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authorInada Naoki <songofacandy@gmail.com>2023-08-05 16:22:48 +0000
committerJonathan Amsterdam <jba@google.com>2023-08-07 14:26:37 +0000
commit8a6acecfab2879ba4e26487c99f204ede8b3d935 (patch)
treef30c54a5cf1dd7737c828b2d0f75bd2d8c6bdbbf /src/database
parent009c628b4d3a34b4b0ad1ad4aeef07a698931949 (diff)
downloadgo-8a6acecfab2879ba4e26487c99f204ede8b3d935.tar.xz
database/sql: add Null[T]
Generic version of NullString, NullInt64, etc. Fixes #60370 Change-Id: I166a05a6126e8b8571db5cbb026303bb6551d56b GitHub-Last-Rev: 3c8d2d5141c36f034d2124e19ee090620363ba24 GitHub-Pull-Request: golang/go#60677 Reviewed-on: https://go-review.googlesource.com/c/go/+/501700 Reviewed-by: Jonathan Amsterdam <jba@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Russ Cox <rsc@golang.org>
Diffstat (limited to 'src/database')
-rw-r--r--src/database/sql/sql.go33
-rw-r--r--src/database/sql/sql_test.go17
2 files changed, 48 insertions, 2 deletions
diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
index 836fe83e2e..7a57c7de36 100644
--- a/src/database/sql/sql.go
+++ b/src/database/sql/sql.go
@@ -391,6 +391,39 @@ func (n NullTime) Value() (driver.Value, error) {
return n.Time, nil
}
+// Null represents a value that may be null.
+// Null implements the Scanner interface so
+// it can be used as a scan destination:
+//
+// var s Null[string]
+// err := db.QueryRow("SELECT name FROM foo WHERE id=?", id).Scan(&s)
+// ...
+// if s.Valid {
+// // use s.V
+// } else {
+// // NULL value
+// }
+type Null[T any] struct {
+ V T
+ Valid bool
+}
+
+func (n *Null[T]) Scan(value any) error {
+ if value == nil {
+ n.V, n.Valid = *new(T), false
+ return nil
+ }
+ n.Valid = true
+ return convertAssign(&n.V, value)
+}
+
+func (n Null[T]) Value() (driver.Value, error) {
+ if !n.Valid {
+ return nil, nil
+ }
+ return n.V, nil
+}
+
// Scanner is an interface used by Scan.
type Scanner interface {
// Scan assigns a value from a database driver.
diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
index e6a5cd912a..f1c946d4e4 100644
--- a/src/database/sql/sql_test.go
+++ b/src/database/sql/sql_test.go
@@ -1803,6 +1803,18 @@ func TestNullStringParam(t *testing.T) {
nullTestRun(t, spec)
}
+func TestGenericNullStringParam(t *testing.T) {
+ spec := nullTestSpec{"nullstring", "string", [6]nullTestRow{
+ {Null[string]{"aqua", true}, "", Null[string]{"aqua", true}},
+ {Null[string]{"brown", false}, "", Null[string]{"", false}},
+ {"chartreuse", "", Null[string]{"chartreuse", true}},
+ {Null[string]{"darkred", true}, "", Null[string]{"darkred", true}},
+ {Null[string]{"eel", false}, "", Null[string]{"", false}},
+ {"foo", Null[string]{"black", false}, nil},
+ }}
+ nullTestRun(t, spec)
+}
+
func TestNullInt64Param(t *testing.T) {
spec := nullTestSpec{"nullint64", "int64", [6]nullTestRow{
{NullInt64{31, true}, 1, NullInt64{31, true}},
@@ -1916,8 +1928,9 @@ func nullTestRun(t *testing.T, spec nullTestSpec) {
}
// Can't put null val into non-null col
- if _, err := stmt.Exec(6, "bob", spec.rows[5].nullParam, spec.rows[5].notNullParam); err == nil {
- t.Errorf("expected error inserting nil val with prepared statement Exec")
+ row5 := spec.rows[5]
+ if _, err := stmt.Exec(6, "bob", row5.nullParam, row5.notNullParam); err == nil {
+ t.Errorf("expected error inserting nil val with prepared statement Exec: NULL=%#v, NOT-NULL=%#v", row5.nullParam, row5.notNullParam)
}
_, err = db.Exec("INSERT|t|id=?,name=?,nullf=?", 999, nil, nil)