enhance: Handle legacy proxy load fields request (milvus-io#37565)

Related to milvus-io#35415

In rolling upgrade, legacy proxy may dispatch load request wit empty
load field list. The upgraded querycoord may report error by mistake
that load field list is changed.

This PR:

- Auto field empty load field list with all user field ids
- Refine the error messag when load field list updates
- Refine load job unit test with service cases

Signed-off-by: Congqi Xia <[email protected]>

internal/querycoordv2/job/job_load.go

@@ -27,11 +27,13 @@ import (
 	"go.opentelemetry.io/otel/trace"
 	"go.uber.org/zap"
 
+	"github.com/milvus-io/milvus-proto/go-api/v2/schemapb"
 	"github.com/milvus-io/milvus/internal/proto/querypb"
 	"github.com/milvus-io/milvus/internal/querycoordv2/meta"
 	"github.com/milvus-io/milvus/internal/querycoordv2/observers"
 	"github.com/milvus-io/milvus/internal/querycoordv2/session"
 	"github.com/milvus-io/milvus/internal/querycoordv2/utils"
+	"github.com/milvus-io/milvus/pkg/common"
 	"github.com/milvus-io/milvus/pkg/eventlog"
 	"github.com/milvus-io/milvus/pkg/log"
 	"github.com/milvus-io/milvus/pkg/metrics"
@@ -109,8 +111,15 @@ func (job *LoadCollectionJob) PreExecute() error {
 		return merr.WrapErrParameterInvalid(collection.GetReplicaNumber(), req.GetReplicaNumber(), "can't change the replica number for loaded collection")
 	}
 
+	// handle legacy proxy load request
+	if len(req.GetLoadFields()) == 0 {
+		req.LoadFields = lo.FilterMap(req.GetSchema().GetFields(), func(field *schemapb.FieldSchema, _ int) (int64, bool) {
+			return field.GetFieldID(), field.GetFieldID() >= common.StartOfUserFieldID
+		})
+	}
+
 	if !funcutil.SliceSetEqual(collection.GetLoadFields(), req.GetLoadFields()) {
-		log.Warn("collection with different load field list exists, release this collection first before chaning its replica number",
+		log.Warn("collection with different load field list exists, release this collection first before chaning its load fields",
 			zap.Int64s("loadedFieldIDs", collection.GetLoadFields()),
 			zap.Int64s("reqFieldIDs", req.GetLoadFields()),
 		)
@@ -314,8 +323,15 @@ func (job *LoadPartitionJob) PreExecute() error {
 		return merr.WrapErrParameterInvalid(collection.GetReplicaNumber(), req.GetReplicaNumber(), "can't change the replica number for loaded partitions")
 	}
 
+	// handle legacy proxy load request
+	if len(req.GetLoadFields()) == 0 {
+		req.LoadFields = lo.FilterMap(req.GetSchema().GetFields(), func(field *schemapb.FieldSchema, _ int) (int64, bool) {
+			return field.GetFieldID(), field.GetFieldID() >= common.StartOfUserFieldID
+		})
+	}
+
 	if !funcutil.SliceSetEqual(collection.GetLoadFields(), req.GetLoadFields()) {
-		log.Warn("collection with different load field list exists, release this collection first before chaning its replica number",
+		log.Warn("collection with different load field list exists, release this collection first before chaning its load fields",
 			zap.Int64s("loadedFieldIDs", collection.GetLoadFields()),
 			zap.Int64s("reqFieldIDs", req.GetLoadFields()),
 		)