CDRIVER-506 update read preferences docs

Author: ajdavis

doc/mongoc_client_set_read_prefs.page

@@ -16,6 +16,8 @@
 mongoc_client_set_read_prefs (mongoc_client_t           *client,
                               const mongoc_read_prefs_t *read_prefs);]]></code></synopsis>
     <p>Sets the default read preferences to use with future operations upon <code>client</code>.</p>
+    <p>The global default is to read from the replica set primary.</p>
+	<p>Please see the MongoDB website for a description of <link href="http://docs.mongodb.org/manual/core/read-preference/">Read Preferences</link>.</p>
   </section>
 
   <section id="parameters">

doc/mongoc_collection_set_read_prefs.page

@@ -29,6 +29,8 @@ mongoc_collection_set_read_prefs (mongoc_collection_t       *collection,
   <section id="description">
     <title>Description</title>
     <p>Sets the default read preferences to use for operations on <code>collection</code> not specifying a read preference.</p>
+    <p>The global default is MONGOC_READ_PRIMARY: if the client is connected to a replica set it reads from the primary, otherwise it reads from the current MongoDB server.</p>
+	<p>Please see the MongoDB website for a description of <link href="http://docs.mongodb.org/manual/core/read-preference/">Read Preferences</link>.</p>
   </section>
 
 </page>

doc/mongoc_database_set_read_prefs.page

@@ -20,6 +20,8 @@ mongoc_database_set_read_prefs (mongoc_database_t         *database,
                                 const mongoc_read_prefs_t *read_prefs);
 ]]></code></synopsis>
     <p>This function sets the default read preferences to use on operations performed with <code>database</code>. Collections created with <link xref="mongoc_database_get_collection">mongoc_database_get_collection()</link> after this call will inherit these read preferences.</p>
+    <p>The global default is MONGOC_READ_PRIMARY: if the client is connected to a replica set it reads from the primary, otherwise it reads from the current MongoDB server.</p>
+	<p>Please see the MongoDB website for a description of <link href="http://docs.mongodb.org/manual/core/read-preference/">Read Preferences</link>.</p>
   </section>
 
   <section id="parameters">

doc/mongoc_read_mode_t.page

@@ -24,7 +24,8 @@
 
   <section id="description">
     <title>Description</title>
-    <p>This enum describes how reads should be dispatched. Please see the MongoDB website for a description of <link href="http://docs.mongodb.org/manual/core/read-preference/">Read Preferences</link>.</p>
+    <p>This enum describes how reads should be dispatched. The default is MONGOC_READ_PRIMARY.</p>
+	<p>Please see the MongoDB website for a description of <link href="http://docs.mongodb.org/manual/core/read-preference/">Read Preferences</link>.</p>
   </section>
 
 </page>

doc/mongoc_read_prefs_t.page

@@ -13,7 +13,7 @@
   <section id="description">
     <title>Synopsis</title>
     <p><link xref="mongoc_read_prefs_t">mongoc_read_prefs_t</link> provides an abstraction on top of the MongoDB connection read prefences. It allows for hinting to the driver which nodes in a replica set should be accessed first.</p>
-    <p>You can specify a read preference mode on connection objects, database objects, collection objects, or per-operation.  Generally, it makes the most sense to stick with *READ_PRIMARY*.  All of the other modes come with caveats that won't be covered in great detail here.</p>
+    <p>You can specify a read preference mode on connection objects, database objects, collection objects, or per-operation.  Generally, it makes the most sense to stick with the global default, <code>MONGOC_READ_PRIMARY</code>.  All of the other modes come with caveats that won't be covered in great detail here.</p>
   </section>
 
   <section id="read-modes">
@@ -25,19 +25,19 @@
       </tr>
       <tr>
         <td><p>MONGOC_READ_SECONDARY</p></td>
-        <td><p>All operations read from the secondary members of the replica set.</p></td>
+        <td><p>All operations read from among the nearest secondary members of the replica set.</p></td>
       </tr>
       <tr>
         <td><p>MONGOC_READ_PRIMARY_PREFERRED</p></td>
         <td><p>In most situations, operations read from the primary but if it is unavailable, operations read from secondary members.</p></td>
       </tr>
       <tr>
         <td><p>MONGOC_READ_SECONDARY_PREFERRED</p></td>
-        <td><p>In most situations, operations read from secondary members but if no secondary members are available, operations read from the primary.</p></td>
+        <td><p>In most situations, operations read from among the nearest secondary members, but if no secondaries are available, operations read from the primary.</p></td>
       </tr>
       <tr>
         <td><p>MONGOC_READ_NEAREST</p></td>
-        <td><p>Operations read from the nearest member of the replica set, irrespective of the member’s type.</p></td>
+        <td><p>Operations read from among the nearest members of the replica set, irrespective of the member’s type.</p></td>
       </tr>
     </table>
   </section>
@@ -56,7 +56,7 @@
       <item><p>nearest</p></item>
     </list>
 
-    <p>Tags are not compatible with primary and, in general, only apply when selecting a secondary member of a set for a read operation. However, the nearest read mode, when combined with a tag set will select the nearest member that matches the specified tag set, which may be a primary or secondary.</p>
+    <p>Tags are not compatible with <code>MONGOC_READ_PRIMARY</code> and, in general, only apply when selecting a secondary member of a set for a read operation. However, the nearest read mode, when combined with a tag set will select the nearest member that matches the specified tag set, which may be a primary or secondary.</p>
 
     <p>All interfaces use the same member selection logic to choose the member to which to direct read operations, basing the choice on read preference mode and tag sets.</p>
   </section>