libtabula::DBDriver Class Reference

Provides a thin abstraction layer over the underlying database client library. More...

#include <dbdriver.h>

Collaboration diagram for libtabula::DBDriver:
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List of all members.

Public Types

enum  nr_code { nr_more_results, nr_last_result, nr_error, nr_not_supported }
 

Result code returned by next_result().

More...

Public Member Functions

 DBDriver ()
 Create object.
 DBDriver (const DBDriver &other)
 Duplicate an existing driver.
virtual ~DBDriver ()
 Destroy object.
ulonglong affected_rows ()
 Return the number of rows affected by the last query.
std::string client_version () const
 Get database client library version.
bool connect (const MYSQL &mysql)
 Establish a new connection using the same parameters as an existing connection.
virtual bool connect (const char *host, const char *socket_name, unsigned int port, const char *db, const char *user, const char *password)
 Connect to database server.
bool connected () const
 Return true if we have an active connection to the database server.
void copy (const DBDriver &other)
 Establish a new connection as a copy of an existing one.
bool create_db (const char *db) const
 Ask the database server to create a database.
void data_seek (MYSQL_RES *res, ulonglong offset) const
 Seeks to a particualr row within the result set.
void disconnect ()
 Drop the connection to the database server.
bool drop_db (const std::string &db) const
 Drop a database.
bool enable_ssl (const char *key=0, const char *cert=0, const char *ca=0, const char *capath=0, const char *cipher=0)
 Enable SSL-encrypted connection.
const char * error ()
 Return error message for last MySQL error associated with this connection.
int errnum ()
 Return last MySQL error number associated with this connection.
size_t escape_string (char *to, const char *from, size_t length)
 Return a SQL-escaped version of the given character buffer.
size_t escape_string (std::string *ps, const char *original, size_t length)
 Return a SQL-escaped version of a character buffer.
bool execute (const char *qstr, size_t length)
 Executes the given query string.
MYSQL_ROW fetch_row (MYSQL_RES *res) const
 Returns the next raw C API row structure from the given result set.
const unsigned long * fetch_lengths (MYSQL_RES *res) const
 Returns the lengths of the fields in the current row from a "use" query.
MYSQL_FIELD * fetch_field (MYSQL_RES *res, size_t i=UINT_MAX) const
 Returns information about a particular field in a result set.
void field_seek (MYSQL_RES *res, size_t field) const
 Jumps to the given field within the result set.
void free_result (MYSQL_RES *res) const
 Releases memory used by a result set.
st_mysql_options get_options () const
 Return the connection options object.
std::string ipc_info ()
 Get information about the IPC connection to the database server.
ulonglong insert_id ()
 Get ID generated for an AUTO_INCREMENT column in the previous INSERT query.
bool kill (unsigned long tid)
 Kill a MySQL server thread.
bool more_results ()
 Returns true if there are unconsumed results from the most recent query.
nr_code next_result ()
 Moves to the next result set from a multi-query.
int num_fields (MYSQL_RES *res) const
 Returns the number of fields in the given result set.
ulonglong num_rows (MYSQL_RES *res) const
 Returns the number of rows in the given result set.
bool ping ()
 "Pings" the MySQL database
int protocol_version ()
 Returns version number of MySQL protocol this connection is using.
std::string query_info ()
 Returns information about the last executed query.
bool refresh (unsigned options)
 Asks the database server to refresh certain internal data structures.
bool result_empty ()
 Returns true if the most recent result set was empty.
bool select_db (const char *db)
 Asks the database server to switch to a different database.
std::string server_version ()
 Get the database server's version number.
bool set_option (Option *o)
 Sets a connection option.
bool set_option (mysql_option moption, const void *arg=0)
 Set MySQL C API connection option.
bool set_option (unsigned int option, bool arg)
 Set MySQL C API connection option.
bool set_option_default (Option *o)
 Same as set_option(), except that it won't override a previously-set option.
bool shutdown ()
 Ask database server to shut down.
std::string server_status ()
 Returns the database server's status.
MYSQL_RES * store_result ()
 Saves the results of the query just execute()d in memory and returns a pointer to the MySQL C API data structure the results are stored in.
unsigned long thread_id ()
 Returns the MySQL server thread ID for this connection.
MYSQL_RES * use_result ()
 Returns a result set from the last-executed query which we can walk through in linear fashion, which doesn't store all result sets in memory.

