public void setUpdateStrategy(String strategy) throws TikaConfigException {
        switch (strategy.toLowerCase(Locale.US)) {
            case "overwrite" :
                setUpdateStrategy(UpdateStrategy.OVERWRITE);
                break;
            case "upsert" :
                setUpdateStrategy(UpdateStrategy.UPSERT);
                break;
            default :
                throw new TikaConfigException("'overwrite' and 'upsert' are the two options so " +
                        "far. I regret I don't understand: " + strategy);
        }
    }
Specify the field in the first Metadata that should be
used as the id field for the document.

@param idField
tika-pipes/tika-emitters/tika-emitter-opensearch/src/main/java/org/apache/tika/pipes/emitter/opensearch/OpenSearchEmitter.java