etcdserver, clientv3: add "!=" to txn

adding != to compare is a requested functionality from a etcd user

FIX etcd-io#6719

Documentation/dev-guide/api_reference_v3.md

@@ -427,7 +427,7 @@ Empty field.
 | Field | Description | Type |
 | ----- | ----------- | ---- |
 | key | key is the first key to delete in the range. | bytes |
-| range_end | range_end is the key following the last key to delete for the range [key, range_end). If range_end is not given, the range is defined to contain only the key argument. If range_end is '\0', the range is all keys greater than or equal to the key argument. | bytes |
+| range_end | range_end is the key following the last key to delete for the range [key, range_end). If range_end is not given, the range is defined to contain only the key argument. If range_end is one bit larger than the given key, then the range is all the all keys with the prefix (the given key). If range_end is '\0', the range is all keys greater than or equal to the key argument. | bytes |
 | prev_kv | If prev_kv is set, etcd gets the previous key-value pairs before deleting it. The previous key-value pairs will be returned in the delte response. | bool |
 
 
@@ -762,7 +762,7 @@ From google paxosdb paper: Our implementation hinges around a powerful primitive
 | Field | Description | Type |
 | ----- | ----------- | ---- |
 | key | key is the key to register for watching. | bytes |
-| range_end | range_end is the end of the range [key, range_end) to watch. If range_end is not given, only the key argument is watched. If range_end is equal to '\0', all keys greater than or equal to the key argument are watched. | bytes |
+| range_end | range_end is the end of the range [key, range_end) to watch. If range_end is not given, only the key argument is watched. If range_end is equal to '\0', all keys greater than or equal to the key argument are watched. If the range_end is one bit larger than the given key, then all keys with the prefix (the given key) will be watched. | bytes |
 | start_revision | start_revision is an optional revision to watch from (inclusive). No start_revision is "now". | int64 |
 | progress_notify | progress_notify is set so that the etcd server will periodically send a WatchResponse with no events to the new watcher if there are no recent events. It is useful when clients wish to recover a disconnected watcher starting from a recent known revision. The etcd server may decide how often it will send notifications based on current load. | bool |
 | filters | filter out put event. filter out delete event. filters filter the events at server side before it sends back to the watcher. | (slice of) FilterType |

Documentation/dev-guide/apispec/swagger/rpc.swagger.json

@@ -978,7 +978,8 @@
       "enum": [
         "EQUAL",
         "GREATER",
-        "LESS"
+        "LESS",
+        "NOT_EQUAL"
       ],
       "default": "EQUAL"
     },
@@ -1518,7 +1519,7 @@
         "range_end": {
           "type": "string",
           "format": "byte",
-          "description": "range_end is the key following the last key to delete for the range [key, range_end).\nIf range_end is not given, the range is defined to contain only the key argument.\nIf range_end is '\\0', the range is all keys greater than or equal to the key argument."
+          "description": "range_end is the key following the last key to delete for the range [key, range_end).\nIf range_end is not given, the range is defined to contain only the key argument.\nIf range_end is one bit larger than the given key, then the range is all\nthe all keys with the prefix (the given key).\nIf range_end is '\\0', the range is all keys greater than or equal to the key argument."
         }
       }
     },

clientv3/compare.go

@@ -36,6 +36,8 @@ func Compare(cmp Cmp, result string, v interface{}) Cmp {
 	switch result {
 	case "=":
 		r = pb.Compare_EQUAL
+	case "!=":
+		r = pb.Compare_NOT_EQUAL
 	case ">":
 		r = pb.Compare_GREATER
 	case "<":

e2e/ctl_v3_txn_test.go

@@ -40,6 +40,11 @@ func txnTestSuccess(cx ctlCtx) {
 		cx.t.Fatalf("txnTestSuccess ctlV3Put error (%v)", err)
 	}
 	rqs := []txnRequests{
+		{
+			compare:  []string{`value("key1") != "value2"`, `value("key2") != "value1"`},
+			ifSucess: []string{"get key1", "get key2"},
+			results:  []string{"SUCCESS", "key1", "value1", "key2", "value2"},
+		},
 		{
 			compare:  []string{`version("key1") = "1"`, `version("key2") = "1"`},
 			ifSucess: []string{"get key1", "get key2", `put "key \"with\" space" "value \x23"`},
@@ -60,14 +65,27 @@ func txnTestSuccess(cx ctlCtx) {
 }
 
 func txnTestFail(cx ctlCtx) {
-	rqs := txnRequests{
-		compare:  []string{`version("key") < "0"`},
-		ifSucess: []string{`put key "success"`},
-		ifFail:   []string{`put key "fail"`},
-		results:  []string{"FAILURE", "OK"},
-	}
-	if err := ctlV3Txn(cx, rqs); err != nil {
-		cx.t.Fatal(err)
+	if err := ctlV3Put(cx, "key1", "value1", ""); err != nil {
+		cx.t.Fatalf("txnTestSuccess ctlV3Put error (%v)", err)
+	}
+	rqs := []txnRequests{
+		{
+			compare:  []string{`version("key") < "0"`},
+			ifSucess: []string{`put key "success"`},
+			ifFail:   []string{`put key "fail"`},
+			results:  []string{"FAILURE", "OK"},
+		},
+		{
+			compare:  []string{`value("key1") != "value1"`},
+			ifSucess: []string{`put key1 "success"`},
+			ifFail:   []string{`put key1 "fail"`},
+			results:  []string{"FAILURE", "OK"},
+		},
+	}
+	for _, rq := range rqs {
+		if err := ctlV3Txn(cx, rq); err != nil {
+			cx.t.Fatal(err)
+		}
 	}
 }
 

etcdserver/apply.go

@@ -451,6 +451,10 @@ func (a *applierV3backend) applyCompare(c *pb.Compare) (int64, bool) {
 		if result != 0 {
 			return rev, false
 		}
+	case pb.Compare_NOT_EQUAL:
+		if result == 0 {
+			return rev, false
+		}
 	case pb.Compare_GREATER:
 		if result != 1 {
 			return rev, false