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mariadb/storage/example/ha_example.cc
Sergei Golubchik 98a39b0c91 Merge branch '10.4' into 10.5
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/* Copyright (c) 2004, 2013, Oracle and/or its affiliates.
Copyright (c) 2010, 2014, SkySQL Ab.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
/**
@file ha_example.cc
@brief
The ha_example engine is a stubbed storage engine for example purposes only;
it does almost nothing at this point. Its purpose is to provide a source
code illustration of how to begin writing new storage engines; see also
storage/example/ha_example.h.
Additionally, this file includes an example of a daemon plugin which does
nothing at all - absolutely nothing, even less than example storage engine.
But it shows that one dll/so can contain more than one plugin.
@details
ha_example will let you create/open/delete tables, but
nothing further (for example, indexes are not supported nor can data
be stored in the table). It also provides new status (example_func_example)
and system (example_ulong_var and example_enum_var) variables.
Use this example as a template for implementing the same functionality in
your own storage engine. You can enable the example storage engine in your
build by doing the following during your build process:<br> ./configure
--with-example-storage-engine
Once this is done, MySQL will let you create tables with:<br>
CREATE TABLE <table name> (...) ENGINE=EXAMPLE;
The example storage engine is set up to use table locks. It
implements an example "SHARE" that is inserted into a hash by table
name. You can use this to store information of state that any
example handler object will be able to see when it is using that
table.
Please read the object definition in ha_example.h before reading the rest
of this file.
@note
When you create an EXAMPLE table, the MySQL Server creates a table .frm
(format) file in the database directory, using the table name as the file
name as is customary with MySQL. No other files are created. To get an idea
of what occurs, here is an example select that would do a scan of an entire
table:
@code
ha_example::store_lock
ha_example::external_lock
ha_example::info
ha_example::rnd_init
ha_example::extra
ENUM HA_EXTRA_CACHE Cache record in HA_rrnd()
ha_example::rnd_next
ha_example::rnd_next
ha_example::rnd_next
ha_example::rnd_next
ha_example::rnd_next
ha_example::rnd_next
ha_example::rnd_next
ha_example::rnd_next
ha_example::rnd_next
ha_example::extra
ENUM HA_EXTRA_NO_CACHE End caching of records (def)
ha_example::external_lock
ha_example::extra
ENUM HA_EXTRA_RESET Reset database to after open
@endcode
Here you see that the example storage engine has 9 rows called before
rnd_next signals that it has reached the end of its data. Also note that
the table in question was already opened; had it not been open, a call to
ha_example::open() would also have been necessary. Calls to
ha_example::extra() are hints as to what will be occuring to the request.
A Longer Example can be found called the "Skeleton Engine" which can be
found on TangentOrg. It has both an engine and a full build environment
for building a pluggable storage engine.
Happy coding!<br>
-Brian
*/
#ifdef USE_PRAGMA_IMPLEMENTATION
#pragma implementation // gcc: Class implementation
#endif
#include <my_global.h>
#include <mysql/plugin.h>
#include "ha_example.h"
#include "sql_class.h"
static handler *example_create_handler(handlerton *hton,
TABLE_SHARE *table,
MEM_ROOT *mem_root);
handlerton *example_hton;
static MYSQL_THDVAR_ULONG(varopt_default, PLUGIN_VAR_RQCMDARG,
"default value of the VAROPT table option", NULL, NULL, 5, 0, 100, 0);
/**
Structure for CREATE TABLE options (table options).
It needs to be called ha_table_option_struct.
The option values can be specified in the CREATE TABLE at the end:
CREATE TABLE ( ... ) *here*
*/
struct ha_table_option_struct
{
const char *strparam;
ulonglong ullparam;
uint enumparam;
bool boolparam;
ulonglong varparam;
};
/**
Structure for CREATE TABLE options (field options).
It needs to be called ha_field_option_struct.
The option values can be specified in the CREATE TABLE per field:
CREATE TABLE ( field ... *here*, ... )
*/
struct ha_field_option_struct
{
const char *complex_param_to_parse_it_in_engine;
};
/*
no example here, but index options can be declared similarly
using the ha_index_option_struct structure.
