Improve performance of NeptuneAnalyticsGraph

[michaelnchin]

Improved the graph schema retrieval performance of NeptuneAnalyticsGraph by using the pg_schema algorithm.

Before:

After:

[3coins]

cc @krlawrence
cc @bechbd

[3coins]

@michaelnchin
Thanks for this performance improvement 🚀. Code looks good, but would be great if one of @krlawrence or @bechbd can review.

One small question, would users need an option within NeptuneOpenCypherQAChain and NeptuneSparqlQAChain to allow them to switch to a False in any scenario?

[michaelnchin]

Yes, I think users should be able to control this from the chain level also - will add separate options there.

[bechbd]

Along the same note, is there any reason to keep around the old method for an NA graph? From the end user perspective this should still give the same (or better) result.

[michaelnchin]

Discussed offline with @bechbd. While the pg_schema algorithm is a brand new feature, all Neptune Analytics graph instances are automatically upgraded to the newest version, and should therefore support it.

Since there are no concerns around backwards compatibility, we will revise this PR to always use pg_schema for graph schema retrieval.

[krlawrence]

I took a quick and had no major comments. Thanks for making this improvement.