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README.pod

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](#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.

driver-name

Database Driver name for the connection

native-message

Unmodified message received from the database server.

code

Int return code from the local client library for the call; typically -1. This is not an SQL state.

why

A Str indicating why the exception was thrown. Typically 'Error'.

message

Human friendly and more informative version of the database message.

is-temporary

A Boolean flag which when true indicates that the transaction may succeed if retried. Connectivity issues, serialization issues and other temporary items may set this as True.

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:

message

PG_DIAG_MESSAGE_PRIMARY - The primary human-readable error message (typically one line). Always present.

message-detail

PG_DIAG_MESSAGE_DETAIL - Detail: an optional secondary error message carrying more detail about the problem. Might run to multiple lines.

message-hint

PG_DIAG_MESSAGE_HINT - Hint: an optional suggestion what to do about the problem. This is intended to differ from detail in that it offers advice (potentially inappropriate) rather than hard facts. Might run to multiple lines.

context

PG_DIAG_CONTEXT - An indication of the context in which the error occurred. Presently this includes a call stack traceback of active procedural language functions and internally-generated queries. The trace is one entry per line, most recent first.

type

PG_DIAG_SEVERITY_NONLOCALIZED - The severity; the field contents are ERROR, FATAL, or PANIC (in an error message), or WARNING, NOTICE, DEBUG, INFO, or LOG (in a notice message). This is identical to the PG_DIAG_SEVERITY field except that the contents are never localized. This is present only in reports generated by PostgreSQL versions 9.6 and later.

type-localized

PG_DIAG_SEVERITY - The severity; the field contents are ERROR, FATAL, or PANIC (in an error message), or WARNING, NOTICE, DEBUG, INFO, or LOG (in a notice message), or a localized translation of one of these. Always present.

sqlstate

PG_DIAG_SQLSTATE - The SQLSTATE code for the error. The SQLSTATE code identifies the type of error that has occurred; it can be used by front-end applications to perform specific operations (such as error handling) in response to a particular database error. For a list of the possible SQLSTATE codes, see Appendix A. This field is not localizable, and is always present.

statement

Statement provided to prepare() or execute()

statement-name

Statement Name provided to prepare() or created internally

statement-position

PG_DIAG_STATEMENT_POSITION - A string containing a decimal integer indicating an error cursor position as an index into the original statement string. The first character has index 1, and positions are measured in characters not bytes.

internal-position

PG_DIAG_INTERNAL_POSITION - This is defined the same as the PG_DIAG_STATEMENT_POSITION field, but it is used when the cursor position refers to an internally generated command rather than the one submitted by the client. The PG_DIAG_INTERNAL_QUERY field will always appear when this field appears.

internal-query

PG_DIAG_INTERNAL_QUERY - The text of a failed internally-generated command. This could be, for example, a SQL query issued by a PL/pgSQL function.

dbname

Database Name from libpq pg-db()

host

Host from libpq pg-host()

user

User from libpq pg-user()

port

Port from libpq pg-port()

schema

PG_DIAG_SCHEMA_NAME - If the error was associated with a specific database object, the name of the schema containing that object, if any.

table

PG_DIAG_TABLE_NAME - If the error was associated with a specific table, the name of the table. (Refer to the schema name field for the name of the table's schema.)

column

PG_DIAG_COLUMN_NAME - If the error was associated with a specific table column, the name of the column. (Refer to the schema and table name fields to identify the table.)

datatype

PG_DIAG_DATATYPE_NAME - If the error was associated with a specific data type, the name of the data type. (Refer to the schema name field for the name of the data type's schema.)

constraint

PG_DIAG_CONSTRAINT_NAME - If the error was associated with a specific constraint, the name of the constraint. Refer to fields listed above for the associated table or domain. (For this purpose, indexes are treated as constraints, even if they weren't created with constraint syntax.)

source-file

PG_DIAG_SOURCE_FILE - The file name of the source-code location where the error was reported.

source-line

PG_DIAG_SOURCE_LINE - The line number of the source-code location where the error was reported.

source-function

PG_DIAG_SOURCE_FUNCTION - The name of the source-code function reporting the error.

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:

SQLState Class 08XXX

All connection exceptions (possible temporary network issues)

SQLState 40001

serialization_failure - Two or more transactions conflicted in a manner which may succeed if executed later.

SQLState 40P01

deadlock_detected - Two or more transactions had locking conflicts resulting in a deadlock and this transaction being rolled back.

SQLState Class 57XXX

Operator Intervention (early/forced connection termination).

SQLState 72000

snapshot_too_old - The transaction took too long to execute. It may succeed during a quieter period.

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 miliseconds; 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.

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);

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

Required Client-C libraries

DBDish::mysql by default searchs for 'mysql' (libmysql.ddl) on Windows and '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'));

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.

DEPRECATED

These will be removed on June 2022.

$sth.fetchrow()

deprecated in favour of $sth.row()

$sth.fetchrow_hashref()

deprecated in favour of $sth.row(:hash)

$sth.fetchall_hashref()

deprecated in favour of $sth.allrows(:hash-of-arrays)

$sth.fetchall-hash()

deprecated in favour of $sth.allrows(:hash-of-arrays)

$sth.fetchall-AoH()

deprecated in favour of $sth.allrows(:array-of-hash)

$sth.fetchrow_array()

deprecated in favour of $sth.row()

$sth.fetchrow_hashref()

deprecated in favour of $sth.row(:hash)

$sth.fetchrow_arrayref()

deprecated in favour of $sth.row(:hash)

$sth.fetch()

deprecated in favour of $sth.row()

$sth.fetchall_arrayref()

deprecated in favour of $sth.allrows(:array-of-hash)

$sth.mysql_insertid

deprecated in favour of $sth.insert-id

$dbh.mysql_insertid

deprecated in favour of $dbh.insert-id

$dbh.disconnect

deprecated in favour of $sth.dispose

$dbh.install_driver

deprecated in favour of $sth.install-driver

$dbh.selectrow_arrayref

deprecated in favor of $sth = $dbh.prepare.execute(); $sth.row

$dbh.selectrow_hashref

deprecated in favor of $sth = $dbh.prepare.execute(); $sth.row(:hash)

$dbh.selectall_arrayref

deprecated in favor of $sth = $dbh.prepare.execute(); $sth.allrows

$dbh.selectall_hashref

deprecated in favor of $sth = $dbh.prepare.execute(); $sth.allrows(:array-of-hashes)

$dbh.selectcol_arrayref

deprecated in favor of $sth = $dbh.prepare.execute(); $sth.allrows(:array-of-hashes)

$dbh.quote-identity($str)

deprecated in favor of $dbh.quote($str, :as-id)

SEE ALSO

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

This README and the documention 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:

DBIish::Transaction

A wrapper for managing transactions, including automatic retry for temporary failures.

DBIish::Pool

Connection reuse for DBIish to reduce loads on high-volume or heavily encrypted database sessions.

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:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

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.

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