Merge pull request #102 from vapor/longtext-crash-repro

[Repro] Longtext columns cause crash on low memory systems

Author: tanner0101

Sources/MySQL/Bind/Bind.swift

@@ -56,12 +56,13 @@ public final class Bind {
                  MYSQL_TYPE_TIME:
             length = MemoryLayout<MYSQL_TIME>.size
         default:
-            length = Int(field.cField.length)
+            length = Int(field.cField.max_length)
         }
 
         cBind.buffer_length = UInt(length)
-        
         cBind.buffer = UnsafeMutableRawPointer.allocate(bytes: length, alignedTo: MemoryLayout<Void>.alignment)
+        
+        
         cBind.length = UnsafeMutablePointer<UInt>.allocate(capacity: 1)
         cBind.is_null = UnsafeMutablePointer<my_bool>.allocate(capacity: 1)
         cBind.error = UnsafeMutablePointer<my_bool>.allocate(capacity: 1)

Sources/MySQL/Connection.swift

@@ -76,6 +76,14 @@ public final class Connection {
         guard let statement = mysql_stmt_init(cConnection) else {
             throw lastError
         }
+        
+        // important! this must be set for field.max_length
+        // to be properly filled
+        var truth: my_bool = 1
+        guard mysql_stmt_attr_set(statement, STMT_ATTR_UPDATE_MAX_LENGTH, &truth)  == 0 else {
+            throw lastError
+        }
+        
         defer {
             mysql_stmt_close(statement)
         }
@@ -110,8 +118,20 @@ public final class Connection {
             mysql_free_result(metadata)
         }
 
+        // Execute the statement!
+        // The data is ready to be fetched when this completes.
+        guard mysql_stmt_execute(statement) == 0 else {
+            throw lastError
+        }
+        
+        // buffers the data on the client
+        // important! sets the max_length field
+        mysql_stmt_store_result(statement)
+        
         // Parse the fields (columns) that will be returned
         // by this statement.
+        // important! field information should not be parsed
+        // until mysql_stmt_store_result has been called.
         let fields = try Fields(metadata, self)
 
         // Use the fields data to create output bindings.
@@ -124,12 +144,6 @@ public final class Connection {
             throw lastError
         }
 
-        // Execute the statement!
-        // The data is ready to be fetched when this completes.
-        guard mysql_stmt_execute(statement) == 0 else {
-            throw lastError
-        }
-
         var results: [StructuredData] = []
 
         // This single dictionary is reused for all rows in the result set

Tests/MySQLTests/MySQLTests.swift

@@ -15,6 +15,7 @@ class MySQLTests: XCTestCase {
         ("testTransaction", testTransaction),
         ("testTransactionFailed", testTransactionFailed),
         ("testBlob", testBlob),
+        ("testLongtext", testLongtext),
     ]
 
     var mysql: MySQL.Database!
@@ -270,7 +271,30 @@ class MySQLTests: XCTestCase {
             XCTFail("Timeout test failed.")
         }
     }
-    
+
+    func testLongtext() throws {
+        let conn = try mysql.makeConnection()
+        try conn.execute("DROP TABLE IF EXISTS items")
+        try conn.execute("CREATE TABLE `items` ( " +
+            "`id` int(10) unsigned NOT NULL AUTO_INCREMENT, " +
+            "`title` varchar(255) NOT NULL DEFAULT '', " +
+            "`imageUrl` varchar(255) NOT NULL DEFAULT '', " +
+            "`html` longtext NOT NULL, " +
+            "`isPrivate` tinyint(1) unsigned NOT NULL, " +
+            "`isBusiness` tinyint(1) unsigned NOT NULL, " +
+            "PRIMARY KEY (`id`)) " +
+            "ENGINE=InnoDB AUTO_INCREMENT=13 DEFAULT CHARSET=utf8;")
+
+        try conn.execute("INSERT INTO `items` (`id`, `title`, `imageUrl`, `html`, `isPrivate`, `isBusiness`) " +
+            "VALUES (1, 'test1', '12A34264-E5F6-48D4-AB27-422C4FD03277_10.jpeg', '<p>html</p>', 1, 1)")
+
+        let retrieved = try conn.execute("SELECT * from items")
+        XCTAssertEqual(retrieved.array?.count ?? 0, 1)
+        XCTAssertEqual(retrieved[0, "id"], 1)
+        XCTAssertEqual(retrieved[0, "title"], "test1")
+        XCTAssertEqual(retrieved[0, "html"]?.bytes?.makeString(), "<p>html</p>")
+    }
+
     func testPerformance() throws {
         let conn = try mysql.makeConnection()
         try conn.execute("DROP TABLE IF EXISTS things")