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raku-community-modules / DBIish

Database interface for Raku
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NAME

DBIish - a simple database interface for Raku

SYNOPSIS

use v6;
use DBIish;

my $dbh = DBIish.connect("SQLite", :database<example-db.sqlite3>);

$dbh.execute(q:to/STATEMENT/);
    DROP TABLE IF EXISTS nom
    STATEMENT

$dbh.execute(q:to/STATEMENT/);
    CREATE TABLE nom (
        name        varchar(4),
        description varchar(30),
        quantity    int,
        price       numeric(5,2)
    )
    STATEMENT

$dbh.execute(q:to/STATEMENT/);
    INSERT INTO nom (name, description, quantity, price)
    VALUES ( 'BUBH', 'Hot beef burrito', 1, 4.95 )
    STATEMENT

my $sth = $dbh.prepare(q:to/STATEMENT/);
    INSERT INTO nom (name, description, quantity, price)
    VALUES ( ?, ?, ?, ? )
    STATEMENT

$sth.execute('TAFM', 'Mild fish taco', 1, 4.85);
$sth.execute('BEOM', 'Medium size orange juice', 2, 1.20);

# For one-off execution
$sth = $dbh.execute(q:to/STATEMENT/);
    SELECT name, description, quantity, price, quantity*price AS amount
    FROM nom
    STATEMENT
say $sth.rows; # 3

for $sth.allrows() -> $row {
    say $row[0];  # BUBH␤TAFM␤BEOM
}

$sth.dispose;

# For efficient multiple execution
$sth = $dbh.prepare('SELECT description FROM nom WHERE name = ?');
for <TAFM BEOM> -> $name {
    for $sth.execute($name).allrows(:array-of-hash) -> $row {
        say $row<description>;
    }
}

$dbh.dispose;

DESCRIPTION

The DBIish project provides a simple database interface for Raku.

It's not a port of the Perl 5 DBI and does not intend to become one. It is, however, a simple and useful database interface for Raku that works now. It looks like a DBI, and it talks like a DBI (although it only offers a subset of the functionality).

Connecting to, and disconnecting from, a database

You obtain a DataBaseHandler by calling the static DBIish.connect method, passing as the only positional argument the driver name followed by any required named arguments.

Those named arguments are driver specific, but commonly required ones are: database, user and password.

For the different syntactic forms of named arguments see the language documentation.

For example, for connect to a database 'hierarchy' on PostgreSQL, with the user in $user and using the function get-secret to obtain you password, you can:

my $dbh = DBIish.connect('Pg', :database<hierarchy>, :$user, password => get-secret());

See ahead more examples.

To disconnect from a database and free the allocated resources you should call the dispose method:

$dbh.dispose;

Executing queries

execute

For a single execution of a query you may use execute directly. This starts the query within the database and returns a StatementHandle which will be used for Retrieving Data.

$dbh.execute(q:to/SQL/);
  CREATE TABLE tab (
    id serial PRIMARY KEY
    col text
  );
  SQL

Errors occurring within the database for an SQL statement will typically throw an exception within Raku. The level of detail within the exception object depends on the database driver.

$dbh.execute('CREATE TABLE failtab ( id );');

CATCH {
   when X::DBDish::DBError {
      say .message;
   }
}

In order to build a query dynamically without risk of SQL injection you need to use parameter binding. The ? will be replaced by an escaped copy of the parameter provided after the query.

my $value-id = 19;
$dbh.execute('INSERT INTO tab (id) VALUES (?)', $value-id);

my $value-text = q{Complex text ' value " with quotes};
$dbh.execute('INSERT INTO tab (id, col) VALUES (?, ?)', $value-id, $value-text);

# Undefined or Nil values will be converted to NULL by parameter binding.
my $value-nil;
$dbh.execute('INSERT INTO tab (id, col) VALUES (?, ?), $value-id, $value-nil);

Parameter binding should be used where-ever possible, even if the number of parameters is dynamic. In this case the number of elements for IN is dynamic. The number of ?'s is scaled to fit the list of items, and the list is provided to execute as individual items.

