Memory allocations in batch.newMergeIterator

[cyriltovena]

I was on-call today and some queries (very high cardinality) causes allocations and therefore GC rate to go crazy, we're running ab3e836

here is the snapshot of traces alloc space:

And a drilldown on the code

see gc over time the first peak was a new deployment,

I don't think something has been introduced recently but we should at least try to reuse memory in that function. For high cardinality it would help a lot.

[bboreham]

Duplicate of #1195 ?

[cyriltovena]

Very much related yes ! Feel free to close.