Their values can be specified in the CREATE TABLE per index:
CREATE TABLE ( field ..., .., INDEX .... *here*, ... )
*/
ha_create_table_option example_table_option_list[]=
{
/*
one numeric option, with the default of UINT_MAX32, valid
range of values 0..UINT_MAX32, and a "block size" of 10
(any value must be divisible by 10).
*/
HA_TOPTION_NUMBER("ULL", ullparam, UINT_MAX32, 0, UINT_MAX32, 10),
/*
one option that takes an arbitrary string
*/
HA_TOPTION_STRING("STR", strparam),
/*
one enum option. a valid values are strings ONE and TWO.
A default value is 0, that is "one".
*/
HA_TOPTION_ENUM("one_or_two", enumparam, "one,two", 0),
/*
one boolean option, the valid values are YES/NO, ON/OFF, 1/0.
The default is 1, that is true, yes, on.
*/
HA_TOPTION_BOOL("YESNO", boolparam, 1),
/*
one option defined by the system variable. The type, the range, or
a list of allowed values is the same as for the system variable.
*/
HA_TOPTION_SYSVAR("VAROPT", varparam, varopt_default),
HA_TOPTION_END
};
ha_create_table_option example_field_option_list[]=
{
/*
If the engine wants something more complex than a string, number, enum,
or boolean - for example a list - it needs to specify the option
as a string and parse it internally.
*/
HA_FOPTION_STRING("COMPLEX", complex_param_to_parse_it_in_engine),
HA_FOPTION_END
};
/**
@brief
Function we use in the creation of our hash to get key.
*/
#ifdef HAVE_PSI_INTERFACE
static PSI_mutex_key ex_key_mutex_Example_share_mutex;
static PSI_mutex_info all_example_mutexes[]=
{
{ &ex_key_mutex_Example_share_mutex, "Example_share::mutex", 0}
};
static void init_example_psi_keys()
{
const char* category= "example";
int count;
count= array_elements(all_example_mutexes);
mysql_mutex_register(category, all_example_mutexes, count);
}
#else
static void init_example_psi_keys() { }
#endif
/**
@brief
If frm_error() is called then we will use this to determine
the file extensions that exist for the storage engine. This is also
used by the default rename_table and delete_table method in
handler.cc and by the default discover_many method.
For engines that have two file name extensions (separate meta/index file
and data file), the order of elements is relevant. First element of engine
file name extensions array should be meta/index file extention. Second
element - data file extention. This order is assumed by
prepare_for_repair() when REPAIR TABLE ... USE_FRM is issued.
@see
rename_table method in handler.cc and
delete_table method in handler.cc
*/
static const char *ha_example_exts[] = {
NullS
};
Example_share::Example_share()
{
thr_lock_init(&lock);
mysql_mutex_init(ex_key_mutex_Example_share_mutex,
&mutex, MY_MUTEX_INIT_FAST);
}
static int example_init_func(void *p)
{
DBUG_ENTER("example_init_func");
init_example_psi_keys();
example_hton= (handlerton *)p;
example_hton->create= example_create_handler;
example_hton->flags= HTON_CAN_RECREATE;
example_hton->table_options= example_table_option_list;
example_hton->field_options= example_field_option_list;
example_hton->tablefile_extensions= ha_example_exts;
example_hton->drop_table= [](handlerton *, const char*) { return -1; };
DBUG_RETURN(0);
}
/**
@brief
Example of simple lock controls. The "share" it creates is a
structure we will pass to each example handler. Do you have to have
one of these? Well, you have pieces that are used for locking, and
they are needed to function.
*/
Example_share *ha_example::get_share()
{
Example_share *tmp_share;
DBUG_ENTER("ha_example::get_share()");
lock_shared_ha_data();
if (!(tmp_share= static_cast<Example_share*>(get_ha_share_ptr())))
{
tmp_share= new Example_share;
if (!tmp_share)
goto err;
set_ha_share_ptr(static_cast<Handler_share*>(tmp_share));
}
err:
unlock_shared_ha_data();
DBUG_RETURN(tmp_share);
}
static handler* example_create_handler(handlerton *hton,
TABLE_SHARE *table,
MEM_ROOT *mem_root)
{
return new (mem_root) ha_example(hton, table);
}
ha_example::ha_example(handlerton *hton, TABLE_SHARE *table_arg)
:handler(hton, table_arg)
{}
/**
@brief
Used for opening tables. The name will be the name of the file.
@details
A table is opened when it needs to be opened; e.g. when a request comes in
for a SELECT on the table (tables are not open and closed for each request,
they are cached).
Called from handler.cc by handler::ha_open(). The server opens all tables by
calling ha_open() which then calls the handler specific open().
@see
handler::ha_open() in handler.cc
*/
int ha_example::open(const char *name, int mode, uint test_if_locked)
{
DBUG_ENTER("ha_example::open");
if (!(share = get_share()))
DBUG_RETURN(1);
thr_lock_data_init(&share->lock,&lock,NULL);
#ifndef DBUG_OFF
ha_table_option_struct *options= table->s->option_struct;
DBUG_ASSERT(options);
DBUG_PRINT("info", ("strparam: '%-.64s' ullparam: %llu enumparam: %u "\
"boolparam: %u",
(options->strparam ? options->strparam : "<NULL>"),
options->ullparam, options->enumparam, options->boolparam));
#endif
DBUG_RETURN(0);
}
/**
@brief
Closes a table.
@details
Called from sql_base.cc, sql_select.cc, and table.cc. In sql_select.cc it is
only used to close up temporary tables or during the process where a
temporary table is converted over to being a myisam table.
For sql_base.cc look at close_data_tables().
@see
sql_base.cc, sql_select.cc and table.cc
*/
int ha_example::close(void)
{
DBUG_ENTER("ha_example::close");
DBUG_RETURN(0);
}
/**
@brief
write_row() inserts a row. No extra() hint is given currently if a bulk load
is happening. buf() is a byte array of data. You can use the field
information to extract the data from the native byte array type.
@details
Example of this would be:
@code
for (Field **field=table->field ; *field ; field++)
{
...
}
@endcode
See ha_tina.cc for an example of extracting all of the data as strings.
ha_berekly.cc has an example of how to store it intact by "packing" it
for ha_berkeley's own native storage type.
See the note for update_row() on auto_increments and timestamps. This
case also applies to write_row().
Called from item_sum.cc, item_sum.cc, sql_acl.cc, sql_insert.cc,
sql_insert.cc, sql_select.cc, sql_table.cc, sql_udf.cc, and sql_update.cc.
@see
item_sum.cc, item_sum.cc, sql_acl.cc, sql_insert.cc,
sql_insert.cc, sql_select.cc, sql_table.cc, sql_udf.cc and sql_update.cc
*/
int ha_example::write_row(const uchar *buf)
{
DBUG_ENTER("ha_example::write_row");
/*
Example of a successful write_row. We don't store the data
anywhere; they are thrown away. A real implementation will
probably need to do something with 'buf'. We report a success
here, to pretend that the insert was successful.
*/
DBUG_RETURN(0);
}
/**
@brief
Yes, update_row() does what you expect, it updates a row. old_data will have
the previous row record in it, while new_data will have the newest data in it.
Keep in mind that the server can do updates based on ordering if an ORDER BY
clause was used. Consecutive ordering is not guaranteed.
@details
Currently new_data will not have an updated auto_increament record, or
and updated timestamp field. You can do these for example by doing:
@code
if (table->next_number_field && record == table->record[0])
update_auto_increment();
@endcode
Called from sql_select.cc, sql_acl.cc, sql_update.cc, and sql_insert.cc.
@see
sql_select.cc, sql_acl.cc, sql_update.cc and sql_insert.cc
*/
int ha_example::update_row(const uchar *old_data, const uchar *new_data)
{
DBUG_ENTER("ha_example::update_row");
DBUG_RETURN(HA_ERR_WRONG_COMMAND);
}
/**
@brief
This will delete a row. buf will contain a copy of the row to be deleted.
The server will call this right after the current row has been called (from
either a previous rnd_nexT() or index call).
@details
If you keep a pointer to the last row or can access a primary key it will
make doing the deletion quite a bit easier. Keep in mind that the server does
not guarantee consecutive deletions. ORDER BY clauses can be used.
Called in sql_acl.cc and sql_udf.cc to manage internal table
information. Called in sql_delete.cc, sql_insert.cc, and
sql_select.cc. In sql_select it is used for removing duplicates
while in insert it is used for REPLACE calls.
@see
sql_acl.cc, sql_udf.cc, sql_delete.cc, sql_insert.cc and sql_select.cc
*/
int ha_example::delete_row(const uchar *buf)
{
DBUG_ENTER("ha_example::delete_row");
DBUG_RETURN(HA_ERR_WRONG_COMMAND);
}
/**
@brief
Positions an index cursor to the index specified in the handle. Fetches the
row if available. If the key value is null, begin at the first key of the
index.
*/
int ha_example::index_read_map(uchar *buf, const uchar *key,
key_part_map keypart_map __attribute__((unused)),
enum ha_rkey_function find_flag
__attribute__((unused)))
{
int rc;
DBUG_ENTER("ha_example::index_read");
rc= HA_ERR_WRONG_COMMAND;
DBUG_RETURN(rc);
}
/**
@brief
Used to read forward through the index.
*/
int ha_example::index_next(uchar *buf)
{
int rc;
DBUG_ENTER("ha_example::index_next");
rc= HA_ERR_WRONG_COMMAND;
DBUG_RETURN(rc);
}
/**
@brief
Used to read backwards through the index.
*/
int ha_example::index_prev(uchar *buf)
{
int rc;
DBUG_ENTER("ha_example::index_prev");
rc= HA_ERR_WRONG_COMMAND;
DBUG_RETURN(rc);
}
/**
@brief
index_first() asks for the first key in the index.
@details
Called from opt_range.cc, opt_sum.cc, sql_handler.cc, and sql_select.cc.
@see
opt_range.cc, opt_sum.cc, sql_handler.cc and sql_select.cc
*/
int ha_example::index_first(uchar *buf)
{
int rc;
DBUG_ENTER("ha_example::index_first");
rc= HA_ERR_WRONG_COMMAND;
DBUG_RETURN(rc);
}
/**
@brief
index_last() asks for the last key in the index.
@details
Called from opt_range.cc, opt_sum.cc, sql_handler.cc, and sql_select.cc.
@see
opt_range.cc, opt_sum.cc, sql_handler.cc and sql_select.cc
*/
int ha_example::index_last(uchar *buf)
{
int rc;
DBUG_ENTER("ha_example::index_last");
rc= HA_ERR_WRONG_COMMAND;
DBUG_RETURN(rc);
}
/**
@brief
rnd_init() is called when the system wants the storage engine to do a table
scan. See the example in the introduction at the top of this file to see when
rnd_init() is called.
@details
Called from filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc,
and sql_update.cc.
@see
filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc and sql_update.cc
*/
int ha_example::rnd_init(bool scan)
{
DBUG_ENTER("ha_example::rnd_init");
DBUG_RETURN(0);
}
int ha_example::rnd_end()
{
DBUG_ENTER("ha_example::rnd_end");
DBUG_RETURN(0);
}
/**
@brief
This is called for each row of the table scan. When you run out of records
you should return HA_ERR_END_OF_FILE. Fill buff up with the row information.
The Field structure for the table is the key to getting data into buf
in a manner that will allow the server to understand it.
@details
Called from filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc,
and sql_update.cc.
@see
filesort.cc, records.cc, sql_handler.cc, sql_select.cc, sql_table.cc and sql_update.cc
*/
int ha_example::rnd_next(uchar *buf)
{
int rc;
DBUG_ENTER("ha_example::rnd_next");
rc= HA_ERR_END_OF_FILE;
DBUG_RETURN(rc);
}
/**
@brief
position() is called after each call to rnd_next() if the data needs
to be ordered. You can do something like the following to store
the position:
@code
my_store_ptr(ref, ref_length, current_position);
@endcode
@details
The server uses ref to store data. ref_length in the above case is
the size needed to store current_position. ref is just a byte array
that the server will maintain. If you are using offsets to mark rows, then
current_position should be the offset. If it is a primary key like in
BDB, then it needs to be a primary key.
