+        if (try_move_to_prewhere
+            && storage && storage->canMoveConditionsToPrewhere()
+            && query.where() && !query.prewhere()
+            && !query.hasJoin()) /// Join may produce rows with nulls or default values, it's difficult to analyze if they affected or not.
         {
             /// PREWHERE optimization: transfer some condition from WHERE to PREWHERE if enabled and viable
             if (const auto & column_sizes = storage->getColumnSizes(); !column_sizes.empty())

tests/queries/0_stateless/02534_join_prewhere_bug_44062.reference

@@ -0,0 +1,38 @@
+-- { echoOn }
+
+SELECT * FROM test1 LEFT JOIN test2 ON test1.col1 = test2.col1
+WHERE test2.col1 IS NULL
+ORDER BY test2.col1
+;
+12321	-30	\N	\N
+SELECT * FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NULL
+ORDER BY test2.col1
+;
+\N	\N	12321	-30
+SELECT * FROM test1 LEFT JOIN test2 ON test1.col1 = test2.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+123	123	123	5600
+321	-32	321	5601
+SELECT * FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+123	5600	123	123
+321	5601	321	-32
+SELECT test2.col1, test1.* FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+123	123	123
+321	321	-32
+SELECT test2.col3, test1.* FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+5600	123	123
+5601	321	-32
+DROP TABLE IF EXISTS test1;
+DROP TABLE IF EXISTS test2;

tests/queries/0_stateless/02534_join_prewhere_bug_44062.sql

@@ -0,0 +1,43 @@
+
+CREATE OR REPLACE TABLE test1 ( `col1` UInt64, `col2` Int8 ) ENGINE = MergeTree ORDER BY col1;
+CREATE OR REPLACE TABLE test2 ( `col1` UInt64, `col3` Int16 ) ENGINE = MergeTree ORDER BY col1;
+
+INSERT INTO test1 VALUES (123, 123), (12321, -30), (321, -32);
+INSERT INTO test2 VALUES (123, 5600), (321, 5601);
+
+SET join_use_nulls = 1;
+
+-- { echoOn }
+
+SELECT * FROM test1 LEFT JOIN test2 ON test1.col1 = test2.col1
+WHERE test2.col1 IS NULL
+ORDER BY test2.col1
+;
+
+SELECT * FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NULL
+ORDER BY test2.col1
+;
+
+SELECT * FROM test1 LEFT JOIN test2 ON test1.col1 = test2.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+
+SELECT * FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+
+SELECT test2.col1, test1.* FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+
+SELECT test2.col3, test1.* FROM test2 RIGHT JOIN test1 ON test2.col1 = test1.col1
+WHERE test2.col1 IS NOT NULL
+ORDER BY test2.col1
+;
+
+DROP TABLE IF EXISTS test1;
+DROP TABLE IF EXISTS test2;