fix(messages): sync exact channel pinned counts

internal/store/postgres/channel_message_history.go

@@ -79,6 +79,24 @@ AND EXISTS (
 		baseArgs = append(baseArgs, filter.MinID)
 		base += fmt.Sprintf(" AND id > $%d", len(baseArgs))
 	}
+	out := domain.ChannelHistory{Channel: channel, Self: member, Channels: extraChannels}
+	needExactTotal := filter.NeedTotalCount || filter.CountOnly
+	exactTotal := 0
+	if needExactTotal {
+		// Exact totals are opt-in. messages.search first/count-only pages and
+		// messages.getSearchCounters need protocol-exact Count, while ordinary
+		// getHistory pages must stay on the single bounded page query.
+		if err := s.db.QueryRow(ctx,
+			"SELECT count(*)::int FROM channel_messages WHERE "+base,
+			baseArgs...,
+		).Scan(&exactTotal); err != nil {
+			return domain.ChannelHistory{}, fmt.Errorf("count channel history: %w", err)
+		}
+		out.Count = exactTotal
+	}
+	if filter.CountOnly {
+		return out, nil
+	}
 	scanList := func(sql string, queryArgs []any) ([]domain.ChannelMessage, error) {
 		rows, err := s.db.Query(ctx, sql, queryArgs...)
 		if err != nil {
@@ -102,7 +120,6 @@ AND EXISTS (
 	// store 层二次钳制 add_offset 到 [-100,100]（与私聊 ListMessagesByUser 对齐）：
 	// 即便某个 caller 漏在 RPC 层钳制，也不会把客户端巨大值变成大 SQL OFFSET 跳扫。
 	addOffset := domain.ClampMessageHistoryAddOffset(filter.AddOffset)
-	out := domain.ChannelHistory{Channel: channel, Self: member, Channels: extraChannels}
 	hasMoreOlder := false
 	// 锚点条件：offset_date 优先按日期、否则按消息 id（对齐私聊）；
 	// 二者皆空时向更新方向退化为空、向更旧方向退化为全部（取最新）。
@@ -199,9 +216,11 @@ AND EXISTS (
 		}
 		out.Messages = older
 	}
-	out.Count = len(out.Messages)
-	if hasMoreOlder {
-		out.Count = len(out.Messages) + 1
+	if !needExactTotal {
+		out.Count = len(out.Messages)
+		if hasMoreOlder {
+			out.Count = len(out.Messages) + 1
+		}
 	}
 	if err := s.populateChannelMessageReplies(ctx, s.db, viewerUserID, channel, out.Messages); err != nil {
 		return domain.ChannelHistory{}, err

internal/store/postgres/channel_multi_pin_integration_test.go

@@ -3,6 +3,7 @@ package postgres
 import (
 	"context"
 	"errors"
+	"strings"
 	"testing"
 
 	"telesrv/internal/domain"
@@ -98,6 +99,70 @@ func TestChannelMultiPin(t *testing.T) {
 			t.Fatalf("filterPinned message %d lacks pinned flag", msg.ID)
 		}
 	}
+	// 普通历史热路径保留 bounded has-more hint，不为每页额外 COUNT。
+	hint, err := channels.ListChannelHistory(ctx, owner.ID, domain.ChannelHistoryFilter{
+		ChannelID: channelID, PinnedOnly: true, Limit: 1,
+	})
+	if err != nil {
+		t.Fatalf("filterPinned hint page: %v", err)
+	}
+	if len(hint.Messages) != 1 || hint.Count != 2 {
+		t.Fatalf("filterPinned hint messages/count = %d/%d, want 1/2", len(hint.Messages), hint.Count)
+	}
+	// messages.search 首屏显式请求精确总数；页大小不能污染 Count。
+	exact, err := channels.ListChannelHistory(ctx, owner.ID, domain.ChannelHistoryFilter{
+		ChannelID: channelID, PinnedOnly: true, Limit: 1, NeedTotalCount: true,
+	})
+	if err != nil {
+		t.Fatalf("filterPinned exact page: %v", err)
+	}
+	if len(exact.Messages) != 1 || exact.Count != 3 {
+		t.Fatalf("filterPinned exact messages/count = %d/%d, want 1/3", len(exact.Messages), exact.Count)
+	}
+	// messages.getSearchCounters/limit=0 只计数，不加载消息及 reply/reaction companion。
+	countOnly, err := channels.ListChannelHistory(ctx, owner.ID, domain.ChannelHistoryFilter{
+		ChannelID: channelID, PinnedOnly: true, NeedTotalCount: true, CountOnly: true,
+	})
+	if err != nil {
+		t.Fatalf("filterPinned count-only: %v", err)
+	}
+	if len(countOnly.Messages) != 0 || countOnly.Count != 3 {
+		t.Fatalf("filterPinned count-only messages/count = %d/%d, want 0/3", len(countOnly.Messages), countOnly.Count)
+	}
+	// 精确计数只扫描该频道的 pinned 部分索引，不能退化为全频道消息扫描。
+	tx, err := pool.Begin(ctx)
+	if err != nil {
+		t.Fatalf("begin pinned count explain: %v", err)
+	}
+	defer tx.Rollback(ctx)
+	if _, err := tx.Exec(ctx, "SET LOCAL enable_seqscan = off"); err != nil {
+		t.Fatalf("disable seqscan for pinned count explain: %v", err)
+	}
+	rows, err := tx.Query(ctx, `EXPLAIN (COSTS OFF)
+SELECT count(*)::int
+FROM channel_messages
+WHERE channel_id = $1 AND NOT deleted AND pinned`, channelID)
+	if err != nil {
+		t.Fatalf("explain pinned count: %v", err)
+	}
+	var plan strings.Builder
+	for rows.Next() {
+		var line string
+		if err := rows.Scan(&line); err != nil {
+			rows.Close()
+			t.Fatalf("scan pinned count plan: %v", err)
+		}
+		plan.WriteString(line)
+		plan.WriteByte('\n')
+	}
+	if err := rows.Err(); err != nil {
+		rows.Close()
+		t.Fatalf("read pinned count plan: %v", err)
+	}
+	rows.Close()
+	if !strings.Contains(plan.String(), "channel_messages_live_pinned_idx") {
+		t.Fatalf("pinned count plan misses partial index:\n%s", plan.String())
+	}
 	// 普通历史页的消息行直接携带 pinned 标志（多置顶都标，不只最新）。
 	page, err := channels.ListChannelHistory(ctx, member.ID, domain.ChannelHistoryFilter{ChannelID: channelID, Limit: 50})
 	if err != nil {

internal/store/postgres/star_gift_lifecycle_migration_integration_test.go

@@ -14,7 +14,7 @@ func TestStarGiftLifecycleMigrationsApply(t *testing.T) {
 	if err != nil {
 		t.Fatalf("migrate star gift lifecycle schema: %v", err)
 	}
-	if status.Dirty || status.Empty || status.Version != 148 {
-		t.Fatalf("migration status = %+v, want clean version 148", status)
+	if status.Dirty || status.Empty || status.Version != 149 {
+		t.Fatalf("migration status = %+v, want clean version 149", status)
 	}
 }