Static Public Member Functions

static size_t escape_string_no_conn (char *to, const char *from, size_t length)
 SQL-escapes the given string without reference to the character set of a database server.
static size_t escape_string_no_conn (std::string *ps, const char *original=0, size_t length=0)
 SQL-escapes the given string without reference to the character set of a database server.
static bool thread_aware ()
 Returns true if Libtabula and the underlying MySQL C API library were both compiled with thread awareness.
static void thread_end ()
 Tells the underlying MySQL C API library that this thread is done using the library.
static bool thread_start ()
 Tells the underlying C API library that the current thread will be using the library's services.

Protected Member Functions

bool connect_prepare ()
 Does things common to both connect() overloads, before each go and establish the connection in their different ways.
bool set_option_impl (Option *o)
 Common implementation of set_option(Option*) and the delayed option setting code in connect_prepare().

Detailed Description

Provides a thin abstraction layer over the underlying database client library.

This class does as little as possible to adapt between its public interface and the interface required by the underlying C API. That is, in fact, its only mission. The high-level interfaces indended for use by Libtabula users are in Connection, Query, Result, and ResUse, all of which delegate the actual database communication to an object of this type, created by Connection. If you really need access to the low-level database driver, get it via Connection::driver(); don't create DBDriver objects directly.

Currently this is a concrete class for wrapping the MySQL C API. In the future, it may be turned into an abstract base class, with subclasses for different database server types.


Member Enumeration Documentation

Result code returned by next_result().

Enumerator:
nr_more_results 

success, with more results to come

nr_last_result 

success, last result received

nr_error 

problem retrieving next result

nr_not_supported 

this C API doesn't support "next result"


Constructor & Destructor Documentation

libtabula::DBDriver::DBDriver ( const DBDriver other  ) 

Duplicate an existing driver.

Parameters:
other existing DBDriver object

This establishes a new database server connection with the same parameters as the other driver's.

References copy().


Member Function Documentation

ulonglong libtabula::DBDriver::affected_rows (  )  [inline]

Return the number of rows affected by the last query.

Wraps mysql_affected_rows() in the MySQL C API.

Referenced by libtabula::Query::affected_rows().

std::string libtabula::DBDriver::client_version (  )  const [inline]

Get database client library version.

Wraps mysql_get_client_info() in the MySQL C API.

Referenced by libtabula::Connection::client_version(), and set_option_impl().

bool libtabula::DBDriver::connect ( const char *  host,
const char *  socket_name,
unsigned int  port,
const char *  db,
const char *  user,
const char *  password 
) [virtual]

Connect to database server.

If you call this method on an object that is already connected to a database server, the previous connection is dropped and a new connection is established.

References connect_prepare().

bool libtabula::DBDriver::connect ( const MYSQL &  mysql  ) 

Establish a new connection using the same parameters as an existing connection.

Parameters:
mysql existing MySQL C API connection object

References connect_prepare().

Referenced by libtabula::Connection::connect(), and copy().

bool libtabula::DBDriver::connected (  )  const [inline]

Return true if we have an active connection to the database server.

This does not actually check whether the connection is viable, it just indicates whether there was previously a successful connect() call and no disconnect(). Call ping() to actually test the connection's viability.

Referenced by connect_prepare(), libtabula::Connection::connected(), copy(), set_option(), and ~DBDriver().

void libtabula::DBDriver::copy ( const DBDriver other  ) 

Establish a new connection as a copy of an existing one.

Parameters:
other the connection to copy

References connect(), and connected().

Referenced by libtabula::Connection::copy(), and DBDriver().

bool libtabula::DBDriver::create_db ( const char *  db  )  const

Ask the database server to create a database.

Parameters:
db name of database to create
Returns:
true if database was created successfully
void libtabula::DBDriver::data_seek ( MYSQL_RES *  res,
ulonglong  offset 
) const [inline]

Seeks to a particualr row within the result set.

Wraps mysql_data_seek() in MySQL C API.

void libtabula::DBDriver::disconnect (  ) 

Drop the connection to the database server.

This method should only be used by Libtabula library internals. Unless you use the default constructor, this object should always be connected.

Referenced by connect_prepare(), libtabula::Connection::disconnect(), and ~DBDriver().

bool libtabula::DBDriver::drop_db ( const std::string &  db  )  const

Drop a database.

Parameters:
db name of database to destroy
Returns:
true if database was created successfully
bool libtabula::DBDriver::enable_ssl ( const char *  key = 0,
const char *  cert = 0,
const char *  ca = 0,
const char *  capath = 0,
const char *  cipher = 0 
)

Enable SSL-encrypted connection.

