Batch remove offers in OffersProcessor

[bartekn]

What version are you using?

1.11.1

What did you do?

Processor durations stats added in #3224 revealed that OffersProcessor (green line) is much slower than other processors:

Comparing this to Ledger Entry Change chart we can see that there are a lot of offer removals in ledgers:

It looks like batching offer removals could largely improve the speed of ingestion:

go/services/horizon/internal/ingest/processors/offers_processor.go

Lines 85 to 90 in f1c5d71

	case change.Pre != nil && change.Post == nil:
	// Removed
	action = "removing"
	offer := change.Pre.Data.MustOffer()
	offerID = offer.OfferId
	rowsAffected, err = p.offersQ.RemoveOffer(int64(offer.OfferId), p.sequence)

. Because batch removals can be useful for other processors (and services) we should create a new struct in support/db similar to BatchInsertBuilder. Actually we don't DELETE offers but we update deleted flag. We should change the query to use IN instead of =.

[bartekn]

2x improvement!

[ire-and-curses]

Wow, super cool!