[bugfix] Account timeline: exclude self-replies that mention other accounts (#2670)

* Account timeline: exclude self-replies that mention other accounts

* Add index for querying unmentioned statuses

* remove now unused statuses_account_id_id_idx

---------

Co-authored-by: tobi <tobi.smethurst@protonmail.com>

internal/db/bundb/migrations/20240220204526_add_statuses_mentions_is_null_or_empty_idx.go

@@ -0,0 +1,82 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package migrations
+
+import (
+	"context"
+
+	gtsmodel "github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/uptrace/bun"
+	"github.com/uptrace/bun/dialect"
+)
+
+func init() {
+	up := func(ctx context.Context, db *bun.DB) error {
+		var expression string
+		switch db.Dialect().Name() {
+		case dialect.PG:
+			expression = "(mentions IS NULL OR CARDINALITY(mentions) = 0)"
+		case dialect.SQLite:
+			expression = "(mentions IS NULL OR json_array_length(mentions) = 0)"
+		default:
+			panic("db conn was neither pg not sqlite")
+		}
+
+		return db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+			// Remove previous index for viewing
+			// statuses created by account.
+			if _, err := tx.
+				NewDropIndex().
+				Index("statuses_account_id_id_idx").
+				IfExists().
+				Exec(ctx); err != nil {
+				return err
+			}
+
+			// Add new index for viewing statuses created
+			// by account, which includes mentions in the index.
+			if _, err := tx.
+				NewCreateIndex().
+				Model((*gtsmodel.Status)(nil)).
+				Index("statuses_account_view_idx").
+				Column(
+					"account_id",
+					"in_reply_to_account_id",
+					"in_reply_to_uri",
+				).
+				ColumnExpr(expression).
+				ColumnExpr("id DESC").
+				IfNotExists().
+				Exec(ctx); err != nil {
+				return err
+			}
+
+			return nil
+		})
+	}
+
+	down := func(ctx context.Context, db *bun.DB) error {
+		return db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+			return nil
+		})
+	}
+
+	if err := Migrations.Register(up, down); err != nil {
+		panic(err)
+	}
+}