Skip to main content

Constants

The following sections contain the module constants, also known as parameter types. These can only be changed as part of a runtime upgrade. On the api, these are exposed via api.consts.<module>.<method>.

(NOTE: These were generated from a static/snapshot view of a recent default Polkadot runtime. Some items may not be available in older nodes, or in any customized implementations.)

auctions​

endingPeriod: u32​

  • interface: api.consts.auctions.endingPeriod
  • summary: The number of blocks over which an auction may be retroactively ended.

leasePeriodsPerSlot: u32​

  • interface: api.consts.auctions.leasePeriodsPerSlot

sampleLength: u32​

  • interface: api.consts.auctions.sampleLength

  • summary: The length of each sample to take during the ending period.

    EndingPeriod / SampleLength = Total # of Samples

slotRangeCount: u32​

  • interface: api.consts.auctions.slotRangeCount

babe​

epochDuration: u64​

  • interface: api.consts.babe.epochDuration
  • summary: The amount of time, in slots, that each epoch should last. NOTE: Currently it is not possible to change the epoch duration after the chain has started. Attempting to do so will brick block production.

expectedBlockTime: u64​

  • interface: api.consts.babe.expectedBlockTime
  • summary: The expected average block time at which BABE should be creating blocks. Since BABE is probabilistic it is not trivial to figure out what the expected average block time should be based on the slot duration and the security parameter c (where 1 - c represents the probability of a slot being empty).

maxAuthorities: u32​

  • interface: api.consts.babe.maxAuthorities
  • summary: Max number of authorities allowed

maxNominators: u32​

  • interface: api.consts.babe.maxNominators
  • summary: The maximum number of nominators for each validator.

balances​

existentialDeposit: u128​

  • interface: api.consts.balances.existentialDeposit

  • summary: The minimum amount required to keep an account open. MUST BE GREATER THAN ZERO!

    If you really need it to be zero, you can enable the feature insecure_zero_ed for this pallet. However, you do so at your own risk: this will open up a major DoS vector. In case you have multiple sources of provider references, you may also get unexpected behaviour if you set this to zero.

    Bottom line: Do yourself a favour and make it at least one!

maxFreezes: u32​

  • interface: api.consts.balances.maxFreezes
  • summary: The maximum number of individual freeze locks that can exist on an account at any time.

maxLocks: u32​

  • interface: api.consts.balances.maxLocks
  • summary: The maximum number of locks that should exist on an account. Not strictly enforced, but used for weight estimation.

maxReserves: u32​

  • interface: api.consts.balances.maxReserves
  • summary: The maximum number of named reserves that can exist on an account.

beefy​

maxAuthorities: u32​

  • interface: api.consts.beefy.maxAuthorities
  • summary: The maximum number of authorities that can be added.

maxNominators: u32​

  • interface: api.consts.beefy.maxNominators
  • summary: The maximum number of nominators for each validator.

maxSetIdSessionEntries: u64​

  • interface: api.consts.beefy.maxSetIdSessionEntries

  • summary: The maximum number of entries to keep in the set id to session index mapping.

    Since the SetIdSession map is only used for validating equivocations this value should relate to the bonding duration of whatever staking system is being used (if any). If equivocation handling is not enabled then this value can be zero.

bounties​

bountyDepositBase: u128​

  • interface: api.consts.bounties.bountyDepositBase
  • summary: The amount held on deposit for placing a bounty proposal.

bountyDepositPayoutDelay: u32​

  • interface: api.consts.bounties.bountyDepositPayoutDelay
  • summary: The delay period for which a bounty beneficiary need to wait before claim the payout.

bountyUpdatePeriod: u32​

  • interface: api.consts.bounties.bountyUpdatePeriod
  • summary: Bounty duration in blocks.

bountyValueMinimum: u128​

  • interface: api.consts.bounties.bountyValueMinimum
  • summary: Minimum value for a bounty.

curatorDepositMax: Option<u128>​

  • interface: api.consts.bounties.curatorDepositMax
  • summary: Maximum amount of funds that should be placed in a deposit for making a proposal.

curatorDepositMin: Option<u128>​

  • interface: api.consts.bounties.curatorDepositMin
  • summary: Minimum amount of funds that should be placed in a deposit for making a proposal.

curatorDepositMultiplier: Permill​

  • interface: api.consts.bounties.curatorDepositMultiplier

  • summary: The curator deposit is calculated as a percentage of the curator fee.

