Release notes for the binary beta release of MDBMS 1.0
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WARNING:
This is beta software, and is not guaranteed to work. Although it is tested
thoroughly, it may still contain bugs. However, a server crash will most
likely leave the database intact, since the database system files are not
altered when a query is running. You are still advised to backup your data
often, by using the 'dumpdb' utility. This system has run many days under heavy
use without problems, but don't expect it to do the same thing on your machine.
COPYING:
This beta version of MDBMS is free and can be copied freely. It may be used
for all purposes, but remember that there are shortcomings, and that it is not
guaranteed to work. I cannot be held responsible for any loss in any way
resulting from the use of this software. Please send bug reports to
marty@hinttech.com
WHAT'S GOOD:
- rich SQL subset (including subselects, group by, multiple attribute keys,
foreign keys with automatic referential integrity (on delete cascade,..) )
- no configuration
- no directory filled with obscure system binaries, just launch 'db' and it's
ready
- easy web interface with the included MGEN cgi-bin
- small system requirements (About 1 Mb of diskspace and 4 MB RAM)
- full security with GRANT/REVOKE on SELECT, UPDATE, DELETE, INSERT, DROP
WHAT'S BAD (what am I working on):
- still working on speed improvements (syncing can be slow)
- current set of documentation
INSTALLATION:
Untar the file in a directory. The database system consists of:
- The database server 'db'.
- A set of utilities:
* dumpdb converts the contents of a database to SQL "insert" statements.
* getdb is a command line utility to read data from the database.
* todb is a utility to send the contents of a file to the database.
- The MGEN cgi-bin, which can be used to create dynamic HTML pages,
filled with data from the database.
- A C library to access the database from a C or C++ program.
STARTUP:
Executing db with the -h flag will show all command line flags available.
Start the database by typing 'db&'. There is no configuration nessecary.
The system files are expected to be in the current directory.
If no system files are found, they will be created. To completely destroy
the current databases, kill the server, remove the system files
(*.db *.map *.bin) and restart the server.
USING THE DATABASE:
The system opens TCP ports 2223 (human interface port) and 2224 (Fast Open
database Protocol port (FOP)).
Port 2223 implements an Ingres SQL-monitor like interface. Queries can be
entered at the '*' prompt. Multiple lines can be used to enter a query.
When ready, use '\g' to execute the query. Note that all SQL statements should
end with a semicolon (';'). If not, you'll get a parse error. Online help
is available by using the '\h <command>' option.
A summary of supported SQL statements is included in this document.
Port 2224 implements an easy ASCII based protocol, which is used by the
C-library and the 'mgen' cgi-bin. This protocol will be documented later.
Multiple connections can be established to the server. Every connection can
run their own queries without having to wait for other queries. Queries on
port 2224, which is used by client software run with twice the priority of
queries on port 2223.
The Meta data is stored in a database called 'system'. To access this data,
open the 'system' database by using the 'open system;' command. The following
tables can be found here:
'databases' : Contains a list of databases in the system. (worldreadable)
'tables' : Contains the tables in the system. (worldreadable)
'users' : Contains a list of users, for security features.
(Readable/writeable only for system user)
'storage' : Contains a list of low level files in use. Will be used later
to store more low level files with different page sizes.
(worldreadable)
'grants' : Contains a list of privileges granted to users (world readable)
Note that you should be careful with these tables. The system user has all
privileges on all tables, even the system tables.
STOPPING THE SERVER
To stop the server, simply kill it using the UNIX 'kill' command, or press
control-C if the server is running in the foreground.
The database will now continue running, until all requests have been handled.
After this, it will sync the system files and quit.
SECURITY
MDBMS offers security based on users. Initially there's only one user:the
user 'system', who has all prviliges and no password. The system user can
create other users with the 'create user' command. Passwords can be changed
with 'set pw=<password>'. Once a connection is established to the server,
it is assigned the anonymous user. You can switch to a different user with
the 'user' command.
Only the system user can create a database. When the 'authorization' option
of 'create database' is used, all privileges for this database are assigned
to the specified user. This user can then create tables in the database.
To allow other users to access data, the 'grant' command is used. For example:
to allow user 'marty' to select and to update a table called 'papers', you can
type: grant select,update on papers to marty;
The special user 'all' can be used to grant priviliges to all users (even to the
anonymous user). For example: To make table 'papers' world readable, you type:
grant select on papers to all.
SQL SUMMARY REFERENCE FOR MDBMS
MDBMS implements a rich subset of SQL. Not all of the SQL features are
included yet, but development will continue. Below is a summary of SQL
features which are included and a summary of features not yet included.
features included:
- creation of multiple databases, using 'create database' command.
- creation of tables using 'create table' command.
- primary keys, which may consist of multiple attributes.
- foreign keys, with CASCADE, SET NULL and RESTRICT rules.
- expressions can be used: 'select month*(salary+10)' or 'where salary-200>20'.
- the aggregate functions MIN, MAX, AVG, SUM and COUNT, which may contain
expressions: 'select avg(salary/12)'.
- NULL values and NOT NULL definitions.
- subselects by using IN and EXISTS operators.
- joins between tables, including table aliasing: 'select test.name from
employees test'.
- WHERE clause including boolean logic with AND, OR and NOT.
- GROUP BY clause (although HAVING is currently not supported)
- ORDER BY clause
- UPDATE statement
- DELETE statement
- DROP TABLE statement
- GRANT/REVOKE on SELECT, INSERT, DELETE, UPDATE, DROP with support for
WITH GRANT OPTION.
- HELP statement to view the structure of tables
- data types
integer : defined as the UNIX integer
float : defined as the UNIX double
money : defined as the UNIX double
char : defined as a single character
varchar(x): defined as an unlimited string; x is only used for the
table size on the human interface port. Clients using the
FOP port, will have access to the full string.
date : defined as either a time, a date or both. The UNIX time_t
definition is used internally, which limits this type to values
after January 1 1970.
features not yet included:
- distinct operator
- a HAVING clause
- table locking (this may cause problems when deleting data, while an other
query is fetching the data at the same time. Concurrent inserts are OK)
- no indices yet
- no views yet