Prepared_statement: a statement that can contain placeholders. More...

#include <sql_prepare.h>

Public Member Functions
	Prepared_statement (THD *thd_arg)

virtual	~Prepared_statement ()
	Destroy this prepared statement, cleaning up all used memory and resources. More...

bool	set_name (const LEX_CSTRING &name)

const LEX_CSTRING &	name () const

ulong	id () const

bool	is_in_use () const

bool	is_sql_prepare () const

void	set_sql_prepare (bool prepare=true)

void	deallocate (THD *thd)
	Common part of DEALLOCATE PREPARE and mysqld_stmt_close. More...

bool	prepare (THD thd, const char packet, size_t packet_length, Item_param **orig_param_array)
	Parse statement text, validate the statement, and prepare it for execution. More...

bool	execute_loop (THD thd, String expanded_query, bool open_cursor)
	Execute a prepared statement. More...

bool	execute_server_runnable (THD thd, Server_runnable server_runnable)

PSI_prepared_stmt *	get_PS_prepared_stmt ()

bool	set_parameters (THD thd, String expanded_query, bool has_new_types, PS_PARAM *parameters)
	Assign parameter values from the execute packet. More...

bool	set_parameters (THD thd, String expanded_query)
	Assign parameter values from specified variables. More...

void	trace_parameter_types (THD *thd)

void	close_cursor ()

Public Attributes
Query_arena	m_arena
	Memory allocation arena, for permanent allocations to statement. More...

Item_param **	m_param_array {nullptr}
	Array of parameters used for statement, may be NULL if there are none. More...

Server_side_cursor *	m_cursor {nullptr}
	Pointer to cursor, may be NULL if statement never used with a cursor. More...

const Protocol *	m_active_protocol {nullptr}
	Used to check that the protocol is stable during execution. More...

uint	m_param_count {0}
	Number of parameters expected for statement. More...

uint	m_last_errno {0}

char	m_last_error [MYSQL_ERRMSG_SIZE]

const ulong	m_id
	Uniquely identifies each statement object in thread scope; change during statement lifetime. More...

LEX *	m_lex {nullptr}

LEX_CSTRING	m_query_string {NULL_CSTR}
	The query string associated with this statement. More...

PSI_prepared_stmt *	m_prepared_stmt {nullptr}
	Performance Schema interface for a prepared statement. More...

Private Member Functions
bool	prepare_query (THD *thd)
	Perform semantic analysis of query and send a response packet to client. More...

void	cleanup_stmt (THD *thd)

void	setup_stmt_logging (THD *thd)

bool	check_parameter_types ()
	Check resolved parameter types versus actual parameter types. More...

void	copy_parameter_types (Item_param **from_param_array)
	Copy parameter metada data from parameter array into current prepared stmt. More...

bool	set_db (const LEX_CSTRING &db_length)
	Remember the current database. More...

bool	execute (THD thd, String expanded_query, bool open_cursor)
	Execute a prepared statement that has already been prepared. More...

bool	reprepare (THD *thd)
	Reprepare this prepared statement. More...

bool	validate_metadata (THD thd, Prepared_statement copy)
	Validate statement result set metadata (if the statement returns a result set). More...

void	swap_prepared_statement (Prepared_statement *copy)
	Swap the MEM_ROOT allocated data of two prepared statements. More...

bool	insert_parameters_from_vars (THD thd, List< LEX_STRING > &varnames, String query)
	Assign prepared statement parameters from user variables. More...

bool	insert_parameters (THD thd, String query, bool has_new_types, PS_PARAM *parameters)
	Assign parameter values from data supplied by the client. More...

Private Attributes
bool	m_used_as_cursor {false}
	True if statement is used with cursor, false if used in regular execution. More...

Query_result *	m_regular_result {nullptr}
	Query result used when statement is used in regular execution. More...

Query_result *	m_cursor_result {nullptr}
	Query result used when statement is used with a cursor. More...