    This deposit has optional upper and lower bounds with CuratorDepositMax and CuratorDepositMin.

dataDepositPerByte: u128​

  • interface: api.consts.bounties.dataDepositPerByte
  • summary: The amount held on deposit per byte within the tip report reason or bounty description.

maximumReasonLength: u32​

  • interface: api.consts.bounties.maximumReasonLength

  • summary: Maximum acceptable reason length.

    Benchmarks depend on this value, be sure to update weights file when changing this value

childBounties​

childBountyValueMinimum: u128​

  • interface: api.consts.childBounties.childBountyValueMinimum
  • summary: Minimum value for a child-bounty.

maxActiveChildBountyCount: u32​

  • interface: api.consts.childBounties.maxActiveChildBountyCount
  • summary: Maximum number of child bounties that can be added to a parent bounty.

claims​

prefix: Bytes​

  • interface: api.consts.claims.prefix

convictionVoting​

maxVotes: u32​

  • interface: api.consts.convictionVoting.maxVotes

  • summary: The maximum number of concurrent votes an account may have.

    Also used to compute weight, an overly large value can lead to extrinsics with large weight estimation: see delegate for instance.

voteLockingPeriod: u32​

  • interface: api.consts.convictionVoting.voteLockingPeriod

  • summary: The minimum period of vote locking.

    It should be no shorter than enactment period to ensure that in the case of an approval, those successful voters are locked into the consequences that their votes entail.

crowdloan​

minContribution: u128​

  • interface: api.consts.crowdloan.minContribution
  • summary: The minimum amount that may be contributed into a crowdloan. Should almost certainly be at least ExistentialDeposit.

palletId: FrameSupportPalletId​

  • interface: api.consts.crowdloan.palletId
  • summary: PalletId for the crowdloan pallet. An appropriate value could be PalletId(*b"py/cfund")

removeKeysLimit: u32​

  • interface: api.consts.crowdloan.removeKeysLimit
  • summary: Max number of storage keys to remove per extrinsic call.

electionProviderMultiPhase​

betterSignedThreshold: Perbill​

  • interface: api.consts.electionProviderMultiPhase.betterSignedThreshold
  • summary: The minimum amount of improvement to the solution score that defines a solution as "better" in the Signed phase.

maxWinners: u32​

  • interface: api.consts.electionProviderMultiPhase.maxWinners

  • summary: The maximum number of winners that can be elected by this ElectionProvider implementation.

    Note: This must always be greater or equal to T::DataProvider::desired_targets().

minerMaxLength: u32​

  • interface: api.consts.electionProviderMultiPhase.minerMaxLength

minerMaxVotesPerVoter: u32​

  • interface: api.consts.electionProviderMultiPhase.minerMaxVotesPerVoter

minerMaxWeight: SpWeightsWeightV2Weight​

  • interface: api.consts.electionProviderMultiPhase.minerMaxWeight

minerMaxWinners: u32​

  • interface: api.consts.electionProviderMultiPhase.minerMaxWinners

minerTxPriority: u64​

  • interface: api.consts.electionProviderMultiPhase.minerTxPriority
  • summary: The priority of the unsigned transaction submitted in the unsigned-phase

offchainRepeat: u32​

  • interface: api.consts.electionProviderMultiPhase.offchainRepeat

  • summary: The repeat threshold of the offchain worker.

    For example, if it is 5, that means that at least 5 blocks will elapse between attempts to submit the worker's solution.

signedDepositByte: u128​

  • interface: api.consts.electionProviderMultiPhase.signedDepositByte
  • summary: Per-byte deposit for a signed solution.

signedDepositWeight: u128​

  • interface: api.consts.electionProviderMultiPhase.signedDepositWeight
  • summary: Per-weight deposit for a signed solution.

signedMaxRefunds: u32​

  • interface: api.consts.electionProviderMultiPhase.signedMaxRefunds
  • summary: The maximum amount of unchecked solutions to refund the call fee for.

signedMaxSubmissions: u32​

  • interface: api.consts.electionProviderMultiPhase.signedMaxSubmissions

  • summary: Maximum number of signed submissions that can be queued.

    It is best to avoid adjusting this during an election, as it impacts downstream data structures. In particular, SignedSubmissionIndices<T> is bounded on this value. If you update this value during an election, you must ensure that SignedSubmissionIndices.len() is less than or equal to the new value. Otherwise, attempts to submit new solutions may cause a runtime panic.

signedMaxWeight: SpWeightsWeightV2Weight​

  • interface: api.consts.electionProviderMultiPhase.signedMaxWeight

  • summary: Maximum weight of a signed solution.