my @value-list = 1 .. 6;
my $parameter-bind-marks = @value-list.map({'?'}).join(',')  # ?,?,?,?,?,?
my $query = 'SELECT id FROM tab WHERE id IN (%s)'.sprintf($parameter-bind-marks);
$dbh.execute($query, |@value-list);

All database drivers support basic Raku types like Int, Rat, Str, and Buf; some databases may support additional complex types such as an Array of Str or Array of Int which may simplify the above example significantly. Please see database specific documentation for additional type support.

prepare

Execute performs a couple of steps on the client side, and often the database side as well, which may be cached if a query is going to be executed several times. For simple queries, prepare() may increase performance by up to 50%

This is an inefficient example of running a query multiple times:

for 1 .. 100 -> $id {
  $dbh.execute('INSERT INTO tab (id) VALUES (?)', $id);
}

This example is more efficient as it uses prepare to decrease overhead on the client side; often on the server-side too as the database may only need to parse the SQL once.

my $sth = $dbh.prepare('INSERT INTO tab (id) VALUES (?)');
for 1 .. 100 -> $id {
  $sth.execute($id);
}

Retrieving data

DBIish provides the row and allrows methods to fetch values from a StatementHandle object returned by execute. These functions provide you typed values; for example an int4 field in the database will be provided as an Int scalar in Raku.

row

row take the hash adverb if you want to have the values in a Hash form instead of a plain Array

Example:

my $sth = $dbh.execute('SELECT id, col FROM tab WHERE id = ?', $value-id);

my @values = $sth.row();
my %values = $sth.row(:hash);

allrows

allrows lazily returns all the rows as a list of arrays. If you want to fetch the values in a hash form, use one of the two adverbs array-of-hash or hash-of-array

Example:

my $sth = $dbh.execute('SELECT id, col FROM tab');

my @data = $sth.allrows(); # [[1, 'val1'], [3, 'val2']]
my @data = $sth.allrows(:array-of-hash); # [ ( id => 1, col => 'val1'), ( id => 3, col => 'val2') ]
my %data = $sth.allrows(:hash-of-array); # id => [1, 3], col => ['val1', 'val2']

for $sth.allrows(:array-of-hash) -> $row {
  say $row<id>;  # 1␤3
}

# Or as a shorter example:
for $dbh.execute('SELECT id, col FROM tab').allrows(:array-of-hash) -> $row {
   say $row<id>  # 1␤3
}

dispose

After you have fetched all data using the statement handle, you can free its memory immediately using dispose.

$sth.dispose;

server-version

server-version returns a Version object for the version of the server you are connected to. Not all drivers support this function (some may not connect to a server at all) so it's best to wrap in a can.

my Version $version = $dbh.server-version() if $dbh.can('server-version');

Statement Exceptions

All exceptions for a query result are thrown as or inherit X::DBDish::DBError. Additional functionality may be provided by the database driver.

Advanced Query Building

In general you should use the ? parameter for substitution whenever possible. The database driver will ensure values are properly escaped prior to insertion into the database. However, if you need to create a query string by hand then you can use quote to help prevent an SQL injection attack from being successful.

quote($literal) and quote($identifier, :as-id)

Using parameter substitution is preferred:

my $val = 'literal';
$dbh.execute('INSERT INTO tab VALUES (?)', $val);

However, if you must build the query directly you can:

my $val = 'literal';
my $query = 'INSERT INTO tab VALUES (%s)'.sprintf( $dbh.quote($val) );
$dbh.execute($query);

To build a query with a dynamic identifier:

# Notice that C<?> is still used for the value being inserted; it is still recommended where possible.
my $id = 'table';
my $val = 'literal';
my $query = 'INSERT INTO %s VALUES (?)'.sprintf( $dbh.quote($id, :as-id) );
$dbh.execute($query, $val);

INSTALLATION

$ zef install DBIish

DBDish CLASSES

Some DBDish drivers install together with DBIish.pm6 and are maintained as a single project.

Search the Raku ecosystem for additional DBDish drivers such as ODBC.

