[2.3.0-beta1] Datenbank aktualisieren Exception

[Mynyx]

Fatal error: Uncaught exception Exception with message Query error: Duplicate entry '' for key 'uniqid' (ALTER TABLE tl_iso_product_collection ADD UNIQUE KEY uniqid (uniqid);) thrown in system/modules/core/library/Contao/Database/Statement.php on line 295
#0 system/modules/core/library/Contao/Database.php(207): Contao\Database\Statement->query('ALTER TABLE tl...') #1 system/modules/repository/classes/RepositoryManager.php(477): Contao\Database->query('ALTER TABLE tl...')
#2 system/modules/repository/classes/RepositoryBackendModule.php(153): RepositoryManager->update('database')
#3 system/modules/core/classes/BackendModule.php(98): RepositoryBackendModule->compile()
#4 system/modules/repository/classes/RepositoryBackendModule.php(72): Contao\BackendModule->generate()
#5 system/modules/repository/classes/RepositoryManager.php(57): RepositoryBackendModule->generate()
#6 system/modules/core/classes/Backend.php(423): RepositoryManager->generate()
#7 system/modules/core/controllers/BackendMain.php(131): Contao\Backend->getBackendModule('repository_mana...')
#8 contao/main.php(20): Contao\BackendMain->run()
#9 {main}

[zonky2]

I had the same error during the update by 2.2.4 to 2.3.5

Fatal error: Uncaught exception Exception with message Query error: Duplicate entry '' for key 'uniqid' (ALTER TABLE `tl_iso_product_collection` ADD UNIQUE KEY `uniqid` (`uniqid`);) thrown in system/modules/core/library/Contao/Database/Statement.php on line 295

#0 system/modules/core/library/Contao/Database.php(207): Contao\Database\Statement->query('ALTER TABLE `tl...')
#1 system/modules/repository/classes/RepositoryManager.php(477): Contao\Database->query('ALTER TABLE `tl...')
#2 system/modules/repository/classes/RepositoryBackendModule.php(153): RepositoryManager->update('database')
#3 system/modules/core/classes/BackendModule.php(98): RepositoryBackendModule->compile()
#4 system/modules/repository/classes/RepositoryBackendModule.php(72): Contao\BackendModule->generate()
#5 system/modules/repository/classes/RepositoryManager.php(57): RepositoryBackendModule->generate()
#6 system/modules/core/classes/Backend.php(423): RepositoryManager->generate()
#7 system/modules/core/controllers/BackendMain.php(131): Contao\Backend->getBackendModule('repository_mana...')
#8 contao/main.php(20): Contao\BackendMain->run()
#9 {main}

may be, you should update the db migration with
ALTER TABLE tl_iso_product_collectionCHANGEuniqid uniqid VARCHAR(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL;