using batchupdate for add method

[gianielsevier]

Using jdbcTemplate batchUpdate improving the performance of multiple upsert

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[markpollack]

Thanks! I fixed one unrelated issue in reviewing this. I do wonder how good using batch as a default strategy is, for example if the number of documents gets to be very large. Perhaps a case for having something like Spring Batch manage this with 'chunks' would be useful to have in the future.

[markpollack]

merged in 2a60426

[gianielsevier]

merged in 2a60426

Thanks for accepting my PR @markpollack.
I've tested the original version using a dataset of 126k records from the medium csv file here. and it took more or less 17 minutes to ingest the whole file.
Using the batch update approach it reduced to 11 minutes.

I also compared ingesting the same dataset using the neo4j vector store which took around 12 minutes to process the whole file and Redis that had a similar time to process (12 minutes)

I can give more implementation details about the benchmark if you like.

Cheers.