This file contains the implementation of prepared statements. More...

#include "sql/sql_prepare.h"
#include "my_config.h"
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <limits>
#include <memory>
#include <unordered_map>
#include <utility>
#include "decimal.h"
#include "field_types.h"
#include "m_ctype.h"
#include "m_string.h"
#include "map_helpers.h"
#include "my_alloc.h"
#include "my_byteorder.h"
#include "my_command.h"
#include "my_compiler.h"
#include "my_dbug.h"
#include "my_sqlcommand.h"
#include "my_sys.h"
#include "my_time.h"
#include "mysql/com_data.h"
#include "mysql/components/services/log_shared.h"
#include "mysql/plugin_audit.h"
#include "mysql/psi/mysql_mutex.h"
#include "mysql/psi/mysql_ps.h"
#include "mysql/udf_registration_types.h"
#include "mysql_com.h"
#include "mysql_time.h"
#include "mysqld_error.h"
#include "scope_guard.h"
#include "sql/auth/auth_acls.h"
#include "sql/auth/auth_common.h"
#include "sql/auth/sql_security_ctx.h"
#include "sql/binlog.h"
#include "sql/debug_sync.h"
#include "sql/derror.h"
#include "sql/field.h"
#include "sql/handler.h"
#include "sql/item.h"
#include "sql/item_func.h"
#include "sql/log.h"
#include "sql/mdl.h"
#include "sql/my_decimal.h"
#include "sql/mysqld.h"
#include "sql/opt_trace.h"
#include "sql/protocol.h"
#include "sql/protocol_classic.h"
#include "sql/psi_memory_key.h"
#include "sql/query_options.h"
#include "sql/query_result.h"
#include "sql/resourcegroups/resource_group_basic_types.h"
#include "sql/resourcegroups/resource_group_mgr.h"
#include "sql/session_tracker.h"
#include "sql/set_var.h"
#include "sql/sp_cache.h"
#include "sql/sql_audit.h"
#include "sql/sql_base.h"
#include "sql/sql_class.h"
#include "sql/sql_cmd.h"
#include "sql/sql_cmd_ddl_table.h"
#include "sql/sql_const.h"
#include "sql/sql_cursor.h"
#include "sql/sql_db.h"
#include "sql/sql_digest_stream.h"
#include "sql/sql_handler.h"
#include "sql/sql_insert.h"
#include "sql/sql_lex.h"
#include "sql/sql_list.h"
#include "sql/sql_parse.h"
#include "sql/sql_profile.h"
#include "sql/sql_query_rewrite.h"
#include "sql/sql_rewrite.h"
#include "sql/sql_view.h"
#include "sql/system_variables.h"
#include "sql/table.h"
#include "sql/thd_raii.h"
#include "sql/thr_malloc.h"
#include "sql/transaction.h"
#include "sql/window.h"
#include "sql_string.h"
#include "violite.h"

Classes
class	anonymous_namespace{sql_prepare.cc}::Execute_sql_statement
	Execute one SQL statement in an isolated context. More...

class	anonymous_namespace{sql_prepare.cc}::Query_fetch_protocol_binary
	A result class used to send cursor rows using the binary protocol. More...

class	Protocol_local
	Protocol_local: a helper class to intercept the result of the data written to the network. More...

class	Statement_backup

Namespaces
namespace	resourcegroups

namespace	anonymous_namespace{sql_prepare.cc}

Functions
static void	rewrite_query (THD *thd)
	Rewrite the current query (to obfuscate passwords etc.). More...

static void	log_execute_line (THD *thd)
	Unless we're doing dynamic SQL, write the current query to the general query log if it's open. More...

static void	set_parameter_type (Item_param param, enum enum_field_types type, bool unsigned_type, const CHARSET_INFO cs_source)
	Set source parameter type based on information from protocol buffer. More...

static bool	set_parameter_value (Item_param param, const uchar *pos, ulong len)
	Set parameter value from protocol buffer. More...

bool	is_param_long_data_type (Item_param *param)
	Check whether this parameter data type is compatible with long data. More...

static void	swap_parameter_array (Item_param param_array_dst, Item_param param_array_src, uint param_count)
	Setup data conversion routines using an array of parameter markers from the original prepared statement. More...

