NAME
DBD::Sprite - Perl extension for DBI, providing database emmulation via flat files. AUTHOR
This module is Copyright (C) 2000 by
Jim Turner
Email: jim.turner@lmco.com
All rights reserved.
You may distribute this module under the terms of either the GNU General
Public License or the Artistic License, as specified in the Perl README
file.
JSprite.pm is a derived work by Jim Turner from Sprite.pm, a module
written and copyrighted (c) 1995-1998, by Shishir Gurdavaram
(shishir@ora.com).SYNOPSIS
use DBI;
$dbh = DBI->connect("DBI:Sprite:spritedb",'user','password')
or die "Cannot connect: " . $DBI::errstr;
$sth = $dbh->prepare("CREATE TABLE a (id INTEGER, name CHAR(10))")
or die "Cannot prepare: " . $dbh->errstr();
$sth->execute() or die "Cannot execute: " . $sth->errstr();
$sth->finish();
$dbh->disconnect();DESCRIPTION
DBD::Sprite is a DBI extension module adding database emulation via flat-files to Perl's database-independent database interface. Unlike other DBD::modules, DBD::Sprite does not require you to purchase or obtain a database. Every thing you need to prototype database-independent applications using Perl and DBI are included here. You will, however, probably wish to obtain a real database, such as "mysql", for your production and larger data needs. This is because emulating databases and SQL with flat text files gets very slow as the size of your "database" grows to a non-trivial size (a few dozen records or so per table).
DBD::Sprite is built upon an old Perl module called "Sprite", written by Shishir Gurdavaram. This code was used as a starting point. It was completly reworked and many new features were added, producing a module called "JSprite.pm" (Jim Turner's Sprite). This was then merged in to DBI::DBD to produce what you are installing now. (DBD::Sprite). JSprite.pm is included in this module as a separate file, and is required.
Many thanks go to Mr. Gurdavaram.
The main advantage of DBD::Sprite is the ability to develop and test prototype applications on personal machines (or other machines which do not have an Oracle licence or some other "mainstream" database) before releasing them on "production" machines which do have a "real" database. This can all be done with minimal or no changes to your Perl code.
Another advantage of DBD::Sprite is that you can use Perl's regular expressions to search through your data. Maybe, someday, more "real" databases will include this feature too!
DBD::Sprite provides the ability to emulate basic database tables and SQL calls via flat-files. The primary use envisioned for this to permit website developers who can not afford to purchase an Oracle licence to prototype and develop Perl applications on their own equipment for later hosting at larger customer sites where Oracle is used. :-)
DBD::Sprite attempts to do things in as database-independent manner as possible, but where differences occurr, JSprite most closely emmulates Oracle, for example "sequences/autonumbering". JSprite uses tiny one-line text files called "sequence files" (.seq). and "seq_file_name.NEXTVAL" function to insert into autonumbered fields. The reason for this is that the Author works in an Oracle shop and wrote this module to allow himself to work on code on his PC, and machines which did not have Oracle on them, since obtaining Oracle licences was sometimes time-consuming.
DBD::Sprite is similar to DBD::CSV, but differs in the following ways:
1) It creates and works on true "databases" with user-ids and passwords,
2) The database author specifies the field delimiters, record delimiters,
user, password, table file path, AND extension for each database.
3) Transactions (commits and rollbacks) are fully supported!
4) Autonumbering and user-defined functions are supported.
5) You don't need any other modules or databases. (NO prerequisites
except Perl 5 and the DBI module!
6) Quotes are not used around data.
7) It is not necessary to call the "$dbh->quote()" method all the time
in your sql.
8) NULL is handled as an empty string.
9) Users can "register" their own data-conversion functions for use in
sql. See "fn_register" method below.INSTALLATION
Installing this module (and the prerequisites from above) is quite
simple. You just fetch the archive, extract it with
gzip -cd DBD-Sprite-0.1000.tar.gz | tar xf -
(this is for Unix users, Windows users would prefer WinZip or something
similar) and then enter the following:
cd DBD-Sprite-#.###
perl Makefile.PL
make
make test
If any tests fail, let me know. Otherwise go on with
make install
Note that you almost definitely need root or administrator permissions.
