[D7] PollCreateTestCase - invalid input syntax for integer on PostgreSQL

Problem/Motivation

There is an exception in PollCreateTestCase (testPollCreate) when running this test on PostgreSQL database.

The issue is that we cannot pass empty string as key to db_merge() because this function does db_select() first and then only db_insert()/db_update(). MySQL is not affected because it is not such strict for data types.

Problematic parts:

testPollCreate()

  $vote_count = '2000';
  $node->choice[] = array(
    'chid' => '',
    'chtext' => $new_option,
    'chvotes' => (int) $vote_count,
    'weight' => 1000,
  );

  node_save($node);

poll_update()

  // Poll choices with empty titles signifies removal. We remove all votes to
  // the removed options, so people who voted on them can vote again.
  foreach ($node->choice as $key => $choice) {
    if (!empty($choice['chtext'])) {
      db_merge('poll_choice')
        ->key(array('chid' => $choice['chid']))
        ->fields(array(
          'chtext' => $choice['chtext'],
          'chvotes' => (int) $choice['chvotes'],
          'weight' => $choice['weight'],
        ))
        ->insertFields(array(
          'nid' => $node->nid,
          'chtext' => $choice['chtext'],
          'chvotes' => (int) $choice['chvotes'],
          'weight' => $choice['weight'],
        ))
        ->execute();
    }
    else {
      db_delete('poll_vote')
        ->condition('nid', $node->nid)
        ->condition('chid', $key)
        ->execute();
      db_delete('poll_choice')
        ->condition('nid', $node->nid)
        ->condition('chid', $choice['chid'])
        ->execute();
    }
  }

In db_merge() this code will throw an exception:

PDOException: SQLSTATE[22P02]: Invalid text representation: 7 ERROR:  invalid input syntax for integer: ""
LINE 4: WHERE ( (chid = '') )
                        ^: SELECT 1 AS expression
FROM 
{poll_choice} poll_choice
WHERE ( (chid = :db_condition_placeholder_0) ); Array
(
    [:db_condition_placeholder_0] => 
)
 in poll_update() (line 597 of /var/www/html/modules/poll/poll.module).

Steps to reproduce

Run Poll tests for Drupal 7.x-dev in PostgreSQL.

Proposed resolution

Replace empty string with NULL.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet