From 2561314d7a4782af0777ce768310c2b751901ad9 Mon Sep 17 00:00:00 2001
From: Ti Chi Robot <ti-community-prow-bot@tidb.io>
Date: Thu, 18 May 2023 18:45:36 +0800
Subject: [PATCH] partition: fix split and scatter region for truncate
 partition (#43271) (#43743)

close pingcap/tidb#43028, close pingcap/tidb#43174
---
 ddl/db_partition_test.go | 33 ++++++++++++++++++++++++++
 ddl/ddl_api.go           | 50 ++++++++++++++++++++++++----------------
 2 files changed, 63 insertions(+), 20 deletions(-)

diff --git a/ddl/db_partition_test.go b/ddl/db_partition_test.go
index 7b9e2f5a3e0b7..90d98b663c0da 100644
--- a/ddl/db_partition_test.go
+++ b/ddl/db_partition_test.go
@@ -1537,6 +1537,39 @@ func TestAlterTableTruncatePartitionByListColumns(t *testing.T) {
 	tk.MustQuery("select * from t").Check(testkit.Rows())
 }
 
+func TestAlterTableTruncatePartitionPreSplitRegion(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	atomic.StoreUint32(&ddl.EnableSplitTableRegion, 1)
+	tk.MustExec("set @@global.tidb_scatter_region=1;")
+	tk.MustExec("use test;")
+
+	tk.MustExec("drop table if exists t1;")
+	tk.MustExec(`CREATE TABLE t1 (id int, c varchar(128), key c(c)) partition by range (id) (
+		partition p0 values less than (10), 
+		partition p1 values less than MAXVALUE)`)
+	re := tk.MustQuery("show table t1 regions")
+	rows := re.Rows()
+	require.Len(t, rows, 2)
+	tk.MustExec(`alter table t1 truncate partition p0`)
+	re = tk.MustQuery("show table t1 regions")
+	rows = re.Rows()
+	require.Len(t, rows, 2)
+
+	tk.MustExec("drop table if exists t2;")
+	tk.MustExec(`CREATE TABLE t2(id bigint(20) NOT NULL AUTO_INCREMENT, PRIMARY KEY (id) NONCLUSTERED) SHARD_ROW_ID_BITS=4 PRE_SPLIT_REGIONS=3 PARTITION BY RANGE (id) (
+		PARTITION p1 VALUES LESS THAN (10),
+		PARTITION p2 VALUES LESS THAN (20),
+		PARTITION p3 VALUES LESS THAN (MAXVALUE))`)
+	re = tk.MustQuery("show table t2 regions")
+	rows = re.Rows()
+	require.Len(t, rows, 24)
+	tk.MustExec(`alter table t2 truncate partition p3`)
+	re = tk.MustQuery("show table t2 regions")
+	rows = re.Rows()
+	require.Len(t, rows, 24)
+}
+
 func TestCreateTableWithKeyPartition(t *testing.T) {
 	store := testkit.CreateMockStore(t, mockstore.WithDDLChecker())
 
diff --git a/ddl/ddl_api.go b/ddl/ddl_api.go
index eb2e20df13b63..4509aa0d954e9 100644
--- a/ddl/ddl_api.go
+++ b/ddl/ddl_api.go
@@ -4232,30 +4232,35 @@ func (d *ddl) TruncateTablePartition(ctx sessionctx.Context, ident ast.Ident, sp
 		return errors.Trace(dbterror.ErrPartitionMgmtOnNonpartitioned)
 	}
 
-	var pids []int64
-	if spec.OnAllPartitions {
-		pids = make([]int64, len(meta.GetPartitionInfo().Definitions))
-		for i, def := range meta.GetPartitionInfo().Definitions {
-			pids[i] = def.ID
+	getTruncatedParts := func(pi *model.PartitionInfo) (*model.PartitionInfo, error) {
+		if spec.OnAllPartitions {
+			return pi.Clone(), nil
 		}
-	} else {
+		var defs []model.PartitionDefinition
 		// MySQL allows duplicate partition names in truncate partition
 		// so we filter them out through a hash
-		pidMap := make(map[int64]bool)
+		posMap := make(map[int]bool)
 		for _, name := range spec.PartitionNames {
-			pid, err := tables.FindPartitionByName(meta, name.L)
-			if err != nil {
-				return errors.Trace(err)
+			pos := pi.FindPartitionDefinitionByName(name.L)
+			if pos < 0 {
+				return nil, errors.Trace(table.ErrUnknownPartition.GenWithStackByArgs(name.L, ident.Name.O))
+			}
+			if _, ok := posMap[pos]; !ok {
+				defs = append(defs, pi.Definitions[pos])
+				posMap[pos] = true
 			}
-			pidMap[pid] = true
-		}
-		// linter makezero does not handle changing pids to zero length,
-		// so create a new var and then assign to pids...
-		newPids := make([]int64, 0, len(pidMap))
-		for pid := range pidMap {
-			newPids = append(newPids, pid)
 		}
-		pids = newPids
+		pi = pi.Clone()
+		pi.Definitions = defs
+		return pi, nil
+	}
+	pi, err := getTruncatedParts(meta.GetPartitionInfo())
+	if err != nil {
+		return err
+	}
+	pids := make([]int64, 0, len(pi.Definitions))
+	for i := range pi.Definitions {
+		pids = append(pids, pi.Definitions[i].ID)
 	}
 
 	job := &model.Job{
@@ -4269,11 +4274,16 @@ func (d *ddl) TruncateTablePartition(ctx sessionctx.Context, ident ast.Ident, sp
 	}
 
 	err = d.DoDDLJob(ctx, job)
+	err = d.callHookOnChanged(job, err)
 	if err != nil {
 		return errors.Trace(err)
 	}
-	err = d.callHookOnChanged(job, err)
-	return errors.Trace(err)
+	if _, tb, err := d.getSchemaAndTableByIdent(ctx, ident); err == nil {
+		if p, err := getTruncatedParts(tb.Meta().GetPartitionInfo()); err == nil {
+			d.preSplitAndScatter(ctx, tb.Meta(), p)
+		}
+	}
+	return nil
 }
 
 func (d *ddl) DropTablePartition(ctx sessionctx.Context, ident ast.Ident, spec *ast.AlterTableSpec) error {