Prepared statements and streaming columns

The setXXXStream methods request stream data between the application and the database.

JDBC allows an IN parameter to be set to a Java input stream for passing in large amounts of data in smaller chunks. When the statement is run, the JDBC driver makes repeated calls to this input stream. Derby supports the following JDBC stream methods for PreparedStatement objects:

setBinaryStream
Use for streams that contain uninterpreted bytes
setAsciiStream
Use for streams that contain ASCII characters
setCharacterStream
Use for streams that contain characters

Note: Derby does not support the setNCharacterStream method or the deprecated setUnicodeStream method.

Note: These methods do not require that you specify the length of the stream. However, if you omit the length argument when the stream object is a LOB greater than a single page in size, performance will be impaired if you later retrieve the length of the LOB. If you are simply inserting or reading data, performance is unaffected.

The stream object passed to setBinaryStream and setAsciiStream can be either a standard Java stream object or the user's own subclass that implements the standard java.io.InputStream interface. The object passed to setCharacterStream must be a subclass of the abstract java.io.Reader class.

According to the JDBC standard, streams can be stored only in columns with the data types shown in the following table. The word "Preferred" indicates the preferred target data type for the type of stream. See Mapping of java.sql.Types to SQL types.

Table 1. Streamable JDBC data types
Column Data Type	Corresponding Java Type	AsciiStream	CharacterStream	BinaryStream
CLOB	java.sql.Clob	Yes	Yes	No
CHAR	None	Yes	Yes	No
VARCHAR	None	Yes	Yes	No
LONGVARCHAR	None	Preferred	Preferred	No
BINARY	None	Yes	Yes	Yes
BLOB	java.sql.Blob	Yes	Yes	Yes
VARBINARY	None	Yes	Yes	Yes
LONGVARBINARY	None	Yes	Yes	Preferred

Note: Streams cannot be stored in columns of the other built-in data types or columns of user-defined data types.

Example

The following code fragment shows how a user can store a streamed, ASCII-encoded java.io.File in a LONG VARCHAR column:

    Statement s = conn.createStatement();
    s.executeUpdate("CREATE TABLE atable (a INT, b LONG VARCHAR)");
    conn.commit();

    java.io.File file = new java.io.File("derby.txt");
    int fileLength = (int) file.length();

    // create an input stream
    java.io.InputStream fin = new java.io.FileInputStream(file);
    PreparedStatement ps = conn.prepareStatement(
        "INSERT INTO atable VALUES (?, ?)");
    ps.setInt(1, 1);

    // set the value of the input parameter to the input stream
    ps.setAsciiStream(2, fin, fileLength);
    ps.execute();
    conn.commit();