Reprepare_observer Class Reference

An interface that is used to take an action when the locking module notices that a table version has changed since the last execution. More...

#include <sql_prepare.h>

Public Member Functions
bool	report_error (THD *thd)
	Check if a change of metadata is OK. More...
bool	is_invalidated () const
void	reset_reprepare_observer ()
bool	can_retry () const

Private Attributes
bool	m_invalidated {false}
int	m_attempt {0}

Static Private Attributes
static constexpr int	MAX_REPREPARE_ATTEMPTS = 3

Detailed Description

An interface that is used to take an action when the locking module notices that a table version has changed since the last execution.

"Table" here may refer to any kind of table – a base table, a temporary table, a view or an information schema table.

When we open and lock tables for execution of a prepared statement, we must verify that they did not change since statement prepare. If some table did change, the statement parse tree may be no longer valid, e.g. in case it contains optimizations that depend on table metadata.

This class provides an interface (a method) that is invoked when such a situation takes place. The implementation of the method simply reports an error, but the exact details depend on the nature of the SQL statement.

At most 1 instance of this class is active at a time, in which case THD::m_reprepare_observer is not NULL.

See also

check_and_update_table_version() for details of the version tracking algorithm

Open_tables_state::m_reprepare_observer for the life cycle of metadata observers.

Member Function Documentation

can_retry()

bool Reprepare_observer::can_retry ( ) const

inline

Returns

true if prepared statement can (and will) be retried

is_invalidated()

bool Reprepare_observer::is_invalidated ( ) const

inline

Returns

true if some table metadata is changed and statement should be re-prepared.

report_error()

bool Reprepare_observer::report_error

(

THD *

thd

)

Check if a change of metadata is OK.

Push an error to the error stack and return true for now.

In future the signature of this method may be extended to accept the old and the new versions, but since currently the check is very simple, we only need the THD to report an error.

reset_reprepare_observer()

void Reprepare_observer::reset_reprepare_observer ( )

inline

Member Data Documentation

m_attempt

int Reprepare_observer::m_attempt {0}

private

m_invalidated

bool Reprepare_observer::m_invalidated {false}

private

MAX_REPREPARE_ATTEMPTS

constexpr int Reprepare_observer::MAX_REPREPARE_ATTEMPTS = 3

staticconstexprprivate

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

• sql/sql_prepare.h
• sql/sql_prepare.cc