server: a Get that selects nothing reads the row, and nothing else

apps/server/app/x-select.go

@@ -118,8 +118,22 @@ func (w *fileWork) xSelectInit() {
 		") {")
 	w.P("	if m != nil {")
 	w.P("		", name_x, "Select(q, m)")
-	w.P("	} else {")
+	// Only a list edge is loaded. A row holds the key of every other one in
+	// the column the edge is kept in, and `Proto()` answers with it when
+	// nothing was loaded -- which is the whole of what a Get with no select
+	// answers for an edge. Loading it anyway was a query for each edge of
+	// every row read, and an answer that was worse: the neighbour read with
+	// its key and nothing else, so every other field of it at its zero value
+	// and its timestamps in the year 1, as though that were the row.
+	opened := false
 	for p := range w.Entity.Edges() {
+		if !p.IsList() {
+			continue
+		}
+		if !opened {
+			w.P("	} else {")
+			opened = true
+		}
 		name_p := work.Name(p.Name()).Ent()
 		name_y := p.Target().Name()
 		w.P("		q.With", name_p, "(select", name_y, "Key)")

apps/server/app/x-snapshot.go

@@ -16,6 +16,11 @@ func (w *fileWork) xSnapshots() {
 		", p ", w.entPkg().Ident(name_x), ", lock bool) (*", w.ent.Ident(name_x), ", error) {")
 	w.P("	q := s.Db.", name_x, ".Query().Where(p)")
 	for edge := range w.Entity.Edges() {
+		// A list edge only: the key of any other is in the row, and
+		// `Proto()` answers with it -- see [fileWork.xSelectInit].
+		if !edge.IsList() {
+			continue
+		}
 		target := edge.Target().Name()
 		pkg := w.ent + "/" + protogen.GoImportPath(strings.ToLower(target))
 		w.P("q.With", work.Name(edge.Name()).Ent(), "(func(q *", w.ent.Ident(target+"Query"), "){q.Select(", pkg.Ident("FieldId"), ")})")

internal/apptest/server/bare/x-get_test.go

@@ -2,10 +2,15 @@ package bare_test
 
 import (
 	context "context"
+	"sync/atomic"
 	"testing"
 
 	"github.com/lesomnus/z"
+	"github.com/protobuf-orm/ent/dialect"
+	"github.com/protobuf-orm/ent/dialect/sql"
 	pb "github.com/protobuf-orm/protoc-gen-orm-ent/internal/apptest"
+	"github.com/protobuf-orm/protoc-gen-orm-ent/internal/apptest/ent"
+	"github.com/protobuf-orm/protoc-gen-orm-ent/internal/apptest/server/bare"
 	"github.com/stretchr/testify/require"
 )
 
@@ -22,6 +27,22 @@ func TestGet(t *testing.T) {
 		x.NotEmpty(w.GetTenant().GetId())
 		x.Equal(tenant.GetId(), w.GetTenant().GetId())
 	}))
+	t.Run("empty select answers an edge with its key and nothing else", T(func(ctx context.Context, x *require.Assertions, c *Client) {
+		tenant, err := c.Tenant().Add(ctx, pb.TenantAddRequest_builder{}.Build())
+		x.NoError(err)
+		x.True(tenant.HasDateCreated())
+
+		v, err := c.User().Add(ctx, pb.UserAddRequest_builder{Tenant: tenant.Ref()}.Build())
+		x.NoError(err)
+
+		// A reference, and not the tenant read with its key alone: that
+		// answered every other field of it at its zero value, and a tenant
+		// created in the year 1.
+		w, err := c.User().Get(ctx, v.Pick())
+		x.NoError(err)
+		x.Equal(tenant.GetId(), w.GetTenant().GetId())
+		x.False(w.GetTenant().HasDateCreated())
+	}))
 	t.Run("select field of edge", T(func(ctx context.Context, x *require.Assertions, c *Client) {
 		tenant, err := c.Tenant().Add(ctx, pb.TenantAddRequest_builder{
 			Alias: z.Ptr("foo"),
@@ -47,3 +68,39 @@ func TestGet(t *testing.T) {
 		x.Equal(tenant.GetAlias(), w.GetTenant().GetAlias())
 	}))
 }
+
+// A Get that selects nothing is one query, however many edges the row has: the
+// row holds each neighbour's key, which is all such a Get answers for one. It
+// was a query for the row and one more for each edge.
+func TestAGetThatSelectsNothingIsOneQuery(t *testing.T) {
+	x := require.New(t)
+	ctx := t.Context()
+
+	driver, err := sql.Open("sqlite3", "file:get-one-query?mode=memory&cache=shared&_fk=1")
+	x.NoError(err)
+	defer driver.Close()
+	driver.DB().SetMaxOpenConns(1)
+
+	var n atomic.Int32
+	db := ent.NewClient(ent.Driver(dialect.DebugWithContext(driver, func(context.Context, ...any) { n.Add(1) })))
+	x.NoError(db.Schema.Create(ctx))
+	s, err := bare.NewServer(db)
+	x.NoError(err)
+
+	org, err := s.Tenant().Add(ctx, pb.TenantAddRequest_builder{}.Build())
+	x.NoError(err)
+	holder, err := s.User().Add(ctx, pb.UserAddRequest_builder{Tenant: org.Ref(), Alias: z.Ptr("holder")}.Build())
+	x.NoError(err)
+	deputy, err := s.User().Add(ctx, pb.UserAddRequest_builder{Tenant: org.Ref(), Alias: z.Ptr("deputy")}.Build())
+	x.NoError(err)
+	seat, err := s.Seat().Add(ctx, pb.SeatAddRequest_builder{Holder: holder.Ref(), Org: org.Ref(), Deputy: deputy.Ref()}.Build())
+	x.NoError(err)
+
+	n.Store(0)
+	got, err := s.Seat().Get(ctx, seat.Pick())
+	x.NoError(err)
+	x.EqualValues(1, n.Load(), "three edges, and one query")
+	x.Equal(holder.GetId(), got.GetHolder().GetId())
+	x.Equal(org.GetId(), got.GetOrg().GetId())
+	x.Equal(deputy.GetId(), got.GetDeputy().GetId())
+}