Currently the following backends are included:

Pg (PostgreSQL)

Supports basic CRUD operations and prepared statements with placeholders

my $dbh = DBIish.connect('Pg', :host<db01.yourdomain.com>, :port(5432),
        :database<blerg>, :user<myuser>, password => get-secret());

Pg supports the following named arguments: host, hostaddr, port, database (or its alias dbname), user, password, connect-timeout, client-encoding, options, application-name, keepalives, keepalives-idle, keepalives-interval, sslmode, requiressl, sslcert, sslkey, sslrootcert, sslcrl, requirepeer, krbsrvname, gsslib, and service.

See your PostgreSQL documentation for details.

Parameter Substitution

In addition to the ? style of parameter substitution supported by all drivers, PostgreSQL also supports numbered parameter. The advantage is that a numbered parameter may be reused

$dbh.execute('INSERT INTO tab VALUES ($1, $2, $2 - $1)', $var1, $var2);

This is equivalent to the below statement except the subtraction operation is performed by PostgreSQL:

$dbh.execute('INSERT INTO tab VALUES (?, ?, ?)', $var1, $var2, $var2 - $var1);

pg arrays

Pg arrays are supported for both writing via execute and retrieval via row/allrows. You will get the properly typed array according to the field type.

Passing an array to execute is now implemented. But you can also use the pg-array-str method on your Pg StatementHandle to convert an Array to a string Pg can understand:

# Insert an array via an execute statement
my $sth = $dbh.execute('INSERT INTO tab (array_column) VALUES ($1);', @data);

# Prepare an insertion of an array field
my $sth = $dbh.prepare('INSERT INTO tab (array_column) VALUES ($1);');
$sth.execute(@data1);   # or $sth.execute($sth.pg-array-str(@data1));
$sth.execute(@data2);

# Retrieve the array values back again.
for $dbh.execute('SELECT array_column FROM tab').allrows() -> $row {
   my @array-column = $row[0];
}

# Check if "value" is in the dataset. This is similar to an IN statement.
my $sth = $dbh.prepare('SELECT * FROM tab WHERE value = ANY($1)');
$sth.execute(@data);

# If a datatype is needed you can cast the placeholder with the PostgreSQL datatype.
my $sth = $dbh.prepare('SELECT * FROM tab WHERE value = ANY($1::_cidr)');
$sth.execute(['127.0.0.1', '10.0.0.1']);

pg-consume-input

Consume available input from the server, buffering the read data if there is any. This is only necessary if you are planning on calling pg-notifies without having requested input by other means (such as an execute.)

pg-notifies

$ret = $dbh.pg-notifies;

Looks for any asynchronous notifications received and returns a pg-notify object that looks like this

    class pg-notify {
        has Str                           $.relname; # Channel Name
        has int32                         $.be_pid; # Backend pid
        has Str                           $.extra; # Payload
    }

or nothing if there are no pending notifications.

In order to receive the notifications you should execute the PostgreSQL command "LISTEN" prior to calling pg-notifies the first time; if you have not executed any other commands in the meantime you will also need to execute pg-consume-input first.

For example:

$dbh.execute("LISTEN foo");

loop {
    $dbh.pg-consume-input
    if $dbh.pg-notifies -> $not {
        say $not;
    }
}

The payload is optional and will always be an empty string for PostgreSQL servers less than version 9.0.

ping

Test to see if the connection is still considered live.

$dbh.ping

Statement Exceptions

Exceptions for a query result are thrown as X::DBDish::DBError::Pg objects (inherits X::DBDish::DBError) and have the following additional attributes (described with a PG_DIAG_* source name) as provided by the PostgreSQL client library libpq:

Please see the PostgreSQL documentation for additional information.

A special is-temporary() method returns True if an immediate retry of the full transaction should be attempted:

It is set to true when the SQLState is any of the following codes:

pg-socket

    my Int $socket = $dbh.pg-socket;

Returns the file description number of the connection socket to the server.

