On-Disk Database Format

We store the database in RocksDB. This document is an attempt to give hints about how to navigate it.

RocksDB

The column families are defined in DBCol, defined in core/store/src/columns.rs
The column families are seen on the rocksdb side as per the col_name function defined in core/store/src/db/rocksdb.rs

The trie is stored in column family State, number 5
In this family, each key is of the form ShardUId | CryptoHash where ShardUId: u64 and CryptoHash: [u8; 32]

The state changes are stored in column family StateChanges, number 35
In this family, each key is of the form BlockHash | Column | AdditionalInfo where:
- BlockHash: [u8; 32] is the block hash for this change
- Column: u8 is defined near the top of core/primitives/src/trie_key.rs
- AdditionalInfo depends on Column and it can be found in the code for the TrieKey struct, same file as Column

Contract deployments happen with Column = 0x01
AdditionalInfo is the account id for which the contract is being deployed
The key value contains the contract code alongside other pieces of data. It is possible to extract the contract code by removing everything until the wasm magic number, 0061736D01000000
As such, it is possible to dump all the contracts that were ever deployed on-chain using this command on an archival node:
```
ldb --db=~/.near/data scan --column_family=col35 --hex | \
    grep -E '^0x.{64}01' | \
    sed 's/0061736D01000000/x/' | \
    sed 's/^.*x/0061736D01000000/' | \
    grep -v ' : '
```
(Note that the last grep is required because not every such value appears to contain contract code) We should implement a feature to state-viewer that’d allow better visualization of this data, but in the meantime this seems to work.