This chapter describes a lot of things that you need to know when
working on the MySQL code. If you plan to contribute to MySQL
development, want to have access to the bleeding-edge in-between
versions code, or just want to keep track of development, follow the
instructions in section 2.3.4 Installing from the Development Source Tree.
If you are interested in MySQL internals, you should also subscribe
to our internals
mailing list. This list is relatively low
traffic. For details on how to subscribe, please see
section 1.6.1.1 The MySQL Mailing Lists.
All developers at MySQL AB are on the internals
list and we
help other people who are working on the MySQL code. Feel free to
use this list both to ask questions about the code and to send
patches that you would like to contribute to the MySQL project!
The MySQL server creates the following threads:
process_alarm()
to force timeouts on connections
that have been idle too long.
mysqld
is compiled with -DUSE_ALARM_THREAD
, a dedicated
thread that handles alarms is created. This is only used on some systems where
there are problems with sigwait()
or if one wants to use the
thr_alarm()
code in ones application without a dedicated signal
handling thread.
--flush_time=#
option, a dedicated thread is created
to flush all tables at the given interval.
INSERT DELAYED
gets its
own thread.
--master-host
, a slave replication thread will be
started to read and apply updates from the master.
mysqladmin processlist
only shows the connection, INSERT DELAYED
,
and replication threads.
Until recently, our main full-coverage test suite was based on proprietary
customer data and for that reason has not been publicly available. The only
publicly available part of our testing process consisted of the crash-me
test, a Perl DBI/DBD benchmark found in the sql-bench
directory, and
miscellaneous tests located in tests
directory. The lack of a
standardised publicly available test suite has made it difficult for our users,
as well developers, to do regression tests on the MySQL code. To
address this problem, we have created a new test system that is included in
the source and binary distributions starting in Version 3.23.29.
The current set of test cases doesn't test everything in MySQL, but it should catch most obvious bugs in the SQL processing code, OS/library issues, and is quite thorough in testing replication. Our eventual goal is to have the tests cover 100% of the code. We welcome contributions to our test suite. You may especially want to contribute tests that examine the functionality critical to your system, as this will ensure that all future MySQL releases will work well with your applications.
The test system consist of a test language interpreter
(mysqltest
), a shell script to run all
tests(mysql-test-run
), the actual test cases written in a special
test language, and their expected results. To run the test suite on
your system after a build, type make test
or
mysql-test/mysql-test-run
from the source root. If you have
installed a binary distribution, cd
to the install root
(eg. /usr/local/mysql
), and do scripts/mysql-test-run
.
All tests should succeed. If not, you should try to find out why and
report the problem if this is a bug in MySQL.
See section 12.1.2.3 Reporting Bugs in the MySQL Test Suite.
If you have a copy of mysqld
running on the machine where you want to
run the test suite you do not have to stop it, as long as it is not using
ports 9306
and 9307
. If one of those ports is taken, you should
edit mysql-test-run
and change the values of the master and/or slave
port to one that is available.
You can run one individual test case with
mysql-test/mysql-test-run test_name
.
If one test fails, you should test running mysql-test-run
with
the --force
option to check if any other tests fails.
You can use the mysqltest
language to write your own test cases.
Unfortunately, we have not yet written full documentation for it.
You can, however, look at our current test cases and use
them as an example. The following points should help you get started:
mysql-test/t/*.test
;
terminated statements and is similar to the
input of mysql
command-line client. A statement by default is a query
to be sent to MySQL server, unless it is recognised as internal
command (eg. sleep
).
SELECT
, SHOW
,
EXPLAIN
, etc., must be preceded with @/path/to/result/file
. The
file must contain the expected results. An easy way to generate the result
file is to run mysqltest -r < t/test-case-name.test
from
mysql-test
directory, and then edit the generated result files, if
needed, to adjust them to the expected output. In that case, be very careful
about not adding or deleting any invisible characters - make sure to only
change the text and/or delete lines. If you have to insert a line, make sure
the fields are separated with a hard tab, and there is a hard tab at the end.
You may want to use od -c
to make sure your text editor has not messed
anything up during edit. We, of course, hope that you will never have to edit
the output of mysqltest -r
as you only have to do it when you find a
bug.
mysql-test/r
directory and name them test_name.result
. If the
test produces more than one result, you should use test_name.a.result
,
test_name.b.result
, etc.
--error error-number
. The error number can be
a list of possible error numbers separated with ','
.
source include/master-slave.inc;
. To switch between
master and slave, use connection master;
and connection slave;
.
If you need to do something on an alternate connection, you can do
connection master1;
for the master, and connection slave1;
for
the slave.
let $1=1000; while ($1) { # do your queries here dec $1; }
sleep
command. It supports fractions
of a second, so you can do sleep 1.3;
, for example, to sleep 1.3
seconds.
mysql-test/t/test_name-slave.opt
. For
the master, put them in mysql-test/t/test_name-master.opt
.
If your MySQL version doesn't pass the test suite you should do the following:
mysqlbug
script
so that we can get information about your system and MySQL
version. See section 1.6.1.3 How to Report Bugs or Problems.
mysql-test-run
, as well as
contents of all .reject
files in mysql-test/r
directory.
cd mysql-test mysql-test-run --local test-nameIf this fails, then you should configure MySQL with
--with-debug
and run mysql-test-run
with the
--debug
option. If this also fails send the trace file
`var/tmp/master.trace' to ftp://support.mysql.com/pub/mysql/secret
so that we can examine it. Please remember to also include a full
description of your system, the version of the mysqld binary and how you
compiled it.
mysql-test-run
with the --force
option to
see if there is any other test that fails.
Result length mismatch
or Result
content mismatch
it means that the output of the test didn't match
exactly the expected output. This could be a bug in MySQL or
that your mysqld version produces slight different results under some
circumstances.
Failed test results are put in a file with the same base name as the
result file with the .reject
extension. If your test case is
failing, you should do a diff on the two files. If you cannot see how
they are different, examine both with od -c
and also check their
lengths.
mysql-test/var/log
directory for hints of what went wrong.
mysql-test-run
with the --gdb
and/or --debug
options.
See section E.1.2 Creating Trace Files.
If you have not compiled MySQL for debugging you should probably
do that. Just specify the --with-debug
options to configure
!
See section 2.3 Installing a MySQL Source Distribution.
There are two ways to add new functions to MySQL:
CREATE FUNCTION
and DROP FUNCTION
statements.
See section 12.2.1 CREATE FUNCTION/DROP FUNCTION
Syntax.
mysqld
server and become
available on a permanent basis.
Each method has advantages and disadvantages:
Whichever method you use to add new functions, they may be used just like
native functions such as ABS()
or SOUNDEX()
.
CREATE FUNCTION/DROP FUNCTION
SyntaxCREATE [AGGREGATE] FUNCTION function_name RETURNS {STRING|REAL|INTEGER} SONAME shared_library_name DROP FUNCTION function_name
A user-definable function (UDF) is a way to extend MySQL with a new
function that works like native (built in) MySQL function such as
ABS()
and CONCAT()
.
AGGREGATE
is a new option for MySQL Version 3.23. An
AGGREGATE
function works exactly like a native MySQL
GROUP
function like SUM
or COUNT()
.
CREATE FUNCTION
saves the function's name, type, and shared library
name in the mysql.func
system table. You must have the
INSERT
and DELETE
privileges for the mysql
database
to create and drop functions.
All active functions are reloaded each time the server starts, unless
you start mysqld
with the --skip-grant-tables
option. In
this case, UDF initialisation is skipped and UDFs are unavailable.
(An active function is one that has been loaded with CREATE FUNCTION
and not removed with DROP FUNCTION
.)
For instructions on writing user-definable functions, see section 12.2 Adding New Functions to MySQL. For the UDF mechanism to work, functions must be written in C or
C++, your operating system must support dynamic loading and you must have
compiled mysqld
dynamically (not statically).
Note that to make AGGREGATE
work, you must have a
mysql.func
table that contains the column type
. If you do not
have this table, you should run the script
mysql_fix_privilege_tables
to create it.
For the UDF mechanism to work, functions must be written in C or C++ and your operating system must support dynamic loading. The MySQL source distribution includes a file `sql/udf_example.cc' that defines 5 new functions. Consult this file to see how UDF calling conventions work.