SQLite

Supports basic CRUD operations and prepared statements with placeholders

my $dbh = DBIish.connect('SQLite', :database<thefile>);

The :database parameter can be an absolute file path as well (or even an IO::Path object):

my $dbh = DBIish.connect('SQLite', database => '/path/to/sqlite.db' );

If the SQLite library was compiled to be threadsafe (which is usually the case), then it is possible to use SQLite from multiple threads. This can be introspected:

say DBIish.install-driver('SQLite').threadsafe;

SQLite does support using one connection object concurrently, however other databases may not; if portability is a concern, then only use a particular connection object from one thread at a time (and so have multiple connection objects).

When using a SQLite database concurrently (from multiple threads, or even multiple processes), operations may not be able to happen immediately due to the database being locked. DBIish sets a default timeout of 10000 milliseconds; this can be changed by passing the busy-timeout option to connect.

my $dbh = DBIish.connect('SQLite', :database<thefile>, :60000busy-timeout);

Passing a value less than or equal to zero will disable the timeout, resulting in any operation that cannot take place immediately producing a database locked error.

Function rows()

Since SQLite may retrieve records in the background, the rows() method will not be accurate until all records have been retrieved from the database. A warning is thrown when this may be the case.

This warning message may be suppressed using a CONTROL phaser:

CONTROL {
    when CX::Warn {
        when .message.starts-with('SQLite rows()') { .resume }
        default { .rethrow }
    }
}

Making rows() accurate for all calls would require the driver pre-retrieving and caching all records with a large performance and memory penalty, then providing the records as requested.

For best performance you are recommended to use:

while my $row = $sth.row {
    # Do something with all records as retrieved
}

if my $row = $sth.row {
    # Do something with a single record
}

MySQL

Supports basic CRUD operations and prepared statements with placeholders

my $dbh = DBIish.connect('mysql', :host<db02.yourdomain.com>, :port(3306),
        :database<blerg>, :user<myuser>, :$password);

# Or via socket:
my $dbh = DBIish.connect('mysql', :socket<mysql.sock>,
        :database<blerg>, :user<myuser>, :$password);

MySQL driver supports the following named arguments: connection-timeout, read-timeout, write-timeout

See your MySQL documentation for details.

Since MariaDB uses the same wire protocol as MySQL, the `mysql` backend also works for MariaDB.

Statement Exceptions

Exceptions for a query result are thrown as X::DBDish::DBError::mysql objects (inherits X::DBDish::DBError) and have the following additional attributes as provided by the MySQL client libraries.

Required Client-C libraries

DBDish::mysql by default searches for 'mysql' (libmysql.ddl) on Windows, and 'mariadb' (libmariadb.so.xx where xx in 0 .. 4) then 'mysqlclient' (libmysqlclient.so.xx where xx in 16..21) on POSIX systems.

Remember that Windows uses PATH to locate the library. On POSIX, unversionized *.so files installed by "dev" packages aren't needed nor used, you need the run-time versionized library.

On POSIX you can use the $DBIISH_MYSQL_LIB environment variable to request another client library to be searched and loaded.

Example using the unadorned name:

DBIISH_MYSQL_LIB=mariadb rakudo t/25-mysql-common.t

Using the absolute path in uninstalled DBIish:

DBIISH_MYSQL_LIB=/lib64/libmariadb.so.3 rakudo -t lib t/25-mysql-common.t

With MariaBD-Embedded:

DBIISH_MYSQL_LIB=mariadbd rakudo -I lib t/01-basic.t

insert-id

Returns the AUTO_INCREMENT value of the most recently inserted record.

my $sth = $dbh.execute( 'INSERT INTO tab (description) VALUES (?)', $description );

my $id = $sth.insert-id;

# or
my $id = $dbh.insert-id;

Oracle

Supports basic CRUD operations and prepared statements with placeholders

my $dbh = DBIish.connect('Oracle', database => 'XE', :user<sysadm>, :password('secret'));

By default connections to Oracle will apply this session alteration in an attempt to ensure the formatted "TIMESTAMP WITH TIME ZONE" field string will be compatible with DateTime and returned to the user as DateTime.new($ts_str).

