API Use mysql-safe table namespace separator

src/ORM/DataObjectSchema.php

@@ -24,12 +24,10 @@ class DataObjectSchema
      * Default separate for table namespaces. Can be set to any string for
      * databases that do not support some characters.
      *
-     * Defaults to \ to to conform to 3.x convention.
-     *
      * @config
      * @var string
      */
-    private static $table_namespace_separator = '\\';
+    private static $table_namespace_separator = '_';
 
     /**
      * Cache of database fields

tests/php/ORM/DataObjectSchemaTest.php

@@ -9,6 +9,7 @@ use SilverStripe\ORM\DataObjectSchema;
 use SilverStripe\ORM\Tests\DataObjectSchemaTest\BaseClass;
 use SilverStripe\ORM\Tests\DataObjectSchemaTest\BaseDataClass;
 use SilverStripe\ORM\Tests\DataObjectSchemaTest\ChildClass;
+use SilverStripe\ORM\Tests\DataObjectSchemaTest\DefaultTableName;
 use SilverStripe\ORM\Tests\DataObjectSchemaTest\GrandChildClass;
 use SilverStripe\ORM\Tests\DataObjectSchemaTest\HasFields;
 use SilverStripe\ORM\Tests\DataObjectSchemaTest\NoFields;
@@ -31,7 +32,8 @@ class DataObjectSchemaTest extends SapphireTest
         HasFields::Class,
         NoFields::class,
         WithCustomTable::class,
-        WithRelation::class
+        WithRelation::class,
+        DefaultTableName::class
     );
 
     /**
@@ -49,6 +51,11 @@ class DataObjectSchemaTest extends SapphireTest
             'DOSTWithCustomTable',
             $schema->tableName(WithCustomTable::class)
         );
+        // Default table name is FQN
+        $this->assertEquals(
+            'SilverStripe_ORM_Tests_DataObjectSchemaTest_DefaultTableName',
+            $schema->tableName(DefaultTableName::class)
+        );
     }
 
     /**

tests/php/ORM/DataObjectSchemaTest/DefaultTableName.php

@@ -0,0 +1,14 @@
+<?php
+
+
+namespace SilverStripe\ORM\Tests\DataObjectSchemaTest;
+
+use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\DataObject;
+
+class DefaultTableName extends DataObject implements TestOnly
+{
+    private static $db = [
+        'Title' => 'Varchar',
+    ];
+}