For mysqld
to be able to use UDF functions, you should configure MySQL
with --with-mysqld-ldflags=-rdynamic
The reason is that to on
many platforms (including Linux) you can load a dynamic library (with
dlopen()
) from a static linked program, which you would get if
you are using --with-mysqld-ldflags=-all-static
If you want to
use an UDF that needs to access symbols from mysqld
(like the
metaphone
example in `sql/udf_example.cc' that uses
default_charset_info
), you must link the program with
-rdynamic
(see man dlopen
).
If you are using a precompiled version of the server, use MySQL-Max, which supports dynamic loading.
For each function that you want to use in SQL statements, you should define
corresponding C (or C++) functions. In the discussion below, the name
``xxx'' is used for an example function name. To distinguish between SQL and
C/C++ usage, XXX()
(uppercase) indicates an SQL function call, and
xxx()
(lowercase) indicates a C/C++ function call.
The C/C++ functions that you write to implement the interface for
XXX()
are:
xxx()
(required)
SQL type | C/C++ type |
STRING | char *
|
INTEGER | long long
|
REAL | double
|
xxx_init()
(optional)
xxx()
. It can be used to:
XXX()
.
REAL
functions) the maximum number of decimals.
NULL
.
xxx_deinit()
(optional)
xxx()
. It should deallocate any
memory allocated by the initialisation function.
When an SQL statement invokes XXX()
, MySQL calls the
initialisation function xxx_init()
to let it perform any required
setup, such as argument checking or memory allocation. If xxx_init()
returns an error, the SQL statement is aborted with an error message and the
main and deinitialisation functions are not called. Otherwise, the main
function xxx()
is called once for each row. After all rows have been
processed, the deinitialisation function xxx_deinit()
is called so it
can perform any required cleanup.
For aggregate functions (like SUM()
), you must also provide the
following functions:
xxx_reset()
(required)
xxx_add()
(required)
When using aggregate UDFs, MySQL works the following way:
xxx_init()
to let the aggregate function allocate the memory it
will need to store results.
GROUP BY
expression.
xxx_reset()
function.
xxx_add()
function.
xxx()
to get the result for the aggregate.
xxx_deinit()
to let the UDF free any memory it has allocated.
All functions must be thread-safe (not just the main function,
but the initialisation and deinitialisation functions as well). This means
that you are not allowed to allocate any global or static variables that
change! If you need memory, you should allocate it in xxx_init()
and free it in xxx_deinit()
.
The main function should be declared as shown here. Note that the return
type and parameters differ, depending on whether you will declare the SQL
function XXX()
to return STRING
, INTEGER
, or REAL
in the CREATE FUNCTION
statement:
For STRING
functions:
char *xxx(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long *length, char *is_null, char *error);
For INTEGER
functions:
long long xxx(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error);
For REAL
functions:
double xxx(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error);
The initialisation and deinitialisation functions are declared like this:
my_bool xxx_init(UDF_INIT *initid, UDF_ARGS *args, char *message); void xxx_deinit(UDF_INIT *initid);
The initid
parameter is passed to all three functions. It points to a
UDF_INIT
structure that is used to communicate information between
functions. The UDF_INIT
structure members are listed below. The
initialisation function should fill in any members that it wishes to change.
(To use the default for a member, leave it unchanged.):
my_bool maybe_null
xxx_init()
should set maybe_null
to 1
if xxx()
can return NULL
. The default value is 1
if any of the
arguments are declared maybe_null
.
unsigned int decimals
1.34
, 1.345
, and 1.3
, the default would be 3,
because 1.345
has 3 decimals.
unsigned int max_length
initid->decimals
. (For numeric functions, the length
includes any sign or decimal point characters.)
If you want to return a blob, you can set this to 65K or 16M; this
memory is not allocated but used to decide which column type to use if
there is a need to temporary store the data.
char *ptr
initid->ptr
to communicate allocated memory
between functions. In xxx_init()
, allocate the memory and assign it
to this pointer:
initid->ptr = allocated_memory;In
xxx()
and xxx_deinit()
, refer to initid->ptr
to use
or deallocate the memory.
Here follows a description of the different functions you need to define when you want to create an aggregate UDF function.
