Read the AS page from bounded lookups (closes #104)

The AS page and /api/v1/as/{asn} grouped every route the AS originates
by prefix, reading one table row per peer and prefix and sorting them
all. They now take the AS's prefixes one at a time: one search of a new
index on origin_asn and prefix, which replaces the origin_asn index and
is written exactly when it was, and one search of the prefix and
last_updated index for the time of the prefix's newest route. Neither
reads the table. For a prefix more than one AS originates, that time is
now the newest route's from any origin. A hand-run benchmark reads an
AS of 5,000 prefixes from 500 peers.

Model: opus-5-5

internal/database/database.go

@@ -1673,8 +1673,9 @@ func (d *Database) GetASDetails(asn int) (*ASN, []LiveRoute, error) {
 	return d.GetASDetailsContext(context.Background(), asn)
 }
 
-// GetASDetailsContext returns detailed information about an AS including
-// prefixes with context support
+// GetASDetailsContext returns the AS and the prefixes it originates, the IPv4
+// ones first, each once with the time of its newest route. It makes two index
+// searches per prefix, however many peers carry the prefix.
 func (d *Database) GetASDetailsContext(
 	ctx context.Context, asn int,
 ) (*ASN, []LiveRoute, error) {
@@ -1701,27 +1702,12 @@ func (d *Database) GetASDetailsContext(
 	asnInfo.Handle = handle.String
 	asnInfo.Description = description.String
 
-	// Get prefixes announced by this AS from both tables
-	queryV4 := `
-		SELECT prefix, mask_length, MAX(last_updated) as last_updated
-		FROM live_routes_v4
-		WHERE origin_asn = ?
-		GROUP BY prefix, mask_length
-	`
-
-	allPrefixes, err := d.originPrefixes(ctx, queryV4, asn, ipVersionV4)
+	allPrefixes, err := d.originPrefixes(ctx, asn, ipVersionV4)
 	if err != nil {
 		return &asnInfo, nil, err
 	}
 
-	queryV6 := `
-		SELECT prefix, mask_length, MAX(last_updated) as last_updated
-		FROM live_routes_v6
-		WHERE origin_asn = ?
-		GROUP BY prefix, mask_length
-	`
-
-	prefixesV6, err := d.originPrefixes(ctx, queryV6, asn, ipVersionV6)
+	prefixesV6, err := d.originPrefixes(ctx, asn, ipVersionV6)
 	if err != nil {
 		return &asnInfo, allPrefixes, err
 	}
@@ -2452,66 +2438,87 @@ func (d *Database) scanRouteTimestamp(
 	}
 }
 
-// originPrefixes runs query, which selects the prefix, mask length and latest
-// last_updated of every prefix asn originates in the live route table of
-// ipVersion. Rows that fail to scan or whose timestamp does not parse are
-// logged and skipped.
+// The AS page lists the prefixes an AS originates one at a time, each in two
+// index searches that read no table row: one of the origin_asn and prefix
+// index for the AS's first prefix after the previous one, and one of the
+// prefix and last_updated index for the time of its newest route. Neither
+// reads more for a prefix that more peers carry.
+const (
+	nextOriginPrefixV4SQL = `SELECT prefix FROM live_routes_v4
+		WHERE origin_asn = ? AND prefix > ? ORDER BY prefix LIMIT 1`
+	newestRouteTimeV4SQL = `SELECT last_updated FROM live_routes_v4
+		WHERE prefix = ? ORDER BY last_updated DESC LIMIT 1`
+
+	nextOriginPrefixV6SQL = `SELECT prefix FROM live_routes_v6
+		WHERE origin_asn = ? AND prefix > ? ORDER BY prefix LIMIT 1`
+	newestRouteTimeV6SQL = `SELECT last_updated FROM live_routes_v6
+		WHERE prefix = ? ORDER BY last_updated DESC LIMIT 1`
+)
+
+// originPrefixes returns every prefix asn originates in the live route table
+// of ipVersion, in text order, each with its mask length and the time of the
+// prefix's newest route, whichever AS that route names as origin. A prefix
+// whose routes were all withdrawn between the two searches is left out.
 func (d *Database) originPrefixes(
-	ctx context.Context, query string, asn, ipVersion int,
+	ctx context.Context, asn, ipVersion int,
 ) ([]LiveRoute, error) {
-	family := ipv4Family
+	family, nextSQL, newestSQL := ipv4Family, nextOriginPrefixV4SQL,
+		newestRouteTimeV4SQL
 	if ipVersion == ipVersionV6 {
-		family = ipv6Family
+		family, nextSQL, newestSQL = ipv6Family, nextOriginPrefixV6SQL,
+			newestRouteTimeV6SQL
 	}
 