Called from filesort.cc, sql_select.cc, sql_delete.cc, and sql_update.cc.
@see
filesort.cc, sql_select.cc, sql_delete.cc and sql_update.cc
*/
void ha_example::position(const uchar *record)
{
DBUG_ENTER("ha_example::position");
DBUG_VOID_RETURN;
}
/**
@brief
This is like rnd_next, but you are given a position to use
to determine the row. The position will be of the type that you stored in
ref. You can use ha_get_ptr(pos,ref_length) to retrieve whatever key
or position you saved when position() was called.
@details
Called from filesort.cc, records.cc, sql_insert.cc, sql_select.cc, and sql_update.cc.
@see
filesort.cc, records.cc, sql_insert.cc, sql_select.cc and sql_update.cc
*/
int ha_example::rnd_pos(uchar *buf, uchar *pos)
{
int rc;
DBUG_ENTER("ha_example::rnd_pos");
rc= HA_ERR_WRONG_COMMAND;
DBUG_RETURN(rc);
}
/**
@brief
::info() is used to return information to the optimizer. See my_base.h for
the complete description.
@details
Currently this table handler doesn't implement most of the fields really needed.
SHOW also makes use of this data.
You will probably want to have the following in your code:
@code
if (records < 2)
records = 2;
@endcode
The reason is that the server will optimize for cases of only a single
record. If, in a table scan, you don't know the number of records, it
will probably be better to set records to two so you can return as many
records as you need. Along with records, a few more variables you may wish
to set are:
records
deleted
data_file_length
index_file_length
delete_length
check_time
Take a look at the public variables in handler.h for more information.
Called in filesort.cc, ha_heap.cc, item_sum.cc, opt_sum.cc, sql_delete.cc,
sql_delete.cc, sql_derived.cc, sql_select.cc, sql_select.cc, sql_select.cc,
sql_select.cc, sql_select.cc, sql_show.cc, sql_show.cc, sql_show.cc, sql_show.cc,
sql_table.cc, sql_union.cc, and sql_update.cc.
@see
filesort.cc, ha_heap.cc, item_sum.cc, opt_sum.cc, sql_delete.cc, sql_delete.cc,
sql_derived.cc, sql_select.cc, sql_select.cc, sql_select.cc, sql_select.cc,
sql_select.cc, sql_show.cc, sql_show.cc, sql_show.cc, sql_show.cc, sql_table.cc,
sql_union.cc and sql_update.cc
*/
int ha_example::info(uint flag)
{
DBUG_ENTER("ha_example::info");
DBUG_RETURN(0);
}
/**
@brief
extra() is called whenever the server wishes to send a hint to
the storage engine. The myisam engine implements the most hints.
ha_innodb.cc has the most exhaustive list of these hints.
@see
ha_innodb.cc
*/
int ha_example::extra(enum ha_extra_function operation)
{
DBUG_ENTER("ha_example::extra");
DBUG_RETURN(0);
}
/**
@brief
Used to delete all rows in a table, including cases of truncate and cases where
the optimizer realizes that all rows will be removed as a result of an SQL statement.
@details
Called from item_sum.cc by Item_func_group_concat::clear(),
Item_sum_count_distinct::clear(), and Item_func_group_concat::clear().
Called from sql_delete.cc by mysql_delete().
Called from sql_select.cc by JOIN::reinit().
Called from sql_union.cc by st_select_lex_unit::exec().
@see
Item_func_group_concat::clear(), Item_sum_count_distinct::clear() and
Item_func_group_concat::clear() in item_sum.cc;
mysql_delete() in sql_delete.cc;
JOIN::reinit() in sql_select.cc and
st_select_lex_unit::exec() in sql_union.cc.
*/
int ha_example::delete_all_rows()
{
DBUG_ENTER("ha_example::delete_all_rows");
DBUG_RETURN(HA_ERR_WRONG_COMMAND);
}
/**
@brief
This create a lock on the table. If you are implementing a storage engine
that can handle transacations look at ha_berkely.cc to see how you will
want to go about doing this. Otherwise you should consider calling flock()
here. Hint: Read the section "locking functions for mysql" in lock.cc to understand
this.