static bool	send_statement (THD thd, const Prepared_statement stmt, uint no_columns, Query_result result, const mem_root_deque< Item > *types)

static bool	mysql_test_set_fields (THD thd, Prepared_statement stmt, Table_ref tables, List< set_var_base > var_list)
	Validate and prepare for execution SET statement expressions. More...

static bool	select_like_stmt_test (THD thd, Query_result result, ulonglong added_options)

static bool	mysql_test_create_view (THD thd, Prepared_statement stmt)
	Validate and prepare for execution CREATE VIEW statement. More...

const char *	fieldtype2str (enum enum_field_types type)

static bool	init_param_array (THD thd, Prepared_statement stmt)
	Initialize array of parameters in statement from LEX. More...

void	mysqld_stmt_prepare (THD thd, const char query, uint length, Prepared_statement *stmt)
	COM_STMT_PREPARE handler. More...

bool	mysql_stmt_precheck (THD thd, const COM_DATA com_data, enum enum_server_command cmd, Prepared_statement **stmt)
	Searches for the statement with the specified id and validates it. More...

static const char *	get_dynamic_sql_string (LEX lex, size_t query_len)
	Get an SQL statement text from a user variable or from plain text. More...

void	mysql_sql_stmt_prepare (THD *thd)
	SQLCOM_PREPARE implementation. More...

static void	reset_stmt_parameters (Prepared_statement *stmt)
	Clears parameters from data left from previous execution or long data. More...

void	mysqld_stmt_execute (THD thd, Prepared_statement stmt, bool has_new_types, ulong execute_flags, PS_PARAM *parameters)
	COM_STMT_EXECUTE handler: execute a previously prepared statement. More...

void	mysql_sql_stmt_execute (THD *thd)
	SQLCOM_EXECUTE implementation. More...

void	mysqld_stmt_fetch (THD thd, Prepared_statement stmt, ulong num_rows)
	COM_STMT_FETCH handler: fetches requested amount of rows from cursor. More...

void	mysqld_stmt_reset (THD thd, Prepared_statement stmt)
	Reset a prepared statement in case there was a recoverable error. More...

void	mysqld_stmt_close (THD thd, Prepared_statement stmt)
	Delete a prepared statement from memory. More...

void	mysql_sql_stmt_close (THD *thd)
	SQLCOM_DEALLOCATE implementation. More...

void	mysql_stmt_get_longdata (THD thd, Prepared_statement stmt, uint param_number, uchar *str, ulong length)
	Handle long data in pieces from client. More...

bool	ask_to_reprepare (THD *thd)
	Requests for repreparation of statement. More...

static bool	disable_general_log (THD *thd)
	Disables the general log for the current session by setting the OPTION_LOG_OFF bit in thd->variables.option_bits. More...

Detailed Description

This file contains the implementation of prepared statements.

When one prepares a statement:

Server gets the query from client with command 'COM_STMT_PREPARE'; in the following format: [COM_STMT_PREPARE:1] [query]
Parse the query and recognize any parameter markers '?' and store its information list in lex->param_list
Allocate a new statement for this prepare; and keep this in 'thd->stmt_map'.

Without executing the query, return back to client the total number of parameters along with result-set metadata information (if any) in the following format:

    [STMT_ID:4]
    [Column_count:2]
    [Param_count:2]
    [Params meta info (stubs only for now)]  (if Param_count > 0)
    [Columns meta info] (if Column_count > 0)

During prepare the tables used in a statement are opened, but no locks are acquired. Table opening will block any DDL during the operation, and we do not need any locks as we neither read nor modify any data during prepare. Tables are closed after prepare finishes.

When one executes a statement:

Server gets the command 'COM_STMT_EXECUTE' to execute the previously prepared query. If there are any parameter markers, then the client will send the data in the following format:
```
    [COM_STMT_EXECUTE:1]
    [STMT_ID:4]
    [NULL_BITS:(param_count+7)/8)]
    [TYPES_SUPPLIED_BY_CLIENT(0/1):1]
    [[length]data]
    [[length]data] .. [[length]data].
```
(Note: Except for string/binary types; all other types will not be supplied with length field)
If it is a first execute or types of parameters were altered by client, then setup the conversion routines.
Assign parameter items from the supplied data.
Execute the query without re-parsing and send back the results to client

During execution of prepared statement tables are opened and locked the same way they would for normal (non-prepared) statement execution. Tables are unlocked and closed after the execution.

