Merging #43085

tests/queries/0_stateless/02478_projection_and_alter_low_cardinality.sql

@@ -0,0 +1,28 @@
+DROP TABLE IF EXISTS testing;
+
+CREATE TABLE testing
+(
+    a String,
+    b String,
+    c String,
+    d String,
+    PROJECTION proj_1
+    (
+        SELECT b, c
+        ORDER BY d
+    )
+)
+ENGINE = MergeTree()
+PRIMARY KEY (a)
+ORDER BY (a, b)
+SETTINGS index_granularity = 8192, index_granularity_bytes = 0, min_bytes_for_wide_part = 0;
+
+INSERT INTO testing SELECT randomString(5), randomString(5), randomString(5), randomString(5) FROM numbers(10);
+
+OPTIMIZE TABLE testing FINAL;
+
+ALTER TABLE testing MODIFY COLUMN c LowCardinality(String) SETTINGS mutations_sync=2;
+
+SELECT * FROM system.mutations WHERE database = currentDatabase() AND table = 'testing' AND not is_done;
+
+DROP TABLE testing;