doc: remove stale shortid collision TODO #34989

1. 
   w0xlt commented at 6:58 pm on April 1, 2026: contributor

   PartiallyDownloadedBlock::InitData() already treats duplicate short IDs in a compact block as READ_STATUS_FAILED.

   For an honest peer, block-level short-ID collisions are rare enough that failing the compact block early is preferable to scanning the mempool or attempting selective recovery (see #34932 (comment))

   This removes the old TODO suggesting that both collided transactions should be requested, since that comment no longer matches the intended handling.

   No behavior change. Comment-only cleanup.

2. doc: remove stale shortid collision TODO

   PartiallyDownloadedBlock::InitData() intentionally treats duplicate short IDs in a compact block as READ_STATUS_FAILED.
   
   For an honest peer, block-level short-ID collisions are rare enough that failing the compact block early is preferable to spending CPU scanning the mempool or attempting selective recovery.
   
   Remove the old TODO that suggested requesting both collided transactions, since it since it points at unwanted behavior.

   fc9987dfc6
3. DrahtBot added the label Docs on Apr 1, 2026
4. 
   DrahtBot commented at 6:59 pm on April 1, 2026: contributor

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5. 
   gmaxwell commented at 0:58 am on April 2, 2026: contributor

   Point of clarification, AJ’s 1 in 8.8m number is right for single reconstructions, but a network of 80,000 nodes does 80,000 reconstructions per block, and 144 blocks a day.

   A node somewhere on the network will fail reconstruction (under the extreme example of 8000 txn blocks) due to a duplicate shortid in the block once every 3.7 days.

   Perhaps that’s a cost not worth worrying too much about, but if you go reasoning from the without-multiple-comparisons number you might think it’s evidence of broken peers and go disconnecting them and such. :P

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