perf(db): keyset pagination for revision prefixes

Keyset по id/ord вместо OFFSET; anti-join для RevisionDiff.

Co-authored-by: Cursor <[email protected]>

internal/repository/postgres.go

@@ -789,12 +789,7 @@ func (p *Postgres) ListRevisionPrefixes(tenantID, revisionID string, cursor stri
 	if limit <= 0 {
 		limit = 50
 	}
-	off := 0
+	afterID, off, useOffset := store.ParsePrefixPageCursor(cursor)
-	if cursor != "" {
-		if n, err := strconv.Atoi(cursor); err == nil && n >= 0 {
-			off = n
-		}
-	}
 	ctx := context.Background()
 	var one int
 	if err := p.pool.QueryRow(ctx, `
@@ -805,34 +800,52 @@ func (p *Postgres) ListRevisionPrefixes(tenantID, revisionID string, cursor stri
 		}
 		return nil, "", false
 	}
-	rows, err := p.pool.Query(ctx, `
+	var rows pgx.Rows
-		SELECT prefix::text, community_id::text, source FROM revision_materialized_prefix
+	var err error
-		WHERE revision_id=$1 ORDER BY id
+	if useOffset {
-		LIMIT $2 OFFSET $3`, revisionID, limit+1, off)
+		rows, err = p.pool.Query(ctx, `
+			SELECT id, prefix::text, community_id::text, source FROM revision_materialized_prefix
+			WHERE revision_id=$1::uuid ORDER BY id
+			LIMIT $2 OFFSET $3`, revisionID, limit+1, off)
+	} else {
+		var afterArg any
+		if afterID != nil {
+			afterArg = *afterID
+		}
+		rows, err = p.pool.Query(ctx, `
+			SELECT id, prefix::text, community_id::text, source FROM revision_materialized_prefix
+			WHERE revision_id=$1::uuid AND ($2::bigint IS NULL OR id > $2::bigint)
+			ORDER BY id
+			LIMIT $3`, revisionID, afterArg, limit+1)
+	}
 	if err != nil {
 		return nil, "", false
 	}
 	defer rows.Close()
 	var all []store.PrefixRow
+	var ids []int64
 	for rows.Next() {
+		var rowID int64
 		var pr store.PrefixRow
 		var comm *string
-		if err := rows.Scan(&pr.Prefix, &comm, &pr.Source); err != nil {
+		if err := rows.Scan(&rowID, &pr.Prefix, &comm, &pr.Source); err != nil {
 			continue
 		}
 		pr.CommunityID = comm
+		ids = append(ids, rowID)
 		all = append(all, pr)
 	}
 	agentDebugNDJSON3214("B", "repository/postgres.go:ListRevisionPrefixes", "list_prefixes_fetched", map[string]any{
-		"rows": len(all), "limit": limit, "offset": off,
+		"rows": len(all), "limit": limit, "keyset": !useOffset,
 	})
 	more := len(all) > limit
 	if more {
 		all = all[:limit]
+		ids = ids[:limit]
 	}
 	next := ""
-	if more {
+	if more && len(ids) > 0 {
-		next = fmt.Sprintf("%d", off+limit)
+		next = store.FormatPrefixPageCursor(ids[len(ids)-1])
 	}
 	if len(all) == 0 {
 		return nil, "", false
@@ -896,21 +909,21 @@ func (p *Postgres) RevisionDiff(tenantID, aID, bID string) (map[string]any, erro
 	ctx := context.Background()
 	var unchanged int
 	err := p.pool.QueryRow(ctx, `
-		SELECT COUNT(*)::int FROM (
+		SELECT COUNT(*)::int FROM revision_materialized_prefix b
-			SELECT prefix FROM revision_materialized_prefix WHERE revision_id=$1::uuid
+		INNER JOIN revision_materialized_prefix a
-			INTERSECT
+			ON a.revision_id = $1::uuid AND a.prefix = b.prefix
-			SELECT prefix FROM revision_materialized_prefix WHERE revision_id=$2::uuid
+		WHERE b.revision_id = $2::uuid`, aID, bID).Scan(&unchanged)
-		) t`, aID, bID).Scan(&unchanged)
 	if err != nil {
 		return nil, err
 	}
-	// added: в B, нет в A; removed: в A, нет в B — без загрузки полных снапшотов в память.
 	rowsAdded, err := p.pool.Query(ctx, `
-		SELECT prefix::text FROM (
+		SELECT b.prefix::text
-			SELECT prefix FROM revision_materialized_prefix WHERE revision_id=$1::uuid
+		FROM revision_materialized_prefix b
-			EXCEPT
+		LEFT JOIN revision_materialized_prefix a
-			SELECT prefix FROM revision_materialized_prefix WHERE revision_id=$2::uuid
+			ON a.revision_id = $1::uuid AND a.prefix = b.prefix
-		) s ORDER BY 1 LIMIT $3`, bID, aID, maxRevisionDiffRows+1)
+		WHERE b.revision_id = $2::uuid AND a.prefix IS NULL
+		ORDER BY b.prefix
+		LIMIT $3`, aID, bID, maxRevisionDiffRows+1)
 	if err != nil {
 		return nil, err
 	}
@@ -929,11 +942,13 @@ func (p *Postgres) RevisionDiff(tenantID, aID, bID string) (map[string]any, erro
 	}
 	addedTruncated := len(added) >= maxRevisionDiffRows
 	rowsRem, err := p.pool.Query(ctx, `
-		SELECT prefix::text FROM (
+		SELECT a.prefix::text
-			SELECT prefix FROM revision_materialized_prefix WHERE revision_id=$1::uuid
+		FROM revision_materialized_prefix a
-			EXCEPT
+		LEFT JOIN revision_materialized_prefix b
-			SELECT prefix FROM revision_materialized_prefix WHERE revision_id=$2::uuid
+			ON b.revision_id = $2::uuid AND b.prefix = a.prefix
-		) s ORDER BY 1 LIMIT $3`, aID, bID, maxRevisionDiffRows+1)
+		WHERE a.revision_id = $1::uuid AND b.prefix IS NULL
+		ORDER BY a.prefix
+		LIMIT $3`, aID, bID, maxRevisionDiffRows+1)
 	if err != nil {
 		return nil, err
 	}