Query_result *	m_aux_result {nullptr}
	Auxiliary query result object, saved for proper destruction. More...

bool	m_is_sql_prepare {false}
	Flag that specifies preparation state. More...

bool	m_in_use {false}
	Flag that prevents recursive invocation of prepared statements. More...

bool	m_with_log {false}

LEX_CSTRING	m_name {NULL_CSTR}
	Name of the prepared statement. More...

LEX_CSTRING	m_db {NULL_CSTR}
	Name of the current (default) database. More...

MEM_ROOT	m_mem_root
	The memory root to allocate parsed tree elements (instances of Item, Query_block and other classes). More...

Detailed Description

Prepared_statement: a statement that can contain placeholders.

Constructor & Destructor Documentation

◆ Prepared_statement()

Prepared_statement::Prepared_statement ( THD * thd_arg )

◆ ~Prepared_statement()

Prepared_statement::~Prepared_statement ( )

virtual

Destroy this prepared statement, cleaning up all used memory and resources.

This is called from deallocate() to handle COM_STMT_CLOSE and DEALLOCATE PREPARE or when THD ends and all prepared statements are freed.

Member Function Documentation

◆ check_parameter_types()

bool Prepared_statement::check_parameter_types ( )

private

Check resolved parameter types versus actual parameter types.

Assumes that parameter values have been assigned to the parameters.

Returns: true if parameter types are compatible, false otherwise.

◆ cleanup_stmt()

void Prepared_statement::cleanup_stmt ( THD * thd )

private

◆ close_cursor()

void Prepared_statement::close_cursor ( )

◆ copy_parameter_types()

void Prepared_statement::copy_parameter_types ( Item_param ** from_param_array )

private

Copy parameter metada data from parameter array into current prepared stmt.

Parameters

from_param_array Parameter array to copy from.

◆ deallocate()

void Prepared_statement::deallocate ( THD * thd )

Common part of DEALLOCATE PREPARE and mysqld_stmt_close.

◆ execute()

bool Prepared_statement::execute	(	THD *	thd,
		String *	expanded_query,
		bool	open_cursor
	)

private

Execute a prepared statement that has already been prepared.

Parameters

thd	current thread.
expanded_query	A query for binlogging which has all parameter markers ('?') replaced with their actual values.
open_cursor	True if an attempt to open a cursor should be made. Currently used only in the binary protocol.

Note

Preconditions:

Caller must ensure that thd->change_list and thd->item_list are empty; This function will free them after execution.

Postconditions.

There are no items in thd->change_list.
thd->mem_root may contain memory allocated during execution.

Returns: false if success, true if error

◆ execute_loop()

bool Prepared_statement::execute_loop	(	THD *	thd,
		String *	expanded_query,
		bool	open_cursor
	)

Execute a prepared statement.

Re-prepare it a limited number of times if necessary.

Try to execute a prepared statement. If there is a metadata validation error, prepare a new copy of the prepared statement, swap the old and the new statements, and try again. If there is a validation error again, repeat the above, but perform not more than a maximum number of times. Reprepare_observer ensures that a prepared statement execution is retried not more than a maximum number of times.

Note: We have to try several times in a loop since we release metadata locks on tables after prepared statement prepare. Therefore, a DDL statement may sneak in between prepare and execute of a new statement. If a prepared statement execution is retried for a maximum number of times then we give up.

Parameters

thd	current thread.
expanded_query	Query string.
open_cursor	Flag to specify if a cursor should be used.

Returns: a bool value representing the function execution status.

Return values

true	error: either statement execution is retried for a maximum number of times or some general error.
false	successfully executed the statement, perhaps after having reprepared it a few times.