Note that the following function is NOT needed or used by MySQL 4.1.1. You can keep still have define his function if you want to have your code work with both MySQL 4.0 and MySQL 4.1.1
char *xxx_reset(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error);
This function is called when MySQL finds the first row in a new group. In the function you should reset any internal summary variables and then set the given argument as the first argument in the group.
In many cases this is implemented internally by reseting all variables
(for example by calling xxx_clear()
and then calling
xxx_add()
.
The following function is only required by MySQL 4.1.1 and above:
char *xxx_clear(UDF_INIT *initid, char *is_null, char *error);
This function is called when MySQL needs to reset the summary results.
This will be called at the beginning for each new group but can also be
called to reset the values for a query where there was no matching rows.
is_null
will be set to point to CHAR(0)
before calling
xxx_clear()
.
You can use the error
pointer to store a byte if something went
wrong .
char *xxx_add(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error);
This function is called for all rows that belongs to the same group, except for the first row. In this you should add the value in UDF_ARGS to your internal summary variable.
The xxx()
function should be declared identical as when you
define a simple UDF function. See section 12.2.2.1 UDF Calling Sequences for simple functions.
This function is called when all rows in the group has been processed.
You should normally never access the args
variable here but
return your value based on your internal summary variables.
All argument processing in xxx_reset()
and xxx_add()
should be done identically as for normal UDFs. See section 12.2.2.3 Argument Processing.
The return value handling in xxx()
should be done identically as
for a normal UDF. See section 12.2.2.4 Return Values and Error Handling.
The pointer argument to is_null
and error
is the same for
all calls to xxx_reset()
, xxx_clear()
, xxx_add()
and
xxx()
.
You can use this to remember that you got an error or if the xxx()
function should return NULL
. Note that you should not store a string
into *error
! This is just a 1 byte flag!
is_null
is reset for each group (before calling xxx_clear()
error
is never reset.
If isnull
or error
are set after xxx()
then MySQL
will return NULL
as the result for the group function.
The args
parameter points to a UDF_ARGS
structure that has the
members listed here:
unsigned int arg_count
if (args->arg_count != 2) { strcpy(message,"XXX() requires two arguments"); return 1; }
enum Item_result *arg_type
STRING_RESULT
, INT_RESULT
, and REAL_RESULT
.
To make sure that arguments are of a given type and return an
error if they are not, check the arg_type
array in the initialisation
function. For example:
if (args->arg_type[0] != STRING_RESULT || args->arg_type[1] != INT_RESULT) { strcpy(message,"XXX() requires a string and an integer"); return 1; }As an alternative to requiring your function's arguments to be of particular types, you can use the initialisation function to set the
arg_type
elements to the types you want. This causes MySQL to coerce
arguments to those types for each call to xxx()
. For example, to
specify coercion of the first two arguments to string and integer, do this in
xxx_init()
:
args->arg_type[0] = STRING_RESULT; args->arg_type[1] = INT_RESULT;
char **args
args->args
communicates information to the initialisation function
about the general nature of the arguments your function was called with. For a
constant argument i
, args->args[i]
points to the argument
value. (See below for instructions on how to access the value properly.)
For a non-constant argument, args->args[i]
is 0
.
A constant argument is an expression that uses only constants, such as
3
or 4*7-2
or SIN(3.14)
. A non-constant argument is an
expression that refers to values that may change from row to row, such as
column names or functions that are called with non-constant arguments.
For each invocation of the main function, args->args
contains the
actual arguments that are passed for the row currently being processed.
Functions can refer to an argument i
as follows:
STRING_RESULT
is given as a string pointer plus a
length, to allow handling of binary data or data of arbitrary length. The
string contents are available as args->args[i]
and the string length
is args->lengths[i]
. You should not assume that strings are
null-terminated.
INT_RESULT
, you must cast
args->args[i]
to a long long
value:
long long int_val; int_val = *((long long*) args->args[i]);
REAL_RESULT
, you must cast
args->args[i]
to a double
value:
double real_val; real_val = *((double*) args->args[i]);
unsigned long *lengths
lengths
array indicates the
maximum string length for each argument. You should not change these.
For each invocation of the main function, lengths
contains the
actual lengths of any string arguments that are passed for the row
currently being processed. For arguments of types INT_RESULT
or
REAL_RESULT
, lengths
still contains the maximum length of
the argument (as for the initialisation function).