-	rows, err := d.db.QueryContext(ctx, query, asn)
+	nextStmt, err := d.db.PrepareContext(ctx, nextSQL)
 	if err != nil {
-		return nil, fmt.Errorf("failed to query %s prefixes: %w", family, err)
+		return nil, fmt.Errorf("failed to prepare %s prefix query: %w",
+			family, err)
 	}
-	defer func() { _ = rows.Close() }()
+	defer func() { _ = nextStmt.Close() }()
+
+	newestStmt, err := d.db.PrepareContext(ctx, newestSQL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to prepare %s route time query: %w",
+			family, err)
+	}
+	defer func() { _ = newestStmt.Close() }()
 
 	var routes []LiveRoute
 
-	for rows.Next() {
-		var (
-			route          LiveRoute
-			lastUpdatedStr string
-		)
+	previous := "" // every prefix sorts after the empty string
+
+	for {
+		var prefix string
+
+		err := nextStmt.QueryRowContext(ctx, asn, previous).Scan(&prefix)
+		if errors.Is(err, sql.ErrNoRows) {
+			return routes, nil
+		}
 
-		err := rows.Scan(&route.Prefix, &route.MaskLength, &lastUpdatedStr)
 		if err != nil {
-			d.logger.Error("Failed to scan "+family+" prefix row",
-				"error", err, "asn", asn)
+			return nil, fmt.Errorf("failed to list %s prefixes: %w", family, err)
+		}
 
+		previous = prefix
+		route := LiveRoute{Prefix: prefix, IPVersion: ipVersion, OriginASN: asn}
+
+		err = newestStmt.QueryRowContext(ctx, prefix).Scan(&route.LastUpdated)
+		if errors.Is(err, sql.ErrNoRows) {
 			continue
 		}
 
-		// Parse the timestamp string
-		route.LastUpdated, err = time.Parse("2006-01-02 15:04:05-07:00",
-			lastUpdatedStr)
 		if err != nil {
-			// Try without timezone
-			route.LastUpdated, err = time.Parse("2006-01-02 15:04:05",
-				lastUpdatedStr)
-			if err != nil {
-				d.logger.Error("Failed to parse timestamp",
-					"error", err, "timestamp", lastUpdatedStr)
+			return nil, fmt.Errorf("failed to query route time of %s: %w",
+				prefix, err)
+		}
 
-				continue
-			}
+		route.MaskLength, err = prefixMaskLength(prefix)
+		if err != nil {
+			return nil, err
 		}
 
-		route.OriginASN = asn
-		route.IPVersion = ipVersion
 		routes = append(routes, route)
 	}
-
-	err = rows.Err()
-	if err != nil {
-		return nil, fmt.Errorf("failed to read %s prefixes: %w", family, err)
-	}
-
-	return routes, nil
 }
 
 // firstPrefixesByLength returns the first n prefixes, in text order, with the

internal/database/database_internal_test.go

@@ -10,6 +10,7 @@ import (
 	"net/netip"
 	"slices"
 	"strconv"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -1214,6 +1215,138 @@ func TestLiveRouteUpdateSetsOriginWhenItChanges(t *testing.T) {
 	}
 }
 
