Tendermint version 0.34.20

ABCI app vega

Environment:

• OS ubuntu 20.04

What happened:
We're testing out switching to using the postgres indexer to facilitate building a block explorer. I noticed a bunch entries missing in the tx_results table, and in the log I see messages like

txindex/indexer_service.go:88 deduplicate batch {"height": 412}

Digging into it a little it seems that this is because txIdxr.Get(hash) is not implemented by the BackportTxIndexer that is used when the postgres indexer is enabled. I think it would not be too tricky to implement, and I'm happy to have a stab at that, but thought I had better check here first because I don't fully understand the purpose of DeduplicateBatch.

Also we've noticed that when enabling the postgres indexer tendermint cannot keep up with its peers and keeps going out of sync so I'm a bit loathe to add in more PG queries; I figure this sort of thing could possibly be solved with an ON CONFLICT DO xxx clause but I'm not sure if I could make that fit in nicely with the backend-agnostic framework you have.

What you expected to happen:

No errors in the log, all my TxResults in my postgres DB :)

Have you tried the latest version: yes/no

I haven't tried in 0.35.xx as we have had a bunch of issues with that and have had to revert back to 0.34 for now