The initialisation function should return 0
if no error occurred and
1
otherwise. If an error occurs, xxx_init()
should store a
null-terminated error message in the message
parameter. The message
will be returned to the client. The message buffer is
MYSQL_ERRMSG_SIZE
characters long, but you should try to keep the
message to less than 80 characters so that it fits the width of a standard
terminal screen.
The return value of the main function xxx()
is the function value, for
long long
and double
functions. A string functions should
return a pointer to the result and store the length of the string in the
length
arguments.
Set these to the contents and length of the return value. For example:
memcpy(result, "result string", 13); *length = 13;
The result
buffer that is passed to the calc function is 255 byte
big. If your result fits in this, you don't have to worry about memory
allocation for results.
If your string function needs to return a string longer than 255 bytes,
you must allocate the space for it with malloc()
in your
xxx_init()
function or your xxx()
function and free it in
your xxx_deinit()
function. You can store the allocated memory
in the ptr
slot in the UDF_INIT
structure for reuse by
future xxx()
calls. See section 12.2.2.1 UDF Calling Sequences for simple functions.
To indicate a return value of NULL
in the main function, set
is_null
to 1
:
*is_null = 1;
To indicate an error return in the main function, set the error
parameter to 1
:
*error = 1;
If xxx()
sets *error
to 1
for any row, the function
value is NULL
for the current row and for any subsequent rows
processed by the statement in which XXX()
was invoked. (xxx()
will not even be called for subsequent rows.) Note: in
MySQL versions prior to 3.22.10, you should set both *error
and *is_null
:
*error = 1; *is_null = 1;
Files implementing UDFs must be compiled and installed on the host where the server runs. This process is described below for the example UDF file `udf_example.cc' that is included in the MySQL source distribution. This file contains the following functions:
metaphon()
returns a metaphon string of the string argument.
This is something like a soundex string, but it's more tuned for English.
myfunc_double()
returns the sum of the ASCII values of the
characters in its arguments, divided by the sum of the length of its arguments.
myfunc_int()
returns the sum of the length of its arguments.
sequence([const int])
returns an sequence starting from the given
number or 1 if no number has been given.
lookup()
returns the IP number for a hostname.
reverse_lookup()
returns the hostname for an IP number.
The function may be called with a string "xxx.xxx.xxx.xxx"
or
four numbers.
A dynamically loadable file should be compiled as a sharable object file, using a command something like this:
shell> gcc -shared -o udf_example.so myfunc.cc
You can easily find out the correct compiler options for your system by running this command in the `sql' directory of your MySQL source tree:
shell> make udf_example.o
You should run a compile command similar to the one that make
displays,
except that you should remove the -c
option near the end of the line
and add -o udf_example.so
to the end of the line. (On some systems,
you may need to leave the -c
on the command.)
Once you compile a shared object containing UDFs, you must install it and
tell MySQL about it. Compiling a shared object from `udf_example.cc'
produces a file named something like `udf_example.so' (the exact name
may vary from platform to platform). Copy this file to some directory
searched by the dynamic linker ld
, such as `/usr/lib' or add the
directory in which you placed the shared object to the linker configuration
file (for example, `/etc/ld.so.conf').
On many systems, you can also set the LD_LIBRARY
or
LD_LIBRARY_PATH
environment variable to point at the directory where
you have your UDF function files. The dlopen
manual page tells you
which variable you should use on your system. You should set this in
mysql.server
or mysqld_safe
startup scripts and restart
mysqld
.
After the library is installed, notify mysqld
about the new
functions with these commands:
mysql> CREATE FUNCTION metaphon RETURNS STRING SONAME "udf_example.so"; mysql> CREATE FUNCTION myfunc_double RETURNS REAL SONAME "udf_example.so"; mysql> CREATE FUNCTION myfunc_int RETURNS INTEGER SONAME "udf_example.so"; mysql> CREATE FUNCTION lookup RETURNS STRING SONAME "udf_example.so"; mysql> CREATE FUNCTION reverse_lookup -> RETURNS STRING SONAME "udf_example.so"; mysql> CREATE AGGREGATE FUNCTION avgcost -> RETURNS REAL SONAME "udf_example.so";
Functions can be deleted using DROP FUNCTION
:
mysql> DROP FUNCTION metaphon; mysql> DROP FUNCTION myfunc_double; mysql> DROP FUNCTION myfunc_int; mysql> DROP FUNCTION lookup; mysql> DROP FUNCTION reverse_lookup; mysql> DROP FUNCTION avgcost;
The CREATE FUNCTION
and DROP FUNCTION
statements update the
system table func
in the mysql
database. The function's name,
type and shared library name are saved in the table. You must have the
INSERT
and DELETE
privileges for the mysql
database
to create and drop functions.
