Private Messaging Structure and Usage

UnfoX · September 10, 2009

Hi all,

I'm after a complete and practical private messaging system which has a thread feature. There are some topics in this forum about pm systems but none of them satisfied me enough and they are only related to the database structure. I want to talk about usage also (SQL queries etc.).

The best database design I can find is from this forum (http://www.phpfreaks.com/forums/index.php/topic,262543.msg1237675.html#msg1237675). It has 2 seperate tables. One for private message itself, and second for its relations to the receiver etc.

1st table:

CREATE TABLE IF NOT EXISTS `pm` (

`pmID` int(11) NOT NULL auto_increment,

`parentID` int(11) NOT NULL default '0',

`senderID` int(11) NOT NULL,

`title` varchar(100) default NULL,

`content` text,

`dateSent` datetime default NULL,

`senderDelete` tinyint(4) NOT NULL,

PRIMARY KEY (`pmID`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

2nd table:

CREATE TABLE IF NOT EXISTS `pmInfo` (

`messageID` int(11) NOT NULL auto_increment,

`receiverID` int(11) NOT NULL,

`receiverRead` tinyint(4) NOT NULL,

`dateRead` datetime default NULL,

`receiverDelete` tinyint(4) NOT NULL,

PRIMARY KEY (`messageID`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

Are we all clear on this database structure? If not, please suggest.

Lets say that we all agreed on this db structure. Now what about the usage?

As I know, best practice would be minimizing the SQL queries ran.

Here we go

POSTING MESSAGE

There are two types of posting messages. 1- New thread, 2- Reply

When a new message is sent I call 3 SQL queries:

1- INSERT query to pm table

2- INSERT query to pmInfo table

3- UPDATE query to make parentID = pmID

When a new reply is sent I call 2 SQL queries:

1- INSERT query to pm table

2- INSERT query to pmInfo table

In the PHP side, for a new thread there is no problem. User selects receiver (so receiverID), and parentID is set to pmID. But for the reply, I have some problems.

In the reply form I'm using a hidden input which holds the parentID for that thread. But with this usage, how can I get the receiverID? If I use hidden parentID to get receiverID I need one more SELECT query (which is unwanted) and I may not find the correct receiverID since I may send the main thread to multi-users.

Lets have a table example:

USERS TABLE

userID username

1 Joe

2 Paul

3 Nick

PM TABLE

pmID parentID senderID title content

1 1 1 Hi! Whats up? -> pm(1)

2 2 3 Hello Hi there.. -> pm(2)

3 1 2 null Fine, you? -> this is a reply to pm(1)

4 1 1 null Fine -> this is a reply to the reply above

5 1 2 null Thanks dude -> this is a reply to pm(1)

PMINFO TABLE

messageID receiverID

1 3 -> message sent by Joe to Nick

1 2 -> same message sent to Paul also

2 2 -> a message sent by Nick to Paul

3 1 -> reply sent by Nick to Joe

4 3 -> reply sent by Joe to Nick

5 1 -> reply sent by Paul to Joe

When Joe replies to Nick with the pmID 4, how can I get the Nick's userID from the table? If I select with respect to parentID, Joe sent the same message to Paul also, it can be confused.

Since I'm listing a thread using the parentID in a page, I have no info about the next receiverID.

This is the first question, I wish it is clear enough for you Do you have any suggestions for this issue?

And all other suggestions to any piece of this topic are welcomed

Thanks

Philip · September 11, 2009

tinyint(4)

Should be tinyint(1) [basically making them boolean

 PRIMARY KEY  (`messageID`)

Should be INDEX (`messageID`)

`receiverRead`/ `receiverDelete` should have default values (or null) of 0

When a new message is sent I call 3 SQL queries:
1- INSERT query to pm table

2- INSERT query to pmInfo table

3- UPDATE query to make parentID = pmID

Instead of making that 3rd query (the update), use 0/NULL as a parentID instead. That'll save a query, and you can quickly see what messages are parents and what aren't. Plus, that's why I made that a 0 as a default on that column

UnfoX · September 11, 2009

KingPhilip, thank you for your reply I made the necessery changes in my database. But now I have a question.

