Cluster nodes for serverless (#2336)

* slowly making a serverless systemAPI for ClusterNodes()

* implemented some methods for fb_database_info

* fixed linting

* fixed comments

dax/queryer/queryer.go

@@ -39,6 +39,8 @@ type Queryer struct {
 
 	controller dax.Controller
 
+	systemLayer *systemlayer.SystemLayer
+
 	logger logger.Logger
 }
 
@@ -47,6 +49,7 @@ func New(cfg Config) *Queryer {
 	q := &Queryer{
 		controller:    dax.NewNopController(),
 		orchestrators: make(map[dax.QualifiedDatabaseID]*qualifiedOrchestrator),
+		systemLayer:   systemlayer.NewSystemLayer(),
 		logger:        logger.NopLogger,
 	}
 
@@ -198,17 +201,14 @@ func (q *Queryer) QuerySQL(ctx context.Context, qdbid dax.QualifiedDatabaseID, s
 	// Importer
 	imp := idkserverless.NewImporter(q.controller, qdbid, nil)
 
-	// TODO(tlt): We need a serverless-compatible implementation of the
 	// SystemAPI.
-	sysapi := &featurebase.NopSystemAPI{}
-
-	systemLayer := systemlayer.NewSystemLayer()
+	sysapi := newSystemAPI(q.controller, qdbid)
 
 	// We intentionally don't pass the sql argument here because we're working
 	// with an io.Reader rather than a string and it's just not necessary to
 	// send it as a string to this method. Also, what happens if the sql is a
 	// large BULK INSERT?
-	pl := planner.NewExecutionPlanner(q.Orchestrator(qdbid), sapi, sysapi, systemLayer, imp, q.logger, "")
+	pl := planner.NewExecutionPlanner(q.Orchestrator(qdbid), sapi, sysapi, q.systemLayer, imp, q.logger, "")
 
 	planOp, err := pl.CompilePlan(ctx, st)
 	if err != nil {

dax/queryer/system_api.go

@@ -0,0 +1,58 @@
+package queryer
+
+import (
+	"context"
+
+	featurebase "github.com/featurebasedb/featurebase/v3"
+	"github.com/featurebasedb/featurebase/v3/dax"
+)
+
+// systemAPI is an implementation of the systemAPI.
+type systemAPI struct {
+	featurebase.NopSystemAPI
+	controller dax.Controller
+	qdbid      dax.QualifiedDatabaseID
+}
+
+func newSystemAPI(c dax.Controller, qdbid dax.QualifiedDatabaseID) *systemAPI {
+	return &systemAPI{
+		controller: c,
+		qdbid:      qdbid,
+	}
+}
+
+// ClusterNodes returns a list of featurebase.ClusterNodes
+// with length of the minimum number of workers
+func (s *systemAPI) ClusterNodes() []featurebase.ClusterNode {
+
+	ctx := context.Background()
+
+	qdb, err := s.controller.DatabaseByID(ctx, s.qdbid)
+	if err != nil {
+		return []featurebase.ClusterNode{}
+	}
+	out := make([]featurebase.ClusterNode, qdb.Options.WorkersMin)
+	return out
+}
+
+func (s *systemAPI) PlatformDescription() string {
+	return "Serverless"
+}
+
+func (s *systemAPI) ClusterName() string {
+	return "Serverless"
+}
+
+func (s *systemAPI) ClusterNodeCount() int {
+	ctx := context.Background()
+
+	qdb, err := s.controller.DatabaseByID(ctx, s.qdbid)
+	if err != nil {
+		return -1
+	}
+	return qdb.Options.WorkersMin
+}
+
+func (s *systemAPI) ClusterState() string {
+	return "NORMAL"
+}