Block is a primitive of KeyFilter that filters search in comparison to block number.

Comparator is used to filter over values that belong to key data.

Confidence is a primitive of KeyFilter that filters search to results that have a certain level of finalization.

Timestamp is a primitive of KeyFilter that filters search in comparison to timestamp.

TxHash is a primitive of KeyFilter that filters search to results that contain txHash.

Primitive is the basic building block for KeyFilter.

Visitor should have a per chain per db type implementation that converts primitives to db queries.