When listing the threads, lets say that I'm the user Nick and I'm using such a query:

SELECT * FROM `pm` INNER JOIN pmInfo ON pm.pmID = pmInfo.messageID WHERE receiverID = 3 ORDER BY dateSent DESC

After this query I will have 2 rows:

pmID    parentID    senderID    title        content          messageID      receiverID
4       1             1         null         Fine             4              3           
1       0             1         Hi!          Whats up?        1              3

Since I'm listing the threads, I need to show the last message of the thread. So I need to get rid of the second row.

I can not use LIMIT 1 since there may be other threads. LIMIT returns always 1 message
I can not use parentID <> 0 since the thread may be unreplied. In this case I need to show the parent message

Any suggestions?

3.5k · September 12, 2009

New message, from Joe to Paul and Nick:

INSERT INTO message (id, text, author_id) VALUES (1, 'Hi there', 1);

INSERT INTO inbox (id, message_id, user_id) VALUES (1, 1, 2),  (1, 1, 3);

Paul replies privately:

INSERT INTO message (id, text, author_id) VALUES (2, 'Hi. I don't like Nick very much.', 2);

INSERT INTO inbox (id, parent_message_id, message_id, user_id) VALUES (2, 1, 2, 1);

Nick replies to the thread:

INSERT INTO message (id, text, author_id) VALUES (3, 'Hey! I see Paul is in this thread as well! Hey Paul, you rule!', 3);

INSERT INTO inbox (id, parent_message_id, message_id, user_id) VALUES (3, 1, 3, 1),  (3, 1, 3, 2);

Pretty basic stuff.. The PK values are just for illustration. Normally you would use an AUTO_INCREMENT column.

[attachment deleted by admin]

3.5k · September 12, 2009

For your convenience..

-- -----------------------------------------------------
-- Table `mydb`.`user`
-- -----------------------------------------------------
CREATE  TABLE IF NOT EXISTS `mydb`.`user` (
  `id` INT NOT NULL ,
  PRIMARY KEY (`id`) )
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `mydb`.`message`
-- -----------------------------------------------------
CREATE  TABLE IF NOT EXISTS `mydb`.`message` (
  `id` INT NOT NULL ,
  `text` TEXT NULL ,
  `author_id` INT NOT NULL ,
  PRIMARY KEY (`id`) ,
  INDEX `fk_message_user1` (`author_id` ASC) ,
  CONSTRAINT `fk_message_user1`
    FOREIGN KEY (`author_id` )
    REFERENCES `mydb`.`user` (`id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `mydb`.`inbox`
-- -----------------------------------------------------
CREATE  TABLE IF NOT EXISTS `mydb`.`inbox` (
  `id` INT NOT NULL ,
  `message_id` INT NOT NULL ,
  `parent_message_id` INT NOT NULL ,
  `user_id` INT NOT NULL ,
  PRIMARY KEY (`id`) ,
  INDEX `fk_inbox_message1` (`message_id` ASC) ,
  INDEX `fk_inbox_message2` (`parent_message_id` ASC) ,
  INDEX `fk_inbox_user1` (`user_id` ASC) ,
  CONSTRAINT `fk_inbox_message1`
    FOREIGN KEY (`message_id` )
    REFERENCES `mydb`.`message` (`id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `fk_inbox_message2`
    FOREIGN KEY (`parent_message_id` )
    REFERENCES `mydb`.`message` (`id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `fk_inbox_user1`
    FOREIGN KEY (`user_id` )
    REFERENCES `mydb`.`user` (`id` )
    ON DELETE CASCADE
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

Since I'm listing the threads, I need to show the last message of the thread. So I need to get rid of the second row.

* I can not use LIMIT 1 since there may be other threads. LIMIT returns always 1 message

* I can not use parentID <> 0 since the thread may be unreplied. In this case I need to show the parent message

Any suggestions?

WHERE parent_message_id IS NULL will work just fine for selecting the OPs. A message without parent is a root message, i.e. a thread OP.