When one supplies long data for a placeholder:

Server gets the long data in pieces with command type 'COM_STMT_SEND_LONG_DATA'.
The packet received will have the format as: [COM_STMT_SEND_LONG_DATA:1][STMT_ID:4][parameter_number:2][data]
data from the packet is appended to the long data value buffer for this placeholder.
It's up to the client to stop supplying data chunks at any point. The server doesn't care; also, the server doesn't notify the client whether it got the data or not; if there is any error, then it will be returned at statement execute.

Function Documentation

◆ ask_to_reprepare()

bool ask_to_reprepare ( THD * thd )

Requests for repreparation of statement.

Returns: true if request has been placed.

◆ disable_general_log()

static bool disable_general_log ( THD * thd )

static

Disables the general log for the current session by setting the OPTION_LOG_OFF bit in thd->variables.option_bits.

Parameters

thd	the session

Returns: whether the setting was changed

Return values

false	if the general log was already disabled for this session
true	if the general log was enabled for the session and is now disabled

◆ fieldtype2str()

const char * fieldtype2str ( enum enum_field_types type )

◆ get_dynamic_sql_string()

static const char * get_dynamic_sql_string	(	LEX *	lex,
		size_t *	query_len
	)

static

Get an SQL statement text from a user variable or from plain text.

If the statement is plain text, just assign the pointers, otherwise allocate memory in thd->mem_root and copy the contents of the variable, possibly with character set conversion.

Parameters

[in]	lex	main lex
[out]	query_len	length of the SQL statement (is set only in case of success)

Return values

non-zero	success
0	in case of error (out of memory)

◆ init_param_array()

static bool init_param_array	(	THD *	thd,
		Prepared_statement *	stmt
	)

static

Initialize array of parameters in statement from LEX.

(We need to have quick access to items by number in mysql_stmt_get_longdata). This is to avoid using malloc/realloc in the parser.

◆ is_param_long_data_type()

bool is_param_long_data_type ( Item_param * param )

inline

Check whether this parameter data type is compatible with long data.

Used to detect whether a long data stream has been supplied to a incompatible data type. Notice that VARCHAR type is MYSQL_TYPE_STRING, not MYSQL_TYPE_VARCHAR, when sent on protocol between client and server.

◆ log_execute_line()

static void log_execute_line ( THD * thd )

inlinestatic

Unless we're doing dynamic SQL, write the current query to the general query log if it's open.

If we have a rewritten version of the query, use that instead of the "raw" one.

Side-effect: query may be written to general log if it's open.

Parameters

thd	thread handle

◆ mysql_sql_stmt_close()

void mysql_sql_stmt_close ( THD * thd )

SQLCOM_DEALLOCATE implementation.

Close an SQL prepared statement. As this can be called from Dynamic SQL, we should be careful to not close a statement that is currently being executed.

OK packet is sent in case of success, otherwise an error message is set in THD.

◆ mysql_sql_stmt_execute()

void mysql_sql_stmt_execute ( THD * thd )

SQLCOM_EXECUTE implementation.

Execute prepared statement using parameter values from lex->prepared_stmt_params and send result to the client using text protocol. This is called from mysql_execute_command and therefore should behave like an ordinary query (e.g. not change global THD data, such as warning count, server status, etc). This function uses text protocol to send a possible result set.

In case of success, OK (or result set) packet is sent to the client, otherwise an error is set in THD.

Parameters

thd	thread handle

◆ mysql_sql_stmt_prepare()

void mysql_sql_stmt_prepare ( THD * thd )

SQLCOM_PREPARE implementation.

Prepare an SQL prepared statement. This is called from mysql_execute_command and should therefore behave like an ordinary query (e.g. should not reset any global THD data).

In case of success, OK packet is sent to the client, otherwise an error message is set in THD.

Parameters

thd	thread handle

◆ mysql_stmt_get_longdata()

void mysql_stmt_get_longdata	(	THD *	thd,
		Prepared_statement *	stmt,
		uint	param_number,
		uchar *	str,
		ulong	length
	)

Handle long data in pieces from client.

