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internal/infra/pg/segmentstore.go

internal/infra/pg · 253 lines · 14 declarations · source

Declarations​

const ProjectionSegment​

const ProjectionSegment = "segment"

ProjectionSegment is the projection kind a segment registers as.

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type SegmentStore​

type SegmentStore struct {
	pool   *pgxpool.Pool
	schema Schema
}

SegmentStore reads a subject's formed history and writes the segments that stand in for it.

What a subject's history is​

The subject's own turns, formed and not parked, in log order. A turn that has not formed is not yet memory and may still be parked; a segment written over it would stand in for something the deployment has not admitted. A parked turn is excluded for the same reason the freshness watermark skips it: the driver gave up on it, and it is visible as parked rather than silently summarised.

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func NewSegmentStore​

func NewSegmentStore(pool *pgxpool.Pool, schema Schema) *SegmentStore

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method SegmentStore.Subjects​

func (s *SegmentStore) Subjects(ctx context.Context, scope string, limit int) ([]string, error)

Subjects lists the data subjects in a scope with more formed turns than the verbatim tail, which is every subject the pass may have something to write for.

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method SegmentStore.Formed​

func (s *SegmentStore) Formed(ctx context.Context, scope, subject string) ([]compaction.Turn, error)

Formed reads one subject's formed turns in log order, each with its size in characters.

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method SegmentStore.Segments​

func (s *SegmentStore) Segments(ctx context.Context, scope, subject string) ([]compaction.Segment, error)

Segments reads one subject's segments.

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method SegmentStore.Material​

func (s *SegmentStore) Material(ctx context.Context, scope, subject string, plan compaction.Plan) (compaction.Material, error)

Material loads what a planned segment is written from: the turns in its range at level 1, the summaries of its units above.

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method SegmentStore.turnTexts​

func (s *SegmentStore) turnTexts(ctx context.Context, scope, subject string, from, to int64) ([]compaction.TurnText, error)

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var ErrSegmentConflict​

var ErrSegmentConflict = errors.New("a segment already covers this range")

ErrSegmentConflict says a segment already exists where this one would go: another replica wrote it, or the plan is stale.

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method SegmentStore.Write​

func (s *SegmentStore) Write(ctx context.Context, scope, subject string, plan compaction.Plan, summary compaction.Summary) (compaction.Segment, error)

Write stores a segment and registers it to every observation it covers, in one transaction, so that erasure of any of them reaches it and a segment never exists without its registrations.

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type Assembled​

type Assembled struct {
	Segments   []AssembledSegment
	Turns      []compaction.TurnText
	Characters int
	Truncated  bool
}

Assembled is a context as the API returns it: the segments and the turns, oldest first, with their text, and the cut.

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type AssembledSegment​

type AssembledSegment struct {
	compaction.Segment
	Summary string
}

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method SegmentStore.Context​

func (s *SegmentStore) Context(ctx context.Context, scope, subject string, budget int) (Assembled, error)

Context assembles one subject's history under a budget, with no model call: the planner's choice over what the store holds, then the text of what it chose.

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func isUniqueViolation​

func isUniqueViolation(err error) bool

isUniqueViolation says whether an error is the substrate refusing a duplicate, which for a segment is the one-per-range rule holding against a concurrent writer.

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