repatched for custom dynmaic field definition : https://drupal.org/node/1846860#comment-7805861

1846860-8--dynamic_field_info.patch

@@ -1,8 +1,79 @@
+diff --git a/includes/service.inc b/includes/service.inc
+index 4455235..20e57b8 100644
+--- a/includes/service.inc
++++ b/includes/service.inc
+@@ -27,28 +27,6 @@ class SearchApiSolrService extends SearchApiAbstractService {
+   protected $solr;
+ 
+   /**
+-   * An array of all recognized types.
+-   *
+-   * Maps the type names to the prefixes used for identifying them in the Solr
+-   * schema.
+-   *
+-   * @var array
+-   */
+-  protected static $type_prefixes = array(
+-    'text' => 'tm',
+-    'tokens' => 'tm',
+-    'string' => 's',
+-    'integer' => 'i',
+-    'decimal' => 'f',
+-    'date' => 'd',
+-    'duration' => 'i',
+-    'boolean' => 'b',
+-    'uri' => 's',
+-    'location' => 'loc',
+-    'geohash' => 'geo',
+-  );
+-
+-  /**
+    * Static cache for getFieldNames().
+    *
+    * @var array
+@@ -290,7 +268,8 @@ class SearchApiSolrService extends SearchApiAbstractService {
+    * Overrides SearchApiAbstractService::supportsFeature().
+    */
+   public function supportsFeature($feature) {
+-    $supported = drupal_map_assoc(array(
++    // Search API features.
++    $supported = array(
+       'search_api_autocomplete',
+       'search_api_facets',
+       'search_api_facets_operator_or',
+@@ -300,7 +279,14 @@ class SearchApiSolrService extends SearchApiAbstractService {
+       'search_api_spellcheck',
+       'search_api_data_type_location',
+       'search_api_data_type_geohash',
+-    ));
++    );
++
++    // Custom data types.
++    foreach (search_api_solr_get_dynamic_field_info() as $type => $info) {
++      $supported[] = 'search_api_data_type_' . $type;
++    }
++
++    $supported = drupal_map_assoc($supported);
+     return isset($supported[$feature]);
+   }
+ 
+@@ -495,8 +481,9 @@ class SearchApiSolrService extends SearchApiAbstractService {
+         }
+ 
+         $inner_type = search_api_extract_inner_type($type);
+-        $pref = isset(self::$type_prefixes[$inner_type]) ? self::$type_prefixes[$inner_type] : '';
+-        if ($pref != 'tm') {
++        $type_info = search_api_solr_get_dynamic_field_info($inner_type);
++        $pref = isset($type_info['prefix']) ? $type_info['prefix']: '';
++        if (empty($type_info['always multiValued'])) {
+           $pref .= $type == $inner_type ? 's' : 'm';
+         }
+         if (!empty($this->options['clean_ids'])) {
 diff --git a/search_api_solr.api.php b/search_api_solr.api.php
-index f407407..ec4b190 100644
+index a64c477..cc9b208 100644
 --- a/search_api_solr.api.php
 +++ b/search_api_solr.api.php
-@@ -85,5 +85,45 @@ function hook_search_api_solr_multi_query_alter(array &$call_args, SearchApiMult
+@@ -101,5 +101,45 @@ function hook_search_api_solr_multi_query_alter(array &$call_args, SearchApiMult
  }
  
