Merge pull request ClickHouse#89933 from ClickHouse/backport/25.8/89908

Backport ClickHouse#89908 to 25.8: Fix logical error with empty tuple inside `reverse` and `CAST` function

Author: clickhouse-gh[bot]

src/Functions/FunctionsConversion.h

@@ -4744,6 +4744,13 @@ class FunctionCast final : public IFunctionBase
             const auto * col = arguments.front().column.get();
 
             size_t tuple_size = to_element_types.size();
+
+            if (tuple_size == 0)
+            {
+                /// Preserve the number of rows for empty tuple columns
+                return ColumnTuple::create(col->size());
+            }
+
             const ColumnTuple & column_tuple = typeid_cast<const ColumnTuple &>(*col);
 
             Columns converted_columns(tuple_size);

src/Functions/reverse.cpp

@@ -98,6 +98,13 @@ class FunctionReverse : public IFunction
         if (const ColumnTuple * col_tuple = checkAndGetColumn<ColumnTuple>(column.get()))
         {
             size_t tuple_size = col_tuple->tupleSize();
+
+            if (tuple_size == 0)
+            {
+                /// Preserve the number of rows for empty tuple columns
+                return ColumnTuple::create(col_tuple->size());
+            }
+
             Columns tuple_columns(tuple_size);
             for (size_t i = 0; i < tuple_size; ++i)
             {

tests/queries/0_stateless/03714_empty_tuple_reverse_function.reference

@@ -0,0 +1,13 @@
+()
+()
+()
+()
+()
+()
+()
+()
+()
+Tuple()
+(3,'a',1)
+[()]
+()

tests/queries/0_stateless/03714_empty_tuple_reverse_function.sql

@@ -0,0 +1,27 @@
+SELECT reverse(());
+
+SELECT reverse(tuple());
+
+SELECT reverse(()) FROM numbers(3);
+
+WITH () AS x SELECT reverse(x);
+
+DROP TABLE IF EXISTS table_rev_empty_tuple;
+CREATE TABLE table_rev_empty_tuple
+(
+    x Tuple()
+) ENGINE = Memory;
+
+INSERT INTO table_rev_empty_tuple SELECT tuple() FROM numbers(5);
+
+SELECT reverse(x) FROM table_rev_empty_tuple LIMIT 3;
+
+SELECT toTypeName(reverse(x)) FROM table_rev_empty_tuple LIMIT 1;
+
+DROP TABLE table_rev_empty_tuple;
+
+SELECT reverse((1, 'a', 3));
+
+SELECT reverse([()]);
+
+SELECT reverse((()));

tests/queries/0_stateless/03715_empty_tuple_functions_conversion.reference

@@ -0,0 +1,8 @@
+()
+()
+()
+()
+()
+()
+()
+()

tests/queries/0_stateless/03715_empty_tuple_functions_conversion.sql

@@ -0,0 +1,19 @@
+select CAST((), 'SimpleAggregateFunction(min, Tuple())');
+
+DROP TABLE IF EXISTS tab;
+CREATE TABLE tab (c0 Tuple()) ENGINE = Memory;
+INSERT INTO tab VALUES (()), (()), (());
+
+SELECT CAST(c0, 'SimpleAggregateFunction(min, Tuple())') FROM tab;
+
+DROP TABLE IF EXISTS t0;
+CREATE TABLE t0 (c0 SimpleAggregateFunction(min, Tuple())) ENGINE = MergeTree() ORDER BY tuple();
+INSERT INTO t0 (c0) VALUES (tuple());
+SELECT * FROM t0;
+
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1 (c0 SimpleAggregateFunction(min, Tuple())) ENGINE = MergeTree() ORDER BY tuple() SETTINGS enable_block_number_column = 1, enable_block_offset_column = 1;
+UPDATE t1 SET c0 = () WHERE TRUE;
+INSERT INTO t1 (c0) VALUES (tuple()), (tuple()), (tuple());
+UPDATE t1 SET c0 = () WHERE TRUE;
+SELECT * FROM t1;