    If [Config::MinerConfig] is being implemented to submit signed solutions (outside of this pallet), then [MinerConfig::solution_weight] is used to compare against this value.

signedPhase: u32​

  • interface: api.consts.electionProviderMultiPhase.signedPhase
  • summary: Duration of the signed phase.

signedRewardBase: u128​

  • interface: api.consts.electionProviderMultiPhase.signedRewardBase
  • summary: Base reward for a signed solution

unsignedPhase: u32​

  • interface: api.consts.electionProviderMultiPhase.unsignedPhase
  • summary: Duration of the unsigned phase.

fastUnstake​

deposit: u128​

  • interface: api.consts.fastUnstake.deposit
  • summary: Deposit to take for unstaking, to make sure we're able to slash the it in order to cover the costs of resources on unsuccessful unstake.

grandpa​

maxAuthorities: u32​

  • interface: api.consts.grandpa.maxAuthorities
  • summary: Max Authorities in use

maxNominators: u32​

  • interface: api.consts.grandpa.maxNominators
  • summary: The maximum number of nominators for each validator.

maxSetIdSessionEntries: u64​

  • interface: api.consts.grandpa.maxSetIdSessionEntries

  • summary: The maximum number of entries to keep in the set id to session index mapping.

    Since the SetIdSession map is only used for validating equivocations this value should relate to the bonding duration of whatever staking system is being used (if any). If equivocation handling is not enabled then this value can be zero.

identity​

basicDeposit: u128​

  • interface: api.consts.identity.basicDeposit
  • summary: The amount held on deposit for a registered identity.

byteDeposit: u128​

  • interface: api.consts.identity.byteDeposit
  • summary: The amount held on deposit per encoded byte for a registered identity.

maxRegistrars: u32​

  • interface: api.consts.identity.maxRegistrars
  • summary: Maxmimum number of registrars allowed in the system. Needed to bound the complexity of, e.g., updating judgements.

maxSubAccounts: u32​

  • interface: api.consts.identity.maxSubAccounts
  • summary: The maximum number of sub-accounts allowed per identified account.

maxSuffixLength: u32​

  • interface: api.consts.identity.maxSuffixLength
  • summary: The maximum length of a suffix.

maxUsernameLength: u32​

  • interface: api.consts.identity.maxUsernameLength
  • summary: The maximum length of a username, including its suffix and any system-added delimiters.

pendingUsernameExpiration: u32​

  • interface: api.consts.identity.pendingUsernameExpiration
  • summary: The number of blocks within which a username grant must be accepted.

subAccountDeposit: u128​

  • interface: api.consts.identity.subAccountDeposit
  • summary: The amount held on deposit for a registered subaccount. This should account for the fact that one storage item's value will increase by the size of an account ID, and there will be another trie item whose value is the size of an account ID plus 32 bytes.

indices​

deposit: u128​

  • interface: api.consts.indices.deposit
  • summary: The deposit needed for reserving an index.

messageQueue​

heapSize: u32​

  • interface: api.consts.messageQueue.heapSize

  • summary: The size of the page; this implies the maximum message size which can be sent.

    A good value depends on the expected message sizes, their weights, the weight that is available for processing them and the maximal needed message size. The maximal message size is slightly lower than this as defined by [MaxMessageLenOf].

maxStale: u32​

  • interface: api.consts.messageQueue.maxStale
  • summary: The maximum number of stale pages (i.e. of overweight messages) allowed before culling can happen. Once there are more stale pages than this, then historical pages may be dropped, even if they contain unprocessed overweight messages.

serviceWeight: Option<SpWeightsWeightV2Weight>​

  • interface: api.consts.messageQueue.serviceWeight

  • summary: The amount of weight (if any) which should be provided to the message queue for servicing enqueued items.

    This may be legitimately None in the case that you will call ServiceQueues::service_queues manually.

multisig​

depositBase: u128​

  • interface: api.consts.multisig.depositBase

  • summary: The base amount of currency needed to reserve for creating a multisig execution or to store a dispatch call for later.

    This is held for an additional storage item whose value size is 4 + sizeof((BlockNumber, Balance, AccountId)) bytes and whose key size is 32 + sizeof(AccountId) bytes.

depositFactor: u128​

  • interface: api.consts.multisig.depositFactor

  • summary: The amount of currency needed per unit threshold when creating a multisig execution.

