PG2: A Fast PostgreSQL Driver For Clojure

PG2 is a client library for PostgreSQL server. It succeeds PG(one) -- my early attempt to make a JDBC-free client. Comparing to it, PG2 has the following features:

It's fast. Benchmarks prove up to 3 times performance boost compared to Next.JDBC. A simple HTTP application which reads data from the database and responds with JSON handles 2 times more RPS. For details, see the "benchmarks" below.

It's written in Java with a Clojure layer on top of it. Unfortunately, Clojure is not as fast as Java. For performance sake, I've got to implement most of the logic in pure Java. The Clojure layer is extremely thin and serves only to call certain methods.

It's still Clojure friendly: by default, all the queries return a vector of maps, where the keys are keywords. You don't need to remap the result in any way. But moreover, the library provides dozens of ways to group, index, a reduce a result.

It supports JSON out from the box: There is no need to extend any protocols and so on. Read and write json(b) with ease as Clojure data! Also, JSON reading and writing as really fast, again: 2-3 times faster than in Next.JDBC.

It supports COPY operations: you can easily COPY OUT a table into a stream. You can COPY IN a set of rows without CSV-encoding them because it's held by the library. It also supports binary COPY format, which is faster.

It supports java.time. classes. The ordinary JDBC clients still use Timestamp class for dates, which is horrible. In PG2, all the java.time.* classes are supported for reading and writing.

...And plenty of more features.

Table of Contents

• Installation
• Quick start (Demo)
• Benchmarks
• Authentication
• Connecting the server
• Query and Execute
• Prepared Statements
• Transactions
• Cloning a Connectin
• Cancelling a Query
• Thread Safety
• Result reducers
• COPY IN/OUT
• SSL
• Type Mapping
• JSON support
• Arrays support
• Notify/Listen (PubSub)
• Notices
• Connection Pool
• HoneySQL integration
• Component integration
• Ring middleware
• Debugging
• Running tests
• Running benchmarks

Installation

Quick start (Demo)

Benchmarks

Authentication

Connecting the server

Query and Execute

Prepared Statements

Transactions

Cloning a Connectin

Cancelling a Query

Thread Safety

Result reducers

COPY IN/OUT

SSL

Type Mapping

JSON support

Arrays support

Notify/Listen (PubSub)

Notices

Connection Pool

HoneySQL integration

Component integration

Ring middleware

Debugging

Running tests

Running benchmarks