FRAME itself does not limit the key length.
The concrete value must therefore depend on your storage usage.
A [frame_support::storage::StorageNMap] for example can have an arbitrary number of
keys which are then hashed and concatenated, resulting in arbitrarily long keys.
The migration will halt with a Halted event if this value is too small.
Since there is no real penalty from over-estimating, it is advised to use a large
value. The default is 512 byte.
Maximal number of bytes that a key can have.
FRAME itself does not limit the key length. The concrete value must therefore depend on your storage usage. A [
frame_support::storage::StorageNMap] for example can have an arbitrary number of keys which are then hashed and concatenated, resulting in arbitrarily long keys.Use the state migration RPC to retrieve the length of the longest key in your storage: https://github.com/paritytech/substrate/issues/11642
The migration will halt with a
Haltedevent if this value is too small. Since there is no real penalty from over-estimating, it is advised to use a large value. The default is 512 byte.Some key lengths for reference:
frame_support::storage::StorageValue]: 32 byteframe_support::storage::StorageMap]: 64 byteframe_support::storage::StorageDoubleMap]: 96 byteFor more info see https://www.shawntabrizi.com/blog/substrate/querying-substrate-storage-via-rpc/