Feat/marf compression #6654
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Feat/marf compression #6654
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…ue if it's 0, store a bitmap and non-empty trie ptrs if the list is sparse, and store node patches atop full nodes (and read them back)
…then record the original node from which it was copied so that a TrieNodePatch can be calculated and stored instead
…oid repeating nodes across tries
… each node and see if we can instead patch an existing node instead of storing a (mostly-unchanged) copy
jcnelson
commented
Nov 5, 2025
| .with_compression(true), | ||
| MARFOpenOpts::new(TrieHashCalculationMode::Immediate, "noop", true) | ||
| .with_compression(true), | ||
| */ |
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TODO: revert this comment block
jcnelson
commented
Nov 5, 2025
| + rusqlite::types::ToSql | ||
| + rusqlite::types::FromSql | ||
| + stacks_common::codec::StacksMessageCodec | ||
| + crate::codec::StacksMessageCodec |
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TODO: use stacks_common not crate
jcnelson
commented
Nov 5, 2025
| #[cfg(test)] | ||
| use stacks_common::types::chainstate::BlockHeaderHash; | ||
| use stacks_common::types::chainstate::{ | ||
| use crate::types::chainstate::BlockHeaderHash; |
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TODO: use stacks_common not crate
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This PR implements work discovered in #6593. Specifically, it makes the following changes to the on-disk representation of the MARF:
If a
TriePtris not a back-block pointer, then theback_blockfield is not stored since it's always 0.If a node's children
TriePtrlist is sparse, then instead of storingTriePtr::default()for empty pointers, the system now stores a bitmap of which pointers are non-empty, and then only stores the non-emptyTriePtrs. It only does this if this actually saves space over just storing the entire list (storing the entire list is cheaper if the list is nearly full).Instead of copying a trie node from one trie to the next as part of a copy-on-write, the system will only store a patch from the old node to the new node. It will create a list of up to 16 patches across 16 tries before storing a full copy of the node.
In my (very small scale) benchmarks, this saves over 50% of space.
This PR is still a draft and will likely remain so for some time. It needs a lot more unit tests, and it would benefit significantly from fuzz and property testing against the current implementation. In addition, it will need a lot of performance tuning, since the act of reading a list of patch nodes will slow down reads.