fix segfault in ttl merge with non-physical columns in block

dbms/src/DataStreams/TTLBlockInputStream.cpp

@@ -26,6 +26,7 @@ TTLBlockInputStream::TTLBlockInputStream(
     , date_lut(DateLUT::instance())
 {
     children.push_back(input_);
+    header = children.at(0)->getHeader();
 
     const auto & column_defaults = storage.getColumns().getDefaults();
     ASTPtr default_expr_list = std::make_shared<ASTExpressionList>();
@@ -58,11 +59,6 @@ TTLBlockInputStream::TTLBlockInputStream(
 }
 
 
-Block TTLBlockInputStream::getHeader() const
-{
-    return children.at(0)->getHeader();
-}
-
 Block TTLBlockInputStream::readImpl()
 {
     Block block = children.at(0)->read();
@@ -108,11 +104,13 @@ void TTLBlockInputStream::removeRowsWithExpiredTableTTL(Block & block)
     const auto & current = block.getByName(storage.ttl_table_entry.result_column);
     const IColumn * ttl_column = current.column.get();
 
+    const auto & column_names = header.getNames();
     MutableColumns result_columns;
-    result_columns.reserve(getHeader().columns());
+    result_columns.reserve(column_names.size());
-    for (const auto & name : storage.getColumns().getNamesOfPhysical())
+
+    for (auto it = column_names.begin(); it != column_names.end(); ++it)
     {
-        auto & column_with_type = block.getByName(name);
+        auto & column_with_type = block.getByName(*it);
         const IColumn * values_column = column_with_type.column.get();
         MutableColumnPtr result_column = values_column->cloneEmpty();
         result_column->reserve(block.rows());
@@ -125,13 +123,13 @@ void TTLBlockInputStream::removeRowsWithExpiredTableTTL(Block & block)
                 new_ttl_infos.table_ttl.update(cur_ttl);
                 result_column->insertFrom(*values_column, i);
             }
-            else
+            else if (it == column_names.begin())
                 ++rows_removed;
         }
         result_columns.emplace_back(std::move(result_column));
     }
 
-    block = getHeader().cloneWithColumns(std::move(result_columns));
+    block = header.cloneWithColumns(std::move(result_columns));
 }
 
 void TTLBlockInputStream::removeValuesWithExpiredColumnTTL(Block & block)

dbms/src/DataStreams/TTLBlockInputStream.h

@@ -21,7 +21,7 @@ public:
 
     String getName() const override { return "TTLBlockInputStream"; }
 
-    Block getHeader() const override;
+    Block getHeader() const override { return header; };
 
 protected:
     Block readImpl() override;
@@ -47,6 +47,8 @@ private:
 
     std::unordered_map<String, String> defaults_result_column;
     ExpressionActionsPtr defaults_expression;
+
+    Block header;
 private:
     /// Removes values with expired ttl and computes new min_ttl and empty_columns for part
     void removeValuesWithExpiredColumnTTL(Block & block);

dbms/tests/queries/0_stateless/00933_ttl_simple.reference

@@ -1,5 +1,6 @@
 0	0
 0	0
+5	6
 2000-10-10 00:00:00	0
 2000-10-10 00:00:00	0
 2000-10-10 00:00:00	0

dbms/tests/queries/0_stateless/00933_ttl_simple.sql

@@ -9,6 +9,17 @@ select a, b from ttl_00933_1;
 
 drop table if exists ttl_00933_1;
 
+create table ttl_00933_1 (d DateTime, a Int, b Int) engine = MergeTree order by toDate(d) partition by tuple() ttl d + interval 1 second;
+insert into ttl_00933_1 values (now(), 1, 2);
+insert into ttl_00933_1 values (now(), 3, 4);
+insert into ttl_00933_1 values (now() + 1000, 5, 6);
+optimize table ttl_00933_1 final; -- check ttl merge for part with both expired and unexpired values
+select sleep(1.1) format Null; -- wait if very fast merge happen
+optimize table ttl_00933_1 final;
+select a, b from ttl_00933_1;
+
+drop table if exists ttl_00933_1;
+
 create table ttl_00933_1 (d DateTime, a Int ttl d + interval 1 DAY) engine = MergeTree order by tuple() partition by toDayOfMonth(d);
 insert into ttl_00933_1 values (toDateTime('2000-10-10 00:00:00'), 1);
 insert into ttl_00933_1 values (toDateTime('2000-10-10 00:00:00'), 2);