+// TestGetASDetailsListsEachPrefixOnce stores two IPv4 prefixes and an IPv6
+// prefix an AS originates, two of them from two peers at different times, and
+// a prefix another AS originates. The AS details list each of the AS's
+// prefixes once, IPv4 first and in text order, with its mask length and the
+// time of its newest route.
+func TestGetASDetailsListsEachPrefixOnce(t *testing.T) {
+	t.Parallel()
+
+	db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	const asn, otherASN = 64500, 64501
+
+	ts := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+
+	_, err = db.GetOrCreateASN(asn, ts)
+	if err != nil {
+		t.Fatalf("GetOrCreateASN: %v", err)
+	}
+
+	v4Older := mkV4Route(t, "192.0.2.0/24", asn, ts)
+	v4Newer := mkV4Route(t, "192.0.2.0/24", asn, ts.Add(time.Minute))
+	v4Newer.PeerIP = secondV4PeerIP
+	v4Single := mkV4Route(t, "198.51.100.128/25", asn, ts)
+	v6Newer := mkV6Route(testV6Prefix, asn, ts.Add(time.Minute))
+	v6Older := mkV6Route(testV6Prefix, asn, ts)
+	v6Older.PeerIP = secondV6PeerIP
+	other := mkV4Route(t, "203.0.113.0/24", otherASN, ts)
+
+	err = db.UpsertLiveRouteBatch([]*LiveRoute{
+		v4Older, v4Newer, v4Single, v6Newer, v6Older, other,
+	})
+	if err != nil {
+		t.Fatalf("UpsertLiveRouteBatch: %v", err)
+	}
+
+	_, prefixes, err := db.GetASDetails(asn)
+	if err != nil {
+		t.Fatalf("GetASDetails: %v", err)
+	}
+
+	want := []*LiveRoute{v4Newer, v4Single, v6Newer}
+
+	listedOnce := slices.EqualFunc(prefixes, want,
+		func(got LiveRoute, want *LiveRoute) bool {
+			return got.Prefix == want.Prefix &&
+				got.MaskLength == want.MaskLength &&
+				got.IPVersion == want.IPVersion &&
+				got.OriginASN == asn &&
+				got.LastUpdated.Equal(want.LastUpdated)
+		})
+	if !listedOnce {
+		t.Errorf("GetASDetails listed %+v, want the prefixes and times of %+v",
+			prefixes, want)
+	}
+}
+
+// TestASPrefixQueriesUseCoveringIndexes checks the plan of each query that
+// lists the prefixes an AS originates: a search of a covering index and no
+// temporary B-tree, so the list reads one index entry per prefix, not one
+// table row per route. Grouping the AS's routes by prefix read every route's
+// row and sorted them in a temporary B-tree
+// (https://git.eeqj.de/sneak/routewatch/issues/104).
+func TestASPrefixQueriesUseCoveringIndexes(t *testing.T) {
+	t.Parallel()
+
+	db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	tests := []struct {
+		query string
+		args  []any
+		index string
+	}{
+		{nextOriginPrefixV4SQL, []any{0, ""}, "idx_live_routes_v4_origin_prefix"},
+		{newestRouteTimeV4SQL, []any{""}, "idx_live_routes_v4_prefix_last_updated"},
+		{nextOriginPrefixV6SQL, []any{0, ""}, "idx_live_routes_v6_origin_prefix"},
+		{newestRouteTimeV6SQL, []any{""}, "idx_live_routes_v6_prefix_last_updated"},
+	}
+
+	for _, tt := range tests {
+		plan := queryPlan(t, db, tt.query, tt.args...)
+
+		if !strings.Contains(plan, "USING COVERING INDEX "+tt.index+" ") ||
+			strings.Contains(plan, "TEMP B-TREE") {
+			t.Errorf("plan of %s:\n%s\nwant a search of covering index %s "+
+				"and no temporary B-tree", tt.query, plan, tt.index)
+		}
+	}
+}
+
+// queryPlan returns the steps of EXPLAIN QUERY PLAN for query, one per line.
+func queryPlan(t *testing.T, db *Database, query string, args ...any) string {
+	t.Helper()
+
+	rows, err := db.db.QueryContext(t.Context(), "EXPLAIN QUERY PLAN "+query,
+		args...)
+	if err != nil {
+		t.Fatalf("EXPLAIN QUERY PLAN %s: %v", query, err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	var steps []string
+
+	for rows.Next() {
+		var (
+			id, parent, unused int
+			detail             string
+		)
+
+		err := rows.Scan(&id, &parent, &unused, &detail)
+		if err != nil {
+			t.Fatalf("reading the plan of %s: %v", query, err)
+		}
+
+		steps = append(steps, detail)
+	}
+
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("reading the plan of %s: %v", query, err)
+	}
+
+	return strings.Join(steps, "\n")
+}
+
 // TestUpdatePrefixesBatchKeepsFirstSeen writes a prefix, then a batch with it
 // and a new prefix. Only the new prefix is inserted and counted, and the known
 // one keeps its first_seen time.
@@ -1518,3 +1651,66 @@ func writeBenchBatch(
 		b.Fatalf("UpdatePrefixesBatch: %v", err)
 	}
 }
+
+// Parameters for BenchmarkGetASDetailsWithFiveHundredPeers: the AS originates
+// benchASPrefixes prefixes and every one of benchASPeers peers has a route for
+// each, 2.5 million routes in all.
+const (
+	benchASPrefixes = 5000
+	benchASPeers    = 500
+)
+
+// BenchmarkGetASDetailsWithFiveHundredPeers times the read behind the AS page
+// for an AS that originates 5,000 IPv4 prefixes, each from 500 peers. It
+// builds that database first, one peer at a time, which takes some minutes and
+// about a GB of disk under TMPDIR. It is run by hand, not by make test, for
+// example in the test image:
+//
+//	go test -run '^$' -bench GetASDetails -benchtime 10x ./internal/database/
+func BenchmarkGetASDetailsWithFiveHundredPeers(b *testing.B) {
+	db, err := New(&config.Config{StateDir: b.TempDir()}, logger.New())
+	if err != nil {
+		b.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	ts := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+
+	_, err = db.GetOrCreateASN(benchFirstASN, ts)
+	if err != nil {
+		b.Fatalf("GetOrCreateASN: %v", err)
+	}
+
+	for peer := range benchASPeers {
+		peerIP := fmt.Sprintf("198.18.%d.%d", peer/256, peer%256)
+
+		routes := make([]*LiveRoute, 0, benchASPrefixes)
+		for prefix := range benchASPrefixes {
+			routes = append(routes, &LiveRoute{
+				Prefix: fmt.Sprintf("%d.%d.%d.0/%d",
+					1+prefix>>16, (prefix>>8)%256, prefix%256, benchMaskLength),
+				MaskLength:  benchMaskLength,
+				IPVersion:   ipVersionV4,
+				OriginASN:   benchFirstASN,
+				PeerIP:      peerIP,
+				ASPath:      []int{benchFirstASN + 1 + peer, benchFirstASN},
+				NextHop:     peerIP,
+				LastUpdated: ts,
+			})
+		}
+
+		writeBenchBatch(b, db, routes, nil, ts)
+	}
+
+	for b.Loop() {
+		_, prefixes, err := db.GetASDetails(benchFirstASN)
+		if err != nil {
+			b.Fatalf("GetASDetails: %v", err)
+		}
+
+		if len(prefixes) != benchASPrefixes {
+			b.Fatalf("GetASDetails listed %d prefixes, want %d",
+				len(prefixes), benchASPrefixes)
+		}
+	}
+}