@details
Called from lock.cc by lock_external() and unlock_external(). Also called
from sql_table.cc by copy_data_between_tables().
@see
lock.cc by lock_external() and unlock_external() in lock.cc;
the section "locking functions for mysql" in lock.cc;
copy_data_between_tables() in sql_table.cc.
*/
int ha_example::external_lock(THD *thd, int lock_type)
{
DBUG_ENTER("ha_example::external_lock");
DBUG_RETURN(0);
}
/**
@brief
The idea with handler::store_lock() is: The statement decides which locks
should be needed for the table. For updates/deletes/inserts we get WRITE
locks, for SELECT... we get read locks.
@details
Before adding the lock into the table lock handler (see thr_lock.c),
mysqld calls store lock with the requested locks. Store lock can now
modify a write lock to a read lock (or some other lock), ignore the
lock (if we don't want to use MySQL table locks at all), or add locks
for many tables (like we do when we are using a MERGE handler).
Berkeley DB, for example, changes all WRITE locks to TL_WRITE_ALLOW_WRITE
(which signals that we are doing WRITES, but are still allowing other
readers and writers).
When releasing locks, store_lock() is also called. In this case one
usually doesn't have to do anything.
In some exceptional cases MySQL may send a request for a TL_IGNORE;
This means that we are requesting the same lock as last time and this
should also be ignored. (This may happen when someone does a flush
table when we have opened a part of the tables, in which case mysqld
closes and reopens the tables and tries to get the same locks at last
time). In the future we will probably try to remove this.
Called from lock.cc by get_lock_data().
@note
In this method one should NEVER rely on table->in_use, it may, in fact,
refer to a different thread! (this happens if get_lock_data() is called
from mysql_lock_abort_for_thread() function)
@see
get_lock_data() in lock.cc
*/
THR_LOCK_DATA **ha_example::store_lock(THD *thd,
THR_LOCK_DATA **to,
enum thr_lock_type lock_type)
{
if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK)
lock.type=lock_type;
*to++= &lock;
return to;
}
/**
@brief
Used to delete a table. By the time delete_table() has been called all
opened references to this table will have been closed (and your globally
shared references released). The variable name will just be the name of
the table. You will need to remove any files you have created at this point.
@details
If you do not implement this, the default delete_table() is called from
handler.cc and it will delete all files with the file extensions returned
by bas_ext().
Called from handler.cc by delete_table and ha_create_table(). Only used
during create if the table_flag HA_DROP_BEFORE_CREATE was specified for
the storage engine.
@see
delete_table and ha_create_table() in handler.cc
*/
int ha_example::delete_table(const char *name)
{
DBUG_ENTER("ha_example::delete_table");
/* This is not implemented but we want someone to be able that it works. */
DBUG_RETURN(0);
}
/**
@brief
Given a starting key and an ending key, estimate the number of rows that
will exist between the two keys.
The handler can also optionally update the 'pages' parameter with the page
number that contains the min and max keys. This will help the optimizer
to know if two ranges are partly on the same pages and if the min and
max key are on the same page.
@details
end_key may be empty, in which case determine if start_key matches any rows.
Called from opt_range.cc by check_quick_keys().
@see
check_quick_keys() in opt_range.cc
*/
ha_rows ha_example::records_in_range(uint inx,
const key_range *min_key,
const key_range *max_key,
page_range *pages)
{
DBUG_ENTER("ha_example::records_in_range");
DBUG_RETURN(10); // low number to force index usage
}
/**
@brief
create() is called to create a database. The variable name will have the name
of the table.
@details
When create() is called you do not need to worry about
opening the table. Also, the .frm file will have already been
created so adjusting create_info is not necessary. You can overwrite
the .frm file at this point if you wish to change the table
definition, but there are no methods currently provided for doing
so.
Called from handle.cc by ha_create_table().
