squash w/ first commit. optional -> variant

server/genquery2/include/irods/private/genquery2_ast_types.hpp

@@ -3,9 +3,9 @@
 
 #include <boost/variant.hpp>
 
-#include <optional>
 #include <string>
 #include <utility>
+#include <variant>
 #include <vector>
 
 namespace irods::experimental::genquery2
@@ -193,19 +193,18 @@ namespace irods::experimental::genquery2
         condition() = default;
 
         condition(column column, condition_expression expression)
-            : column{std::move(column)}
+            : lhs{std::move(column)}
             , expression{std::move(expression)}
         {
         }
 
         condition(function func, condition_expression expression)
-            : function{std::move(func)}
+            : lhs{std::move(func)}
             , expression{std::move(expression)}
         {
         }
 
-        column column;
-        std::optional<function> function;
+        std::variant<column, function> lhs;
         condition_expression expression;
     }; // struct condition
 

server/genquery2/src/genquery2_sql.cpp

@@ -875,13 +875,6 @@ namespace irods::experimental::genquery2
         // order to generate the proper SQL.
         _state.ast_column_ptrs.push_back(&_function.column);
 
-#if 0
-        // Aggregate functions are not allowed in the WHERE clause of an SQL statement!
-        if (!_state.in_select_clause) {
-            throw std::invalid_argument{"aggregate functions not allowed in where clause"};
-        }
-#endif
-
         auto [is_special_column, table_alias] =
             setup_column_for_post_processing(_state, _function.column, iter->second);
         const std::string_view alias =
@@ -1012,14 +1005,14 @@ namespace irods::experimental::genquery2
 
     auto to_sql(gq_state& _state, const condition& _condition) -> std::string
     {
-        if (_condition.function) {
+        if (const auto* fn = std::get_if<function>(&_condition.lhs); fn) {
             return fmt::format("{}{}",
-                               to_sql(_state, *_condition.function),
+                               to_sql(_state, *fn),
                                boost::apply_visitor(sql_visitor{_state}, _condition.expression));
         }
 
         return fmt::format("{}{}",
-                           to_sql(_state, _condition.column),
+                           to_sql(_state, std::get<column>(_condition.lhs)),
                            boost::apply_visitor(sql_visitor{_state}, _condition.expression));
     } // to_sql