  /**
@@ -49,15 +120,13 @@ index f407407..ec4b190 100644
   * @} End of "addtogroup hooks".
   */
 diff --git a/search_api_solr.module b/search_api_solr.module
-index 9e30397..b75319b 100644
+index cfab380..52ae956 100644
 --- a/search_api_solr.module
 +++ b/search_api_solr.module
-@@ -143,3 +143,81 @@ function search_api_solr_cron() {
-     }
-   }
+@@ -113,6 +113,84 @@ function search_api_solr_search_api_server_update(SearchApiServer $server) {
  }
-+
-+/**
+ 
+ /**
 + * Returns either all dynamic field types, or a specific one.
 + *
 + * @param $type
@@ -113,93 +182,29 @@ index 9e30397..b75319b 100644
 +      'always multiValued' => FALSE,
 +    ),
 +    'duration' => array(
-+      'i',
++      'prefix' => 'i',
 +      'always multiValued' => FALSE,
 +    ),
 +    'boolean' => array(
-+      'b',
++      'prefix' => 'b',
 +      'always multiValued' => FALSE,
 +    ),
 +    'uri' => array(
-+      's',
++      'prefix' => 's',
 +      'always multiValued' => FALSE,
 +    ),
 +    'location' => array(
-+      'loc',
++      'prefix' => 'loc',
 +      'always multiValued' => FALSE,
 +    ),
 +    'geohash' => array(
-+      'geohash',
++      'prefix' => 'geohash',
 +      'always multiValued' => FALSE,
 +    ),
 +  );
 +}
-diff --git a/service.inc b/service.inc
-index 0e8dbee..5054c51 100644
---- a/service.inc
-+++ b/service.inc
-@@ -18,26 +18,6 @@ class SearchApiSolrService extends SearchApiAbstractService {
-   protected $solr;
- 
-   /**
--   * An array of all recognized types mapped to a prefix used for identifying
--   * them in the Solr schema.
--   *
--   * @var array
--   */
--  protected static $type_prefixes = array(
--    'text' => 'tm',
--    'tokens' => 'tm',
--    'string' => 's',
--    'integer' => 'i',
--    'decimal' => 'f',
--    'date' => 'd',
--    'duration' => 'i',
--    'boolean' => 'b',
--    'uri' => 's',
--    'location' => 'loc',
--    'geohash' => 'geohash',
--  );
--
--  /**
-    * @var array
-    */
-   protected $fieldNames = array();
-@@ -222,7 +202,8 @@ class SearchApiSolrService extends SearchApiAbstractService {
-   }
- 
-   public function supportsFeature($feature) {
--    $supported = drupal_map_assoc(array(
-+    // Search API features.
-+    $supported = array(
-       'search_api_autocomplete',
-       'search_api_facets',
-       'search_api_facets_operator_or',
-@@ -231,7 +212,14 @@ class SearchApiSolrService extends SearchApiAbstractService {
-       'search_api_spellcheck',
-       'search_api_data_type_location',
-       'search_api_data_type_geohash',
--    ));
-+    );
 +
-+    // Custom data types.
-+    foreach (search_api_solr_get_dynamic_field_info() as $type => $info) {
-+      $supported[] = 'search_api_data_type_' . $type;
-+    }
-+
-+    $supported = drupal_map_assoc($supported);
-     return isset($supported[$feature]);
-   }
- 
-@@ -395,8 +383,9 @@ class SearchApiSolrService extends SearchApiAbstractService {
-         }
- 
-         $inner_type = search_api_extract_inner_type($type);
--        $pref = isset(self::$type_prefixes[$inner_type]) ? self::$type_prefixes[$inner_type] : '';
--        if ($pref != 'tm') {
-+        $type_info = search_api_solr_get_dynamic_field_info($inner_type);
-+        $pref = isset($type_info['prefix']) ? $type_info['prefix']: '';
-+        if (empty($type_info['always multiValued'])) {
-           $pref .= $type == $inner_type ? 's' : 'm';
-         }
-         $name = $pref . '_' . $key;
++/**
+  * Retrieves a list of all config files of a server.
+  *
+  * @param SearchApiServer $server

includes/service.inc

@@ -26,28 +26,6 @@ class SearchApiSolrService extends SearchApiAbstractService {
    */
   protected $solr;
 
-  /**
-   * An array of all recognized types.
-   *
-   * Maps the type names to the prefixes used for identifying them in the Solr
-   * schema.
-   *
-   * @var array
-   */
-  protected static $type_prefixes = array(
-    'text' => 'tm',
-    'tokens' => 'tm',
-    'string' => 's',
-    'integer' => 'i',
-    'decimal' => 'f',
-    'date' => 'd',
-    'duration' => 'i',
-    'boolean' => 'b',
-    'uri' => 's',
-    'location' => 'loc',
-    'geohash' => 'geo',
-  );
-
   /**
    * Static cache for getFieldNames().
    *
@@ -290,7 +268,8 @@ class SearchApiSolrService extends SearchApiAbstractService {
    * Overrides SearchApiAbstractService::supportsFeature().
    */
   public function supportsFeature($feature) {
-    $supported = drupal_map_assoc(array(
+    // Search API features.
+    $supported = array(
       'search_api_autocomplete',
       'search_api_facets',
       'search_api_facets_operator_or',
@@ -300,7 +279,14 @@ class SearchApiSolrService extends SearchApiAbstractService {
       'search_api_spellcheck',
       'search_api_data_type_location',
       'search_api_data_type_geohash',
-    ));
+    );
+
+    // Custom data types.
+    foreach (search_api_solr_get_dynamic_field_info() as $type => $info) {
+      $supported[] = 'search_api_data_type_' . $type;
+    }
+
+    $supported = drupal_map_assoc($supported);
     return isset($supported[$feature]);
   }
 
@@ -495,8 +481,9 @@ class SearchApiSolrService extends SearchApiAbstractService {
         }
 
