MySQL 9.0.0
Source Code Documentation
histograms::Background_error_handler Class Reference

Custom error handling for histogram updates from the background thread. More...

Inheritance diagram for histograms::Background_error_handler:

Public Member Functions

bool handle_condition (THD *, uint, const char *, Sql_condition::enum_severity_level *level, const char *) override
 Handle a sql condition. More...

Additional Inherited Members

- Protected Member Functions inherited from Internal_error_handler
 Internal_error_handler ()
Internal_error_handlerprev_internal_handler () const
virtual ~Internal_error_handler ()=default

Detailed Description

Custom error handling for histogram updates from the background thread.

Downgrades all errors to warnings. This is done for two reasons:

1) Because errors during background histogram updates are mostly ignorable, i.e., it is not critical that the user does something if histogram statistics fail to be updated.

2) We wish to throttle error log entries from background histogram updates, and this is currently only supported for a priority level of warnings.

Member Function Documentation

◆ handle_condition()

bool histograms::Background_error_handler::handle_condition ( THD thd,
uint  sql_errno,
const char *  sqlstate,
Sql_condition::enum_severity_level level,
const char *  msg 

Handle a sql condition.

This method can be implemented by a subclass to achieve any of the following:

  • mask a warning/error internally, prevent exposing it to the user,
  • mask a warning/error and throw another one instead. When this method returns true, the sql condition is considered 'handled', and will not be propagated to upper layers. It is the responsibility of the code installing an internal handler to then check for trapped conditions, and implement logic to recover from the anticipated conditions trapped during runtime.

This mechanism is similar to C++ try/throw/catch:

  • 'try' correspond to THD::push_internal_handler(),
  • 'throw' correspond to my_error(), which invokes my_message_sql(),
  • 'catch' correspond to checking how/if an internal handler was invoked, before removing it from the exception stack with THD::pop_internal_handler().
thdthe calling thread
sql_errnothe error number for the condition raised.
sqlstatethe SQLSTATE for the condition raised.
levelthe severity level for the condition raised.
msgthe error message for the condition raised.
true if the condition is handled

Implements Internal_error_handler.

The documentation for this class was generated from the following file: