public Execution newExecution(String searchChainId) {
        return new Execution(searchChainRegistry().getChain(searchChainId),
                             new Execution.Context(searchChainRegistry, indexFacts, schemaInfo, specialTokens, rendererRegistry, linguistics, executor));
    }
Creates a new execution starting at a search chain.
An execution instance should be used once to execute a (tree of) search chains.
container-search/src/main/java/com/yahoo/search/searchchain/ExecutionFactory.java