Prevent infinite loops with nested subqueries

db/context.go

@@ -0,0 +1,48 @@
+// Copyright © 2016 Abcum Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package db
+
+import (
+	"context"
+)
+
+func vers(ctx context.Context) int {
+
+	v := ctx.Value(ctxKeyDive)
+
+	switch v {
+	case nil:
+		return 0
+	default:
+		return v.(int)
+	}
+
+}
+
+func dive(ctx context.Context) context.Context {
+
+	v := ctx.Value(ctxKeyDive)
+
+	switch v {
+	case nil:
+		return context.WithValue(ctx, ctxKeyDive, 1)
+	default:
+		if v.(int) > maxRecursiveQueries {
+			panic(errRecursiveOverload)
+		}
+		return context.WithValue(ctx, ctxKeyDive, v.(int)+1)
+	}
+
+}

db/create.go

@@ -76,6 +76,8 @@ func (e *executor) executeCreate(ctx context.Context, stm *sql.CreateStatement)
 
 func (e *executor) fetchCreate(ctx context.Context, stm *sql.CreateStatement, doc *data.Doc) (interface{}, error) {
 
+	ctx = dive(ctx)
+
 	if doc != nil {
 		vars := data.New()
 		vars.Set(doc.Data(), varKeyParent)

db/delete.go

@@ -75,6 +75,8 @@ func (e *executor) executeDelete(ctx context.Context, stm *sql.DeleteStatement)
 
 func (e *executor) fetchDelete(ctx context.Context, stm *sql.DeleteStatement, doc *data.Doc) (interface{}, error) {
 
+	ctx = dive(ctx)
+
 	if doc != nil {
 		vars := data.New()
 		vars.Set(doc.Data(), varKeyParent)

db/insert.go

@@ -54,6 +54,8 @@ func (e *executor) executeInsert(ctx context.Context, stm *sql.InsertStatement)
 
 func (e *executor) fetchInsert(ctx context.Context, stm *sql.InsertStatement, doc *data.Doc) (interface{}, error) {
 
+	ctx = dive(ctx)
+
 	if doc != nil {
 		vars := data.New()
 		vars.Set(doc.Data(), varKeyParent)

db/relate.go

@@ -68,6 +68,8 @@ func (e *executor) executeRelate(ctx context.Context, stm *sql.RelateStatement)
 
 func (e *executor) fetchRelate(ctx context.Context, stm *sql.RelateStatement, doc *data.Doc) (interface{}, error) {
 
+	ctx = dive(ctx)
+
 	if doc != nil {
 		vars := data.New()
 		vars.Set(doc.Data(), varKeyParent)

db/select.go

@@ -84,6 +84,8 @@ func (e *executor) executeSelect(ctx context.Context, stm *sql.SelectStatement)
 
 func (e *executor) fetchSelect(ctx context.Context, stm *sql.SelectStatement, doc *data.Doc) (interface{}, error) {
 
+	ctx = dive(ctx)
+
 	if doc != nil {
 		vars := data.New()
 		vars.Set(doc.Data(), varKeyParent)

db/update.go

@@ -75,6 +75,8 @@ func (e *executor) executeUpdate(ctx context.Context, stm *sql.UpdateStatement)
 
 func (e *executor) fetchUpdate(ctx context.Context, stm *sql.UpdateStatement, doc *data.Doc) (interface{}, error) {
 
+	ctx = dive(ctx)
+
 	if doc != nil {
 		vars := data.New()
 		vars.Set(doc.Data(), varKeyParent)

db/upsert.go

@@ -54,6 +54,8 @@ func (e *executor) executeUpsert(ctx context.Context, stm *sql.UpsertStatement)
 
 func (e *executor) fetchUpsert(ctx context.Context, stm *sql.UpsertStatement, doc *data.Doc) (interface{}, error) {
 
+	ctx = dive(ctx)
+
 	if doc != nil {
 		vars := data.New()
 		vars.Set(doc.Data(), varKeyParent)

db/vars.go

@@ -38,6 +38,7 @@ const (
 	ctxKeyId    = "id"
 	ctxKeyNs    = "ns"
 	ctxKeyDb    = "db"
+	ctxKeyDive  = "dive"
 	ctxKeyVars  = "vars"
 	ctxKeySubs  = "subs"
 	ctxKeySpec  = "spec"
@@ -71,6 +72,10 @@ var (
 	// to process each query statement concurrently.
 	workerCount = runtime.NumCPU() * 2
 
+	// maxRecursiveQueries specifies how many queries will be
+	// processed recursively before the query is cancelled.
+	maxRecursiveQueries = 50
+
 	// queryIdentFailed occurs when a permission query asks
 	// for a field, meaning a document has to be fetched.
 	queryIdentFailed = errors.New("Found ident but no doc available")