magento/magento2 issue 19597 patch. See https://github.com/magento/magento2/issues/19597#issuecomment-573526850 for context

GH-19597-fix-setup-db-status-inaccuracy.patch

diff --git a/Declaration/Schema/Comparator.php b/Declaration/Schema/Comparator.php
--- a/Setup/Declaration/Schema/Comparator.php
+++ b/Setup/Declaration/Schema/Comparator.php
@@ -24,7 +24,38 @@
      */
     public function compare(ElementInterface $first, ElementInterface $second)
     {
+        // Code below pulled from https://github.com/magento/magento2/issues/19597#issuecomment-463611130
+        //Ugly patch (MariaDB compatibility)
+        $firstParams = $first->getDiffSensitiveParams();
+        $secondParams = $second->getDiffSensitiveParams();
+
+        $eqValues = [
+            ['field' => 'default','values' => ['CURRENT_TIMESTAMP', 'current_timestamp()']],
+            ['field' => 'default','values' => ['NULL', '', NULL]],
+        ];
+
+        //standard values
+        foreach($eqValues as $eqValue){
+            $field = $eqValue['field'];
+            $values = $eqValue['values'];
+
+            if(array_key_exists($field,$firstParams) && in_array($secondParams[$field],$values)
+                && array_key_exists($field,$secondParams) && in_array($secondParams[$field],$values)
+            ){
+                $firstParams['default'] = $values[0];
+                $secondParams['default'] = $values[0];
+                continue;
+            }
+
+        }
+
+        //enclosing quotes
+        if(array_key_exists('default',$secondParams)
+            && preg_match("/\\'.*\\'/", $secondParams['default'])){
+            $firstParams['default'] = $secondParams['default'];
+        }
+
         return get_class($first) === get_class($second) &&
-            $first->getDiffSensitiveParams() === $second->getDiffSensitiveParams();
+            $firstParams === $secondParams;
     }
 }
diff --git a/Setup/ExternalFKSetup.php b/Setup/ExternalFKSetup.php
index 4247b7b1a..42642f747 100644
--- a/Setup/ExternalFKSetup.php
+++ b/Setup/ExternalFKSetup.php
@@ -82,8 +82,54 @@ class ExternalFKSetup
             $this->setup->getTable($this->entityTable)
         );
         if (!$entityTableInfo[$this->entityColumn]['PRIMARY']) {
-            $this->dropOldForeignKey();
-            $this->addForeignKeys();
+
+            // find the foreign keys on the entityTable
+
+            $entityForeignKeys = $this->setup->getConnection()->getForeignKeys(
+                $this->setup->getTable($this->entityTable)
+            );
+            $entityForeignKeys = array_filter(
+                $entityForeignKeys,
+                function ($key) {
+                    return $key['COLUMN_NAME'] == $this->entityColumn;
+                }
+            );
+
+            $targetForeignKeys = $this->setup->getConnection()->getForeignKeys(
+                $this->setup->getTable($this->externalTable)
+            );
+
+            // for each found key, create one on the targetTable
+
+            foreach ($entityForeignKeys as $entityForeignKey) {
+
+                $targetForeignKeyName = $this->setup->getFkName(
+                    $this->externalTable,
+                    $this->externalColumn,
+                    $this->setup->getTablePlaceholder($entityForeignKey['REF_TABLE_NAME']),
+                    $entityForeignKey['REF_COLUMN_NAME']
+                );
+
+                // check if the foreign key on the targetTable already exists
+
+                foreach ($targetForeignKeys as $targetForeignKey) {
+                    if ($targetForeignKey['FK_NAME'] === $targetForeignKeyName) {
+                        // skip adding
+                        continue 2;
+                    }
+                }
+
+                // add foreign key on targetTable based on the entityTable FK
+
+                $this->setup->getConnection()->addForeignKey(
+                    $targetForeignKeyName,
+                    $this->setup->getTable($this->externalTable),
+                    $this->externalColumn,
+                    $entityForeignKey['REF_TABLE_NAME'],
+                    $entityForeignKey['REF_COLUMN_NAME'],
+                    $this->onDelete
+                );
+            }
         } else {
             $this->addDefaultForeignKey();
         }
diff --git a/Setup/Declaration/Schema/Diff/TableDiff.php b/Setup/Declaration/Schema/Diff/TableDiff.php
index 87045df86..6814ce627 100644
--- a/Setup/Declaration/Schema/Diff/TableDiff.php
+++ b/Setup/Declaration/Schema/Diff/TableDiff.php
@@ -203,6 +203,14 @@ class TableDiff
             }

             //Elements that should be removed
+            if ($elementType == self::CONSTRAINT_DIFF_TYPE) {
+                foreach (array_keys($generatedElements) as $elementName) {
+                    if (preg_match('/_SEQUENCE_VAL$/', $elementName)) {
+                        // remove auto-generated extra constraints
+                        unset($generatedElements[$elementName]);
+                    }
+                }
+            }
             if ($this->diffManager->shouldBeRemoved($generatedElements)) {
                 $diff = $this->diffManager->registerRemoval($diff, $generatedElements);
             }