TypeError: prepareItemValue() returns NULL

One thing I was wondering is if it would make sense to move the call to prepareItemValue() inside the try/catch block that follows. This would allow the indexing of the current batch to continue, skipping just the affected documents. Currently, an invalid field value causes the entire indexing operation to fail, at least for the current batch (and I think also entirely, e.g. you can't further index anything, as it would always end up at the 'broken' documents again).

Thanks, that is a very good suggestion. By extending the try-catch block we can rely on the exceptions, this is a better solution than filtering out NULL values. It will also catch any other incorrect data types.

Very good solution, thanks