Remove BIP30 enforcement, as it is impossible to trigger since BIP34 #6916

1. 
   sipa commented at 7:25 pm on October 30, 2015: member

   BIP34 guarantees that every coinbase transaction (and thus every transaction derived from it) has a unique txid, assuming no double-SHA256 collisions. @morcos discovered that BIP30 verification always requires access to the database underlying the chainstate cache, as we don’t do negative caching. As BIP30 is the only thing that would need such a negative cache in consensus logic, better to just remove it.
2. Remove BIP30 enforcement, as it is impossible to trigger since BIP34

   BIP34 guarantees that every coinbase transaction (and thus every transaction
   derived from it) has a unique txid, assuming no double-SHA256 collisions.
   
   Alex Morcos discovered that BIP30 verification always requires access to the
   database underlying the chainstate cache, as we don't do negative caching.
   As BIP30 is the only thing that would need such a negative cache in consensus
   logic, better to just remove it.

   663d11964f
3. 
   gmaxwell commented at 7:31 pm on October 30, 2015: contributor

   How does this avoid corruption during initial block download? I give you a run of early blocks that perform overwrites prior to BIP34; eventually you discover that chain is shorter than the good one and try to reorganize it out. Oops: You can’t.
4. 
   sipa commented at 7:37 pm on October 30, 2015: member

   Oops.
5. sipa closed this on Oct 30, 2015

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6. DrahtBot locked this on Sep 8, 2021

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sipa gmaxwell