From 425e7deea9534e28debc8a0ce46070cfdccc7de7 Mon Sep 17 00:00:00 2001
From: sijie-ni-0214 <sijie.ni@zilliz.com>
Date: Thu, 18 Jun 2026 02:24:27 +0800
Subject: [PATCH] fix: Reject dropping active TTL field (#50479)

issue: https://github.com/milvus-io/milvus/issues/50476

This PR rejects dropping a field when it is referenced by the collection
`ttl_field` property. Users need to drop the property first, which
avoids leaving dangling entity-level TTL metadata after Drop Field.

Validation:
- gofumpt -l internal/proxy/task.go internal/proxy/task_test.go
- git diff --check
- TestValidateDropField

Signed-off-by: sijie-ni-0214 <sijie.ni@zilliz.com>
---
 internal/proxy/task.go      |  6 ++++++
 internal/proxy/task_test.go | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/internal/proxy/task.go b/internal/proxy/task.go
index 65c3147fa6..5afccd9b3c 100644
--- a/internal/proxy/task.go
+++ b/internal/proxy/task.go
@@ -1219,6 +1219,12 @@ func validateDropField(schema *schemapb.CollectionSchema, fieldName string) erro
 		return merr.WrapErrParameterInvalidMsg("field not found: %s", fieldName)
 	}
 
+	for _, property := range schema.GetProperties() {
+		if property.GetKey() == common.CollectionTTLFieldKey && property.GetValue() == fieldName {
+			return merr.WrapErrParameterInvalidMsg("cannot drop field %s because it is referenced by collection property %s, drop the property first", fieldName, common.CollectionTTLFieldKey)
+		}
+	}
+
 	// Check: cannot drop system fields
 	if funcutil.SliceContain([]string{common.RowIDFieldName, common.TimeStampFieldName, common.MetaFieldName, common.NamespaceFieldName}, fieldName) {
 		return merr.WrapErrParameterInvalidMsg("cannot drop system field: %s", fieldName)
diff --git a/internal/proxy/task_test.go b/internal/proxy/task_test.go
index c69d7b9f05..3d3e81e8f9 100644
--- a/internal/proxy/task_test.go
+++ b/internal/proxy/task_test.go
@@ -8266,6 +8266,24 @@ func TestValidateDropField(t *testing.T) {
 		assert.Contains(t, err.Error(), "cannot drop dynamic field")
 	})
 
+	t.Run("cannot drop active ttl field", func(t *testing.T) {
+		schema := &schemapb.CollectionSchema{
+			Name: "test_collection",
+			Fields: []*schemapb.FieldSchema{
+				{FieldID: 100, Name: "id", DataType: schemapb.DataType_Int64, IsPrimaryKey: true},
+				{FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector, TypeParams: []*commonpb.KeyValuePair{{Key: "dim", Value: "128"}}},
+				{FieldID: 102, Name: "ttl", DataType: schemapb.DataType_Timestamptz, Nullable: true},
+			},
+			Properties: []*commonpb.KeyValuePair{
+				{Key: common.CollectionTTLFieldKey, Value: "ttl"},
+			},
+		}
+
+		err := validateDropField(schema, "ttl")
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "referenced by collection property ttl_field")
+	})
+
 	t.Run("field referenced by function - input", func(t *testing.T) {
 		err := validateDropField(baseSchema, "scalar_field")
 		assert.Error(t, err)