Parameters:
key the pathname to the key file
cert the pathname to the certificate file
ca the pathname to the certificate authority file
capath directory that contains trusted SSL CA certificates in pem format.
cipher list of allowable ciphers to use
Returns:
False if call fails or the C API library wasn't compiled with SSL support enabled.

Must be called before connection is established.

Wraps mysql_ssl_set() in MySQL C API.

int libtabula::DBDriver::errnum (  )  [inline]

Return last MySQL error number associated with this connection.

Wraps mysql_errno() in the MySQL C API.

Referenced by libtabula::Connection::errnum().

const char* libtabula::DBDriver::error (  )  [inline]

Return error message for last MySQL error associated with this connection.

Can return a Libtabula DBDriver-specific error message if there is one. If not, it simply wraps mysql_error() in the MySQL C API.

Referenced by libtabula::Connection::error(), and libtabula::Connection::set_option().

size_t libtabula::DBDriver::escape_string ( std::string *  ps,
const char *  original,
size_t  length 
)

Return a SQL-escaped version of a character buffer.

Parameters:
ps pointer to C++ string to hold escaped version; if original is 0, also holds the original data to be escaped
original if given, pointer to the character buffer to escape instead of contents of *ps
length if both this and original are given, number of characters to escape instead of ps->length()
Return values:
number of characters placed in *ps

This method has three basic operation modes:

  • Pass just a pointer to a C++ string containing the original data to escape, plus act as receptacle for escaped version
  • Pass a pointer to a C++ string to receive escaped string plus a pointer to a C string to be escaped
  • Pass nonzero for all parameters, taking original to be a pointer to an array of char with given length; does not treat null characters as special

There's a degenerate fourth mode, where ps is zero: simply returns 0, because there is nowhere to store the result.

Note that if original is 0, we always ignore the length parameter even if it is nonzero. Length always comes from ps->length() in this case.

ps is a pointer because if it were a reference, the other overload would be impossible to call: the compiler would complain that the two overloads are ambiguous because std::string has a char* conversion ctor. A nice bonus is that pointer syntax makes it clearer that the first parameter is an "out" parameter.

See also:
comments for escape_string(char*, const char*, size_t) for further details.
escape_string_no_conn(std::string*, const char*, size_t)

References escape_string().

size_t libtabula::DBDriver::escape_string ( char *  to,
const char *  from,
size_t  length 
) [inline]

Return a SQL-escaped version of the given character buffer.

Parameters:
to character buffer to hold escaped version; must point to at least (length * 2 + 1) bytes
from pointer to the character buffer to escape
length number of characters to escape
Return values:
number of characters placed in escaped

Wraps mysql_real_escape_string() in the MySQL C API.

Proper SQL escaping takes the database's current character set into account, however if a database connection isn't available DBDriver also provides a static version of this same method.

See also:
escape_string_no_conn(char*, const char*, size_t)

Referenced by libtabula::SQLStream::escape_string(), libtabula::Query::escape_string(), and escape_string().

size_t libtabula::DBDriver::escape_string_no_conn ( std::string *  ps,
const char *  original = 0,
size_t  length = 0 
) [static]

SQL-escapes the given string without reference to the character set of a database server.

See also:
escape_string(std::string*, const char*, size_t), escape_string_no_conn(char*, const char*, size_t)

References escape_string_no_conn().

static size_t libtabula::DBDriver::escape_string_no_conn ( char *  to,
const char *  from,
size_t  length 
) [inline, static]

SQL-escapes the given string without reference to the character set of a database server.

Wraps mysql_escape_string() in the MySQL C API.

See also:
escape_string(char*, const char*, size_t)

Referenced by libtabula::SQLStream::escape_string(), libtabula::Query::escape_string(), and escape_string_no_conn().

bool libtabula::DBDriver::execute ( const char *  qstr,
size_t  length 
) [inline]

Executes the given query string.

Wraps mysql_real_query() in the MySQL C API.

Referenced by libtabula::Query::exec(), libtabula::Query::execute(), libtabula::Query::store(), and libtabula::Query::use().

MYSQL_FIELD* libtabula::DBDriver::fetch_field ( MYSQL_RES *  res,
size_t  i = UINT_MAX 
) const [inline]

Returns information about a particular field in a result set.