         $inner_type = search_api_extract_inner_type($type);
-        $pref = isset(self::$type_prefixes[$inner_type]) ? self::$type_prefixes[$inner_type] : '';
-        if ($pref != 'tm') {
+        $type_info = search_api_solr_get_dynamic_field_info($inner_type);
+        $pref = isset($type_info['prefix']) ? $type_info['prefix']: '';
+        if (empty($type_info['always multiValued'])) {
           $pref .= $type == $inner_type ? 's' : 'm';
         }
         if (!empty($this->options['clean_ids'])) {

search_api_solr.api.php

@@ -100,6 +100,46 @@ function hook_search_api_solr_multi_query_alter(array &$call_args, SearchApiMult
   }
 }
 
+/**
+ * Define how Search API Solr should index different data types.
+ *
+ * It is important to make sure that any types you define are also declared to
+ * Search API using hook_search_api_data_type_info().
+ *
+ * @return array
+ *   An array containing data type definitions, keyed by their type identifier
+ *   and containing the following keys:
+ *   - prefix: The prefix used by the dynamic field type.
+ *   - always multiValued: (optional) Whether the single/multiple prefix should
+ *     be skipped for this data type. Defaults to FALSE.
+ *
+ * @see hook_search_api_solr_dynamic_field_info_alter()
+ * @see search_api_solr_get_dynamic_field_info()
+ * @see hook_search_api_data_type_info().
+ */
+function hook_search_api_solr_dynamic_field_info() {
+  return array(
+    'example_type' => array(
+      'prefix' => 'ex',
+      // Could be omitted, as FALSE is the default.
+      'always multiValued' => FALSE,
+    ),
+  );
+}
+
+/**
+ * Alter the data type indexing info.
+ *
+ * @param array $infos
+ *   The item type info array, keyed by type identifier.
+ *
+ * @see hook_search_api_solr_dynamic_field_info()
+ */
+function hook_search_api_solr_dynamic_field_info_alter(array &$infos) {
+  // Change the prefix used for example_type.
+  $info['example_type']['prefix'] = 'ex2';
+}
+
 /**
  * @} End of "addtogroup hooks".
  */

search_api_solr.module

@@ -112,6 +112,84 @@ function search_api_solr_search_api_server_update(SearchApiServer $server) {
   }
 }
 
+/**
+ * Returns either all dynamic field types, or a specific one.
+ *
+ * @param $type
+ *   If specified, the type whose definition should be returned.
+ *
+ * @return array
+ *   If $type was not given, an array containing all custom dynamic fields, in
+ *   the format specified by hook_search_api_solr_dynamic_field_info().
+ *   Otherwise, the definition for the given type, or NULL if it is unknown.
+ *
+ * @see hook_search_api_solr_dynamic_field_info().
+ */
+function search_api_solr_get_dynamic_field_info($type = NULL) {
+  $types = &drupal_static(__FUNCTION__);
+  if (!isset($types)) {
+    $types = module_invoke_all('search_api_solr_dynamic_field_info');
+    $types = $types ? $types : array();
+    drupal_alter('search_api_solr_dynamic_field_info', $types);
+  }
+  if (isset($type)) {
+    return isset($types[$type]) ? $types[$type] : NULL;
+  }
+  return $types;
+}
+
+/**
+ * Implements hook_search_api_solr_dynamic_field_info().
+ */
+function search_api_solr_search_api_solr_dynamic_field_info() {
+  return array(
+    'text' => array(
+      'prefix' => 'tm',
+      'always multiValued' => TRUE,
+    ),
+    'tokens' => array(
+      'prefix' => 'tm',
+      'always multiValued' => TRUE,
+    ),
+    'string' => array(
+      'prefix' => 's',
+      'always multiValued' => FALSE,
+    ),
+    'integer' => array(
+      'prefix' => 'i',
+      'always multiValued' => FALSE,
+    ),
+    'decimal' => array(
+      'prefix' => 'f',
+      'always multiValued' => FALSE,
+    ),
+    'date' => array(
+      'prefix' => 'd',
+      'always multiValued' => FALSE,
+    ),
+    'duration' => array(
+      'prefix' => 'i',
+      'always multiValued' => FALSE,
+    ),
+    'boolean' => array(
+      'prefix' => 'b',
+      'always multiValued' => FALSE,
+    ),
+    'uri' => array(
+      'prefix' => 's',
+      'always multiValued' => FALSE,
+    ),
+    'location' => array(
+      'prefix' => 'loc',
+      'always multiValued' => FALSE,
+    ),
+    'geohash' => array(
+      'prefix' => 'geohash',
+      'always multiValued' => FALSE,
+    ),
+  );
+}
+
 /**
  * Retrieves a list of all config files of a server.
  *