ALTER SESSION SET nls_timestamp_tz_format = 'YYYY-MM-DD"T"HH24:MI:SS.FFTZR'

WARNING: This alteration does not include support for these field types. Also until now these types would have thrown an exception as an unknown TYPE.

TIMESTAMP
TIMESTAMP WITH LOCAL TIME ZONE

WARNING: Any form of TIMESTAMP(0) will produce a string not compatible with DateTime due to the ".FF" and the lack of fractional seconds to fulfill it.

You can choose to use this session alteration in an attempt to simplify the use of ISO-8601 timestamps; strictly speaking, formatted as "YYYY-MM-DDTHH:MI:SSZ"; no offsets etc shown but Oracle outo converts to GMT(00:00). This session management forces all client sessions to UTC and sets formats for all DATE and TIMESTAMP types; it does however sacrifice any fraction seconds TIMESTAMPS may be storing. It also insures TIMSTAMP(0) works without causing DateTime.new($ts) to fault.

DBIish.connect( 'Oracle', :alter-session-iso8601, ... );

ALTER SESSION SET time_zone               = '-00:00'
ALTER SESSION SET nls_date_format         = 'YYYY-MM-DD"T"HH24:MI:SS"Z"'
ALTER SESSION SET nls_timestamp_format    = 'YYYY-MM-DD"T"HH24:MI:SS"Z"'
ALTER SESSION SET nls_timestamp_tz_format = 'YYYY-MM-DD"T"HH24:MI:SS"Z"'

WARNING: Preexisting databases that used time zones other than UTC/GMT/-00:00 may need to convert current timestamps to -00:00 to ensure timestamp correctness. It will depend on the type of TIMESTAMP used and how Oracle was configured.

NOTICE: By default DBIish lower-cases FIELD names. This is noticed when data is returned as a hash.

For consumer purists that desire DBIish to leave session management alone, the above behaviors can be disabled using these options in the connect method. These options will allow DBIish to most closely behave like Perl5's DBI defaults. These are my personal favorite settings.

:no-alter-session      # don't alter session
:no-datetime-container # return the date/timestamps as stings
:no-lc-field-names     # return field names unaltered

Threads

I have a long history of using Threads, Oracle and Perl5. I have yet to read any useful online notes regarding successful usage of Raku, threads & DBIish; I thought I'd share recent experience.

Since early 2021 I've successfully implemented my Raku solution for using as many as Eight(8) threads all connected to Oracle performing simultaneous Reads and writes. As with Perl-5 the number one requirement is to ensure each thread creates is own connection handle with Oracle. In case you're interested; its implemented as a layer on top of DBIish that when .enable(N) is used determines the number of worker threads; each capable to handling reads or writes. The primary application delegates writes to the workers and reads are asynchronously delivered where requested. This solution allows the application to stay focused on it's primary purpose while dedicated writers handle the DB updates.

Regards, ancient-wizard

TESTING

The DBIish::CommonTesting module, now with over 100 tests, provides a common unit testing that allows a driver developer to test its driver capabilities and the minimum expected compatibility.

Set environment variable DBIISH_WRITE_TEST=YES to run tests which may leave permanent state changes in the database.

SEE ALSO

The Raku Pod in the doc:DBIish module and examples in the examples directory.

This README and the documentation of the DBIish and the DBDish modules are in the Pod6 format. It can be extracted by running

rakudo --doc <filename>

Or, if Pod::To::HTML is installed,

rakudo --doc=html <filename>

Additional modules of interest may include:

HISTORY

DBIish is based on Martin Berends' MiniDBI project, but unlike MiniDBI, DBDish aims to provide an interface that takes advantage of Raku idioms.

There is/was an intention to integrate with the DBDI project once it has sufficient functionality.

So, while it is indirectly inspired by Perl 5 DBI, there are also many differences.

COPYRIGHT

Written by Moritz Lenz, based on the MiniDBI code by Martin Berends.

See the CREDITS file for a list of all contributors.

LICENSE

Copyright © 2009-2020, the DBIish contributors All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.