From a8f5d9e70fef1202285eab1911f7aa794e0828f6 Mon Sep 17 00:00:00 2001
From: myrrc <me@myrrec.space>
Date: Wed, 9 Sep 2020 15:52:44 +0300
Subject: [PATCH] added the test and comment

---
 src/Columns/ColumnLowCardinality.h                            | 4 ++++
 .../0_stateless/01414_low_cardinality_nullable.reference      | 1 +
 tests/queries/0_stateless/01414_low_cardinality_nullable.sql  | 2 ++
 3 files changed, 7 insertions(+)

diff --git a/src/Columns/ColumnLowCardinality.h b/src/Columns/ColumnLowCardinality.h
index 00f58a133cf..0aeda4567fd 100644
--- a/src/Columns/ColumnLowCardinality.h
+++ b/src/Columns/ColumnLowCardinality.h
@@ -171,6 +171,10 @@ public:
     bool isNumeric() const override { return getDictionary().isNumeric(); }
     bool lowCardinality() const override { return true; }
 
+    /**
+     * Checks if the dictionary column is Nullable(T).
+     * So LC(Nullable(T)) would return true, LC(U) -- false.
+     */
     bool nestedIsNullable() const { return isColumnNullable(*dictionary.getColumnUnique().getNestedColumn()); }
 
     const IColumnUnique & getDictionary() const { return dictionary.getColumnUnique(); }
diff --git a/tests/queries/0_stateless/01414_low_cardinality_nullable.reference b/tests/queries/0_stateless/01414_low_cardinality_nullable.reference
index bf7b6cf4f76..51825f5cb76 100644
--- a/tests/queries/0_stateless/01414_low_cardinality_nullable.reference
+++ b/tests/queries/0_stateless/01414_low_cardinality_nullable.reference
@@ -80,3 +80,4 @@
 1
 1
 1
+2
diff --git a/tests/queries/0_stateless/01414_low_cardinality_nullable.sql b/tests/queries/0_stateless/01414_low_cardinality_nullable.sql
index 6e311f9d519..9a554ead776 100644
--- a/tests/queries/0_stateless/01414_low_cardinality_nullable.sql
+++ b/tests/queries/0_stateless/01414_low_cardinality_nullable.sql
@@ -217,4 +217,6 @@ SELECT count() FROM lc_nullable WHERE has(date_time, toDateTime('1970-01-01 03:0
 SELECT count() FROM lc_nullable WHERE has(str, '100');
 SELECT count() FROM lc_nullable WHERE has(fixed_string, toFixedString('100', 5));
 
+SELECT count() FROM lc_nullable WHERE has(date, toDate(has(u64, 1), '1970-01\002'));
+
 DROP TABLE IF EXISTS lc_nullable;