Module prune 

Satisfiability analysis and schema pruning. Ported from ~/dev/omnist/omnist/ops/prune.py.

A record is satisfiable iff it admits at least one finite document, and prune returns an equivalent schema with everything that can never match removed. Satisfiability is a least fixpoint over the env’s records: a record is satisfiable iff every field with min >= 1 is either a Scalar or a Ref to a satisfiable record (fields with min == 0 never block satisfiability – they simply need not be emitted).

Functions

is_empty

True iff s’s root record is unsatisfiable – the schema’s language (the set of documents it accepts) is empty.

prune

An equivalent schema with everything that can never match removed: records unreachable from root are dropped; fields with max == 0 are dropped; optional (min == 0) fields whose type is an unsatisfiable record are dropped; records left unreachable/unsatisfiable after the above are dropped from the environment too.

satisfiable_set

The set of env record names that admit at least one finite document.