Struct Supports 

#[non_exhaustive]
pub struct Supports {

    pub cancel_execution: bool,
    pub change_priority: bool,
    pub replay_execution: bool,
    pub revoke_lease: bool,
    pub read_execution_state: bool,
    pub read_execution_info: bool,
    pub get_execution_result: bool,
    pub budget_admin: bool,
    pub quota_admin: bool,
    pub rotate_waitpoint_hmac_secret_all: bool,
    pub seed_waitpoint_hmac_secret: bool,
    pub list_pending_waitpoints: bool,
    pub cancel_flow_header: bool,
    pub cancel_flow_wait_timeout: bool,
    pub cancel_flow_wait_indefinite: bool,
    pub ack_cancel_member: bool,
    pub claim_for_worker: bool,
    pub prepare: bool,
    pub subscribe_lease_history: bool,
    pub subscribe_completion: bool,
    pub subscribe_signal_delivery: bool,
    pub subscribe_instance_tags: bool,
    pub stream_durable_summary: bool,
    pub stream_best_effort_live: bool,
}

Per-capability boolean support surface. Flat named-field shape so consumers can dot-access (e.g. caps.supports.cancel_execution) instead of map lookup. #[non_exhaustive] protects future additions from source-breaking consumers; construct via Supports::none or by returning one from crate::engine_backend::EngineBackend::capabilities.

Grouping policy

One bool per operator-visible HTTP surface; admin-only surfaces with many sibling methods roll up to a single bool (e.g. Self::budget_admin covers create_budget / report_usage / reset_budget / get_budget_status / report_usage_admin; Self::quota_admin covers create_quota_policy). Cairn’s operator UI grey-renders at the group level; fine-grained pre-dispatch checks still use crate::engine_error::EngineError::Unavailable.

Field order

Per cairn #277 “in the same order as the parity matrix so cairn can consume by copy-paste.” Keep in sync with docs/POSTGRES_PARITY_MATRIX.md.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

cancel_execution: bool

cancel_execution.

change_priority: bool

change_priority.

replay_execution: bool

replay_execution.

revoke_lease: bool

revoke_lease.

read_execution_state: bool

read_execution_state.

read_execution_info: bool

read_execution_info.

get_execution_result: bool

get_execution_result.

budget_admin: bool

Covers create_budget + report_usage + reset_budget + get_budget_status + report_usage_admin.

quota_admin: bool

Covers create_quota_policy.

rotate_waitpoint_hmac_secret_all: bool

rotate_waitpoint_hmac_secret_all.

seed_waitpoint_hmac_secret: bool

seed_waitpoint_hmac_secret (#280).

list_pending_waitpoints: bool

list_pending_waitpoints.

cancel_flow_header: bool

cancel_flow_header.

cancel_flow_wait_timeout: bool

cancel_flow with CancelFlowWait::WaitTimeout(..).

cancel_flow_wait_indefinite: bool

cancel_flow with CancelFlowWait::WaitIndefinite.

ack_cancel_member: bool

ack_cancel_member.

claim_for_worker: bool

claim_for_worker (requires a wired scheduler on Valkey; Postgres-native on Postgres).

prepare: bool

prepare does non-trivial work (e.g. Valkey FUNCTION LOAD). Postgres reports false — prepare returns NoOp there.

subscribe_lease_history: bool

subscribe_lease_history.

subscribe_completion: bool

subscribe_completion. On Valkey this is pubsub-backed (non-durable cursor, at-most-once over the live subscription window); Postgres is durable via outbox + cursor. Both report true; see the trait method rustdoc for the non-durable-cursor caveat and docs/POSTGRES_PARITY_MATRIX.md for the per-backend semantic.

subscribe_signal_delivery: bool

subscribe_signal_delivery.

subscribe_instance_tags: bool

subscribe_instance_tags. Deferred per #311 (cairn’s instance_tag_backfill pattern is served by list_executions + ScannerFilter::with_instance_tag(..)); reported false on both backends today.

stream_durable_summary: bool

read_summary + durable-summary frames.

stream_best_effort_live: bool

tail_stream (best-effort live tail).

Implementations

impl Supports

pub const fn none() -> Self

Construct a Supports with every field false. Useful as a starting point when assembling a backend-specific capability snapshot. Consumers should never see this directly — capabilities() on a real backend always returns a populated instance.

Trait Implementations

impl Clone for Supports

fn clone(&self) -> Supports

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Supports

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Supports

fn default() -> Supports

Returns the “default value” for a type.

impl PartialEq for Supports

fn eq(&self, other: &Supports) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Supports

impl Eq for Supports

impl StructuralPartialEq for Supports