pick from master #36478
intro a new rule VARIANT_SUB_PATH_PRUNING to prune variant sub path.
for example, variant slot v in table t has two sub path: 'c1' and 'c2',
after this rule, select v['c1'] from t will only scan one sub path 'c1'
of v to reduce scan time.
This rule accomplishes all the work using two components. The Collector
traverses from the top down, collecting all the element_at functions on
the variant types, and recording the required path from the original
variant slot to the current element_at. The Replacer traverses from the
bottom up, generating the slots for the required sub path on scan,
union, and cte consumer. Then, it replaces the element_at with the
corresponding slot.
a05d5cc75e