Add upgrade note about schema_filter change

UPGRADE.md

@@ -10,6 +10,12 @@ Method `Doctrine\ORM\AbstractQuery#useResultCache()` which could be used for bot
 To optimize DB interaction, `Doctrine\ORM\Tools\Pagination\Paginator` no longer fetches identifiers to be able to
 perform the pagination with join collections when max results isn't set in the query.
 
+## Minor BC BREAK: tables filtered with `schema_filter` are no longer created
+
+When generating schema diffs, if a source table is filtered out by a `schema_filter` expression, then a `CREATE TABLE` was
+always generated, even if the table already existed. This has been changed in this release and the table will no longer
+be created.
+
 ## Deprecated number unaware `Doctrine\ORM\Mapping\UnderscoreNamingStrategy`
 
 In the last patch of the `v2.6.x` series, we fixed a bug that was not converting names properly when they had numbers

lib/Doctrine/ORM/Tools/SchemaTool.php

@@ -918,10 +918,9 @@ public function getUpdateSchemaSql(array $classes, $saveMode = false)
     private function createSchemaForComparison(Schema $toSchema) : Schema
     {
         // backup schema assets filter and filter-expression
-        $sm               = $this->em->getConnection()->getSchemaManager();
-        $config           = $this->em->getConnection()->getConfiguration();
-        $filterExpression = method_exists(Configuration::class, 'getFilterSchemaAssetsExpression') ? $config->getFilterSchemaAssetsExpression() : null;
-        $filter           = $config->getSchemaAssetsFilter();
+        $sm     = $this->em->getConnection()->getSchemaManager();
+        $config = $this->em->getConnection()->getConfiguration();
+        $filter = $config->getSchemaAssetsFilter();
 
         if ($filter === null) {
             return $sm->createSchema();
@@ -938,11 +937,7 @@ private function createSchemaForComparison(Schema $toSchema) : Schema
             return $sm->createSchema();
         } finally {
             // restore schema assets filter and filter-expression
-            if ($filterExpression !== null) {
-                $config->setFilterSchemaAssetsExpression($filterExpression);
-            } else {
-                $config->setSchemaAssetsFilter($filter);
-            }
+            $config->setSchemaAssetsFilter($filter);
         }
     }
 }