[BUG] Max aggregation result is defaulted 0 when there is no value from OpenSearch

[tnguyen456]

What is the bug?

MaxAggregate has value as 0 when there is no record match or aggregated field has no values even though OpenSearch returns null

How can one reproduce the bug?

• Create an index with a numeric field
• Send aggregation request for the field
• Since there is no document, the aggregation result is returned as null by OpenSearch but MaxAggregate from java-client has value as 0

What is the expected behavior?

Because value is defaulted to 0, it causes confusion to consumers as there is no way to tell whether 0 means no value or it's actually the max.

The expected behaviour should be returning the same value as OpenSearch

What is your host/environment?

OpenSearch 2.11
OpenSearch java client 2.14

[Xtansia]

Hi @tnguyen456,

Thanks for raising this issue, you definitely make a great point regarding differentiate missing values and true zero.
I'll need to do a little code archaeology to see if I can discern the original reasoning for the behaviour incase it is relevant.
As changing this behaviour would be a breaking change it may not be fixed until the 3.0.0 release, otherwise it would need a backwards compatible change that adds an additional getter (e.g. valueOrNull) with the correct behaviour and the old getter keeps the defaulting logic.

[Xtansia]

And if you're interested in raising a PR to make such a fix yourself, it would be greatly welcomed.

[tnguyen456]

Thanks @Xtansia for quick response.

We've implemented a kinda hacky workaround to override the deserializer to make it work for our cases.

But yeah, I agree that the proper fix should be like what you mentioned.

Probably I will try to come up with an PR.