Besides the access paths for a set of nodes (see m_access_paths), AccessPathSet contains information that is common between all access paths for that set.
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Besides the access paths for a set of nodes (see m_access_paths), AccessPathSet contains information that is common between all access paths for that set.
One would believe num_output_rows would be such a member (a set of tables should produce the same number of output rows no matter the join order), but due to parameterized paths, different access paths could have different outputs. delayed_predicates is another, but currently, it's already efficiently hidden space-wise due to the use of a union.