#[repr(u32)]pub enum DbId {
Service = 0,
WriteOnly = 1,
Subjective = 2,
NativeConstrained = 3,
NativeUnconstrained = 4,
BlockLog = 5,
HistoryEvent = 6,
UiEvent = 7,
MerkleEvent = 8,
BlockProof = 9,
NumDatabases = 10,
}Expand description
Identify database to operate on
Native functions expose a set of databases which serve various purposes. This enum identifies which database to use when invoking those functions.
Variants§
Service = 0
Services should store their tables here
The first 64 bits of the key match the service.
WriteOnly = 1
Data for RPC
Write-only during transactions, and read-only during RPC. Individual nodes may modify this database, expire data from this database, or wipe it entirely at will.
The first 64 bits of the key match the service.
Subjective = 2
Data that is not part of consensus
Only accessible to subjective services during transactions, but readable by all services during RPC. Doesn’t undo from aborting transactions, aborting blocks, or forking blocks. Individual nodes may modify this database or wipe
The first 64 bits of the key match the service.
NativeConstrained = 3
Tables used by native code
This database enforces constraints during write. Only writable by privileged services, but readable by all services.
Some writes to this database indicate chain upgrades. If a privileged service writes to a table that an older node version doesn’t know about, or writes new fields to an existing table that an older node doesn’t know about, then that node will reject the write. If the producers accepted the write into a block, then the node will stop following the chain until it’s upgraded to a newer version.
NativeUnconstrained = 4
Tables used by native code
This database doesn’t enforce constraints during write. Only writable by privileged services, but readable by all services.
BlockLog = 5
Block log
Transactions don’t have access to this, but RPC does.
HistoryEvent = 6
Long-term history event storage
Write-only during transactions, and read-only during RPC. Individual nodes may modify this database, expire data from this database, or wipe it entirely at will.
TODO: this policy may eventually change to allow time-limited read access during transactions.
Key is an auto-incremented, 64-bit unsigned number.
Value must begin with:
- 32 bit: block number
- 64 bit: service
Only usable with these native functions:
TODO: right now the value must begin with the service. Revisit whether beginning with the block number is useful.
UiEvent = 7
Short-term history event storage
These events are erased once the block that produced them becomes final. They notify user interfaces which subscribe to activity.
Write-only during transactions, and read-only during RPC. Individual nodes may modify this database, expire data from this database, or wipe it entirely at will.
Key is an auto-incremented, 64-bit unsigned number.
Value must begin with:
- 32 bit: block number
- 64 bit: service
Only usable with these native functions:
TODO: right now the value must begin with the service. Revisit whether beginning with the block number is useful.
MerkleEvent = 8
Events which go into the merkle tree
TODO: read support; right now only RPC mode can read
Services may produce these events during transactions and may read them up to 1 hour (configurable) after they were produced, or they reach finality, which ever is longer.
Key is an auto-incremented, 64-bit unsigned number.
Value must begin with:
- 32 bit: block number
- 64 bit: service
Only usable with these native functions:
TODO: right now the value must begin with the service. Revisit whether beginning with the block number is useful.
BlockProof = 9
block signatures
NumDatabases = 10
Number of defined databases
This number may grow in the future