include predicate-related entities as pub mod (#47)

Signed-off-by: Yuchen Liang <[email protected]>

Author: yliang412

optd-persistent/src/entities/mod.rs

@@ -20,6 +20,10 @@ pub mod physical_expression;
 pub mod physical_expression_to_statistic_junction;
 pub mod physical_property;
 pub mod plan_cost;
+pub mod predicate;
+pub mod predicate_children;
+pub mod predicate_logical_expression_junction;
+pub mod predicate_physical_expression_junction;
 pub mod statistic;
 pub mod statistic_to_attribute_junction;
 pub mod table_metadata;