If you don't have them, read the ExtUtils::MakeMaker man page for
details on installing in your own directories. the ExtUtils::MakeMaker
manpage.
NOTE: You may also need to copy "makesdb.pl" to /usr/local/bin or
somewhere in your path.GETTING STARTED:
1) cd to where you wish to store your database.
2) run makesdb.pl to create your database, ie.
Database name: mydb
Database user: me
User password: mypassword
Database path: .
Table file extension (default .stb):
Record delimiter (default \n):
Field delimiter (default ::):
This will create a new database text file (mydb.sdb) in the current
directory. This ascii file contains the information you enterred
above. To add additional user-spaces, simply rerun makesdb.pl with
"mydb" as your database name, and enter additional users (name,
password, path, extension, and delimiters). For an example, after
running "make test", look at the file "test.sdb".
When connecting to a Sprite database, Sprite will look in the current
directory, then, if specified, the path in the SPRITE_HOME environment
variable.
The database name, user, and password are used in the "db->connect()"
method described below. The "database path" is where your tables will
be created and reside. Table files are ascii text files which will
have, by default, the extension ".stb" (Sprite table). By default,
each record will be written to a single line (separated by \n --
Windows users should probably use "\r\n"). Each field datum will be
written without quotes separated by the "field delimiter (default:
double-colon). The first line of the table file consists of the
a field name, an equal ("=") sign, an asterisk if it is a key field,
then the datatype and size. This information is included for each
field and separated by the field separator. For an example, after
running "make test", look at the file "testtable.stb".
3) write your script to use DBI, ie:
#!/usr/bin/perl
use DBI;
$dbh = DBI->connect('DBI:Sprite:mydb','me','mypassword') ||
die "Could not connect (".$DBI->err.':'.$DBI->errstr.")!";
...
#CREATE A TABLE, INSERT SOME RECORDS, HAVE SOME FUN!
4) get your application working.
5) rehost your application on a "production" machine and change "Sprite"
to a DBI driver for a "real" database!CREATING AND DROPPING TABLES
You can create and drop tables with commands like the following:
$dbh->do("CREATE TABLE $table (id INTEGER, name CHAR(64))");
$dbh->do("DROP TABLE $table");
Note that currently only the column names will be stored and no other
data. Thus all other information including column type (INTEGER or
CHAR(x), for example), column attributes (NOT NULL, PRIMARY KEY, ...)
will silently be discarded. This may change in a later release.
A drop just removes the file without any warning.
See the DBI(3) manpage for more details.
Table names cannot be arbitrary, due to restrictions of the SQL syntax.
I recommend that table names are valid SQL identifiers: The first
character is alphabetic, followed by an arbitrary number of alphanumeric
characters. If you want to use other files, the file names must start
with '/', './' or '../' and they must not contain white space.INSERTING, FETCHING AND MODIFYING DATA
The following examples insert some data in a table and fetch it back:
First all data in the string:
$dbh->do("INSERT INTO $table VALUES (1, 'foobar')");
Note the use of the quote method for escaping the word 'foobar'. Any
string must be escaped, even if it doesn't contain binary data.
Next an example using parameters:
$dbh->do("INSERT INTO $table VALUES (?, ?)", undef,
2, "It's a string!");
To retrieve data, you can use the following:
my($query) = "SELECT * FROM $table WHERE id > 1 ORDER BY id";
my($sth) = $dbh->prepare($query);
$sth->execute();
while (my $row = $sth->fetchrow_hashref) {
print("Found result row: id = ", $row->{'id'},
", name = ", $row->{'name'});
}
$sth->finish();
Again, column binding works: The same example again.
my($query) = "SELECT * FROM $table WHERE id > 1 ORDER BY id";
my($sth) = $dbh->prepare($query);
$sth->execute();
my($id, $name);
$sth->bind_columns(undef, \$id, \$name);
while ($sth->fetch) {
print("Found result row: id = $id, name = $name\n");
}
$sth->finish();
Of course you can even use input parameters. Here's the same example for
the third time:
my($query) = "SELECT * FROM $table WHERE id = ?";
my($sth) = $dbh->prepare($query);
$sth->bind_columns(undef, \$id, \$name);
for (my($i) = 1; $i <= 2; $i++) {
$sth->execute($id);
if ($sth->fetch) {
print("Found result row: id = $id, name = $name\n");
}
$sth->finish();
}
See the DBI(3) manpage for details on these methods. See the
SQL::Statement(3) manpage for details on the WHERE clause.
Data rows are modified with the UPDATE statement:
$dbh->do("UPDATE $table SET id = 3 WHERE id = 1");
Likewise you use the DELETE statement for removing rows:
$dbh->do("DELETE FROM $table WHERE id > 1");fn_register
Method takes 2 arguments: Function name and optionally, a package name (default is "main").
$dbh->fn_register ('myfn','mypackage');
-or-
use JSprite;
JSprite::fn_register ('myfn',__PACKAGE__);Then, you could say in sql:
insert into mytable values (myfn(?))and bind some value to "?", which is passed to "myfn", and the return-value is inserted into the database. You could also say (without binding):
insert into mytable values (myfn('mystring'))-or (if the function takes a number)-
select field1, field2 from mytable where field3 = myfn(123) Return Value
NoneERROR HANDLING
In the above examples we have never cared about return codes. Of course,
this cannot be recommended. Instead we should have written (for
example):
my($query) = "SELECT * FROM $table WHERE id = ?";
my($sth) = $dbh->prepare($query)
or die "prepare: " . $dbh->errstr();
$sth->bind_columns(undef, \$id, \$name)
or die "bind_columns: " . $dbh->errstr();
for (my($i) = 1; $i <= 2; $i++) {
$sth->execute($id)
or die "execute: " . $dbh->errstr();
if ($sth->fetch) {
print("Found result row: id = $id, name = $name\n");
}
}
$sth->finish($id)
or die "finish: " . $dbh->errstr();
Obviously this is tedious. Fortunately we have DBI's *RaiseError*
attribute:
$dbh->{'RaiseError'} = 1;
$@ = '';
eval {
my($query) = "SELECT * FROM $table WHERE id = ?";
my($sth) = $dbh->prepare($query);
$sth->bind_columns(undef, \$id, \$name);
for (my($i) = 1; $i <= 2; $i++) {
$sth->execute($id);
if ($sth->fetch) {
print("Found result row: id = $id, name = $name\n");
}
}
$sth->finish($id);
};
if ($@) { die "SQL database error: $@"; }
This is not only shorter, it even works when using DBI methods within
subroutines.METADATA
The following attributes are handled by DBI itself and not by DBD::File,
thus they should all work as expected: I have only used the last 3.
Active
ActiveKids
CachedKids
CompatMode (Not used)
InactiveDestroy
Kids
PrintError
RaiseError
Warn
The following DBI attributes are handled by DBD::Sprite:
AutoCommit
Works
ChopBlanks
Should Work
NUM_OF_FIELDS
Valid after `$sth->execute'
NUM_OF_PARAMS
Valid after `$sth->prepare'
NAME
Valid after `$sth->execute'; undef for Non-Select statements.
NULLABLE
Not really working. Always returns an array ref of one's, as
DBD::Sprite always allows NULL (handled as an empty string).
Valid after `$sth->execute'.
PRECISION
Works
SCALE
Works
LongReadLen
Should work
LongTruncOk
Works
These attributes and methods are not supported:
bind_param_inout
CursorName
In addition to the DBI attributes, you can use the following dbh
attributes. These attributes are read-only after "connect".
sprite_dbdir
Path to tables for database.
sprite_dbext
File extension used on table files in the database.
sprite_dbuser
Current database user.
sprite_dbfdelim
Field delimiter string in use for the database.
sprite_dbrdelim
Record delimiter string in use for the database.
The following are environment variables specifically recognized by Sprite.
SPRITE_HOME
Environment variable specifying a path to search for Sprite
databases (*.sdb) files.
