planner: Fix vector not truncated after CBO (#58809)

close #58837

Author: breezewish

pkg/expression/integration_test/integration_test.go

@@ -418,6 +418,24 @@ func TestVectorColumnInfo(t *testing.T) {
 	tk.MustGetErrMsg("create table t(embedding VECTOR(16384))", "vector cannot have more than 16383 dimensions")
 }
 
+func TestVectorExplainTruncate(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("CREATE TABLE t(c VECTOR);")
+
+	// TODO: The output can be improved.
+	tk.MustQuery(`EXPLAIN format='brief' SELECT
+		VEC_COSINE_DISTANCE(c, '[3,100,12345,10000]'),
+		VEC_COSINE_DISTANCE(c, '[11111111111,11111111111.23456789,3.1,5.12456]'),
+		VEC_COSINE_DISTANCE(c, '[-11111111111,-11111111111.23456789,-3.1,-5.12456]')
+	FROM t;`).Check(testkit.Rows(
+		`Projection 10000.00 root  vec_cosine_distance(test.t.c, [3,1e+02,1.2e+04,1e+04])->Column#3, vec_cosine_distance(test.t.c, [1.1e+10,1.1e+10,3.1,5.1])->Column#4, vec_cosine_distance(test.t.c, [-1.1e+10,-1.1e+10,-3.1,-5.1])->Column#5`,
+		`└─TableReader 10000.00 root  data:TableFullScan`,
+		`  └─TableFullScan 10000.00 cop[tikv] table:t keep order:false, stats:pseudo`,
+	))
+}
+
 func TestVectorConstantExplain(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)
@@ -475,6 +493,59 @@ func TestVectorConstantExplain(t *testing.T) {
 	tk.ResultSetToResult(rs, fmt.Sprintf("%v", rs))
 }
 
+func TestVectorIndexExplain(t *testing.T) {
+	store := testkit.CreateMockStoreWithSchemaLease(t, 1*time.Second, mockstore.WithMockTiFlash(2))
+
+	tk := testkit.NewTestKit(t, store)
+
+	tiflash := infosync.NewMockTiFlash()
+	infosync.SetMockTiFlash(tiflash)
+	defer func() {
+		tiflash.Lock()
+		tiflash.StatusServer.Close()
+		tiflash.Unlock()
+	}()
+
+	failpoint.Enable("github.com/pingcap/tidb/pkg/ddl/MockCheckVectorIndexProcess", `return(1)`)
+	defer func() {
+		require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/pkg/ddl/MockCheckVectorIndexProcess"))
+	}()
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1")
+	tk.MustExec(`
+		create table t1 (
+			vec vector(100)
+		)
+	`)
+	tk.MustExec("alter table t1 set tiflash replica 1;")
+	tk.MustExec("alter table t1 add vector index ((vec_cosine_distance(vec))) USING HNSW;")
+	tbl, _ := domain.GetDomain(tk.Session()).InfoSchema().TableByName(context.Background(), ast.NewCIStr("test"), ast.NewCIStr("t1"))
+	tbl.Meta().TiFlashReplica = &model.TiFlashReplicaInfo{
+		Count:     1,
+		Available: true,
+	}
+
+	vb := strings.Builder{}
+	vb.WriteString("[")
+	for i := 0; i < 100; i++ {
+		if i > 0 {
+			vb.WriteString(",")
+		}
+		vb.WriteString("100")
+	}
+	vb.WriteString("]")
+
+	tk.MustQuery(fmt.Sprintf("explain format = 'brief' select * from t1 order by vec_cosine_distance(vec, '%s') limit 1", vb.String())).Check(testkit.Rows(
+		`TopN 1.00 root  Column#5, offset:0, count:1`,
+		`└─TableReader 1.00 root  MppVersion: 2, data:ExchangeSender`,
+		`  └─ExchangeSender 1.00 mpp[tiflash]  ExchangeType: PassThrough`,
+		`    └─TopN 1.00 mpp[tiflash]  Column#5, offset:0, count:1`,
+		`      └─Projection 1.00 mpp[tiflash]  test.t1.vec, vec_cosine_distance(test.t1.vec, [1e+02,1e+02,1e+02,1e+02,1e+02,(95 more)...])->Column#5`,
+		`        └─TableFullScan 1.00 mpp[tiflash] table:t1, index:vector_index(vec) keep order:false, stats:pseudo, annIndex:COSINE(vec..[1e+02,1e+02,1e+02,1e+02,1e+02,(95 more)...], limit:1)`,
+	))
+}
+
 func TestFixedVector(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)

pkg/planner/core/explain.go

@@ -284,7 +284,7 @@ func (p *PhysicalTableScan) OperatorInfo(normalized bool) string {
 			if err != nil {
 				buffer.WriteString("[?]")
 			} else {
-				buffer.WriteString(v.String())
+				buffer.WriteString(v.TruncatedString())
 			}
 		}
 		buffer.WriteString(", limit:")