disable vid reuse compaction (#2276)

The current implementation cannot be used practically since it causes
several full reallocations of the whole free list per deletion - it
needs to be reimplemented, or the chain cannot practically progress
beyond ~2.5M blocks where a lot of removals happen.

Co-authored-by: tersec <[email protected]>

nimbus/db/aristo/aristo_delete.nim

@@ -300,8 +300,13 @@ proc delSubTreeImpl(
  db.layersPutVtx(VertexID(1), wp.vid, leaf)
  db.layersResKey(VertexID(1), wp.vid)
 
- # Squeze list of recycled vertex IDs
- db.top.final.vGen = db.vGen.vidReorg()
+ # Squeeze list of recycled vertex IDs
+ # TODO this causes a reallocation of vGen which slows down subsequent
+ # additions to the list because the sequence must grow which entails a
+ # full copy in addition to this reorg itself - around block 2.5M this
+ # causes significant slowdown as the vid list is >1M entries long
+ # See also EIP-161 which is why there are so many deletions
+ # db.top.final.vGen = db.vGen.vidReorg()
  ok()
 
 
@@ -393,8 +398,13 @@ proc deleteImpl(
  db.layersPutVtx(VertexID(1), wp.vid, leaf)
  db.layersResKey(VertexID(1), wp.vid)
 
- # Squeze list of recycled vertex IDs
- db.top.final.vGen = db.vGen.vidReorg()
+ # Squeeze list of recycled vertex IDs
+ # TODO this causes a reallocation of vGen which slows down subsequent
+ # additions to the list because the sequence must grow which entails a
+ # full copy in addition to this reorg itself - around block 2.5M this
+ # causes significant slowdown as the vid list is >1M entries long
+ # See also EIP-161 which is why there are so many deletions```
+ # db.top.final.vGen = db.vGen.vidReorg()
  ok(emptySubTreeOk)
 
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