Get a part of a long data. To make the protocol efficient, we are not sending any return packets here. If something goes wrong, then we will send the error on 'execute' We assume that the client takes care of checking that all parts are sent to the server. (No checking that we get a 'end of column' in the server is performed).

Parameters

thd	Thread handle
stmt	Pointer to Prepared_statement
param_number	Number of parameters
str	String to append
length	Length of string (including end \0)

◆ mysql_stmt_precheck()

bool mysql_stmt_precheck	(	THD *	thd,
		const COM_DATA *	com_data,
		enum enum_server_command	cmd,
		Prepared_statement **	stmt
	)

Searches for the statement with the specified id and validates it.

Parameters

thd	[in] thread handle
com_data	[in] command data
cmd	[in] command type to be executed
stmt	[out] pointer to Prepared_statement to store it if found

◆ mysql_test_create_view()

static bool mysql_test_create_view	(	THD *	thd,
		Prepared_statement *	stmt
	)

static

Validate and prepare for execution CREATE VIEW statement.

Parameters

thd	current thread
stmt	prepared statement

Note: This function handles create view commands.

Returns: false if success, true if error

Return values

false	Operation was a success.
true	An error occurred.

◆ mysql_test_set_fields()

static bool mysql_test_set_fields	(	THD *	thd,
		Prepared_statement *	stmt,
		Table_ref *	tables,
		List< set_var_base > *	var_list
	)

static

Validate and prepare for execution SET statement expressions.

Parameters

thd	current thread
stmt	prepared statement
tables	list of tables used in this query
var_list	list of expressions

Returns: false if success, true if error

◆ mysqld_stmt_close()

void mysqld_stmt_close	(	THD *	thd,
		Prepared_statement *	stmt
	)

Delete a prepared statement from memory.

Note: we don't send any reply to this command.

◆ mysqld_stmt_execute()

void mysqld_stmt_execute	(	THD *	thd,
		Prepared_statement *	stmt,
		bool	has_new_types,
		ulong	execute_flags,
		PS_PARAM *	parameters
	)

COM_STMT_EXECUTE handler: execute a previously prepared statement.

If there are any parameters, then replace parameter markers with the data supplied from the client, and then execute the statement. This function uses binary protocol to send a possible result set to the client.

In case of success OK packet or a result set is sent to the client, otherwise an error message is set in THD.

Parameters

thd	current thread
stmt	prepared statement
has_new_types	true if parsed parameters have data types defined, otherwise types from last execution will be used
execute_flags	flag used to decide if a cursor should be used
parameters	prepared statement's parsed parameters

◆ mysqld_stmt_fetch()

void mysqld_stmt_fetch	(	THD *	thd,
		Prepared_statement *	stmt,
		ulong	num_rows
	)

COM_STMT_FETCH handler: fetches requested amount of rows from cursor.

Parameters

thd	Thread handle.
stmt	Pointer to the prepared statement.
num_rows	Number of rows to fetch.

◆ mysqld_stmt_prepare()

void mysqld_stmt_prepare	(	THD *	thd,
		const char *	query,
		uint	length,
		Prepared_statement *	stmt
	)

COM_STMT_PREPARE handler.

Given a query string with parameter markers, create a prepared statement from it and send PS info back to the client.

If parameter markers are found in the query, then store the information using Item_param along with maintaining a list in lex->param_array, so that a fast and direct retrieval can be made without going through all field items.

In case of success a new statement id and metadata is sent to the client, otherwise an error message is set in THD.

Parameters

thd	thread handle
query	query to be prepared
length	query string length, including ignored trailing NULL or quote char.
stmt	Prepared_statement to be used for preparation.

Note: This function parses the query and sends the total number of parameters and resultset metadata information back to client (if any), without executing the query i.e. without any log/disk writes. This allows the queries to be re-executed without re-parsing during execute.

◆ mysqld_stmt_reset()

void mysqld_stmt_reset	(	THD *	thd,
		Prepared_statement *	stmt
	)

Reset a prepared statement in case there was a recoverable error.

This function resets statement to the state it was right after prepare. It can be used to:

clear an error happened during mysqld_stmt_send_long_data
cancel long data stream for all placeholders without having to call mysqld_stmt_execute.
close an open cursor Sends 'OK' packet in case of success (statement was reset) or 'ERROR' packet (unrecoverable error/statement not found/etc).

