add file-backed buffering to initial backup output

go.mod

@@ -10,6 +10,7 @@ require (
 )
 
 require (
+	github.com/djherbis/buffer v1.2.0 // indirect
 	github.com/dustin/go-humanize v1.0.0 // indirect
 	github.com/google/uuid v1.1.1 // indirect
 	github.com/jackc/chunkreader/v2 v2.0.1 // indirect

go.sum

@@ -11,6 +11,8 @@ github.com/creack/pty v1.1.7/go.mod h1:lj5s0c3V2DBrqTV7llrYr5NG6My20zk30Fl46Y7Do
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/djherbis/buffer v1.2.0 h1:PH5Dd2ss0C7CRRhQCZ2u7MssF+No9ide8Ye71nPHcrQ=
+github.com/djherbis/buffer v1.2.0/go.mod h1:fjnebbZjCUpPinBRD+TDwXSOeNQ7fPQWLfGQqiAiUyE=
 github.com/dustin/go-humanize v1.0.0 h1:VSnTsYCnlFHaM2/igO1h6X3HA71jcobQuxemgkq4zYo=
 github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
 github.com/go-kit/log v0.1.0/go.mod h1:zbhenjAZHb184qTLMA9ZjW7ThYL0H2mk7Q6pNt4vbaY=

pg2s3.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"filippo.io/age"
+	"github.com/djherbis/buffer"
 	"github.com/jackc/pgx/v4"
 	"github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
@@ -110,8 +111,9 @@ func (c *Client) CreateBackup() (io.Reader, error) {
 	}
 	cmd := exec.Command("pg_dump", args...)
 
-	var backup bytes.Buffer
-	cmd.Stdout = &backup
+	// buffer 32MB to memory, after that buffer to 64MB chunked files
+	backup := buffer.NewUnboundedBuffer(32*1024*1024, 64*1024*1024)
+	cmd.Stdout = backup
 
 	var capture bytes.Buffer
 	cmd.Stderr = &capture
@@ -121,7 +123,7 @@ func (c *Client) CreateBackup() (io.Reader, error) {
 		return nil, errors.New(capture.String())
 	}
 
-	return &backup, nil
+	return backup, nil
 }
 
 func (c *Client) RestoreBackup(backup io.Reader) error {