Wow, that’s new for me.
(Using vextra as short for vExtraTxnForCompact) It seems very reasonable for vextra to be larger, or for it to only contain non-orphan transactions, and then InitData can look through the orphanage as well (the orphans in vextra are kind of “free” memory-wise compared to the others).
In addition to running with a larger -blockreconstructionextratxn, I wonder if we can try to analyze how well we use vextra. Broadly we have (1) replaced transactions (2) orphans (3) transactions that fail validation, you could have a patch that turns the buffer into pairs of <CTransactionRef, OriginEnum>. I wonder if one or two of these types of vextra transactions is usually more useful than the others. (More granular, are there certain TxValidationResults that are particularly helpful/unhelpful? I think TX_CONSENSUS is skippable. I expect this is inconsequential though.)
If most of the reconstructions are orphans, then perhaps we should consider iterating through the whole orphanage in addition to the vextra buffer. fwiw I’m also currently working on a PR to that would make the number of transactions in orphanage potentially much larger, though (in the tens of thousands). So that might be a consideration if we’re thinking about doing this.