@Override
	public void setIsAppendOnly(Boolean isAppendOnly) {
		if (this.isAppendOnly && !isAppendOnly) {
			throw new ValidationException(
				"The given query is not supported by this sink because the sink is configured to " +
				"operate in append mode only. Thus, it only support insertions (no queries " +
				"with updating results).");
		}
	}
Key field indices determined by the query.
elasticsearch5-xh/elasticsearch5-xh-sink/src/main/java/org/apache/flink/streaming/connectors/elasticsearch/ElasticsearchUpsertTableSinkBase.java