string representation for ASTLiteral of DateTime and DateTime64

Author: yakov-olkhovskiy

src/Analyzer/ConstantNode.cpp

@@ -203,7 +203,11 @@ ASTPtr ConstantNode::toASTImpl(const ConvertToASTOptions & options) const
     auto constant_value_ast = std::make_shared<ASTLiteral>(getValue());
 
     if (!options.add_cast_for_constants)
+    {
+        if (WhichDataType(constant_value_type->getTypeId()).isDateTimeOrDateTime64())
+            return std::make_shared<ASTLiteral>(getFieldFromColumnForASTLiteral(constant_value.getColumn(), 0, constant_value.getType()));
         return constant_value_ast;
+    }
 
     // Add cast if constant was created as a result of constant folding.
     // Constant folding may lead to type transformation and literal on shard