internal/database/schema.sql

@@ -128,7 +128,7 @@ CREATE TABLE IF NOT EXISTS live_routes_v6 (
 -- prefix, last_updated: a prefix's routes, for the prefix page and its API
 -- answer, the IP lookup and its peer count, and the check whether a prefix
 -- still has a live route; and a prefix's newest route for the prefix-length
--- pages, in one search whatever the number of peers.
+-- pages and the AS page, in one search whatever the number of peers.
 CREATE INDEX IF NOT EXISTS idx_live_routes_v4_prefix_last_updated ON live_routes_v4(prefix, last_updated);
 CREATE INDEX IF NOT EXISTS idx_live_routes_v6_prefix_last_updated ON live_routes_v6(prefix, last_updated);
 -- mask_length: the prefix-length pages' random sample, the row id range of a
@@ -139,9 +139,10 @@ CREATE INDEX IF NOT EXISTS idx_live_routes_v6_mask_length ON live_routes_v6(mask
 -- prefixes in text order, and the prefix distribution read at startup.
 CREATE INDEX IF NOT EXISTS idx_live_routes_v4_mask_prefix ON live_routes_v4(mask_length, prefix);
 CREATE INDEX IF NOT EXISTS idx_live_routes_v6_mask_prefix ON live_routes_v6(mask_length, prefix);
--- origin_asn: the prefixes an AS originates, for the AS page and its API answer.
-CREATE INDEX IF NOT EXISTS idx_live_routes_v4_origin_asn ON live_routes_v4(origin_asn);
-CREATE INDEX IF NOT EXISTS idx_live_routes_v6_origin_asn ON live_routes_v6(origin_asn);
+-- origin_asn, prefix: the prefixes an AS originates, each in one search
+-- whatever the number of peers, for the AS page and its API answer.
+CREATE INDEX IF NOT EXISTS idx_live_routes_v4_origin_prefix ON live_routes_v4(origin_asn, prefix);
+CREATE INDEX IF NOT EXISTS idx_live_routes_v6_origin_prefix ON live_routes_v6(origin_asn, prefix);
 -- last_updated: the oldest and newest route times in /api/v1/stats and
 -- /status.json.
 CREATE INDEX IF NOT EXISTS idx_live_routes_v4_last_updated ON live_routes_v4(last_updated);