Let say you want to write a sub-select, and have a Propel object returned.

As an example, lets generate the following SQL:

SELECT
    orders.ID,
    orders.TYPE,
    orders.STATUS
FROM
    orders
WHERE
    orders.STATUS IN (
        SELECT
              STATUS.NAME
        FROM
              STATUS
        WHERE
             STATUS.ORDER_TYPE = 'purchase'
    )

Propel does not natively handle this sort of SQL. There are however two ways to create this SQL or to get this data set and have Propel objects returned.

Overview of the different methods

1. Use of Criteria::CUSTOM
   • PRO: Allows the use of an actual sub-select
   • CON: Code is not as readable
   • See http://www.symfony-project.com/snippets/snippet/53 for more information on Criteria::CUSTOM
2. Rewrite the SQL using JOINs
   • PRO: Very readable code
   • CON: Not using a sub-select
   • CON: You may be using a sub-select for SQL performance, so this may be slower

Way 1: Use of Criteria::CUSTOM

$c = new Criteria();
$subSelect = "orders.STATUS IN (
    SELECT
          status.NAME
    FROM
          status
    WHERE
         status.ORDER_TYPE = 'purchase'
    )";
$c->add(StatusPeer.STATUS, $subSelect, Criteria::CUSTOM);
$orders = StatusPeer::doSelect($c);

Way 2: Rewrite the SQL using JOINs

Example of the rewritten SQL:

SELECT
    orders.ID,
    orders.TYPE,
    orders.STATUS
FROM
    orders,
    STATUS
WHERE
    orders.STATUS = STATUS.NAME
    AND STATUS.ORDER_TYPE = 'purchase'

This can be written as follows in your action:

$c = new Criteria();
$c->addJoin (OrderPeer::STATUS, StatusPeer::NAME);
$c->add(StatusPeer.ORDER_TYPE, 'purchase');
$orders = StatusPeer::doSelect($c);

The problem

Let us take the example of snipeet! :-) The function that selects snippets by tags is a custom SQL query. When filtering by tags there is no pager anymore.

Why is that? The problem is that sfPropelPaginate only works with a Criteria object, not with a raw query. As a result you cannot have pagination with raw SQL query which is a rather severe limitation.

The solution

The solution is to first encode the parameter of the query in the criteria (that's the tricky bit) and then to set up a custom peer method.

As i said earlier we will take a simplified version of snipeet as an example. We assume that we have a function that creates a sql statement from a list of tags.

Here we go about setting the dummy criteria that encodes an array of tags:

getCriteriaFromTags($tags)
{
  $c = new Criteria();
  for ($i = 1; $i <= count($tags); ++$i)
  {
    $prefix = 't'.$i;
    // note that that SnippetTagPeer::TABLE_NAME  SnippetTagPeer::NAME are in fact arbitrary
    // any other table and table.column combination would work as well
    $c->addAlias($prefix.SnippetTagPeer::TABLE_NAME, SnippetTagPeer::TABLE_NAME);
    $c->add($prefix.SnippetTagPeer::NAME, $tags[$i-1]);
  }
  return $c;
}

Now you can initialise a sfPropelPaginate object as usual with that Criteria object. When that is done you tell it to use your custom peer method:

$pager->setPeerMethod('doSelectByTags');

Next you code the doSelectByTags method that performs the actual selection from a criteria object:

function doSelectByTags($c)
{
  // first you fetch the tags from the query
  $tags = array();
  foreach($c->keys() as $key)
    $tags[] = $c->get($key);
 
  // here comes your custom sql query 
  // it basically creates a $statement variable from the $tags array
  // .....
 
  // now you have to add the limit and offset:
 $statement->setLimit($c->getLimit());
 $statement->setOffset($c->getOffset());
 // and the rest of the code is as usual
}