◆ execute_server_runnable()

bool Prepared_statement::execute_server_runnable	(	THD *	thd,
		Server_runnable *	server_runnable
	)

◆ get_PS_prepared_stmt()

PSI_prepared_stmt * Prepared_statement::get_PS_prepared_stmt ( )

inline

◆ id()

ulong Prepared_statement::id ( ) const

inline

◆ insert_parameters()

bool Prepared_statement::insert_parameters	(	THD *	thd,
		String *	query,
		bool	has_new_types,
		PS_PARAM *	parameters
	)

private

Assign parameter values from data supplied by the client.

If required, generate a valid non-parameterized query for logging.

Parameters

thd	current thread.
query	The query with parameter markers replaced with values supplied by user that were used to execute the query.
has_new_types	if true, new types of actual parameters are provided, otherwise use the parameters from previous execution.
parameters	Array of actual parameter values. Contains parameter types if has_new_types is true.

Returns: false if success, true if error

Note

m_with_log is set when one of slow or general logs are open. Logging of prepared statements in all cases is performed by means of regular queries: if parameter data was supplied from C API, each placeholder in the query is replaced with its actual value; if we're logging a [Dynamic] SQL prepared statement, parameter markers are replaced with variable names. Example:

   mysqld_stmt_prepare("UPDATE t1 SET a=a*1.25 WHERE a=?")
     --> general logs gets [Prepare] UPDATE t1 SET a*1.25 WHERE a=?"
   mysqld_stmt_execute(stmt);
     --> general and binary logs get
                           [Execute] UPDATE t1 SET a*1.25 WHERE a=1"

If a statement has been prepared using SQL syntax:

   PREPARE stmt FROM "UPDATE t1 SET a=a*1.25 WHERE a=?"
     --> general log gets [Query] PREPARE stmt FROM "UPDATE ..."
   EXECUTE stmt USING @a
     --> general log gets [Query] EXECUTE stmt USING @a;

◆ insert_parameters_from_vars()

bool Prepared_statement::insert_parameters_from_vars	(	THD *	thd,
		List< LEX_STRING > &	varnames,
		String *	query
	)

private

Assign prepared statement parameters from user variables.

If m_with_log is set, also construct query string for binary log.

Parameters

thd	Current thread.
varnames	List of variables. Caller must ensure that number of variables in the list is equal to number of statement parameters
query	The query with parameter markers replaced with corresponding user variables that were used to execute the query.

Returns: false if success, true if error

◆ is_in_use()

bool Prepared_statement::is_in_use ( ) const

inline

◆ is_sql_prepare()

bool Prepared_statement::is_sql_prepare ( ) const

inline

◆ name()

const LEX_CSTRING & Prepared_statement::name ( ) const

inline

◆ prepare()

bool Prepared_statement::prepare	(	THD *	thd,
		const char *	query_str,
		size_t	query_length,
		Item_param **	orig_param_array
	)

Parse statement text, validate the statement, and prepare it for execution.

You should not change global THD state in this function, if at all possible: it may be called from any context, e.g. when executing a COM_* command, and SQLCOM_* command, or a stored procedure.

Parameters

thd	thread handle
query_str	Statement text
query_length	Length of statement string
orig_param_array	Array containing pointers to parameter items that contain data type information for query. This is used during reprepare. = NULL: Derive parameter metadata from query only.

Note: Precondition: The caller must ensure that thd->change_list and thd->item_list is empty: this function will not back them up but will free in the end of its execution.; Postcondition: thd->mem_root contains unused memory allocated during validation.

◆ prepare_query()

bool Prepared_statement::prepare_query ( THD * thd )

private

Perform semantic analysis of query and send a response packet to client.

This function

opens all tables and checks privileges to them.
validates semantics of statement columns and SQL functions by calling fix_fields.
performs global transformations such as semi-join conversion.

Parameters

thd	current thread

Return values

false	success, statement metadata is sent to client
true	error, error message is set in THD (but not sent)

◆ reprepare()

bool Prepared_statement::reprepare ( THD * thd )

private

Reprepare this prepared statement.

Performs a light reset of the Prepared_statement object (resets its MEM_ROOT and clears its MEM_ROOT allocated members), and calls prepare() on it again.

