enhance: [2.4] add param for tuning max VARCHAR length (#38890)

issue: #38882
pr: #38884

Signed-off-by: Patrick Weizhi Xu <[email protected]>
(cherry picked from commit 72fecd4)

Author: PwzXxm

internal/proxy/task.go

@@ -1194,8 +1194,9 @@ func (t *alterCollectionFieldTask) PreExecute(ctx context.Context) error {
 				return merr.WrapErrParameterInvalid("%s should be an integer, but got %T", prop.Key, prop.Value)
 			}
 
-			if value > defaultMaxVarCharLength {
-				return merr.WrapErrParameterInvalid("%s exceeds the maximum allowed value 65535", prop.Value)
+			defaultMaxVarCharLength := Params.ProxyCfg.MaxVarCharLength.GetAsInt64()
+			if int64(value) > defaultMaxVarCharLength {
+				return merr.WrapErrParameterInvalidMsg("%s exceeds the maximum allowed value %s", prop.Value, strconv.FormatInt(defaultMaxVarCharLength, 10))
 			}
 		}
 	}

internal/proxy/util.go

@@ -63,8 +63,6 @@ const (
 	// enableMultipleVectorFields indicates whether to enable multiple vector fields.
 	enableMultipleVectorFields = true
 
-	defaultMaxVarCharLength = 65535
-
 	defaultMaxArrayCapacity = 4096
 
 	defaultMaxSearchRequest = 1024
@@ -363,8 +361,10 @@ func validateMaxLengthPerRow(collectionName string, field *schemapb.FieldSchema)
 		if err != nil {
 			return err
 		}
+
+		defaultMaxVarCharLength := Params.ProxyCfg.MaxVarCharLength.GetAsInt64()
 		if maxLengthPerRow > defaultMaxVarCharLength || maxLengthPerRow <= 0 {
-			return merr.WrapErrParameterInvalidMsg("the maximum length specified for a VarChar should be in (0, 65535]")
+			return merr.WrapErrParameterInvalidMsg("the maximum length specified for a VarChar should be in (0, %d]", defaultMaxVarCharLength)
 		}
 		exist = true
 	}

pkg/util/paramtable/component_param.go

@@ -1303,6 +1303,7 @@ type proxyConfig struct {
 	SkipAutoIDCheck              ParamItem `refreshable:"true"`
 	SkipPartitionKeyCheck        ParamItem `refreshable:"true"`
 	EnablePublicPrivilege        ParamItem `refreshable:"false"`
+	MaxVarCharLength             ParamItem `refreshable:"false"`
 
 	AccessLog AccessLogConfig
 
@@ -1697,6 +1698,14 @@ please adjust in embedded Milvus: false`,
 	}
 	p.EnablePublicPrivilege.Init(base.mgr)
 
+	p.MaxVarCharLength = ParamItem{
+		Key:          "proxy.maxVarCharLength",
+		Version:      "2.4.19",            // hotfix
+		DefaultValue: strconv.Itoa(65535), // 64K
+		Doc:          "maximum number of characters for a varchar field; this value is overridden by the value in a pre-existing schema if applicable",
+	}
+	p.MaxVarCharLength.Init(base.mgr)
+
 	p.GracefulStopTimeout = ParamItem{
 		Key:          "proxy.gracefulStopTimeout",
 		Version:      "2.3.7",