    This is held for adding 32 bytes more into a pre-existing storage value.

maxSignatories: u32​

  • interface: api.consts.multisig.maxSignatories
  • summary: The maximum amount of signatories allowed in the multisig.

nominationPools​

maxPointsToBalance: u8​

  • interface: api.consts.nominationPools.maxPointsToBalance

  • summary: The maximum pool points-to-balance ratio that an open pool can have.

    This is important in the event slashing takes place and the pool's points-to-balance ratio becomes disproportional.

    Moreover, this relates to the RewardCounter type as well, as the arithmetic operations are a function of number of points, and by setting this value to e.g. 10, you ensure that the total number of points in the system are at most 10 times the total_issuance of the chain, in the absolute worse case.

    For a value of 10, the threshold would be a pool points-to-balance ratio of 10:1. Such a scenario would also be the equivalent of the pool being 90% slashed.

maxUnbonding: u32​

  • interface: api.consts.nominationPools.maxUnbonding
  • summary: The maximum number of simultaneous unbonding chunks that can exist per member.

palletId: FrameSupportPalletId​

  • interface: api.consts.nominationPools.palletId
  • summary: The nomination pool's pallet id.

paras​

unsignedPriority: u64​

  • interface: api.consts.paras.unsignedPriority

proxy​

announcementDepositBase: u128​

  • interface: api.consts.proxy.announcementDepositBase

  • summary: The base amount of currency needed to reserve for creating an announcement.

    This is held when a new storage item holding a Balance is created (typically 16 bytes).

announcementDepositFactor: u128​

  • interface: api.consts.proxy.announcementDepositFactor

  • summary: The amount of currency needed per announcement made.

    This is held for adding an AccountId, Hash and BlockNumber (typically 68 bytes) into a pre-existing storage value.

maxPending: u32​

  • interface: api.consts.proxy.maxPending
  • summary: The maximum amount of time-delayed announcements that are allowed to be pending.

maxProxies: u32​

  • interface: api.consts.proxy.maxProxies
  • summary: The maximum amount of proxies allowed for a single account.

proxyDepositBase: u128​

  • interface: api.consts.proxy.proxyDepositBase

  • summary: The base amount of currency needed to reserve for creating a proxy.

    This is held for an additional storage item whose value size is sizeof(Balance) bytes and whose key size is sizeof(AccountId) bytes.

proxyDepositFactor: u128​

  • interface: api.consts.proxy.proxyDepositFactor

  • summary: The amount of currency needed per proxy added.

    This is held for adding 32 bytes plus an instance of ProxyType more into a pre-existing storage value. Thus, when configuring ProxyDepositFactor one should take into account 32 + proxy_type.encode().len() bytes of data.

referenda​

alarmInterval: u32​

  • interface: api.consts.referenda.alarmInterval
  • summary: Quantization level for the referendum wakeup scheduler. A higher number will result in fewer storage reads/writes needed for smaller voters, but also result in delays to the automatic referendum status changes. Explicit servicing instructions are unaffected.

maxQueued: u32​

  • interface: api.consts.referenda.maxQueued
  • summary: Maximum size of the referendum queue for a single track.

submissionDeposit: u128​

  • interface: api.consts.referenda.submissionDeposit
  • summary: The minimum amount to be used as a deposit for a public referendum proposal.

tracks: Vec<(u16,PalletReferendaTrackInfo)>​

  • interface: api.consts.referenda.tracks
  • summary: Information concerning the different referendum tracks.

undecidingTimeout: u32​

  • interface: api.consts.referenda.undecidingTimeout
  • summary: The number of blocks after submission that a referendum must begin being decided by. Once this passes, then anyone may cancel the referendum.

registrar​

dataDepositPerByte: u128​

  • interface: api.consts.registrar.dataDepositPerByte
  • summary: The deposit to be paid per byte stored on chain.

paraDeposit: u128​

  • interface: api.consts.registrar.paraDeposit
  • summary: The deposit to be paid to run a on-demand parachain. This should include the cost for storing the genesis head and validation code.

scheduler​

maximumWeight: SpWeightsWeightV2Weight​

  • interface: api.consts.scheduler.maximumWeight
  • summary: The maximum weight that may be scheduled per block for any dispatchables.

maxScheduledPerBlock: u32​

  • interface: api.consts.scheduler.maxScheduledPerBlock

  • summary: The maximum number of scheduled calls in the queue for a single block.

