From db5300358a14c176a55627536da74d077aff92ae Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Mon, 25 May 2015 09:54:28 -0500
Subject: [PATCH] Allow ConnPool to have MaxConnections of 1

---
 conn_pool.go      |  4 ++--
 conn_pool_test.go | 14 --------------
 stdlib/sql.go     |  6 ++++++
 3 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/conn_pool.go b/conn_pool.go
index 6a02382e..041ac830 100644
--- a/conn_pool.go
+++ b/conn_pool.go
@@ -37,8 +37,8 @@ func NewConnPool(config ConnPoolConfig) (p *ConnPool, err error) {
 	if p.maxConnections == 0 {
 		p.maxConnections = 5
 	}
-	if p.maxConnections < 2 {
-		return nil, errors.New("MaxConnections must be at least 2")
+	if p.maxConnections < 1 {
+		return nil, errors.New("MaxConnections must be at least 1")
 	}
 
 	p.afterConnect = config.AfterConnect
diff --git a/conn_pool_test.go b/conn_pool_test.go
index 724fcf42..f6ce75da 100644
--- a/conn_pool_test.go
+++ b/conn_pool_test.go
@@ -67,20 +67,6 @@ func TestNewConnPoolDefaultsTo5MaxConnections(t *testing.T) {
 	}
 }
 
-func TestNewConnPoolMaxConnectionsCannotBeLessThan2(t *testing.T) {
-	t.Parallel()
-
-	config := pgx.ConnPoolConfig{ConnConfig: *defaultConnConfig, MaxConnections: 1}
-	pool, err := pgx.NewConnPool(config)
-	if err == nil {
-		pool.Close()
-		t.Fatal(`Expected NewConnPool to fail with "MaxConnections must be at least 2" error, but it succeeded`)
-	}
-	if err.Error() != "MaxConnections must be at least 2" {
-		t.Fatalf(`Expected NewConnPool to fail with "MaxConnections must be at least 2" error, but it failed with %v`, err)
-	}
-}
-
 func TestPoolAcquireAndReleaseCycle(t *testing.T) {
 	t.Parallel()
 
diff --git a/stdlib/sql.go b/stdlib/sql.go
index 5871f36c..2292f1c3 100644
--- a/stdlib/sql.go
+++ b/stdlib/sql.go
@@ -109,6 +109,8 @@ func (d *Driver) Open(name string) (driver.Conn, error) {
 // *sql.DB and typecasting to *stdlib.Driver a reference to the pgx.ConnPool can
 // be reaquired later. This allows fast paths targeting pgx to be used while
 // still maintaining compatibility with other databases and drivers.
+//
+// pool connection size must be at least 2.
 func OpenFromConnPool(pool *pgx.ConnPool) (*sql.DB, error) {
 	d := &Driver{Pool: pool}
 	name := fmt.Sprintf("pgx-%d", openFromConnPoolCount)
@@ -126,6 +128,10 @@ func OpenFromConnPool(pool *pgx.ConnPool) (*sql.DB, error) {
 	// that would mean that prepared statements would be lost (which kills
 	// performance if the prepared statements constantly have to be reprepared)
 	stat := pool.Stat()
+
+	if stat.MaxConnections <= 2 {
+		return nil, errors.New("pool connection size must be at least 2")
+	}
 	db.SetMaxIdleConns(stat.MaxConnections - 2)
 	db.SetMaxOpenConns(stat.MaxConnections)