Bulk allocate pool Conns

pool/bench_test.go

@@ -0,0 +1,69 @@
+package pool_test
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/jackc/pgx/v4"
+	"github.com/jackc/pgx/v4/pool"
+	"github.com/stretchr/testify/require"
+)
+
+func BenchmarkMinimalPreparedSelectBaseline(b *testing.B) {
+	config, err := pool.ParseConfig(os.Getenv("PGX_TEST_DATABASE"))
+	require.NoError(b, err)
+
+	config.AfterConnect = func(ctx context.Context, c *pgx.Conn) error {
+		_, err := c.Prepare(ctx, "ps1", "select $1::int8")
+		return err
+	}
+
+	db, err := pool.ConnectConfig(context.Background(), config)
+	require.NoError(b, err)
+
+	conn, err := db.Acquire(context.Background())
+	require.NoError(b, err)
+	defer conn.Release()
+
+	var n int64
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		err = conn.QueryRow(context.Background(), "ps1", i).Scan(&n)
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		if n != int64(i) {
+			b.Fatalf("expected %d, got %d", i, n)
+		}
+	}
+}
+
+func BenchmarkMinimalPreparedSelect(b *testing.B) {
+	config, err := pool.ParseConfig(os.Getenv("PGX_TEST_DATABASE"))
+	require.NoError(b, err)
+
+	config.AfterConnect = func(ctx context.Context, c *pgx.Conn) error {
+		_, err := c.Prepare(ctx, "ps1", "select $1::int8")
+		return err
+	}
+
+	db, err := pool.ConnectConfig(context.Background(), config)
+	require.NoError(b, err)
+
+	var n int64
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		err = db.QueryRow(context.Background(), "ps1", i).Scan(&n)
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		if n != int64(i) {
+			b.Fatalf("expected %d, got %d", i, n)
+		}
+	}
+}

pool/pool.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"runtime"
 	"strconv"
+	"sync"
 	"time"
 
 	"github.com/jackc/pgconn"
@@ -24,6 +25,9 @@ type Pool struct {
 	maxConnLifetime   time.Duration
 	healthCheckPeriod time.Duration
 	closeChan         chan struct{}
+
+	preallocatedConnsMux sync.Mutex
+	preallocatedConns    []Conn
 }
 
 // Config is the configuration struct for creating a pool. It is highly recommended to modify a Config returned by
@@ -212,6 +216,24 @@ func (p *Pool) checkIdleConnsHealth() {
 	}
 }
 
+func (p *Pool) getConn(res *puddle.Resource) *Conn {
+	p.preallocatedConnsMux.Lock()
+
+	if len(p.preallocatedConns) == 0 {
+		p.preallocatedConns = make([]Conn, 128)
+	}
+
+	c := &p.preallocatedConns[len(p.preallocatedConns)-1]
+	p.preallocatedConns = p.preallocatedConns[0 : len(p.preallocatedConns)-1]
+
+	p.preallocatedConnsMux.Unlock()
+
+	c.res = res
+	c.p = p
+
+	return c
+}
+
 func (p *Pool) Acquire(ctx context.Context) (*Conn, error) {
 	for {
 		res, err := p.p.Acquire(ctx)
@@ -220,7 +242,7 @@ func (p *Pool) Acquire(ctx context.Context) (*Conn, error) {
 		}
 
 		if p.beforeAcquire == nil || p.beforeAcquire(res.Value().(*pgx.Conn)) {
-			return &Conn{res: res, p: p}, nil
+			return p.getConn(res), nil
 		}
 
 		res.Destroy()
@@ -234,7 +256,7 @@ func (p *Pool) AcquireAllIdle() []*Conn {
 	conns := make([]*Conn, 0, len(resources))
 	for _, res := range resources {
 		if p.beforeAcquire == nil || p.beforeAcquire(res.Value().(*pgx.Conn)) {
-			conns = append(conns, &Conn{res: res, p: p})
+			conns = append(conns, p.getConn(res))
 		} else {
 			res.Destroy()
 		}