private void computeEffectiveDocsumDef() {
        if ((docsumDefinitions != null) && docsumDefinitions.hasDocsum(askForSummary)) {
            effectiveDocsumDef = docsumDefinitions.getDocsum(askForSummary);
            if (askForFields != null) {
                effectiveDocsumDef = new DocsumDefinition("<unnamed>", effectiveDocsumDef, askForFields);
            }
        }
    }
resolve summary class to use when none provided
container-search/src/main/java/com/yahoo/prelude/fastsearch/PartialSummaryHandler.java