@see
ha_create_table() in handle.cc
*/
int ha_example::create(const char *name, TABLE *table_arg,
HA_CREATE_INFO *create_info)
{
#ifndef DBUG_OFF
ha_table_option_struct *options= table_arg->s->option_struct;
DBUG_ENTER("ha_example::create");
/*
This example shows how to support custom engine specific table and field
options.
*/
DBUG_ASSERT(options);
DBUG_PRINT("info", ("strparam: '%-.64s' ullparam: %llu enumparam: %u "\
"boolparam: %u",
(options->strparam ? options->strparam : "<NULL>"),
options->ullparam, options->enumparam, options->boolparam));
for (Field **field= table_arg->s->field; *field; field++)
{
ha_field_option_struct *field_options= (*field)->option_struct;
DBUG_ASSERT(field_options);
DBUG_PRINT("info", ("field: %s complex: '%-.64s'",
(*field)->field_name.str,
(field_options->complex_param_to_parse_it_in_engine ?
field_options->complex_param_to_parse_it_in_engine :
"<NULL>")));
}
#endif
DBUG_RETURN(0);
}
/**
check_if_supported_inplace_alter() is used to ask the engine whether
it can execute this ALTER TABLE statement in place or the server needs to
create a new table and copy th data over.
The engine may answer that the inplace alter is not supported or,
if supported, whether the server should protect the table from concurrent
accesses. Return values are
HA_ALTER_INPLACE_NOT_SUPPORTED
HA_ALTER_INPLACE_EXCLUSIVE_LOCK
HA_ALTER_INPLACE_SHARED_LOCK
etc
*/
enum_alter_inplace_result
ha_example::check_if_supported_inplace_alter(TABLE* altered_table,
Alter_inplace_info* ha_alter_info)
{
HA_CREATE_INFO *info= ha_alter_info->create_info;
DBUG_ENTER("ha_example::check_if_supported_inplace_alter");
if (ha_alter_info->handler_flags & ALTER_CHANGE_CREATE_OPTION)
{
/*
This example shows how custom engine specific table and field
options can be accessed from this function to be compared.
*/
ha_table_option_struct *param_new= info->option_struct;
ha_table_option_struct *param_old= table->s->option_struct;
/*
check important parameters:
for this example engine, we'll assume that changing ullparam or
boolparam requires a table to be rebuilt, while changing strparam
or enumparam - does not.
For debugging purposes we'll announce this to the user
(don't do it in production!)
*/
if (param_new->ullparam != param_old->ullparam)
{
push_warning_printf(ha_thd(), Sql_condition::WARN_LEVEL_NOTE,
ER_UNKNOWN_ERROR, "EXAMPLE DEBUG: ULL %llu -> %llu",
param_old->ullparam, param_new->ullparam);
DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
}
if (param_new->boolparam != param_old->boolparam)
{
push_warning_printf(ha_thd(), Sql_condition::WARN_LEVEL_NOTE,
ER_UNKNOWN_ERROR, "EXAMPLE DEBUG: YESNO %u -> %u",
param_old->boolparam, param_new->boolparam);
DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
}
}
if (ha_alter_info->handler_flags & ALTER_COLUMN_OPTION)
{
for (uint i= 0; i < table->s->fields; i++)
{
ha_field_option_struct *f_old= table->s->field[i]->option_struct;
ha_field_option_struct *f_new= info->fields_option_struct[i];
DBUG_ASSERT(f_old);
if (f_new)
{
push_warning_printf(ha_thd(), Sql_condition::WARN_LEVEL_NOTE,
ER_UNKNOWN_ERROR, "EXAMPLE DEBUG: Field %`s COMPLEX '%s' -> '%s'",
table->s->field[i]->field_name.str,
f_old->complex_param_to_parse_it_in_engine,
