PMM-685: explain

src/go/mongolib/proto/system.profile.go

@@ -1,7 +1,10 @@
 package proto
 
 import (
+	"strings"
 	"time"
+
+	"gopkg.in/mgo.v2/bson"
 )
 
 type SystemProfile struct {
@@ -74,9 +77,148 @@ type SystemProfile struct {
 	Op             string    `bson:"op"`
 	Protocol       string    `bson:"protocol"`
 	Query          BsonD     `bson:"query"`
+	UpdateObj      BsonD     `bson:"updateobj"`
 	Command        BsonD     `bson:"command"`
 	ResponseLength int       `bson:"responseLength"`
 	Ts             time.Time `bson:"ts"`
 	User           string    `bson:"user"`
 	WriteConflicts int       `bson:"writeConflicts"`
 }
+
+func NewExampleQuery(doc SystemProfile) ExampleQuery {
+	return ExampleQuery{
+		Ns:        doc.Ns,
+		Op:        doc.Op,
+		Query:     doc.Query,
+		Command:   doc.Command,
+		UpdateObj: doc.UpdateObj,
+	}
+}
+
+// ExampleQuery is a subset of SystemProfile
+type ExampleQuery struct {
+	Ns        string `bson:"ns" json:"ns"`
+	Op        string `bson:"op" json:"op"`
+	Query     BsonD  `bson:"query,omitempty" json:"query,omitempty"`
+	Command   BsonD  `bson:"command,omitempty" json:"command,omitempty"`
+	UpdateObj BsonD  `bson:"updateobj,omitempty" json:"updateobj,omitempty"`
+}
+
+func (self ExampleQuery) Db() string {
+	ns := strings.SplitN(self.Ns, ".", 2)
+	if len(ns) > 0 {
+		return ns[0]
+	}
+	return ""
+}
+
+func (self ExampleQuery) ExplainCmd() bson.D {
+	cmd := self.Command
+
+	switch self.Op {
+	case "query":
+		if cmd.Len() == 0 {
+			cmd = self.Query
+		}
+		if cmd.Len() == 0 || cmd[0].Name != "find" {
+			var filter interface{}
+			if cmd.Len() > 0 && cmd[0].Name == "query" {
+				filter = cmd[0].Value
+			} else {
+				filter = cmd
+			}
+
+			coll := ""
+			s := strings.SplitN(self.Ns, ".", 2)
+			if len(s) == 2 {
+				coll = s[1]
+			}
+
+			cmd = BsonD{
+				{"find", coll},
+				{"filter", filter},
+			}
+		}
+	case "update":
+		s := strings.SplitN(self.Ns, ".", 2)
+		coll := ""
+		if len(s) == 2 {
+			coll = s[1]
+		}
+		if cmd.Len() == 0 {
+			cmd = BsonD{
+				{Name: "q", Value: self.Query},
+				{Name: "u", Value: self.UpdateObj},
+			}
+		}
+		cmd = BsonD{
+			{Name: "update", Value: coll},
+			{Name: "updates", Value: []interface{}{cmd}},
+		}
+	case "remove":
+		s := strings.SplitN(self.Ns, ".", 2)
+		coll := ""
+		if len(s) == 2 {
+			coll = s[1]
+		}
+		if cmd.Len() == 0 {
+			cmd = BsonD{
+				{Name: "q", Value: self.Query},
+				// we can't determine if limit was 1 or 0 so we assume 0
+				{Name: "limit", Value: 0},
+			}
+		}
+		cmd = BsonD{
+			{Name: "delete", Value: coll},
+			{Name: "deletes", Value: []interface{}{cmd}},
+		}
+	case "insert":
+		if cmd.Len() == 0 {
+			cmd = self.Query
+		}
+		if cmd.Len() == 0 || cmd[0].Name != "insert" {
+			coll := ""
+			s := strings.SplitN(self.Ns, ".", 2)
+			if len(s) == 2 {
+				coll = s[1]
+			}
+
+			cmd = BsonD{
+				{"insert", coll},
+			}
+		}
+	case "command":
+		if cmd.Len() == 0 || cmd[0].Name != "group" {
+			break
+		}
+
+		if v, ok := cmd[0].Value.(BsonD); ok {
+			for i := range v {
+				// for MongoDB <= 3.2
+				// "$reduce" : function () {}
+				// It is then Unmarshaled as empty value, so in essence not working
+				//
+				// for MongoDB >= 3.4
+				// "$reduce" : {
+				//    "code" : "function () {}"
+				// }
+				// It is then properly Unmarshaled but then explain fails with "not code"
+				//
+				// The $reduce function shouldn't affect explain execution plan (e.g. what indexes are picked)
+				// so we ignore it for now until we find better way to handle this issue
+				if v[i].Name == "$reduce" {
+					v[i].Value = ""
+					cmd[0].Value = v
+					break
+				}
+			}
+		}
+	}
+
+	return bson.D{
+		{
+			Name:  "explain",
+			Value: cmd,
+		},
+	}
+}