Trait mz_persist_types::txn::TxnsCodec

pub trait TxnsCodec: Debug {
    type Key: Debug + Codec + Default;
    type Val: Debug + Codec + Default;

    // Required methods
    fn schemas() -> (<Self::Key as Codec>::Schema, <Self::Val as Codec>::Schema);
    fn encode(e: TxnsEntry) -> (Self::Key, Self::Val);
    fn decode(key: Self::Key, val: Self::Val) -> TxnsEntry;
    fn should_fetch_part(data_id: &ShardId, stats: &PartStats) -> Option<bool>;
}

An abstraction over the encoding format of TxnsEntry.

This enables users of this crate to control how data is written to the txns shard (which will allow mz to present it as a normal introspection source).

Required Associated Types

type Key: Debug + Codec + Default

The K type used in the txns shard.

type Val: Debug + Codec + Default

The V type used in the txns shard.

Required Methods

fn schemas() -> (<Self::Key as Codec>::Schema, <Self::Val as Codec>::Schema)

Returns the Schemas to use with Self::Key and Self::Val.

fn encode(e: TxnsEntry) -> (Self::Key, Self::Val)

Encodes a TxnsEntry in the format persisted in the txns shard.

fn decode(key: Self::Key, val: Self::Val) -> TxnsEntry

Decodes a TxnsEntry from the format persisted in the txns shard.

Implementations should panic if the values are invalid.

fn should_fetch_part(data_id: &ShardId, stats: &PartStats) -> Option<bool>

Returns if a part might include the given data shard based on pushdown stats.

False positives are okay (needless fetches) but false negatives are not (incorrectness). Returns an Option to make ? convenient, None is treated the same as Some(true).

Object Safety

This trait is not object safe.

Implementors