Quicksearch parameters - split_terms and priority

I have been working on build in an extra field to the List View quicksearch on Accounts and Contacts.

Thanks to previous contributors around this.

However, I am experiencing some inconsistent behaviour and am wondering what part the split_terms and priority settings play.

For example...

Accounts

In Accounts module in the \custom\modules\Accounts\clients\base\filters\basic\basic.php I have

      $viewdefs['Accounts']['base']['filter']['basic'] = array(
      'create' => true,
      'quicksearch_field' => array('name', 'my_custom_field'),
      'quicksearch_priority' => 1,
      'quicksearch_split_terms' => false,

      ....

and this seems to work OK

If I type in either a value based on the name field or a value based on my custom field, the List View filters down appropriately.

Contacts

On Contacts, from other posts I see the code references the first_name and last_name 

So I have built in this code...

      $viewdefs['Contacts']['base']['filter']['basic'] = array(
      'create' => true,
      'quicksearch_field' => array('first_name', 'last_name', 'my_custom_field'),
      'quicksearch_priority' => 2,
      'quicksearch_split_terms' => false,

      ....

Before I added my custom field in, List View search would behave like...

Type in 'Gordon'      :   this returns all contacts containing 'Gordon' (first or last name)

Type in 'Gordon V'   :   this returns all contacts containing 'Gordon V'

After I add my custom field in, behaviour is as follows...

Type in 'Gordon'      :   behaviour as before, all contacts containing 'Gordon' (first or last name)

Type in 'Gordon V'   :   initially returns Gordon records but when I type in space V, no records returned

If I type in one of my custom field values on it's own, it returns records containing that value.

I'm wondering if the split_terms and/or priority settings are relevant, but can find no specific documentation on those.

Thanks

Neil