    NOTE: + Dependent pallets' benchmarks might require a higher limit for the setting. Set a higher limit under runtime-benchmarks feature.

slots​

leaseOffset: u32​

  • interface: api.consts.slots.leaseOffset
  • summary: The number of blocks to offset each lease period by.

leasePeriod: u32​

  • interface: api.consts.slots.leasePeriod
  • summary: The number of blocks over which a single period lasts.

staking​

bondingDuration: u32​

  • interface: api.consts.staking.bondingDuration
  • summary: Number of eras that staked funds must remain bonded for.

historyDepth: u32​

  • interface: api.consts.staking.historyDepth

  • summary: Number of eras to keep in history.

    Following information is kept for eras in [current_era - HistoryDepth, current_era]: ErasStakers, ErasStakersClipped, ErasValidatorPrefs, ErasValidatorReward, ErasRewardPoints, ErasTotalStake, ErasStartSessionIndex, ClaimedRewards, ErasStakersPaged, ErasStakersOverview.

    Must be more than the number of eras delayed by session. I.e. active era must always be in history. I.e. active_era > current_era - history_depth must be guaranteed.

    If migrating an existing pallet from storage value to config value, this should be set to same value or greater as in storage.

    Note: HistoryDepth is used as the upper bound for the BoundedVec item StakingLedger.legacy_claimed_rewards. Setting this value lower than the existing value can lead to inconsistencies in the StakingLedger and will need to be handled properly in a migration. The test reducing_history_depth_abrupt shows this effect.

maxExposurePageSize: u32​

  • interface: api.consts.staking.maxExposurePageSize

  • summary: The maximum size of each T::ExposurePage.

    An ExposurePage is weakly bounded to a maximum of MaxExposurePageSize nominators.

    For older non-paged exposure, a reward payout was restricted to the top MaxExposurePageSize nominators. This is to limit the i/o cost for the nominator payout.

    Note: MaxExposurePageSize is used to bound ClaimedRewards and is unsafe to reduce without handling it in a migration.

maxUnlockingChunks: u32​

  • interface: api.consts.staking.maxUnlockingChunks

  • summary: The maximum number of unlocking chunks a [StakingLedger] can have. Effectively determines how many unique eras a staker may be unbonding in.

    Note: MaxUnlockingChunks is used as the upper bound for the BoundedVec item StakingLedger.unlocking. Setting this value lower than the existing value can lead to inconsistencies in the StakingLedger and will need to be handled properly in a runtime migration. The test reducing_max_unlocking_chunks_abrupt shows this effect.

sessionsPerEra: u32​

  • interface: api.consts.staking.sessionsPerEra
  • summary: Number of sessions per era.

slashDeferDuration: u32​

  • interface: api.consts.staking.slashDeferDuration

  • summary: Number of eras that slashes are deferred by, after computation.

    This should be less than the bonding duration. Set to 0 if slashes should be applied immediately, without opportunity for intervention.

stateTrieMigration​

maxKeyLen: u32​

  • interface: api.consts.stateTrieMigration.maxKeyLen

  • summary: 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 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.

    Some key lengths for reference:

system​

blockHashCount: u32​

  • interface: api.consts.system.blockHashCount
  • summary: Maximum number of block number to block hash mappings to keep (oldest pruned first).

blockLength: FrameSystemLimitsBlockLength​

  • interface: api.consts.system.blockLength
  • summary: The maximum length of a block (in bytes).

blockWeights: FrameSystemLimitsBlockWeights​

  • interface: api.consts.system.blockWeights
  • summary: Block & extrinsics weights: base values and limits.

dbWeight: SpWeightsRuntimeDbWeight​

  • interface: api.consts.system.dbWeight
  • summary: The weight of runtime database operations the runtime can invoke.

ss58Prefix: u16​

  • interface: api.consts.system.ss58Prefix

  • summary: The designated SS58 prefix of this chain.

    This replaces the "ss58Format" property declared in the chain spec. Reason is that the runtime should know about the prefix in order to make use of it as an identifier of the chain.

version: SpVersionRuntimeVersion​

  • interface: api.consts.system.version
  • summary: Get the chain's current version.

timestamp​

minimumPeriod: u64​

  • interface: api.consts.timestamp.minimumPeriod

  • summary: The minimum period between blocks.

    Be aware that this is different to the expected period that the block production apparatus provides. Your chosen consensus system will generally work with this to determine a sensible block time. For example, in the Aura pallet it will be double this period on default settings.

transactionPayment​

operationalFeeMultiplier: u8​

  • interface: api.consts.transactionPayment.operationalFeeMultiplier

  • summary: A fee multiplier for Operational extrinsics to compute "virtual tip" to boost their priority

    This value is multiplied by the final_fee to obtain a "virtual tip" that is later added to a tip component in regular priority calculations. It means that a Normal transaction can front-run a similarly-sized Operational extrinsic (with no tip), by including a tip value greater than the virtual tip.

    ``rust,ignore // For Normal` let priority = priority_calc(tip);

    // For Operational let virtual_tip = (inclusion_fee + tip) * OperationalFeeMultiplier; let priority = priority_calc(tip + virtual_tip); ```

    Note that since we use final_fee the multiplier applies also to the regular tip sent with the transaction. So, not only does the transaction get a priority bump based on the inclusion_fee, but we also amplify the impact of tips applied to Operational transactions.

treasury​

burn: Permill​

  • interface: api.consts.treasury.burn
  • summary: Percentage of spare funds (if any) that are burnt per spend period.

maxApprovals: u32​

  • interface: api.consts.treasury.maxApprovals

  • summary: The maximum number of approvals that can wait in the spending queue.

    NOTE: This parameter is also used within the Bounties Pallet extension if enabled.

palletId: FrameSupportPalletId​

  • interface: api.consts.treasury.palletId
  • summary: The treasury's pallet id, used for deriving its sovereign account ID.

payoutPeriod: u32​

  • interface: api.consts.treasury.payoutPeriod
  • summary: The period during which an approved treasury spend has to be claimed.

proposalBond: Permill​

  • interface: api.consts.treasury.proposalBond
  • summary: Fraction of a proposal's value that should be bonded in order to place the proposal. An accepted proposal gets these back. A rejected proposal does not.

proposalBondMaximum: Option<u128>​

  • interface: api.consts.treasury.proposalBondMaximum
  • summary: Maximum amount of funds that should be placed in a deposit for making a proposal.

proposalBondMinimum: u128​

  • interface: api.consts.treasury.proposalBondMinimum
  • summary: Minimum amount of funds that should be placed in a deposit for making a proposal.

spendPeriod: u32​

  • interface: api.consts.treasury.spendPeriod
  • summary: Period between successive spends.

utility​

batchedCallsLimit: u32​

  • interface: api.consts.utility.batchedCallsLimit
  • summary: The limit on the number of batched calls.

vesting​

maxVestingSchedules: u32​

  • interface: api.consts.vesting.maxVestingSchedules

minVestedTransfer: u128​

  • interface: api.consts.vesting.minVestedTransfer
  • summary: The minimum amount transferred to call vested_transfer.

voterList​

bagThresholds: Vec<u64>​

  • interface: api.consts.voterList.bagThresholds

  • summary: The list of thresholds separating the various bags.

    Ids are separated into unsorted bags according to their score. This specifies the thresholds separating the bags. An id's bag is the largest bag for which the id's score is less than or equal to its upper threshold.

    When ids are iterated, higher bags are iterated completely before lower bags. This means that iteration is semi-sorted: ids of higher score tend to come before ids of lower score, but peer ids within a particular bag are sorted in insertion order.

    Expressing the constant​

    This constant must be sorted in strictly increasing order. Duplicate items are not permitted.

    There is an implied upper limit of Score::MAX; that value does not need to be specified within the bag. For any two threshold lists, if one ends with Score::MAX, the other one does not, and they are otherwise equal, the two lists will behave identically.

    Calculation​

    It is recommended to generate the set of thresholds in a geometric series, such that there exists some constant ratio such that threshold[k + 1] == (threshold[k] * constant_ratio).max(threshold[k] + 1) for all k.

    The helpers in the /utils/frame/generate-bags module can simplify this calculation.

    Examples​

    • If BagThresholds::get().is_empty(), then all ids are put into the same bag, and iteration is strictly in insertion order.

    • If BagThresholds::get().len() == 64, and the thresholds are determined according to the procedure given above, then the constant ratio is equal to 2.

    • If BagThresholds::get().len() == 200, and the thresholds are determined according to the procedure given above, then the constant ratio is approximately equal to 1.248.

    • If the threshold list begins [1, 2, 3, ...], then an id with score 0 or 1 will fall into bag 0, an id with score 2 will fall into bag 1, etc.

      Migration​

      In the event that this list ever changes, a copy of the old bags list must be retained. With that List::migrate can be called, which will perform the appropriate migration.