You should not use CREATE FUNCTION
to add a function that has already
been created. If you need to reinstall a function, you should remove it with
DROP FUNCTION
and then reinstall it with CREATE FUNCTION
. You
would need to do this, for example, if you recompile a new version of your
function, so that mysqld
gets the new version. Otherwise, the server
will continue to use the old version.
Active functions are reloaded each time the server starts, unless you start
mysqld
with the --skip-grant-tables
option. In this case, UDF
initialisation is skipped and UDFs are unavailable. (An active function is
one that has been loaded with CREATE FUNCTION
and not removed with
DROP FUNCTION
.)
The procedure for adding a new native function is described here. Note that you cannot add native functions to a binary distribution because the procedure involves modifying MySQL source code. You must compile MySQL yourself from a source distribution. Also note that if you migrate to another version of MySQL (for example, when a new version is released), you will need to repeat the procedure with the new version.
To add a new native MySQL function, follow these steps:
sql_functions[]
array.
sql_functions[]
array and add a function that creates a function
object in `item_create.cc'. Take a look at "ABS"
and
create_funcs_abs()
for an example of this.
If the function prototype is complicated (for example takes a variable number
of arguments), you should add two lines to `sql_yacc.yy'. One
indicates the preprocessor symbol that yacc
should define (this
should be added at the beginning of the file). Then define the function
parameters and add an ``item'' with these parameters to the
simple_expr
parsing rule. For an example, check all occurrences
of ATAN
in `sql_yacc.yy' to see how this is done.
Item_num_func
or
Item_str_func
, depending on whether your function returns a number or a
string.
double Item_func_newname::val() longlong Item_func_newname::val_int() String *Item_func_newname::Str(String *str)If you inherit your object from any of the standard items (like
Item_num_func
), you probably only have to define one of the above
functions and let the parent object take care of the other functions.
For example, the Item_str_func
class defines a val()
function
that executes atof()
on the value returned by ::str()
.
void Item_func_newname::fix_length_and_dec()This function should at least calculate
max_length
based on the
given arguments. max_length
is the maximum number of characters
the function may return. This function should also set maybe_null
= 0
if the main function can't return a NULL
value. The
function can check if any of the function arguments can return
NULL
by checking the arguments maybe_null
variable. You
can take a look at Item_func_mod::fix_length_and_dec
for a
typical example of how to do this.
All functions must be thread-safe (in other words, don't use any global or static variables in the functions without protecting them with mutexes).
If you want to return NULL
, from ::val()
, ::val_int()
or ::str()
you should set null_value
to 1 and return 0.
For ::str()
object functions, there are some additional
considerations to be aware of:
String *str
argument provides a string buffer that may be
used to hold the result. (For more information about the String
type,
take a look at the `sql_string.h' file.)
::str()
function should return the string that holds the result or
(char*) 0
if the result is NULL
.
In MySQL, you can define a procedure in C++ that can access and
modify the data in a query before it is sent to the client. The modification
can be done on row-by-row or GROUP BY
level.
We have created an example procedure in MySQL Version 3.23 to show you what can be done.
Additionally we recommend you to take a look at mylua
.
With this you can use the LUA language to load a procedure at
runtime into mysqld
.
analyse([max elements,[max memory]])
This procedure is defined in the `sql/sql_analyse.cc'. This examines the result from your query and returns an analysis of the results:
max elements
(default 256) is the maximum number of distinct values
analyse
will notice per column. This is used by analyse
to check if
the optimal column type should be of type ENUM
.
max memory
(default 8192) is the maximum memory analyse
should
allocate per column while trying to find all distinct values.
SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max elements,[max memory]])
For the moment, the only documentation for this is the source.
You can find all information about procedures by examining the following files:
Go to the first, previous, next, last section, table of contents.