Julian Lishev > WebTools-1.27 > DBD::WTSprite

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NAME ^

     DBD::WTSprite - 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.

        WTJSprite.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:WTSprite: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::WTSprite is a DBI extension module adding database emulation via flat-files to Perl's database-independent database interface. Unlike other DBD::modules, DBD::WTSprite 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::WTSprite 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 "WTJSprite.pm" (Jim Turner's Sprite). This was then merged in to DBI::DBD to produce what you are installing now. (DBD::WTSprite). WTJSprite.pm is included in this module as a separate file, and is required.

Many thanks go to Mr. Gurdavaram.

The main advantage of DBD::WTSprite 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::WTSprite 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::WTSprite 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::WTSprite attempts to do things in as database-independent manner as possible, but where differences occurr, WTJSprite most closely emmulates Oracle, for example "sequences/autonumbering". WTJSprite 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::WTSprite 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;
                
                $dbh = DBI->connect('DBI:WTSprite:mydb','me','mypassword') || 
                                die "Could not connect (".$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 WTJSprite;
                WTJSprite::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

        None

ERROR 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::WTSprite:

    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::WTSprite 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:WTSprite:mydatabase",'me','mypswd');
            my(@list) = $dbh->func('tables');

        WTJSprite::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 (WTJSprite(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::WTSprite 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::WTSprite 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::WTSprite ^

    Joins
        The current version of the module works with single table SELECTs
        only.  This will be a trick, since the underlying statement object 
        in WTJSprite 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 ^

        WTJSprite(3), DBI(3), perl(1)
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