The following are Sprite-specific options which can be set when connecting.
sprite_CaseTableNames
By default, table names are case-insensitive (as they are in Oracle),
to make table names case-sensitive (as in MySql), so that one could
have two separate tables such as "test" and "TEST", set this option
to 1.
sprite_StrictCharComp (NEW!)
CHAR fields are always right-padded with spaces to fill out
the field. Old (pre 5.17) Sprite behaviour was to require the
padding be included in literals used for testing equality in
"where" clauses. I discovered that Oracle and some other databases
do not require this when testing DBIx-Recordset, so Sprite will
automatically right-pad literals when testing for equality.
To disable this and force the old behavior, set this option to 1.
DRIVER PRIVATE METHODS
DBI->data_sources()
The `data_sources' method returns a list of "databases" (.sdb files)
found in the current directory and, if specified, the path in
the SPRITE_HOME environment variable.
$dbh->tables()
This method returns a list of table names specified in the current
database.
Example:
my($dbh) = DBI->connect("DBI:Sprite:mydatabase",'me','mypswd');
my(@list) = $dbh->func('tables');
JSprite::fn_register ('myfn',__PACKAGE__);
This method takes the name of a user-defined data-conversion function
for use in SQL commands. Your function can optionally take arguments,
but should return a single number or string. Unless your function
is defined in package "main", you must also specify the package name
or "__PACKAGE__" for the current package. For an example, see the
section "INSERTING, FETCHING AND MODIFYING DATA" above or (JSprite(3)).
OTHER SUPPORTING UTILITIES
makesdb.pl
This utility lets you build new Sprite databases and later add
additional user-spaces to them. Simply cd to the directory where
you wish to create / modify a database, and run. It prompts as
follows:
Database name: Enter a 1-word name for your database.
Database user: Enter a 1-word user-name.
User password: Enter a 1-word password for this user.
Database path: Enter a path (no trailing backslash) to store tables.
Table file extension (default .stb):
Record delimiter (default \n):
Field delimiter (default ::):
The last 6 prompts repeat until you do not enter another user-name
allowing you to set up multiple users in a single database. Each
"user" can have it's own separate tables by specifying different
paths, file-extensions, password, and delimiters! You can invoke
"makesdb.pl" on an existing database to add new users. You can
edit it with vi to remove users, delete the 5 lines starting with
the path for that user. The file is all text, except for the
password, which is encrypted for your protection!
RESTRICTIONS
Although DBD::Sprite supports the following datatypes:
NUMBER FLOAT DOUBLE INT INTEGER NUM CHAR VARCHAR VARCHAR2
DATE LONG BLOB and MEMO, there are really only 3 basic datatypes
(NUMBER, CHAR, and VARCHAR). This is because Perl treates
everything as simple strings. The first 5 are all treated as "numbers"
by Perl for sorting purposes and the rest as strings. This is seen
when sorting, ie NUMERIC types sort as 1,5,10,40,200, whereas
STRING types sort these as 1,10,200,40,5. CHAR fields are right-
padded with spaces when stored. LONG-type fields are subject to
truncation by the "LongReadLen" attribute value.
DBD::Sprite works with the tieDBI module, if "Sprite => 1" lines are added
to the "%CAN_BIND" and "%CAN_BINDSELECT" hashes. This should not be
necessary, and I will investigate when I have time.TODO Extensions of DBD::Sprite
Joins
The current version of the module works with single table SELECTs
only. This will be a trick, since the underlying statement object
in JSprite is bound to a single file, I have some ideas and am
starting to seriously look into this. Stay tuned!
Additional Oracle-ish functions built-in. The currently-supported ones
are "SYSTIME", "NUM", and "NULL". "NUM" does nothing, "NULL" returns
an empty string. My first will probably be "TO_DATE".
Whatever Mr. Gurdavaram might wish to add.
KNOWN BUGS * The module is using flock() internally. However, this function is not available on platforms. Using flock() is disabled on MacOS and Windows 95: There's no locking at all (perhaps not so important on these operating systems, as they are for single users anyways).
SEE ALSO
JSprite(3), DBI(3), perl(1)