Question

I am using the MySql Connector C++ to store a JPEG image from a file into the database. I am using the prepared statement. After execution of the prepared statement, only the first 64 bytes of the file are copied into the database.

My research of examples show that no iteration is necessary and the examples assume that the prepared statement loads the entire file. Here is my code:

std::string         statement_text("INSERT INTO ");
statement_text += "picture_image_data";
statement_text += " (";
statement_text += "ID_Picture";
statement_text += ", ";
statement_text += "Image_Data";
statement_text += ") VALUES (?, ?)";    
wxLogDebug("Creating prepared statement using:\n%s\n", statement_text.c_str());
std::string filename("my_image.jpg");
Ptr_Db_Connection                           db_conn(db_mgr.get_db_connection());
boost::shared_ptr<sql::PreparedStatement>   prepared_statement(db_conn->prepareStatement(statement_text));
prepared_statement->setInt(1, picture_id);
std::ifstream   blob_file(filename.c_str());
prepared_statement->setBlob(2, &blob_file);
prepared_statement->execute();
blob_file.close();

Here is the schema of the table:

mysql> describe picture_image_data;
+------------+------------------+------+-----+---------+----------------+
| Field      | Type             | Null | Key | Default | Extra          |
+------------+------------------+------+-----+---------+----------------+
| ID_Picture | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| Image_Data | mediumblob       | YES  |     | NULL    |                |
+------------+------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)

From the MySql Console:

mysql> select ID_Picture, LENGTH(image_data)
    -> FROM picture_image_data
    -> where ID_Picture = 1;
+------------+--------------------+
| ID_Picture | LENGTH(image_data) |
+------------+--------------------+
|          1 |                 65 |
+------------+--------------------+
1 row in set (0.02 sec)

How do I make the prepared statement read the entire file?
Do I need to initialize anything in MySql Connector C++ to make this read more than 64 bytes?

Note: I am using MySql Connector C++ 1.0.5, Visual Studio 2008 and wxWidgets on Windows XP and Vista.

Table creation statement:

CREATE TABLE Picture_Image_Data
(
    ID_Picture INTEGER UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
    Image_Data MEDIUMBLOB
);

Hex dump (via Cygwin) of the image file:

0000000 d8ff e0ff 1000 464a 4649 0100 0101 1c00
0000010 1c00 0000 dbff 4300 0500 0403 0404 0503
0000020 0404 0504 0505 0706 080c 0707 0707 0b0f
0000030 090b 110c 120f 1112 110f 1311 1c16 1317
0000040 1a14 1115 1811 1821 1d1a 1f1d 1f1f 1713
0000050 2422 1e22 1c24 1f1e ff1e 00db 0143 0505
0000060 0705 0706 080e 0e08 141e 1411 1e1e 1e1e
0000070 1e1e 1e1e 1e1e 1e1e 1e1e 1e1e 1e1e 1e1e  

Answer 1

The issue lies in the constructor of the image file:

std::ifstream   blob_file(filename.c_str());

This should have the binary mode attribute:

std::ifstream   blob_file(filename.c_str(), std::ios_base::binary);

The file, a JPEG image, is binary data.

Also, the hex dump at byte 65 shows 1a, which is the Windows OS end of file character:
0000040 1a14 1115 1811 1821 1d1a 1f1d 1f1f 1713

After fixing the constructor, the MySql shows the data size:

mysql> SELECT ID_Picture, LENGTH(Image_Data)
    -> FROM picture_image_data
    -> WHERE ID_Picture = 1;
+------------+--------------------+
| ID_Picture | LENGTH(Image_Data) |
+------------+--------------------+
|          1 |              18453 |
+------------+--------------------+
1 row in set (0.00 sec)