From 693c7c7f7d4fa9d306af6c9ba911c26a0e62bf3c Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sat, 11 Sep 2021 10:59:26 -0500
Subject: [PATCH] Fix NULL being lost when scanning unknown OID into
 sql.Scanner

https://github.com/jackc/pgx/issues/1078
---
 pgtype.go      |  6 +++++-
 pgtype_test.go | 11 +++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/pgtype.go b/pgtype.go
index 4a680844..200fb562 100644
--- a/pgtype.go
+++ b/pgtype.go
@@ -588,7 +588,11 @@ type scanPlanSQLScanner struct{}
 
 func (scanPlanSQLScanner) Scan(ci *ConnInfo, oid uint32, formatCode int16, src []byte, dst interface{}) error {
 	scanner := dst.(sql.Scanner)
-	if formatCode == BinaryFormatCode {
+	if src == nil {
+		// This is necessary because interface value []byte:nil does not equal nil:nil for the binary format path and the
+		// text format path would be converted to empty string.
+		return scanner.Scan(nil)
+	} else if formatCode == BinaryFormatCode {
 		return scanner.Scan(src)
 	} else {
 		return scanner.Scan(string(src))
diff --git a/pgtype_test.go b/pgtype_test.go
index 2506e0a3..85ca55e9 100644
--- a/pgtype_test.go
+++ b/pgtype_test.go
@@ -2,6 +2,7 @@ package pgtype_test
 
 import (
 	"bytes"
+	"database/sql"
 	"errors"
 	"net"
 	"testing"
@@ -211,6 +212,16 @@ func TestConnInfoScanUnknownOIDTextFormat(t *testing.T) {
 	assert.EqualValues(t, 123, n)
 }
 
+func TestConnInfoScanUnknownOIDIntoSQLScanner(t *testing.T) {
+	ci := pgtype.NewConnInfo()
+
+	var s sql.NullString
+	err := ci.Scan(0, pgx.TextFormatCode, []byte(nil), &s)
+	assert.NoError(t, err)
+	assert.Equal(t, "", s.String)
+	assert.False(t, s.Valid)
+}
+
 func BenchmarkConnInfoScanInt4IntoBinaryDecoder(b *testing.B) {
 	ci := pgtype.NewConnInfo()
 	src := []byte{0, 0, 0, 42}