Backport #93038 to 25.12: Proper handle sparse nullable columns in inner/left joins

robot-clickhouse · robot-clickhouse · commit a1525ab2abe3 · 2026-01-21T22:18:47.000Z
diff --git a/src/Interpreters/JoinUtils.cpp b/src/Interpreters/JoinUtils.cpp
@@ -234,7 +234,7 @@ void removeColumnNullability(ColumnWithTypeAndName & column)
 
         if (column.column && column.column->isNullable())
         {
-            column.column = column.column->convertToFullColumnIfConst();
+            column.column = column.column->convertToFullIfNeeded();
             const auto * nullable_col = checkAndGetColumn<ColumnNullable>(column.column.get());
             if (!nullable_col)
             {
diff --git a/tests/queries/0_stateless/03773_nullable_sparse_join.reference b/tests/queries/0_stateless/03773_nullable_sparse_join.reference
diff --git a/tests/queries/0_stateless/03773_nullable_sparse_join.sql b/tests/queries/0_stateless/03773_nullable_sparse_join.sql
@@ -0,0 +1,16 @@
+DROP TABLE IF EXISTS t1;
+DROP TABLE IF EXISTS t2;
+
+SET max_partitions_per_insert_block=99999999;
+SET compatibility='23.3';
+
+CREATE TABLE t1 (`c1` String, `c3` String, `c2` DateTime) ENGINE = MergeTree PARTITION BY toYYYYMM(c2) ORDER BY c1;
+CREATE TABLE t2 (`c4` Int64) ENGINE = MergeTree ORDER BY c4;
+
+INSERT INTO t1 SELECT * FROM generateRandom() LIMIT 9;
+INSERT INTO t2 SELECT * FROM generateRandom() LIMIT 9;
+
+SELECT lo.c4 FROM t1 AS l INNER JOIN t2 AS lo ON toInt64OrNull(l.c3) = lo.c4 FORMAT NULL;
+
+DROP TABLE t1;
+DROP TABLE t2;

Original file line number	Diff line number	Diff line change
`@@ -234,7 +234,7 @@ void removeColumnNullability(ColumnWithTypeAndName & column)`
`234`	`234`
`235`	`235`	`if (column.column && column.column->isNullable())`
`236`	`236`	`{`
`237`		`- column.column = column.column->convertToFullColumnIfConst();`
	`237`	`+ column.column = column.column->convertToFullIfNeeded();`
`238`	`238`	`const auto * nullable_col = checkAndGetColumn<ColumnNullable>(column.column.get());`
`239`	`239`	`if (!nullable_col)`
`240`	`240`	`{`