[bugfix] Replace named unique constraint on header filter header with generic unique directive (#2525)

* [bugfix] Replace named unique constraint on header filter header with generic unique directive

* add migration retry

* the old fixie uppie

* fix constraint name

* my goodness

internal/db/bundb/migrations/20240114112637_postgres_header_filter_fix.go

@@ -0,0 +1,115 @@
+// 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"
+
+	"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 {
+		// Run the first bit in a transaction
+		// since we're not expecting to encounter
+		// errors, and any we do encounter will
+		// stop us in our tracks.
+		err := db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+			// Drop each of the old versions of the
+			// header tables. Normally dropping tables
+			// is a big no-no but this migration happens
+			// while header filters weren't even in a
+			// release yet, so let's go for it.
+			for _, table := range []string{
+				"header_filter_allows",
+				"header_filter_blocks",
+			} {
+				_, err := tx.NewDropTable().
+					IfExists().
+					Table(table).
+					Exec(ctx)
+				if err != nil {
+					return err
+				}
+			}
+
+			// Recreate header tables using
+			// the most up-to-date model.
+			for _, model := range []any{
+				&gtsmodel.HeaderFilterAllow{},
+				&gtsmodel.HeaderFilterBlock{},
+			} {
+				_, err := tx.NewCreateTable().
+					IfNotExists().
+					Model(model).
+					Exec(ctx)
+				if err != nil {
+					return err
+				}
+			}
+
+			return nil
+		})
+		if err != nil {
+			return err
+		}
+
+		// On Postgres the constraints might still
+		// be kicking around from a partial failed
+		// migration, so make sure they're gone now.
+		// Dropping a constraint will also drop any
+		// indexes supporting the constraint, as per:
+		//
+		// https://www.postgresql.org/docs/16/sql-altertable.html#SQL-ALTERTABLE-DESC-DROP-CONSTRAINT
+		//
+		// We run this part outside of a transaction
+		// because we don't check for errors, and we
+		// don't want an error in the first query to
+		// foul the transaction and stop the second
+		// query from running.
+		if db.Dialect().Name() == dialect.PG {
+			for _, table := range []string{
+				"public.header_filter_allows",
+				"public.header_filter_blocks",
+			} {
+				// Just swallow any errors
+				// here, we're not bothered.
+				_, _ = db.ExecContext(
+					ctx,
+					"ALTER TABLE ? DROP CONSTRAINT IF EXISTS ?",
+					bun.Ident(table),
+					bun.Safe("header_regex"),
+				)
+			}
+		}
+
+		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)
+	}
+}

internal/gtsmodel/headerfilter.go

@@ -45,8 +45,8 @@ type HeaderFilterBlock struct{ HeaderFilter }
 // matching regex, and details about its creation.
 type HeaderFilter struct {
 	ID        string    `bun:"type:CHAR(26),pk,nullzero,notnull,unique"`                    // ID of this item in the database
-	Header    string    `bun:",nullzero,notnull,unique:header_regex"`                       // Request header this filter pertains to
-	Regex     string    `bun:",nullzero,notnull,unique:header_regex"`                       // Request header value matching regular expression
+	Header    string    `bun:",nullzero,notnull"`                                           // Canonical request header this filter pertains to.
+	Regex     string    `bun:",nullzero,notnull"`                                           // Request header value matching regular expression.
 	AuthorID  string    `bun:"type:CHAR(26),nullzero,notnull"`                              // Account ID of the creator of this filter
 	Author    *Account  `bun:"-"`                                                           // Account corresponding to AuthorID
 	CreatedAt time.Time `bun:"type:timestamptz,nullzero,notnull,default:current_timestamp"` // when was item created