Add preloader filter

Fix pipeline structure


Fix preloader logic

mongox/common/common.go

@@ -0,0 +1,140 @@
+package common
+
+import (
+	"reflect"
+	"strconv"
+	"strings"
+
+	"github.com/mainnika/mongox-go-driver/mongox"
+	"github.com/mainnika/mongox-go-driver/mongox/errors"
+	"github.com/mainnika/mongox-go-driver/mongox/query"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
+)
+
+func createSimpleLoad(db *mongox.Database, target interface{}, composed *query.Query) (cursor *mongo.Cursor, err error) {
+
+	collection := db.GetCollectionOf(target)
+	opts := options.Find()
+
+	opts.Sort = composed.Sorter()
+	opts.Limit = composed.Limiter()
+	opts.Skip = composed.Skipper()
+
+	return collection.Find(db.Context(), composed.M(), opts)
+}
+
+func createAggregateLoad(db *mongox.Database, target interface{}, composed *query.Query) (cursor *mongo.Cursor, err error) {
+
+	collection := db.GetCollectionOf(target)
+	opts := options.Aggregate()
+
+	pipelineHead := primitive.A{primitive.M{"$match": composed.M()}}
+	pipelineTail := primitive.A{}
+
+	el := reflect.ValueOf(target).Elem()
+	elType := el.Type()
+	numField := elType.NumField()
+	_, preloads := composed.Preloader()
+
+	for i := 0; i < numField; i++ {
+
+		field := elType.Field(i)
+		tag := field.Tag
+
+		preloadTag, ok := tag.Lookup("preload")
+		if !ok {
+			continue
+		}
+		jsonTag, ok := tag.Lookup("json")
+		if jsonTag == "-" {
+			return nil, errors.Malformedf("preload private field is impossible")
+		}
+
+		jsonData := strings.SplitN(jsonTag, ",", 2)
+		jsonName := field.Name
+		if len(jsonData) > 0 {
+			jsonName = strings.TrimSpace(jsonData[0])
+		}
+
+		preloadData := strings.Split(preloadTag, ",")
+		if len(preloadData) == 0 {
+			continue
+		}
+		if len(preloadData) == 1 {
+			panic("there is no foreign field")
+		}
+
+		preloadName := strings.TrimSpace(preloadData[0])
+		if len(preloadName) == 0 {
+			preloadName = jsonName
+		}
+
+		foreignField := strings.TrimSpace(preloadData[1])
+		if len(foreignField) == 0 {
+			panic("there is no foreign field")
+		}
+
+		preloadLimiter := 100
+		if len(preloadData) > 2 {
+
+			stringLimit := strings.TrimSpace(preloadData[2])
+			intLimit := preloadLimiter
+
+			intLimit, err = strconv.Atoi(stringLimit)
+			if err == nil {
+				preloadLimiter = intLimit
+			}
+		}
+
+		for _, preload := range preloads {
+			if preload != preloadName {
+				continue
+			}
+
+			isPtr := el.Field(i).Kind() == reflect.Ptr
+			isSlice := el.Field(i).Kind() == reflect.Slice
+			isIface := el.Field(i).CanInterface()
+			if (!isPtr && !isSlice) || !isIface {
+				continue
+			}
+
+			typ := el.Field(i).Type()
+			lookupCollection := db.GetCollectionOf(reflect.Zero(typ).Interface())
+			lookupVars := primitive.M{"selector": "$_id"}
+			lookupPipeline := primitive.A{
+				// todo: make match from composed query
+				primitive.M{"$match": primitive.M{"$expr": primitive.M{"$eq": primitive.A{"$" + foreignField, "$$selector"}}}},
+			}
+
+			if isSlice && preloadLimiter > 0 {
+				lookupPipeline = append(lookupPipeline, primitive.M{"$limit": preloadLimiter})
+			} else if !isSlice {
+				lookupPipeline = append(lookupPipeline, primitive.M{"$limit": 1})
+			}
+
+			pipelineTail = append(pipelineTail, primitive.M{
+				"$lookup": primitive.M{
+					"from":     lookupCollection.Name(),
+					"let":      lookupVars,
+					"pipeline": lookupPipeline,
+					"as":       jsonName,
+				},
+			})
+
+			if isSlice {
+				continue
+			}
+
+			pipelineTail = append(pipelineTail, primitive.M{
+				"$unwind": primitive.M{
+					"preserveNullAndEmptyArrays": true,
+					"path":                       "$" + jsonName,
+				},
+			})
+		}
+	}
+
+	return collection.Aggregate(db.Context(), append(pipelineHead, pipelineTail...), opts)
+}

mongox/common/loadarray.go

@@ -6,7 +6,7 @@ import (
 	"github.com/mainnika/mongox-go-driver/mongox"
 	"github.com/mainnika/mongox-go-driver/mongox/errors"
 	"github.com/mainnika/mongox-go-driver/mongox/query"
-	"go.mongodb.org/mongo-driver/mongo/options"
+	"go.mongodb.org/mongo-driver/mongo"
 )
 
 // LoadArray loads an array of documents from the database by query
@@ -31,16 +31,17 @@ func LoadArray(db *mongox.Database, target interface{}, filters ...interface{})
 		panic(errors.InternalErrorf("target slice should contain ptrs"))
 	}
 
-	dummy := reflect.Zero(targetSliceElemT)
-	collection := db.GetCollectionOf(dummy.Interface())
-	opts := options.Find()
 	composed := query.Compose(filters...)
+	hasPreloader, _ := composed.Preloader()
 
-	opts.Sort = composed.Sorter()
-	opts.Limit = composed.Limiter()
-	opts.Skip = composed.Skipper()
+	var result *mongo.Cursor
+	var err error
 
-	result, err := collection.Find(db.Context(), composed.M(), opts)
+	if hasPreloader {
+		result, err = createAggregateLoad(db, target, composed)
+	} else {
+		result, err = createSimpleLoad(db, target, composed)
+	}
 	if err != nil {
 		return errors.InternalErrorf("can't create find result: %s", err)
 	}

mongox/common/loadmany.go

@@ -7,7 +7,6 @@ import (
 	"github.com/mainnika/mongox-go-driver/mongox/errors"
 	"github.com/mainnika/mongox-go-driver/mongox/query"
 	"go.mongodb.org/mongo-driver/mongo"
-	"go.mongodb.org/mongo-driver/mongo/options"
 )
 
 // ManyLoader is a controller for a database cursor
@@ -43,15 +42,17 @@ func (l *ManyLoader) Close() error {
 // LoadMany function loads documents one by one into a target channel
 func LoadMany(db *mongox.Database, target interface{}, filters ...interface{}) (*ManyLoader, error) {
 
-	collection := db.GetCollectionOf(target)
-	opts := options.Find()
-	composed := query.Compose(filters...)
+	var cursor *mongo.Cursor
+	var err error
 
-	opts.Sort = composed.Sorter()
-	opts.Limit = composed.Limiter()
-	opts.Skip = composed.Skipper()
+	composed := query.Compose(filters...)
+	hasPreloader, _ := composed.Preloader()
 
-	cursor, err := collection.Find(db.Context(), composed.M(), opts)
+	if hasPreloader {
+		cursor, err = createAggregateLoad(db, target, composed)
+	} else {
+		cursor, err = createSimpleLoad(db, target, composed)
+	}
 	if err != nil {
 		return nil, errors.InternalErrorf("can't create find result: %s", err)
 	}

mongox/query/compose.go

@@ -30,6 +30,7 @@ func Push(q *Query, f interface{}) bool {
 	ok = ok || applySort(q, f)
 	ok = ok || applySkip(q, f)
 	ok = ok || applyProtection(q, f)
+	ok = ok || applyPreloader(q, f)
 
 	return ok
 }
@@ -108,3 +109,13 @@ func applyProtection(q *Query, f interface{}) bool {
 
 	return true
 }
+
+func applyPreloader(q *Query, f interface{}) bool {
+
+	if f, ok := f.(Preloader); ok {
+		q.preloader = f
+		return true
+	}
+
+	return false
+}

mongox/query/preload.go

@@ -0,0 +1,17 @@
+package query
+
+// Preloader is a filter to skip the result
+type Preloader interface {
+	Preload() []string
+}
+
+// Preload is a simple implementation of the Skipper filter
+type Preload []string
+
+var _ Preloader = Preload{}
+
+// Preload returns a preload list
+func (l Preload) Preload() []string {
+
+	return Preload(l)
+}

mongox/query/query.go

@@ -12,6 +12,7 @@ type Query struct {
 	limiter   Limiter
 	sorter    Sorter
 	skipper   Skipper
+	preloader Preloader
 }
 
 // And function pushes the elem query to the $and array of the query
@@ -63,6 +64,22 @@ func (q *Query) Skipper() *int64 {
 	return q.skipper.Skip()
 }
 
+// Preloader is a preloader list for a query
+func (q *Query) Preloader() (empty bool, preloader []string) {
+
+	if q.preloader == nil {
+		return false, nil
+	}
+
+	preloader = q.preloader.Preload()
+
+	if len(preloader) == 0 {
+		return false, nil
+	}
+
+	return true, preloader
+}
+
 // Empty checks the query for any content
 func (q *Query) Empty() bool {