Parameters:
res result set to fetch field information for
i field number to fetch information for, if given

If i parameter is given, this call is like a combination of field_seek() followed by fetch_field() without the i parameter, which otherwise just iterates through the set of fields in the given result set.

Wraps mysql_fetch_field() and mysql_fetch_field_direct() in MySQL C API. (Which one it uses depends on i parameter.)

Referenced by libtabula::ResultBase::ResultBase().

const unsigned long* libtabula::DBDriver::fetch_lengths ( MYSQL_RES *  res  )  const [inline]

Returns the lengths of the fields in the current row from a "use" query.

Wraps mysql_fetch_lengths() in MySQL C API.

Referenced by libtabula::UseQueryResult::fetch_lengths(), and libtabula::StoreQueryResult::StoreQueryResult().

MYSQL_ROW libtabula::DBDriver::fetch_row ( MYSQL_RES *  res  )  const [inline]

Returns the next raw C API row structure from the given result set.

This is for "use" query result sets only. "store" queries have all the rows already.

Wraps mysql_fetch_row() in MySQL C API.

Referenced by libtabula::UseQueryResult::fetch_raw_row(), libtabula::UseQueryResult::fetch_row(), and libtabula::StoreQueryResult::StoreQueryResult().

void libtabula::DBDriver::field_seek ( MYSQL_RES *  res,
size_t  field 
) const [inline]

Jumps to the given field within the result set.

Wraps mysql_field_seek() in MySQL C API.

Referenced by libtabula::ResultBase::ResultBase().

void libtabula::DBDriver::free_result ( MYSQL_RES *  res  )  const [inline]

Releases memory used by a result set.

Wraps mysql_free_result() in MySQL C API.

Referenced by libtabula::StoreQueryResult::StoreQueryResult().

ulonglong libtabula::DBDriver::insert_id (  )  [inline]

Get ID generated for an AUTO_INCREMENT column in the previous INSERT query.

Return values:
0 if the previous query did not generate an ID. Use the SQL function LAST_INSERT_ID() if you need the last ID generated by any query, not just the previous one. This applies to stored procedure calls because this function returns the ID generated by the last query, which was a CALL statement, and CALL doesn't generate IDs. You need to use LAST_INSERT_ID() to get the ID in this case.

Referenced by libtabula::Query::insert_id().

std::string libtabula::DBDriver::ipc_info (  )  [inline]

Get information about the IPC connection to the database server.

String contains info about type of connection (e.g. TCP/IP, named pipe, Unix socket...) and the server hostname.

Wraps mysql_get_host_info() in the MySQL C API.

Referenced by libtabula::Connection::ipc_info().

bool libtabula::DBDriver::kill ( unsigned long  tid  )  [inline]

Kill a MySQL server thread.

Parameters:
tid ID of thread to kill

Wraps mysql_kill() in the MySQL C API.

See also:
thread_id()

Referenced by libtabula::Connection::kill().

bool libtabula::DBDriver::more_results (  )  [inline]

Returns true if there are unconsumed results from the most recent query.

Wraps mysql_more_results() in the MySQL C API.

Referenced by libtabula::Query::more_results().

nr_code libtabula::DBDriver::next_result (  )  [inline]

Moves to the next result set from a multi-query.

Returns:
A code indicating whether we successfully found another result, there were no more results (but still success) or encountered an error trying to find the next result set.

Wraps mysql_next_result() in the MySQL C API, with translation of its return value from magic integers to nr_code enum values.

Referenced by libtabula::Query::store_next().

int libtabula::DBDriver::num_fields ( MYSQL_RES *  res  )  const [inline]

Returns the number of fields in the given result set.

Wraps mysql_num_fields() in MySQL C API.

ulonglong libtabula::DBDriver::num_rows ( MYSQL_RES *  res  )  const [inline]

Returns the number of rows in the given result set.

Wraps mysql_num_rows() in MySQL C API.

bool libtabula::DBDriver::ping (  )  [inline]

"Pings" the MySQL database

This function will try to reconnect to the server if the connection has been dropped. Wraps mysql_ping() in the MySQL C API.

Return values:
true if server is responding, regardless of whether we had to reconnect or not
false if either we already know the connection is down and cannot re-establish it, or if the server did not respond to the ping and we could not re-establish the connection.

Referenced by libtabula::Connection::ping().

int libtabula::DBDriver::protocol_version (  )  [inline]

Returns version number of MySQL protocol this connection is using.

Wraps mysql_get_proto_info() in the MySQL C API.

