The fastest JDBC driver - jdbc

Question

I am getting very confused here..
There are 4 types of JDBC driver:
JDBC-ODBC Bridge Driver (Type 1)
JDBC-Native API (Type 2)
JDBC-Net pure Java (Type 3)
Native-protocol, pure Java driver (Type 4)
But if you search on the web for the fastest JDBC driver, the answer is:
JDBC Net pure Java driver (Type 4)
Isnt't JDBC-Net pure Java the type 3 driver? Why the answer put JDBC-Net pure Java and type 4 together? Thanks a lot!

Answer 1

Your confusion stems from the fact that none of those names are the official names, the official names as defined in the JDBC specification are simply "Type n" with n is 1, 2, 3 or 4. It looks like your unnamed sources tried to attach a summarizing name to the types, and those names just leads to confusion because your different sources used different names for the types.
The JDBC 4.3 specification defines the types as:
9.1 Types of Drivers
There are many possible implementations of JDBC drivers. These
implementations are categorized as follows:
Type 1 — drivers that implement the JDBC API as a mapping to another data access API, such as ODBC. Drivers of this type are generally
dependent on a native library, which limits their portability. The
JDBC-ODBC Bridge driver is an example of a Type 1 driver.
Type 2 — drivers that are written partly in the Java programming language and partly in native code. These drivers use a native client
library specific to the data source to which they connect. Again,
because of the native code, their portability is limited.
Type 3 — drivers that use a pure Java client and communicate with a middleware server using a database-independent protocol. The
middleware server then communicates the client’s requests to the data
source.
Type 4 — drivers that are pure Java often using a network protocol or File I/O to communicate with a specific data source. The client
connects directly to the data source.
None of those types is necessarily the fastest. Given the lack of overhead from going from java code to native code and back, Type 4 drivers are likely the fastest for the same database system. Type 3 will likely be the slowest, because you go from your Java code to a remote middleware server that will then translate to a database specific protocol (possibly using another JDBC driver!) to the actual database. In my experience, type 3 drivers are very rare.
As a counter-example of Type 4 being the fastest, I maintain Jaybird, the JDBC driver for Firebird. Jaybird provides a Type 4 and two Type 2 implementations (one that uses the native client library to connect to remote Firebird servers, and one that offers Firebird Embedded inside your Java process).
In general its Type 4 driver is the fastest for localhost and remote connections, the Jaybird Type 2 'Embedded' driver is usually the fastest overall as that will host the database server in the Java process, foregoing the overhead of the network or inter-process communication. However in that situation using a Type 4 driver is not even possible (using Firebird Embedded requires loading and talking to a native library) so that is a false comparison.
The Jaybird Type 2 'native' driver is usually on par or slightly slower than the Jaybird Type 4, but it might be faster for connections to a Firebird server on the same host as it might use a slightly faster IPC protocol instead of TCP/IP for certain connection strings, if the host is Windows.
Informing your decision purely on 'which type is the fastest' is useless anyway, as some database vendors only offer a Type 4, or a Type 2 and a Type 4, while for example Type 1 is pretty much dead since Oracle dropped the JDBC-ODBC bridge from Java. Type 3 is pretty rare, so you're unlikely to find it anyway.
In general, if available, I recommend choosing Type 4, because it usually has the least hassle (eg Type 2 requires correctly installing the native library, configuring your application to find the native library, etc). However, sometimes a Type 2 driver might offer features not otherwise available (like Firebird Embedded).