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CONCEPT | |
mysql - mySQL support | |
DESCRIPTION | |
On hosts with the mySQL package installed, the driver can be | |
configured to interface with the mySQL database. If that is done, | |
the driver defines the macro __MYSQL__ for LPC programs and | |
activates a number of efuns. | |
-- Configuration -- | |
Create a dedicated user in the mySQL database for the driver. | |
Enter this username and password in the file pkg-mysql.c, function | |
mysql_real_connect(), and compile the driver (the username and | |
password are built into the driver for security reasons). If you | |
choose to not create either a username and/or a password, leave the | |
corresponding entry at 0. | |
Use mysqladmin to create any databases you want to provide - the | |
names are later used in the efun db_connect() to connect to | |
the databases. | |
-- Usage -- | |
The idea behind SQL-support is that you can swap large amounts of | |
data into a database where it can be accessed very easily. | |
As mySQL "limits" the number of connections to 100 and as every | |
connection to the mySQL-server takes time, you should use | |
database serverobjects in your MUD which constantly keep the | |
connection to the mySQL-server. | |
To connect to your mySQL-server, use the efun db_connect(). It | |
takes only one argument which is the name of the database (which | |
must exist). The return-value of db_connect() is an integer | |
representing the unique handle to the database with which you will | |
identify your connection later. | |
To send or retrieve data from this connection, use db_exec(). The | |
first parameter for all efuns dealing with an open connection is | |
always the handle and so is the first argument the handle and the | |
second one the command you want to issue. The return-value is | |
either 0 if there was an error in your command (this can have | |
various reasons), otherwise your handle is returned again. A typical | |
SQL-statement to retrieve data would be like this: | |
select aliases.command from aliases where (name = 'mario' AND | |
alias regexp 'l.*') | |
As you know, mySQL accepts either " or ' to classify strings for | |
parameters. Most likely, you will pass variables and don't know | |
whether they contain one or more of these key-chars (or even other | |
chars that need to be converted). mySQL provides a function for | |
converting just any string into an acceptable argument and this is | |
implemented in db_conv_string(). | |
So the above example with variables looks like this: | |
select aliases.command from aliases where (name ='"+ | |
db_conv_string(name)+"' AND alias regexp '"+ | |
db_conv_string(mask)+"') | |
I left out the db_exec()-stuff, more complete examples will follow. | |
After you initiated a statement that should return rows from the | |
database, use db_fetch() to retrieve the data. db_fetch() returns | |
the data row by row and not all at once. You need to call it until | |
it returns 0. THIS IS IMPORTANT! If stop calling db_fetch() before | |
it reaches the end of data, serious inconsistencies can happen. | |
If you used a DELETE- or UPDATE-statement, you cannot call db_fetch(), | |
but you might be interested in the number of deleted/changed rows | |
which can be queried with db_affected_rows(). | |
After all operations are done in the database, you should use | |
db_close() to close the connection again. If you are using a | |
database-server-concept, place it in the remove()-function. | |
The SQL-efuns have some built-in optimization-features to speed up | |
often used connections. To get a list of all open connections to the | |
mySQL-server, use db_handles() which returns an array of integers | |
with all open handles. | |
-- Security -- | |
Most SQL efuns (unless execute by the master or the simul-efun object) | |
trigger a privilege_violation ("mysql", "<efun_name>"). If a more | |
finegrained control is desired, overload the individual efuns with a | |
nomask simul-efun. | |
The unprivileged efuns are: | |
db_conv_string() | |
-- Caveats -- | |
The driver enables automatic reconnects on the database connections. | |
This means that if a connection is lost - the most common case for | |
this is timeouts, which by default happen after 28800 seconds of | |
inactivity - an attempt will be made to establish a new connection to | |
the database server. When that happens, all session state (temprary | |
tables and state changes from SET statements) will be lost. It's best | |
not to rely on such state. | |
EXAMPLE | |
A simple server to store aliases could be implemented like this: | |
/* | |
** CREATION: | |
** | |
** create table aliases ( | |
** name varchar(15) not NULL, | |
** alias varchar(20) not NULL, | |
** command varchar(255) not NULL, | |
** primary key (name, alias)); | |
*/ | |
#define DATABASE "mud" | |
private int handle; | |
public void create() | |
{ | |
handle = db_connect(DATABASE); | |
} | |
public int remove() | |
{ | |
if ( handle ) | |
db_close(handle); | |
destruct(ME); | |
return !ME; | |
} | |
public int AddAlias(string alias, string command, object ob) | |
{ | |
if ( !handle ) | |
handle = db_connect(DATABASE); | |
if ( !db_exec(handle, | |
"insert into aliases (name, alias, command) values " | |
"('" + getuid(ob) + "','" + db_conv_string(alias) | |
+ "','"+ | |
db_conv_string(command) + "')") ) | |
return -1; | |
return 1; | |
} | |
public int RemoveAlias(string alias, object ob) | |
{ | |
int res; | |
if ( !handle ) | |
handle = db_connect(DATABASE); | |
res = db_exec(handle, | |
"delete from aliases where (name = '"+ | |
getuid(ob) + "' AND alias = '" | |
+ db_conv_string(alias)+ | |
"')"); | |
if ( !res ) | |
return 0; | |
res = db_affected_rows(handle); | |
return (res > 0)?1:-1; | |
} | |
public mixed *QueryAliases(string mask, object ob) | |
{ | |
mixed *result; | |
string *tmp; | |
if ( !handle ) | |
handle = db_connect(DATABASE); | |
if ( !db_exec(handle, | |
"select aliases.alias, aliases.command from aliases where " | |
"(name = '" + getuid(ob)+ | |
"' AND alias regexp '" + db_conv_string(mask) + "')") ) | |
return ({ }); | |
result = ({ }); | |
while ( sizeof(tmp = db_fetch(handle)) ) | |
result += ({ tmp }); | |
return result; | |
} | |
public string QueryAlias(string alias, object ob) | |
{ | |
mixed *result; | |
string *tmp; | |
if ( !handle ) | |
handle = db_connect(DATABASE); | |
if ( !db_exec(handle, | |
"select aliases.command from aliases where " | |
"(name = '" + getuid(ob)+ | |
"' AND alias = '" + db_conv_string(alias) + "')") ) | |
return 0; | |
result = ({ }); | |
while ( sizeof(tmp = db_fetch(handle)) ) | |
result += tmp; | |
return sizeof(result)?result[0]:0; | |
} | |
AUTHOR | |
Mark Daniel Reidel and others. | |
HISTORY | |
mySQL support was added as a package in 3.2.8 and became and | |
integral driver part in 3.2.9. | |
LDMud 3.2.11 added a privilege_violation() call for each efun. | |
SEE ALSO | |
pgsql(C), db_affected_rows(E), db_conv_string(E), db_close(E), | |
db_connect(E), db_exec(E), db_fetch(E), db_handles(E), | |
db_insert_id(E), db_coldefs(E), db_error(E), privilege_violation(A) |