[5.5] [WIP] Prevent database race conditions on replicated databases

src/Illuminate/Database/Connection.php

@@ -108,6 +108,13 @@ class Connection implements ConnectionInterface
      */
     protected $transactions = 0;
 
+    /**
+     * Have there been changes to the database.
+     *
+     * @var int
+     */
+    protected $recordsModified = false;
+
     /**
      * All of the queries run against the connection.
      *
@@ -392,6 +399,19 @@ protected function getPdoForSelect($useReadPdo = true)
         return $useReadPdo ? $this->getReadPdo() : $this->getPdo();
     }
 
+    /**
+     * Set if any records have been modified.
+     *
+     * @param  bool  $changes
+     * @return void
+     */
+    public function setRecordsModified($changes = true)
+    {
+        if (! $this->recordsModified) {
+            $this->recordsModified = $changes;
+        }
+    }
+
     /**
      * Run an insert statement against the database.
      *
@@ -446,6 +466,8 @@ public function statement($query, $bindings = [])
 
             $this->bindValues($statement, $this->prepareBindings($bindings));
 
+            $this->setRecordsModified();
+
             return $statement->execute();
         });
     }
@@ -473,7 +495,11 @@ public function affectingStatement($query, $bindings = [])
 
             $statement->execute();
 
-            return $statement->rowCount();
+            $count = $statement->rowCount();
+
+            $this->setRecordsModified($count > 0);
+
+            return $count;
         });
     }
 
@@ -490,7 +516,11 @@ public function unprepared($query)
                 return true;
             }
 
-            return $this->getPdo()->exec($query) === false ? false : true;
+            $change = ($this->getPdo()->exec($query) === false ? false : true);
+
+            $this->setRecordsModified($change);
+
+            return $change;
         });
     }
 
@@ -897,6 +927,10 @@ public function getReadPdo()
             return $this->getPdo();
         }
 
+        if ($this->getConfig('sticky') && $this->recordsModified) {
+            return $this->getPdo();
+        }
+
         if ($this->readPdo instanceof Closure) {
             return $this->readPdo = call_user_func($this->readPdo);
         }