The resetting of the MEM_ROOT and clearing of the MEM_ROOT allocated members is performed by a swap operation (swap_prepared_statement()) on this Prepared_statement and a newly created, intermediate Prepared_statement. This both clears the data from this object and stores a backup of the original data in the intermediate object. If the repreparation fails, the original data is swapped back into this Prepared_statement.

Parameters

thd	current thread.

Return values

true	an error occurred. Possible errors include incompatibility of new and old result set metadata
false	success, the statement has been reprepared

◆ set_db()

bool Prepared_statement::set_db ( const LEX_CSTRING & db_arg )

private

Remember the current database.

We must reset/restore the current database during execution of a prepared statement since it affects execution environment: privileges, @character_set_database, and other.

Returns: Returns an error if out of memory.

◆ set_name()

bool Prepared_statement::set_name ( const LEX_CSTRING & name )

◆ set_parameters() [1/2]

bool Prepared_statement::set_parameters	(	THD *	thd,
		String *	expanded_query
	)

Assign parameter values from specified variables.

Parameters

thd	current thread
expanded_query	a container with the original SQL statement. '?' placeholders will be replaced with their values in case of success. The result is used for logging and replication

Returns: false if success, true if error (likely a conversion error or out of memory)

◆ set_parameters() [2/2]

bool Prepared_statement::set_parameters	(	THD *	thd,
		String *	expanded_query,
		bool	has_new_types,
		PS_PARAM *	parameters
	)

Assign parameter values from the execute packet.

Parameters

thd	current thread
expanded_query	a container with the original SQL statement. '?' placeholders will be replaced with their values in case of success. The result is used for logging and replication
has_new_types	flag used to signal that new types are provided.
parameters	prepared statement's parsed parameters.

Returns: false if success, true if error (likely a conversion error, out of memory, or malformed packet)

◆ set_sql_prepare()

void Prepared_statement::set_sql_prepare ( bool prepare = true )

inline

◆ setup_stmt_logging()

void Prepared_statement::setup_stmt_logging ( THD * thd )

private

◆ swap_prepared_statement()

void Prepared_statement::swap_prepared_statement ( Prepared_statement * copy )

private

Swap the MEM_ROOT allocated data of two prepared statements.

This is a private helper that is used as part of statement reprepare. It is used in the beginning of reprepare() to clear the MEM_ROOT of the statement before the new preparation, while keeping the data available as some of it is needed later in the repreparation. It is also used for restoring the original data from the copy, should the repreparation fail.

The operation is symmetric. It can be used both for saving an original statement into a backup, and for restoring the original state of the statement from the backup.

◆ trace_parameter_types()

void Prepared_statement::trace_parameter_types ( THD * thd )

◆ validate_metadata()

bool Prepared_statement::validate_metadata	(	THD *	thd,
		Prepared_statement *	copy
	)

private

Validate statement result set metadata (if the statement returns a result set).

Currently we only check that the number of columns of the result set did not change. This is a helper method used during re-prepare.

Parameters

thd	current thread.
copy	the re-prepared prepared statement to verify the metadata of

Return values

true	error, ER_PS_REBIND is reported
false	statement return no or compatible metadata

If this is an SQL prepared statement or EXPLAIN, return false – the metadata of the original SELECT, if any, has not been sent to the client.

Column counts mismatch, update the client

Member Data Documentation

◆ m_active_protocol

const Protocol* Prepared_statement::m_active_protocol {nullptr}

Used to check that the protocol is stable during execution.

◆ m_arena

Query_arena Prepared_statement::m_arena

Memory allocation arena, for permanent allocations to statement.

◆ m_aux_result

Query_result* Prepared_statement::m_aux_result {nullptr}

private

Auxiliary query result object, saved for proper destruction.

◆ m_cursor

Server_side_cursor* Prepared_statement::m_cursor {nullptr}

Pointer to cursor, may be NULL if statement never used with a cursor.

