Blockchain-based hierarchical data storage

1. A blockchain-based hierarchical data storage method comprising:

determining, based on a blockchain stored in a database that includes multiple levels of storage, a block number interval that includes one or more block numbers associated with data nodes to be migrated to a lower level of storage in response to the data nodes meeting a data migration condition, wherein:

each of the data nodes is included in a state Merkle tree and is associated with a block number of a block of the blockchain where the corresponding data node was last updated, and

the lower level of storage corresponds to a storage media with lower storage cost;

determining a migration threshold, wherein the migration threshold is a block number of a target block of the blockchain, and wherein determining the migration threshold comprises, if the block number interval is right-open, determining a right endpoint of the block number interval as the migration threshold, or, if the block number interval is right-closed, determining a sum of the right endpoint and a step size of the one or more block numbers in the block number interval as the migration threshold;

traversing a state Merkle tree corresponding to the target block to identify first one or more target data nodes associated with block numbers smaller than the migration threshold;

changing the block numbers associated with the first one or more target data nodes to the migration threshold;

traversing one or more state Merkle trees corresponding to one or more blocks of the blockchain with the one or more block numbers in the block number interval to identify second one or more target data nodes associated with block numbers smaller than the migration threshold; and

migrating the second one or more target data nodes to the lower level of storage.

2. The method according to claim 1 , wherein the database is a key-value database, the data nodes included in the state Merkle state tree are stored as key-value pairs (KVPs), keys of the KVPs are hash values of corresponding values of the KVPs, and the values of the KVPs are data content of the corresponding data nodes.

3. The method according to claim 1 , further comprising:

determining one or more data nodes updated in a state Merkle tree corresponding to the latest block of the blockchain; and

associating a block number of the latest block with the one or more data nodes.

4. The method according to claim 1 , wherein each of the one or more block numbers is stored in a block number field that is preserved in a corresponding data node.

5. The method according to claim 4 , wherein the block number field is preserved to identify a storage location of a value of the corresponding data node included in the state Merkle state tree.

6. The method according to claim 1 , wherein the state Merkle tree has a tree structure constructed based on a Merkle tree and a prefix tree.

7. The method according to claim 1 , wherein the state Merkle state is a Merkle Patricia Tree (MPT).

8. The method according to claim 1 , wherein the database is a LevelDB database.

9. The method according to claim 1 , wherein the database is a RocksDB database.

10. The method according to claim 1 , wherein the storage media with lower storage cost has lower read-write performance.

11. A computer-implemented system, comprising one or more computers, and one or more computer memory devices interoperably coupled with the one or more computers and having tangible, non-transitory, machine-readable media storing one or more instructions that, when executed by the one or more computers, perform operations comprising:

determining, based on a blockchain stored in a database that includes multiple levels of storage, a block number interval that includes one or more block numbers associated with data nodes to be migrated to a lower level of storage in response to the data nodes meeting a data migration condition, wherein:

each of the data nodes is included in a state Merkle tree and is associated with a block number of a block of the blockchain where the corresponding data node was last updated, and

the lower level of storage corresponds to a storage media with lower storage cost;

determining a migration threshold, wherein the migration threshold is a block number of a target block of the blockchain, and wherein determining the migration threshold comprises, if the block number interval is right-open, determining a right endpoint of the block number interval as the migration threshold, or, if the block number interval is right-closed, determining a sum of the right endpoint and a step size of the one or more block numbers in the block number interval as the migration threshold;

traversing a state Merkle tree corresponding to the target block to identify first one or more target data nodes associated with block numbers smaller than the migration threshold;

changing the block numbers associated with the first one or more target data nodes to the migration threshold;

traversing one or more state Merkle trees corresponding to one or more blocks of the blockchain with the one or more block numbers in the block number interval to identify second one or more target data nodes associated with block numbers smaller than the migration threshold; and

migrating the second one or more target data nodes to the lower level of storage.

12. The computer-implemented system according to claim 11 , wherein the database is a key-value database, the data nodes included in the state Merkle state tree are stored as key-value pairs (KVPs), keys of the KVPs are hash values of corresponding values of the KVPs, and the values of the KVPs are data content of the corresponding data nodes.

13. The computer-implemented system according to claim 11 , further comprising:

determining one or more data nodes updated in a state Merkle tree corresponding to the latest block of the blockchain; and

associating a block number of the latest block with the one or more data nodes.

14. The computer-implemented system according to claim 11 , wherein each of the one or more block numbers is stored in a block number field that is preserved in a corresponding data node.

15. The computer-implemented system according to claim 14 , wherein the block number field is preserved to identify a storage location of a value of the corresponding data node included in the state Merkle state tree.

16. The computer-implemented system according to claim 11 , wherein the state Merkle tree has a tree structure constructed based on a Merkle tree and a prefix tree.

17. The computer-implemented system according to claim 11 , wherein the state Merkle state is a Merkle Patricia Tree (MPT).

18. A non-transitory, computer-readable medium storing one or more instructions executable by a computer system to perform operations comprising:

determining, based on a blockchain stored in a database that includes multiple levels of storage, a block number interval that includes one or more block numbers associated with data nodes to be migrated to a lower level of storage in response to the data nodes meeting a data migration condition, wherein:

each of the data nodes is included in a state Merkle tree and is associated with a block number of a block of the blockchain where the corresponding data node was last updated, and

the lower level of storage corresponds to a storage media with lower storage cost;

determining a migration threshold, wherein the migration threshold is a block number of a target block of the blockchain, and wherein determining the migration threshold comprises, if the block number interval is right-open, determining a right endpoint of the block number interval as the migration threshold, or, if the block number interval is right-closed, determining a sum of the right endpoint and a step size of the one or more block numbers in the block number interval as the migration threshold;

traversing a state Merkle tree corresponding to the target block to identify first one or more target data nodes associated with block numbers smaller than the migration threshold;

changing the block numbers associated with the first one or more target data nodes to the migration threshold;

traversing one or more state Merkle trees corresponding to one or more blocks of the blockchain with the one or more block numbers in the block number interval to identify second one or more target data nodes associated with block numbers smaller than the migration threshold; and

migrating the second one or more target data nodes to the lower level of storage.