title: Java Spring Webflux - inserting an empty Mono result of a filter?
body: <p>Small question please: Does it make sense to save an empty Mono, by that, I mean the result of a filter on a Mono, into a reactive database please?</p>
  <p>A small sample:</p>
  <pre><code>        // step 1 - from some Mono, compute my pojo
          final Mono&lt;MyPojo&gt; myPojoMono = getSomeMonoAndConvertToMyPojo();
  
          // step 2 - based on a predicate, some myPojo are invalid, I do not want to save them, but some are valid, I need to persist them!
          final Mono&lt;MyPojo&gt; validMyPojoMono = myPojoMono.filter(oneMyPojo -&gt; computeIsValidMyPojo(oneMyPojo));
  
          // step 3 - for those who are valid only, I want to persist them. BTW, should I use something else other than .insert(Publisher) which strangely, returns a flux?
          final Flux&lt;PdsResponse&gt; whyFlux  = myReactiveRepository.insert(validMyPojoMono);
          return whyFlux;
  
  </code></pre>
  <p>After step 2, if the predicate does not match, (not sure) the result will be an empty mono.</p>
  <p>Hence, does it make sense to invoke the persistence API on an empty mono please?</p>
  <p>What is the appropriate way to achieve this use case please?</p>
  <p>Thank you</p>