internal/store/memory_crud.go

@@ -1,8 +1,6 @@
 package store
 
 import (
-	"fmt"
-	"strconv"
 	"strings"
 	"time"
 
@@ -795,31 +793,37 @@ func (m *Memory) ListRevisionPrefixes(tenantID, revisionID string, cursor string
 	if limit <= 0 {
 		limit = 50
 	}
+	afterID, off, useOffset := ParsePrefixPageCursor(cursor)
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 	if _, err := m.getRevisionLocked(tenantID, revisionID); err != nil {
 		return nil, "", false
 	}
-	all := m.revPrefixes[revisionID]
+	allRows := m.revPrefixes[revisionID]
-	off := 0
+	start := 0
-	if cursor != "" {
+	if useOffset {
-		if n, err := strconv.Atoi(cursor); err == nil && n >= 0 {
+		start = off
-			off = n
+	} else if afterID != nil {
-		}
+		start = int(*afterID) + 1
 	}
-	end := off + limit
+	if start > len(allRows) {
-	next := ""
-	more := false
-	if end > len(all) {
-		end = len(all)
-	} else {
-		more = true
-		next = fmt.Sprintf("%d", end)
-	}
-	if off >= len(all) {
 		return nil, "", false
 	}
-	return all[off:end], next, more
+	end := start + limit
+	next := ""
+	more := false
+	if end > len(allRows) {
+		end = len(allRows)
+	} else {
+		more = true
+		next = FormatPrefixPageCursor(int64(end - 1))
+	}
+	if start >= end {
+		return nil, "", false
+	}
+	out := make([]PrefixRow, end-start)
+	copy(out, allRows[start:end])
+	return out, next, more
 }
 
 func (m *Memory) ListGlobalSettings(tenantID string) (map[string]any, error) {

internal/store/pagination.go

@@ -0,0 +1,30 @@
+package store
+
+import (
+	"strconv"
+	"strings"
+)
+
+// ParsePrefixPageCursor decodes opaque cursors for revision prefix pagination.
+func ParsePrefixPageCursor(cursor string) (afterID *int64, offset int, useOffset bool) {
+	cursor = strings.TrimSpace(cursor)
+	if cursor == "" {
+		return nil, 0, false
+	}
+	if strings.HasPrefix(cursor, "o:") {
+		n, err := strconv.Atoi(strings.TrimPrefix(cursor, "o:"))
+		if err != nil || n < 0 {
+			return nil, 0, false
+		}
+		return nil, n, true
+	}
+	if n, err := strconv.ParseInt(cursor, 10, 64); err == nil && n >= 0 {
+		return &n, 0, false
+	}
+	return nil, 0, false
+}
+
+// FormatPrefixPageCursor encodes the keyset cursor (last row id or slice index).
+func FormatPrefixPageCursor(lastID int64) string {
+	return strconv.FormatInt(lastID, 10)
+}