You can make this work by using Rules in combination with the Views Bulk Operations module, as further detailed below.
In what follows, I'm assuming that the machine name of your field is field_address (change to whatever fits).
Step 1 - Create a VBO view
Use the Views Bulk Operations (VBO) module to create a view of all relevant nodes, in which you should:
- Add a VBO field to it.
- Add a contextual filter for the
field_address field for which you want to check that its value is unique. Make sure to correctly configure this contextual filter, similar to what is mentioned in this answer to "How to have a field that counts the nodes submitted by the current user?" (credits to Niall Murphy, merci!).
Include a field like nid for each node (no need for any other fields). Just make sure you get exactly 1 row for each node you want to take into consideration.
Here is an export of such VBO view:
$view = new view();
$view->name = 'relevant_nodes';
$view->description = 'Produce a list of node ids that satisfy a specific filter';
$view->tag = 'default';
$view->base_table = 'node';
$view->human_name = 'Relevant nodes';
$view->core = 7;
$view->api_version = '3.0';
$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */
/* Display: Master */
$handler = $view->new_display('default', 'Master', 'default');
$handler->display->display_options['title'] = 'Relevant nodes';
$handler->display->display_options['use_more_always'] = FALSE;
$handler->display->display_options['access']['type'] = 'perm';
$handler->display->display_options['cache']['type'] = 'none';
$handler->display->display_options['query']['type'] = 'views_query';
$handler->display->display_options['exposed_form']['type'] = 'basic';
$handler->display->display_options['pager']['type'] = 'full';
$handler->display->display_options['pager']['options']['items_per_page'] = '10';
$handler->display->display_options['style_plugin'] = 'table';
$handler->display->display_options['style_options']['columns'] = array(
'title' => 'title',
);
$handler->display->display_options['style_options']['default'] = '-1';
$handler->display->display_options['style_options']['info'] = array(
'title' => array(
'sortable' => 0,
'default_sort_order' => 'asc',
'align' => '',
'separator' => '',
'empty_column' => 0,
),
);
/* Field: Content: Nid */
$handler->display->display_options['fields']['nid']['id'] = 'nid';
$handler->display->display_options['fields']['nid']['table'] = 'node';
$handler->display->display_options['fields']['nid']['field'] = 'nid';
/* Field: Content: Title */
$handler->display->display_options['fields']['title']['id'] = 'title';
$handler->display->display_options['fields']['title']['table'] = 'node';
$handler->display->display_options['fields']['title']['field'] = 'title';
$handler->display->display_options['fields']['title']['label'] = '';
$handler->display->display_options['fields']['title']['alter']['word_boundary'] = FALSE;
$handler->display->display_options['fields']['title']['alter']['ellipsis'] = FALSE;
/* Field: Content: Address */
$handler->display->display_options['fields']['field_address']['id'] = 'field_address';
$handler->display->display_options['fields']['field_address']['table'] = 'field_data_field_address';
$handler->display->display_options['fields']['field_address']['field'] = 'field_address';
/* Field: Bulk operations: Content */
$handler->display->display_options['fields']['views_bulk_operations']['id'] = 'views_bulk_operations';
$handler->display->display_options['fields']['views_bulk_operations']['table'] = 'node';
$handler->display->display_options['fields']['views_bulk_operations']['field'] = 'views_bulk_operations';
$handler->display->display_options['fields']['views_bulk_operations']['vbo_settings']['display_type'] = '0';
$handler->display->display_options['fields']['views_bulk_operations']['vbo_settings']['enable_select_all_pages'] = 1;
$handler->display->display_options['fields']['views_bulk_operations']['vbo_settings']['row_clickable'] = 1;
$handler->display->display_options['fields']['views_bulk_operations']['vbo_settings']['force_single'] = 0;
$handler->display->display_options['fields']['views_bulk_operations']['vbo_settings']['entity_load_capacity'] = '10';
/* Contextual filter: Content: Address (field_address) */
$handler->display->display_options['arguments']['field_address_value']['id'] = 'field_address_value';
$handler->display->display_options['arguments']['field_address_value']['table'] = 'field_data_field_address';
$handler->display->display_options['arguments']['field_address_value']['field'] = 'field_address_value';
$handler->display->display_options['arguments']['field_address_value']['default_action'] = 'default';
$handler->display->display_options['arguments']['field_address_value']['default_argument_type'] = 'raw';
$handler->display->display_options['arguments']['field_address_value']['default_argument_options']['index'] = '0';
$handler->display->display_options['arguments']['field_address_value']['summary']['number_of_records'] = '0';
$handler->display->display_options['arguments']['field_address_value']['summary']['format'] = 'default_summary';
$handler->display->display_options['arguments']['field_address_value']['summary_options']['items_per_page'] = '25';
$handler->display->display_options['arguments']['field_address_value']['limit'] = '0';
/* Filter criterion: Content: Published */
$handler->display->display_options['filters']['status']['id'] = 'status';
$handler->display->display_options['filters']['status']['table'] = 'node';
$handler->display->display_options['filters']['status']['field'] = 'status';
$handler->display->display_options['filters']['status']['value'] = 1;
$handler->display->display_options['filters']['status']['group'] = 1;
$handler->display->display_options['filters']['status']['expose']['operator'] = FALSE;
/* Filter criterion: Content: Type */
$handler->display->display_options['filters']['type']['id'] = 'type';
$handler->display->display_options['filters']['type']['table'] = 'node';
$handler->display->display_options['filters']['type']['field'] = 'type';
$handler->display->display_options['filters']['type']['value'] = array(
'article' => 'article',
);
/* Display: Page */
$handler = $view->new_display('page', 'Page', 'page');
$handler->display->display_options['path'] = 'relevant-nodes';
Step 2 - Create a Rule
Create a rule like so:
Rules Event: something like "Before saving content of type Article" seems most appropriate, though you can use any variation that fits.
Rules Condition: "Check number of results returned by a VBO view". And select the VBO view created in the previous step. In doing so, you will be asked to "specify arguments to pass to the view, one per line. You may use token replacement patterns.". The token to be entered there is node:field-address. If the number of results is 1 or more, then you know the value already exists. So within Minimum number of results you should enter the value 1.
Rules Action: this is pretty much up to your own imagination (your question doesn't specify what should happen ...). For example if the Rules Condition is TRUE, you could use "Set a data value", to set the value of that field to whatever fits. Maybe also display an appropriate message, such as (when trying to set the value to HomeIsWhereMyStellaIs):
The value "HomeIsWhereMyStellaIs" has already been used in at least 1 other node ...
Here is an export of a Rule that does (without such "Set a value" though) what is described above (if you have the Rules UI enabled, and a field with the machine name field_address, you should be able to just import this rule):
{ "rules_prevent_multiple_nodes_with_same_field_value" : {
"LABEL" : "Prevent multiple nodes with same field value",
"PLUGIN" : "reaction rule",
"OWNER" : "rules",
"REQUIRES" : [ "views_bulk_operations", "rules" ],
"ON" : { "node_presave--article" : { "bundle" : "article" } },
"IF" : [
{ "views_bulk_operations_condition_result_count" : {
"view" : "relevant_nodes|page",
"args" : [ "node:field-address" ],
"minimum" : "1"
}
}
],
"DO" : [
{ "drupal_message" : {
"message" : "The value \u0022[node:field-address]\u0022 has already been used in at least 1 other node ...",
"type" : "error"
}
}
]
}
}
Note that my Rules Event is limited to "Article" (change to whatever fits), and replace (prior to trying to import this rule) the machine name of field_address to whatever other machine name your field.
Done!
PS: I'm assuming this is about D7.