3.5k · September 12, 2009

Hmokay, so I thought I'd write up a quick example, and ended up spending a couple of hours writing half an ORM

<?php
class Pm_Exception extends Exception {}

class Pm_DataMapper_Statement
{
private $_literal;

public function __construct($literal)
{
	$this->_literal = $literal;
}	

public function __toString()
{
	return (string)$this->_literal;
}
}

class Pm_DataMapper
{
/**
 * @var PDO
 */
private $_pdo;

private $_identityMap = array();

private $_map = array(
	'Pm_User' => array(
		'table' => 'user',
		'properties' => array(
			'_name' => array(
				'type' => PDO::PARAM_STR,
				'column' => 'name'
			)
		)
	),
	'Pm_Message' => array(
		'table' => 'message',
		'properties' => array(
			'_message' => array(
				'type' => PDO::PARAM_STR,
				'column' => 'text'
			),
			'_author' => array(
				'class' => 'Pm_User',
				'type' => PDO::PARAM_INT,
				'column' => 'author_id'
			)
		)
	),
	'Pm_InboxMessage' => array(
		'table' => 'inbox',
		'properties' => array(
			'_message' => array(
				'class' => 'Pm_Message',
				'type' => PDO::PARAM_INT,
				'column' => 'message_id'
			),
			'_parentMessage' => array(
				'class' => 'Pm_Message',
				'type' => PDO::PARAM_INT,
				'column' => 'parent_message_id'
			),
			'_user' => array(
				'class' => 'Pm_User',
				'type' => PDO::PARAM_INT,
				'column' => 'user_id'
			)
		)
	)
);

public function __construct(PDO $dbh)
{
	$this->_pdo = $dbh;	
}

private function _get($class, $id)
{
	return isset($this->_identityMap[$class][$id]) ? $this->_identityMap[$class][$id] : null;
}

private function _set(Pm_DomainObject $object)
{
	$this->_identityMap[get_class($object)][$object->getId()] = $object;
}

private function _getColumns($class)
{
	$spec = $this->_map[$class];

	$columns = array();

	foreach($spec['properties'] as $propSpec)
	{
		$columns[$propSpec['column']] = ":{$propSpec['column']}";
	}

	return $columns;
}

public function factory($class, array $record)
{
	$spec = $this->_map[$class];

	$refl = new ReflectionClass($class);

	$values = array();

	foreach($refl->getMethod('__construct')->getParameters() as $reflParameter)
	{
		$propertySpec = $spec['properties']["_{$reflParameter->getName()}"];

		$value = $record[$propertySpec['column']];

		if(isset($propertySpec['class']) && $value)
		{
			$value = $this->findOneBy($propertySpec['class'], 'id', $value);

			if(!$value)
			{
				throw new Pm_Exception("{$propertySpec['class']}:{$record[$propertySpec['column']]} not found");
			}

		}

		$values[$reflParameter->getPosition()] = $value;
	}

	ksort($values);

	$object = $refl->newInstanceArgs($values);

	$object->setId($record['id']);

	return $object;
}

public function find($class, $id)
{
	return $this->findOneBy($class, 'id', $id);
}

public function findOneBy($class, $argumentName, $propertyValue)
{
	$results = $this->findBy($class, $argumentName, $propertyValue);

	return reset($results);
}

public function findBy($class, $argumentName, $propertyValue)
{
	if($argumentName == 'id' && $this->_get($class, $propertyValue))
	{
		return $this->_get($class, $propertyValue);
	}

	$spec = $this->_map[$class];

	if($propertyValue instanceof Pm_DataMapper_Statement)
	{
		$stmt = $this->_pdo->prepare(
			"SELECT id, $propertyValue AS __statement, " . implode(', ', array_keys($this->_getColumns($class))) . " FROM {$spec['table']} WHERE $argumentName = $propertyValue"
		);

		if(!$stmt->execute())
		{
			throw new Pm_Exception("Execute failed: " . implode(', ', $this->_pdo->errorInfo()));
		}

		return $this->hydrate($class, $stmt);
	}

	if($propertyValue === null)
	{
		$conditionValueString = "IS NULL";
	}
	else
	{
		$conditionValueString = "= :$argumentName";
	}

