Why calcite does not support outer join in materialized view

[hongkang jiang]

Hello everyone，
I have a question about that Calcite does not support outer join in
materialized view. I have been thinking for a long time and still haven't
figured it out. Could anyone help me answer the reason? Thanks very much.
I also found in Calcite's materialization a annotation like that Currently
we only support tablescan-project-filter-inner Join , And the method
MaterializedViewRule. IsValidRelNodePlan () will filter out the outer join.