Parameters

thd	Thread handle
stmt	Pointer to the Prepared_statement

◆ reset_stmt_parameters()

static void reset_stmt_parameters ( Prepared_statement * stmt )

static

Clears parameters from data left from previous execution or long data.

Parameters

stmt	prepared statement for which parameters should be reset

◆ rewrite_query()

static void rewrite_query ( THD * thd )

inlinestatic

Rewrite the current query (to obfuscate passwords etc.).

Side-effect: thd->rewritten_query() may be populated with a rewritten query. If the query is not of a rewritable type, thd->rewritten_query() will be empty.

Parameters

thd	thread handle

◆ select_like_stmt_test()

static bool select_like_stmt_test	(	THD *	thd,
		Query_result *	result,
		ulonglong	added_options
	)

static

Parameters

thd	thread handler
result	query result sink
added_options	options added to query block before preparation

Returns: false if success, true if error

◆ send_statement()

static bool send_statement	(	THD *	thd,
		const Prepared_statement *	stmt,
		uint	no_columns,
		Query_result *	result,
		const mem_root_deque< Item * > *	types
	)

static

◆ set_parameter_type()

static void set_parameter_type	(	Item_param *	param,
		enum enum_field_types	type,
		bool	unsigned_type,
		const CHARSET_INFO *	cs_source
	)

static

Set source parameter type based on information from protocol buffer.

Parameters

param	Parameter to set source type for
type	Field type
unsigned_type	true if type is unsigned (applicable for numeric types)
cs_source	The source collation for non-binary string parameters

If parameter metadata is invalid, set source data type MYSQL_TYPE_INVALID.

◆ set_parameter_value()

static bool set_parameter_value	(	Item_param *	param,
		const uchar **	pos,
		ulong	len
	)

static

Set parameter value from protocol buffer.

Parameters

param	Parameter to set a value for
pos	Pointer to parameter value in protocol buffer
len	Length of parameter value

Returns: false on success, true on error

The function reads a binary valuefrom pos, converts it to the requested type and assigns it to the paramameter.

◆ swap_parameter_array()

static void swap_parameter_array	(	Item_param **	param_array_dst,
		Item_param **	param_array_src,
		uint	param_count
	)

static

Setup data conversion routines using an array of parameter markers from the original prepared statement.

Swap the parameter data of the original prepared statement to the new one.

Used only when we re-prepare a prepared statement. There are two reasons for this function to exist:

1) In the binary client/server protocol, parameter metadata is sent only at first execute. Consequently, if we need to reprepare a prepared statement at a subsequent execution, we may not have metadata information in the packet. In that case we use the parameter array of the original prepared statement to setup parameter types of the new prepared statement.

2) In the binary client/server protocol, we may supply long data in pieces. When the last piece is supplied, we assemble the pieces and convert them from client character set to the connection character set. After that the parameter value is only available inside the parameter, the original pieces are lost, and thus we can only assign the corresponding parameter of the reprepared statement from the original value.

Parameters

[out]	param_array_dst	parameter markers of the new statement
[in]	param_array_src	parameter markers of the original statement
[in]	param_count	total number of parameters. Is the same in src and dst arrays, since the statement query is the same

Classes

Namespaces

Functions

Detailed Description

Function Documentation

◆ ask_to_reprepare()

◆ disable_general_log()

◆ fieldtype2str()

◆ get_dynamic_sql_string()

◆ init_param_array()

◆ is_param_long_data_type()

◆ log_execute_line()

◆ mysql_sql_stmt_close()

◆ mysql_sql_stmt_execute()

◆ mysql_sql_stmt_prepare()

◆ mysql_stmt_get_longdata()

◆ mysql_stmt_precheck()

◆ mysql_test_create_view()

◆ mysql_test_set_fields()

◆ mysqld_stmt_close()

◆ mysqld_stmt_execute()

◆ mysqld_stmt_fetch()

◆ mysqld_stmt_prepare()

◆ mysqld_stmt_reset()

◆ reset_stmt_parameters()

◆ rewrite_query()

◆ select_like_stmt_test()

◆ send_statement()

◆ set_parameter_type()

◆ set_parameter_value()

◆ swap_parameter_array()