custom NullBytea type for riverdatabasesql

As #650 illustrates, the riverdatabasesql driver has issues with
encoding arrays of byte arrays (`bytea[]`) and just byte arrays in
general because the underlying pq implementation used by sqlc doesn't
differentiate between nil vs empty slices. Fix this with a custom type.

Fixes #650.

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- `riverdatabasesql` driver: properly handle `nil` values in `bytea[]` inputs. This fixes the driver's handling of empty unique keys on insert for non-unique jobs with the newer unique jobs implementation. [PR #739](https://github.com/riverqueue/river/pull/739).
+
 ## [0.16.0] - 2024-01-27
 
 ### Added

riverdriver/riverdatabasesql/internal/dbsqlc/sqlc.yaml

@@ -32,6 +32,11 @@ sql:
           ttl: "TTL"
 
         overrides:
+          - db_type: "bytea"
+            go_type:
+              import: "github.com/riverqueue/river/riverdriver/riverdatabasesql/internal/pgtypealias"
+              type: "NullBytea"
+
           # `database/sql` really does not play nicely with json/jsonb. If it's
           # left as `[]byte` or `json.RawMessage`, `database/sql` will try to
           # encode it as binary (with a \x) which Postgres won't accept as

riverdriver/riverdatabasesql/internal/pgtypealias/null_bytea.go

@@ -0,0 +1,39 @@
+package pgtypealias
+
+import (
+	"database/sql/driver"
+	"fmt"
+)
+
+// NullBytea is a custom type for PostgreSQL bytea that returns SQL NULL when
+// the underlying slice is nil or empty. This override takes over for the base
+// type `bytea`, so that when sqlc generates code for arrays of bytea, each
+// element is a NullBytea and properly handles nil values. This is in contrast
+// to the default behavior of pq.Array in this scenario.
+//
+// See https://github.com/riverqueue/river/issues/650 for more information.
+type NullBytea []byte //nolint:recvcheck
+
+// Value implements the driver.Valuer interface. It returns nil when the
+// underlying slice is nil or empty, ensuring that missing values are sent as
+// SQL NULL.
+func (nb NullBytea) Value() (driver.Value, error) {
+	if len(nb) == 0 {
+		return nil, nil //nolint:nilnil
+	}
+	return []byte(nb), nil
+}
+
+// Scan implements the sql.Scanner interface.
+func (nb *NullBytea) Scan(src interface{}) error {
+	if src == nil {
+		*nb = nil
+		return nil
+	}
+	b, ok := src.([]byte)
+	if !ok {
+		return fmt.Errorf("nullBytea.Scan: got %T, expected []byte", src)
+	}
+	*nb = append((*nb)[0:0], b...)
+	return nil
+}

riverdriver/riverdatabasesql/river_database_sql_driver.go

@@ -212,7 +212,7 @@ func (e *Executor) JobInsertFastMany(ctx context.Context, params []*riverdriver.
 		ScheduledAt:  make([]time.Time, len(params)),
 		State:        make([]string, len(params)),
 		Tags:         make([]string, len(params)),
-		UniqueKey:    make([][]byte, len(params)),
+		UniqueKey:    make([]pgtypealias.NullBytea, len(params)),
 		UniqueStates: make([]pgtypealias.Bits, len(params)),
 	}
 	now := time.Now().UTC()
@@ -270,7 +270,7 @@ func (e *Executor) JobInsertFastManyNoReturning(ctx context.Context, params []*r
 		ScheduledAt:  make([]time.Time, len(params)),
 		State:        make([]dbsqlc.RiverJobState, len(params)),
 		Tags:         make([]string, len(params)),
-		UniqueKey:    make([][]byte, len(params)),
+		UniqueKey:    make([]pgtypealias.NullBytea, len(params)),
 		UniqueStates: make([]pgtypealias.Bits, len(params)),
 	}
 	now := time.Now().UTC()