Referenced by libtabula::Connection::protocol_version().

string libtabula::DBDriver::query_info (  ) 

Returns information about the last executed query.

Wraps mysql_info() in the MySQL C API

Referenced by libtabula::Query::info().

bool libtabula::DBDriver::refresh ( unsigned  options  )  [inline]

Asks the database server to refresh certain internal data structures.

Wraps mysql_refresh() in the MySQL C API. There is no corresponding interface for this in higher level Libtabula classes because it was undocumented until recently, and it's a pretty low-level thing. It's designed for things like MySQL Administrator.

bool libtabula::DBDriver::result_empty (  )  [inline]

Returns true if the most recent result set was empty.

Wraps mysql_field_count() in the MySQL C API, returning true if it returns 0.

Referenced by libtabula::Query::result_empty().

std::string libtabula::DBDriver::server_status (  )  [inline]

Returns the database server's status.

String is similar to that returned by the mysqladmin status command. Among other things, it contains uptime in seconds, and the number of running threads, questions and open tables.

Wraps mysql_stat() in the MySQL C API.

Referenced by libtabula::Connection::server_status().

std::string libtabula::DBDriver::server_version (  )  [inline]

Get the database server's version number.

Wraps mysql_get_server_info() in the MySQL C API.

Referenced by libtabula::Connection::server_version().

bool libtabula::DBDriver::set_option ( unsigned int  option,
bool  arg 
)

Set MySQL C API connection option.

Manipulates the MYSQL.client_flag bit mask. This allows these flags to be treated the same way as any other connection option, even though the C API handles them differently.

bool libtabula::DBDriver::set_option ( Option o  ) 

Sets a connection option.

This is the database-independent high-level option setting interface that Connection::set_option() calls. There are several private overloads that actually implement the option setting.

See also:
Connection::set_option(Option*) for commentary

References connected(), and set_option_impl().

Referenced by libtabula::Connection::set_option().

bool libtabula::DBDriver::shutdown (  ) 

Ask database server to shut down.

User must have the "shutdown" privilege.

Wraps mysql_shutdown() in the MySQL C API.

Referenced by libtabula::Connection::shutdown().

MYSQL_RES* libtabula::DBDriver::store_result (  )  [inline]

Saves the results of the query just execute()d in memory and returns a pointer to the MySQL C API data structure the results are stored in.

See also:
use_result()

Wraps mysql_store_result() in the MySQL C API.

Referenced by libtabula::Query::store(), and libtabula::Query::store_next().

bool libtabula::DBDriver::thread_aware (  )  [static]

Returns true if Libtabula and the underlying MySQL C API library were both compiled with thread awareness.

This is based in part on a MySQL C API function mysql_thread_safe(). We deliberately don't call this wrapper thread_safe() because it's a misleading name: linking to thread-aware versions of the Libtabula and C API libraries doesn't automatically make your program "thread-safe". See the chapter on threads in the user manual for more information and guidance.

static void libtabula::DBDriver::thread_end (  )  [inline, static]

Tells the underlying MySQL C API library that this thread is done using the library.

This exists because the MySQL C API library allocates some per-thread memory which it doesn't release until you call this.

unsigned long libtabula::DBDriver::thread_id (  )  [inline]

Returns the MySQL server thread ID for this connection.

This has nothing to do with threading on the client side. It's a server-side thread ID, to be used with kill().

Referenced by libtabula::Connection::thread_id().

static bool libtabula::DBDriver::thread_start (  )  [inline, static]

Tells the underlying C API library that the current thread will be using the library's services.

Return values:
True if there was no problem

The Libtabula user manual's chapter on threads details two major strategies for dealing with connections in the face of threads. If you take the simpler path, creating one DBDriver object per thread, it is never necessary to call this function; the underlying C API will call it for you when you establish the first database server connection from that thread. If you use a more complex connection management strategy where it's possible for one thread to establish a connection that another thread uses, you must call this from each thread that can use the database before it creates any Libtabula objects. If you use a DBDriverPool object, this applies; DBDriverPool isn't smart enough to call this for you, and the MySQL C API won't do it, either.

MYSQL_RES* libtabula::DBDriver::use_result (  )  [inline]

Returns a result set from the last-executed query which we can walk through in linear fashion, which doesn't store all result sets in memory.

See also:
store_result

Wraps mysql_use_result() in the MySQL C API.

Referenced by libtabula::Query::use().


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

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