adding backwards compatibility

this commit also adds support for ordering systemTables and implements the method

sql3/planner/compileselect.go

@@ -406,7 +406,7 @@ func (p *ExecutionPlanner) compileSource(scope *PlanOpQuery, source parser.Sourc
 		tableName := strings.ToLower(parser.IdentName(sourceExpr.Name))
 
 		// doing this check here because we don't have a 'system' flag that exists in the FB schema
-		st, ok := systemTables[tableName]
+		st, ok := systemTables.table(tableName)
 		if ok {
 			var op types.PlanOperator
 			op = NewPlanOpSystemTable(p, st)

sql3/planner/compileshow.go

@@ -235,7 +235,7 @@ func (p *ExecutionPlanner) compileShowCreateTableStatement(ctx context.Context,
 	}
 
 	// get the system table
-	systemTable, ok := systemTables[fbTableDDL]
+	systemTable, ok := systemTables.table(fbTableDDL)
 	if !ok {
 		return nil, sql3.NewErrInternalf("unable to find system table fb_table_ddl")
 	}

sql3/planner/executionplannersystemtables.go

@@ -50,7 +50,7 @@ func (s *systemTableDefinitionsWrapper) TableByName(ctx context.Context, tname d
 	tbl, err := s.schemaAPI.TableByName(ctx, tname)
 	if err != nil {
 		if isTableNotFoundError(err) {
-			st, ok := systemTables[string(tname)]
+			st, ok := systemTables.table(string(tname))
 			if !ok {
 				return nil, dax.NewErrTableNameDoesNotExist(tname)
 			}
@@ -73,10 +73,10 @@ func (s *systemTableDefinitionsWrapper) Tables(ctx context.Context) ([]*dax.Tabl
 	}
 
 	// Append the system tables.
-	for tblName, st := range systemTables {
+	for _, st := range systemTables.ordered() {
 		ii, err := indexInfoFromSystemTable(st)
 		if err != nil {
-			return nil, errors.Wrapf(err, "converting system table to table: %s", tblName)
+			return nil, errors.Wrapf(err, "converting system table to table: %s", st.name)
 		}
 		tbls = append(tbls, pilosa.IndexInfoToTable(ii))
 	}

sql3/planner/opsystemtable.go

@@ -6,6 +6,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"sort"
 
 	pilosa "github.com/featurebasedb/featurebase/v3"
 	"github.com/featurebasedb/featurebase/v3/pql"
@@ -22,6 +23,9 @@ const (
 	fbExecRequests        = "fb_exec_requests"
 	fbPerformanceCounters = "fb_performance_counters"
 
+	fbClusterInfo  = "fb_cluster_info"
+	fbClusterNodes = "fb_cluster_nodes"
+
 	fbTableDDL = "fb_table_ddl"
 )
 
@@ -31,7 +35,37 @@ type systemTable struct {
 	requiresFanout bool
 }
 
-var systemTables = map[string]*systemTable{
+type systemTableMap map[string]*systemTable
+
+
+// table enables backwards compatibility with changing the system table names
+// from fb_cluster_nodes and fb_cluster_info to fb_database_nodes and fb_database_info
+// respectively.
+func (s systemTableMap) table(name string) (*systemTable, bool) {
+	switch name {
+	case fbClusterInfo:
+		name = fbDatabaseInfo
+	case fbClusterNodes:
+		name = fbDatabaseNodes
+	}
+
+	t, ok := s[name]
+	return t, ok
+}
+
+// ordered returns the map as an ordered slice of systemTable.
+func (s systemTableMap) ordered() []*systemTable {
+	out := make([]*systemTable, 0, len(s))
+	for _, v := range s {
+		out = append(out, v)
+	}
+	sort.Slice(out, func(i, j int) bool {
+		return out[i].name < out[j].name
+	})
+	return out
+}
+
+var systemTables = systemTableMap{
 	fbDatabaseInfo: {
 		name: fbDatabaseInfo,
 		schema: types.Schema{

sql3/planner/wireprotocol.go

@@ -105,7 +105,7 @@ func newMessagePlanOp(p *ExecutionPlanner, reader io.Reader) (*messagePlanOp, er
 	}
 	name := string(bname)
 
-	st, ok := systemTables[name]
+	st, ok := systemTables.table(name)
 	if !ok {
 		return nil, sql3.NewErrInternalf("unexpected system table name %s", name)
 	}