phpmysqlmoodleazure-mysql-database

How can I solve the ddl execute error on Moodle 3.8.4?

I'm using Moodle 3.8.4 connected with the Azure Database for MySQL server. I'm trying to duplicate an activity by right-clicking on an activity and selecting Edit->Duplicate.

duplicate_activity_moodle

I've set the debugging mode to DEVELOPER, then I see the following error message:

> Unknown table 'learn_nprod.mdl_backup_ids_temp'
DROP TABLE mdl_backup_ids_temp
Error code: ddlexecuteerror
* line 492 of /lib/dml/moodle_database.php: ddl_change_structure_exception thrown
* line 1072 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->query_end()
* line 77 of /lib/ddl/database_manager.php: call to mysqli_native_moodle_database->change_database_structure()
* line 332 of /lib/ddl/database_manager.php: call to database_manager->execute_sql_arr()
* line 171 of /backup/util/dbops/backup_controller_dbops.class.php: call to database_manager->drop_table()
* line 40 of /backup/moodle2/backup_stepslib.php: call to backup_controller_dbops::drop_backup_ids_temp_table()
* line 34 of /backup/util/plan/backup_execution_step.class.php: call to create_and_clean_temp_stuff->define_execution()
* line 181 of /backup/util/plan/base_task.class.php: call to backup_execution_step->execute()
* line 178 of /backup/util/plan/base_plan.class.php: call to base_task->execute()
* line 119 of /backup/util/plan/backup_plan.class.php: call to base_plan->execute()
* line 375 of /backup/controller/backup_controller.class.php: call to backup_plan->execute()
* line 3530 of /course/lib.php: call to backup_controller->execute_plan()
* line 3518 of /course/externallib.php: call to duplicate_module()
* line 250 of /lib/externallib.php: call to core_course_external::edit_module()
* line 79 of /lib/ajax/service.php: call to external_api::call_external_function()

Also, I discovered that the backup job is freezed to 0%: backup_job

On Azure MySQL I changed the values from:

wait_timeout = 440, max_heap_table_size = 16777216, tmp_table_size = 16777216, innodb_strict_mode = ON

To:

wait_timeout = 3600, max_heap_table_size = 2147483648, tmp_table_size = 536870912, innodb_strict_mode = OFF

and I restarted the Azure MySQL Server. This action solved my issue only for some minutes. Are any suggestions to bypass this error?
MySQL settings are on this link.

Update: I followed this solution, which practically it not uses the temp tables however I don't understand why is this happening and also if it will have an impact on the DB.

Solution

  • I solved the issue by editing the following file: ./htdocs/lib/dml/mysqli_native_moodle_database.php I changed this line :

    $sql = "SHOW TABLES LIKE '$prefix%'";

    to this:

    $sql = "SHOW FULL TABLES LIKE '$prefix%'";

    It seems that the Azure MySQL Server is caching the temporary tables before the DROP query.