aarondb/projection_index

projection_index — non-authoritative index lifecycle

Index state is a replayable projection of an ordered source. Queries are only available while the index is healthy; the source remains authoritative.

Types

Error

pub type Error {
  InvalidSchemaVersion
  OffsetGap(expected: Int, received: Int)
  NotQueryable(Health)
}

Constructors

```
InvalidSchemaVersion
```
```
OffsetGap(expected: Int, received: Int)
```
```
NotQueryable(Health)
```

Health

pub type Health {
  Building
  Rebuilding
  Queryable
  Degraded(reason: String)
  Failed(reason: String)
}

Constructors

```
Building
```
```
Rebuilding
```
```
Queryable
```
```
Degraded(reason: String)
```
```
Failed(reason: String)
```

Index

pub type Index {
  Index(
    schema_version: Int,
    generation: Int,
    health: Health,
    last_applied_offset: Int,
    values: List(String),
  )
}

Constructors

Index(
  schema_version: Int,
  generation: Int,
  health: Health,
  last_applied_offset: Int,
  values: List(String),
)

Values

apply

pub fn apply(
  index: Index,
  offset: Int,
  value: String,
) -> Result(Index, Error)

begin_rebuild

pub fn begin_rebuild(
  index: Index,
  schema_version: Int,
) -> Result(Index, Error)

Marks the current projection unavailable while a separate generation is built.

degrade

pub fn degrade(index: Index, reason: String) -> Index

fail

pub fn fail(index: Index, reason: String) -> Index

failure_reason

pub fn failure_reason(index: Index) -> option.Option(String)

new

pub fn new(schema_version: Int) -> Result(Index, Error)

query

pub fn query(index: Index) -> Result(List(String), Error)

swap

pub fn swap(
  current: Index,
  replacement: Index,
  source_high_watermark: Int,
) -> Result(Index, Error)

The caller swaps only a fully caught-up replacement. This makes a partial rebuild unqueryable instead of returning silently incomplete answers.