	$column = isset($spec['properties']["_$argumentName"]['column']) ? $spec['properties']["_$argumentName"]['column'] : $argumentName;

	$stmt = $this->_pdo->prepare(
		"SELECT id, " . implode(', ', array_keys($this->_getColumns($class))) . " FROM {$spec['table']} WHERE $column $conditionValueString"
	);

	$stmt->bindParam(":$argumentName", $propertyValue, $spec['properties']["_$argumentName"]['type']);

	if(!$stmt->execute())
	{
		throw new Pm_Exception("Execute failed: " . implode(', ', $this->_pdo->errorInfo()));
	}

	return $this->hydrate($class, $stmt);
}

public function hydrate($class, PDOStatement $stmt)
{
	$result = array();

	foreach($stmt->fetchAll(PDO::FETCH_ASSOC) as $record)
	{
		if($this->_get($class, $record['id']))
		{
			$result[] = $this->_get($class, $record['id']);

			continue;
		}

		$result[] = $this->factory($class, $record);
	}

	return $result;
}

public function save(Pm_DomainObject $object)
{
	$spec = $this->_map[get_class($object)];

	$props = array();

	foreach((array)$object as $prop => $value)
	{
		$props[substr($prop, strrpos($prop, '_'))] = $value;
	}

	$values = array_intersect_key($props, $spec['properties']);

	foreach($spec['properties'] as $propName => $propSpec)
	{
		if($values[$propName] instanceof Pm_DomainObject)
		{
			if(!$values[$propName]->isStored())
			{
				$this->save($values[$propName]);
			}

			$values[$propName] = $values[$propName]->getId();
		}
	}

	$columns = $this->_getColumns(get_class($object));

	if(!$object->isStored())
	{
		$stmt = $this->_pdo->prepare("INSERT INTO {$spec['table']} (" . implode(', ', array_keys($columns)) . ") VALUES (" . implode(', ', $columns) . ")");

		foreach($spec['properties'] as $propName => $propSpec)
		{
			$stmt->bindParam(":{$propSpec['column']}", $values[$propName], $propSpec['type']);
		}

		if(!$stmt->execute())
		{
			throw new Pm_Exception("Execute failed ({$this->_pdo->errorCode()}): " . implode(', ', $this->_pdo->errorInfo()));
		}

		$object->setId((int)$this->_pdo->lastInsertId());	
	}
	else 
	{
		$sets = array();

		foreach($columns as $name => $mark)
		{
			$sets[] = "$name = $mark";
		}

		$stmt = $this->_pdo->prepare("UPDATE {$spec['table']} SET " . implode(', ', $sets) . " WHERE id = " . (int)$object->getId());

		foreach($spec['properties'] as $propName => $propSpec)
		{
			$stmt->bindParam(":{$propSpec['column']}", $values[$propName], $propSpec['type']);
		}

		if(!$stmt->execute())
		{
			throw new Pm_Exception("Execute failed: " . implode(', ', $this->_pdo->errorInfo()));
		}
	}
}
}
abstract class Pm_DomainObject
{
/**
 * @var int
 */
private $_id;

public function getId()
{
	return $this->_id;
}

public function isStored()
{
	return (bool)$this->_id;
}

public function setId($id)
{
	if($this->_id)
	{
		throw new Pm_Exception("ID already set");
	}

	$this->_id = $id;
}
}

class Pm_User extends Pm_DomainObject
{
/**
 * @var string
 */
private $_name;	

public function __construct($name)
{
	$this->_name = $name;
}
}
class Pm_Message extends Pm_DomainObject
{
/**
 * @var string
 */
private $_message;

/**
 * @var User
 */
private $_author;


public function __construct($message, Pm_User $author)
{
	$this->_author = $author;

	$this->_message = $message;
}
}
class Pm_InboxMessage extends Pm_DomainObject
{
/**
 * @var Pm_Message
 */
private $_message;

