If there are predicates over the same path in $or, they are translated into $in during match expression optimization. It also provides deduplication, so for the query above, we'd get a.b $in [ 1.0 ].

Currently, ABT translation and optimization transforms a singleton $in array into an Operations::Eq and extracts the value from the array. However, parameter binding in SBE stores all $in arrays as inListData (regardless of the size), and expects to use isMember to perform matching. We cannot compare an integer in a query predicate to an InListData member containing that element, so no matches are returned in the above case.

Proposed Fix: In Bonsai, bind a single value when parameterizing $in’s with singleton lists in bind_input_params.