Interface ExternalPredicateCallback

engine/seminaivebottomup.go:85–92

ExternalPredicateCallback is used to query external data sources. An atom `mydb(input1, ..., inputN, OutputVar1, ..., OutputVarN)` is evaluated as follows: - the engine checks whether the fact store contains any facts of the shape `mydb(input1, ..., inputN, _, ..., _)`. If so, we use those for eval

// but is also free to ignore them. In any case, when constant filter arguments
// are present, only matching facts will be added to the store.
type ExternalPredicateCallback interface {
	// If true, the engine will pass any subgoals of the clause that mention output variables
	// to ExecuteQuery. Otherwise, the pushdown argument will be empty.
	ShouldPushdown() bool
	ShouldQuery(inputs []ast.Constant, filters []ast.BaseTerm, pushdown []ast.Term) bool
	ExecuteQuery(inputs []ast.Constant, filters []ast.BaseTerm, pushdown []ast.Term,
		cb func([]ast.BaseTerm)) error
}

// EvalOptions are used to configure the evaluation.
type EvalOptions struct {