f_new->complex_param_to_parse_it_in_engine);
}
else
DBUG_PRINT("info", ("old field %i did not changed", i));
}
}
DBUG_RETURN(HA_ALTER_INPLACE_EXCLUSIVE_LOCK);
}
struct st_mysql_storage_engine example_storage_engine=
{ MYSQL_HANDLERTON_INTERFACE_VERSION };
static ulong srv_enum_var= 0;
static ulong srv_ulong_var= 0;
static double srv_double_var= 0;
const char *enum_var_names[]=
{
"e1", "e2", NullS
};
TYPELIB enum_var_typelib=
{
array_elements(enum_var_names) - 1, "enum_var_typelib",
enum_var_names, NULL
};
static MYSQL_SYSVAR_ENUM(
enum_var, // name
srv_enum_var, // varname
PLUGIN_VAR_RQCMDARG, // opt
"Sample ENUM system variable.", // comment
NULL, // check
NULL, // update
0, // def
&enum_var_typelib); // typelib
static MYSQL_THDVAR_INT(int_var, PLUGIN_VAR_RQCMDARG, "-1..1",
NULL, NULL, 0, -1, 1, 0);
static MYSQL_SYSVAR_ULONG(
ulong_var,
srv_ulong_var,
PLUGIN_VAR_RQCMDARG,
"0..1000",
NULL,
NULL,
8,
0,
1000,
0);
static MYSQL_SYSVAR_DOUBLE(
double_var,
srv_double_var,
PLUGIN_VAR_RQCMDARG,
"0.500000..1000.500000",
NULL,
NULL,
8.5,
0.5,
1000.5,
0); // reserved always 0
static MYSQL_THDVAR_DOUBLE(
double_thdvar,
PLUGIN_VAR_RQCMDARG,
"0.500000..1000.500000",
NULL,
NULL,
8.5,
0.5,
1000.5,
0);
static MYSQL_THDVAR_INT(
deprecated_var, PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_DEPRECATED, "-1..1",
NULL, NULL, 0, -1, 1, 0);
static struct st_mysql_sys_var* example_system_variables[]= {
MYSQL_SYSVAR(enum_var),
MYSQL_SYSVAR(ulong_var),
MYSQL_SYSVAR(int_var),
MYSQL_SYSVAR(double_var),
MYSQL_SYSVAR(double_thdvar),
MYSQL_SYSVAR(deprecated_var),
MYSQL_SYSVAR(varopt_default),
NULL
};
// this is an example of SHOW_SIMPLE_FUNC and of my_snprintf() service
// If this function would return an array, one should use SHOW_FUNC
static int show_func_example(MYSQL_THD thd, struct st_mysql_show_var *var,
char *buf)
{
var->type= SHOW_CHAR;
var->value= buf; // it's of SHOW_VAR_FUNC_BUFF_SIZE bytes
my_snprintf(buf, SHOW_VAR_FUNC_BUFF_SIZE,
"enum_var is %lu, ulong_var is %lu, int_var is %d, "
"double_var is %f, %.6b", // %b is a MySQL extension
srv_enum_var, srv_ulong_var, THDVAR(thd, int_var),
srv_double_var, "really");
return 0;
}
static struct st_mysql_show_var func_status[]=
{
{"func_example", (char *)show_func_example, SHOW_SIMPLE_FUNC},
{0,0,SHOW_UNDEF}
};
struct st_mysql_daemon unusable_example=
{ MYSQL_DAEMON_INTERFACE_VERSION };
maria_declare_plugin(example)
{
MYSQL_STORAGE_ENGINE_PLUGIN,
&example_storage_engine,
"EXAMPLE",
"Brian Aker, MySQL AB",
"Example storage engine",
PLUGIN_LICENSE_GPL,
example_init_func, /* Plugin Init */
NULL, /* Plugin Deinit */
0x0001, /* version number (0.1) */
func_status, /* status variables */
example_system_variables, /* system variables */
"0.1", /* string version */
MariaDB_PLUGIN_MATURITY_EXPERIMENTAL /* maturity */
},
{
MYSQL_DAEMON_PLUGIN,
&unusable_example,
"UNUSABLE",
"Sergei Golubchik",
"Unusable Daemon",
PLUGIN_LICENSE_GPL,
NULL, /* Plugin Init */
NULL, /* Plugin Deinit */
0x030E, /* version number (3.14) */
NULL, /* status variables */
NULL, /* system variables */
"3.14.15.926" , /* version, as a string */
MariaDB_PLUGIN_MATURITY_EXPERIMENTAL /* maturity */
}
maria_declare_plugin_end;
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