/**
 * @var Pm_Message
 */
private $_parentMessage;

/**
 * @var User
 */
private $_user;


public function __construct(Pm_Message $message, Pm_Message $parentMessage = null, Pm_User $user)
{
	$this->_user = $user;

	$this->_message = $message;

	$this->_parentMessage = $parentMessage;
}
}
class Pm_Service
{
/**
 * @var Pm_DataMapper
 */
private $_mapper;

public function __construct(Pm_DataMapper $mapper)
{
	$this->_mapper = $mapper;
}

public function send(Pm_Message $message, array $users, Pm_Message $parentMessage = null)
{
	foreach($users as $user)
	{
		$inboxMessage = new Pm_InboxMessage($message, $parentMessage, $user);

		$this->_mapper->save($inboxMessage);

		if(!$inboxMessage->getId())
		{
			return false;
		}
	}

	return true;

}
}

/**
* Use case
*/
$mapper = new Pm_DataMapper(new Pdo('mysql:dbname=pm;host=127.0.0.1;port=3306', 'root', '40333'));

$service = new Pm_Service($mapper);

$joe = ($user = $mapper->findOneBy('Pm_User', 'name', 'Joe')) ? $user : new Pm_User('Joe');
$paul = ($user = $mapper->findOneBy('Pm_User', 'name', 'Paul')) ? $user : new Pm_User('Paul');
$nick = ($user = $mapper->findOneBy('Pm_User', 'name', 'Nick')) ? $user : new Pm_User('Nick');

/**
* Joe starts conversation
*/
$op = new Pm_Message('Hi there', $joe);

/**
* Sends it to both Paul and Nick
*/
$service->send($op, array($paul, $nick));

/**
* When Paul finds the message, he responds to Joe, but not to Nick
*/
$service->send(new Pm_Message('Hi. I don\'t like Nick very much.', $paul), array($joe), $op);

/**
* But Nick thinks Paul is awesome, so he responds to both
*/
$service->send(new Pm_Message('Hey! I see Paul is in this thread as well! Hey Paul, you rule!', $nick), array($joe, $paul), $op);

/**
* If we want the ops in a mailbox we look for NULL values
*/
echo '<pre>'; 
var_dump($mapper->findBy('Pm_InboxMessage', 'parentMessage', null));
echo '</pre>';

Since I'm listing the threads, I need to show the last message of the thread. So I need to get rid of the second row.

* I can not use LIMIT 1 since there may be other threads. LIMIT returns always 1 message

* I can not use parentID <> 0 since the thread may be unreplied. In this case I need to show the parent message

Any suggestions?

I'm sorry, I misread this (I read what I want to read sometimes). I don't think there is a way with the adjacency list model (the parent_id thing) to do this, but it is trivial with nested set: WHERE 0 = (right – left - 1) / 2. Nested Set (Modified Preorder Tree Traversal) is a little more work to implement though.

3.5k · September 12, 2009

Oh and here's an updated schema:

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;

CREATE TABLE  `inbox` (
  `id` int(11) NOT NULL auto_increment,
  `message_id` int(11) NOT NULL,
  `parent_message_id` int(11) default NULL,
  `user_id` int(11) NOT NULL,
  PRIMARY KEY  (`id`),
  KEY `fk_inbox_message1` (`message_id`),
  KEY `fk_inbox_message2` (`parent_message_id`),
  KEY `fk_inbox_user1` (`user_id`),
  CONSTRAINT `fk_inbox_message1` FOREIGN KEY (`message_id`) REFERENCES `message` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_inbox_message2` FOREIGN KEY (`parent_message_id`) REFERENCES `message` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_inbox_user1` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE  `message` (
  `id` int(11) NOT NULL auto_increment,
  `text` text NOT NULL,
  `author_id` int(11) NOT NULL,
  PRIMARY KEY  (`id`),
  KEY `fk_message_user1` (`author_id`),
  CONSTRAINT `fk_message_user1` FOREIGN KEY (`author_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE  `user` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;

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Private Messaging Structure and Usage

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