◆ m_cursor_result

Query_result* Prepared_statement::m_cursor_result {nullptr}

private

Query result used when statement is used with a cursor.

◆ m_db

LEX_CSTRING Prepared_statement::m_db {NULL_CSTR}

private

Name of the current (default) database.

If there is the current (default) database, "db" contains its name. If there is no current (default) database, "db" is NULL and "db_length" is 0. In other words, "db", "db_length" must either be NULL, or contain a valid database name.

Note: this attribute is set and allocated by the slave SQL thread (for the THD of that thread); that thread is (and must remain, for now) the only responsible for freeing this member.

◆ m_id

const ulong Prepared_statement::m_id

Uniquely identifies each statement object in thread scope; change during statement lifetime.

◆ m_in_use

bool Prepared_statement::m_in_use {false}

private

Flag that prevents recursive invocation of prepared statements.

◆ m_is_sql_prepare

bool Prepared_statement::m_is_sql_prepare {false}

private

Flag that specifies preparation state.

◆ m_last_errno

uint Prepared_statement::m_last_errno {0}

◆ m_last_error

char Prepared_statement::m_last_error[MYSQL_ERRMSG_SIZE]

◆ m_lex

LEX* Prepared_statement::m_lex {nullptr}

◆ m_mem_root

MEM_ROOT Prepared_statement::m_mem_root

private

The memory root to allocate parsed tree elements (instances of Item, Query_block and other classes).

◆ m_name

LEX_CSTRING Prepared_statement::m_name {NULL_CSTR}

private

Name of the prepared statement.

◆ m_param_array

Item_param** Prepared_statement::m_param_array {nullptr}

Array of parameters used for statement, may be NULL if there are none.

◆ m_param_count

uint Prepared_statement::m_param_count {0}

Number of parameters expected for statement.

◆ m_prepared_stmt

PSI_prepared_stmt* Prepared_statement::m_prepared_stmt {nullptr}

Performance Schema interface for a prepared statement.

◆ m_query_string

LEX_CSTRING Prepared_statement::m_query_string {NULL_CSTR}

The query string associated with this statement.

◆ m_regular_result

Query_result* Prepared_statement::m_regular_result {nullptr}

private

Query result used when statement is used in regular execution.

◆ m_used_as_cursor

bool Prepared_statement::m_used_as_cursor {false}

private

True if statement is used with cursor, false if used in regular execution.

◆ m_with_log

bool Prepared_statement::m_with_log {false}

private

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

sql/sql_prepare.h
sql/sql_prepare.cc

Public Member Functions

Public Attributes

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ Prepared_statement()

◆ ~Prepared_statement()

Member Function Documentation

◆ check_parameter_types()

◆ cleanup_stmt()

◆ close_cursor()

◆ copy_parameter_types()

◆ deallocate()

◆ execute()

◆ execute_loop()

◆ execute_server_runnable()

◆ get_PS_prepared_stmt()

◆ id()

◆ insert_parameters()

◆ insert_parameters_from_vars()

◆ is_in_use()

◆ is_sql_prepare()

◆ name()

◆ prepare()

◆ prepare_query()

◆ reprepare()

◆ set_db()

◆ set_name()

◆ set_parameters() [1/2]

◆ set_parameters() [2/2]

◆ set_sql_prepare()

◆ setup_stmt_logging()

◆ swap_prepared_statement()

◆ trace_parameter_types()

◆ validate_metadata()

Member Data Documentation

◆ m_active_protocol

◆ m_arena

◆ m_aux_result

◆ m_cursor

◆ m_cursor_result

◆ m_db

◆ m_id

◆ m_in_use

◆ m_is_sql_prepare

◆ m_last_errno

◆ m_last_error

◆ m_lex

◆ m_mem_root

◆ m_name

◆ m_param_array

◆ m_param_count

◆ m_prepared_stmt

◆ m_query_string

◆ m_regular_result

◆ m_used_as_cursor

◆ m_with_log