Merge branch '5.x' of https://github.com/craftcms/cms into 6.x

# Conflicts:
#	CHANGELOG.md
#	src/elements/Entry.php
#	tests/unit/services/EntriesTest.php

Author: brandonkelly

src/Entry/Elements/Entry.php

@@ -2518,9 +2518,13 @@ private function _saveAuthors(): void
                 ->all();
         }
 
-        DB::table(Table::ENTRIES_AUTHORS)
-            ->where('entryId', $this->id)
-            ->delete();
+        // Only issue the delete if there’s something to delete: an unconditional delete for a brand-new
+        // entry ID can take a gap lock on the primary index and deadlock against other transactions
+        // inserting authors for their own new entries.
+        $authorsQuery = DB::table(Table::ENTRIES_AUTHORS)->where('entryId', $this->id);
+        if ($authorsQuery->exists()) {
+            $authorsQuery->delete();
+        }
 
         if (! empty($this->_authorIds)) {
             $data = [];

tests/Feature/Entry/EntriesTest.php

@@ -13,11 +13,40 @@
 use CraftCms\Cms\Section\Enums\SectionType;
 use CraftCms\Cms\Section\Models\Section;
 use CraftCms\Cms\Site\Models\Site;
+use CraftCms\Cms\Support\Facades\Elements;
 use CraftCms\Cms\Support\Facades\Sections;
 use CraftCms\Cms\User\Models\User;
+use Illuminate\Database\Events\QueryExecuted;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Support\Facades\Event;
 
+/**
+ * Records which `entries_authors` write statements (delete/insert) run during $callback.
+ *
+ * @return string[]
+ */
+function captureEntriesAuthorsCommands(Closure $callback): array
+{
+    $commands = [];
+
+    DB::listen(function (QueryExecuted $query) use (&$commands) {
+        $sql = strtolower(ltrim($query->sql));
+        if (! str_contains($sql, 'entries_authors')) {
+            return;
+        }
+
+        if (str_starts_with($sql, 'delete')) {
+            $commands[] = 'delete';
+        } elseif (str_starts_with($sql, 'insert')) {
+            $commands[] = 'insert';
+        }
+    });
+
+    $callback();
+
+    return $commands;
+}
+
 beforeEach(function () {
     $this->entries = app(Entries::class);
 });
@@ -205,3 +234,57 @@
         ->pluck('authorId')
         ->all())->toBe([$newAuthor->id, $newAuthor->id]);
 });
+
+it('does not delete missing author rows when saving an entry’s authors for the first time', function () {
+    $entryType = EntryType::factory()->create();
+    $section = Section::factory()->withEntryTypes($entryType)->create([
+        'type' => SectionType::Channel,
+    ]);
+    $author = User::factory()->create();
+
+    $entry = Entry::factory()
+        ->forSection($section)
+        ->forEntryType($entryType)
+        ->createElement();
+    $entry->setAuthorIds([$author->id]);
+
+    $commands = captureEntriesAuthorsCommands(fn () => Elements::saveElement($entry));
+
+    // No existing rows to delete yet, so the save shouldn’t issue a delete (which would otherwise
+    // take a needless gap lock on the primary index and risk deadlocking against other transactions
+    // inserting authors for their own new entries).
+    expect($commands)->not->toContain('delete');
+    expect($commands)->toContain('insert');
+    expect(DB::table(Table::ENTRIES_AUTHORS)
+        ->where('entryId', $entry->id)
+        ->pluck('authorId')
+        ->all())->toBe([$author->id]);
+});
+
+it('deletes existing author rows when an entry’s authors change', function () {
+    $entryType = EntryType::factory()->create();
+    $section = Section::factory()->withEntryTypes($entryType)->create([
+        'type' => SectionType::Channel,
+    ]);
+    $oldAuthor = User::factory()->create();
+    $newAuthor = User::factory()->create();
+
+    $entry = Entry::factory()
+        ->forSection($section)
+        ->forEntryType($entryType)
+        ->createElement();
+    $entry->setAuthorIds([$oldAuthor->id]);
+    Elements::saveElement($entry);
+
+    $entry->setAuthorIds([$newAuthor->id]);
+
+    $commands = captureEntriesAuthorsCommands(fn () => Elements::saveElement($entry));
+
+    // The old author row does exist this time, so the existing rows must still be removed.
+    expect($commands)->toContain('delete');
+    expect($commands)->toContain('insert');
+    expect(DB::table(Table::ENTRIES_AUTHORS)
+        ->where('entryId', $entry->id)
+        ->pluck('authorId')
+        ->all())->toBe([$newAuthor->id]);
+});