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ddl: refine pre-split region logic #11794

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Aug 20, 2019
Merged

ddl: refine pre-split region logic #11794

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c560a43
ddl: refine pre-split region logic
crazycs520 Aug 20, 2019
f01de9e
Merge branch 'master' into fix-pre-split
bb7133 Aug 20, 2019
15aa1ae
Merge branch 'master' into fix-pre-split
crazycs520 Aug 20, 2019
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18 changes: 8 additions & 10 deletions ddl/split_region.go
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Original file line number Diff line number Diff line change
Expand Up @@ -45,14 +45,14 @@ func splitTableRegion(store kv.SplitableStore, tbInfo *model.TableInfo, scatter

func splitPreSplitedTable(store kv.SplitableStore, tbInfo *model.TableInfo, scatter bool) {
// Example:
// ShardRowIDBits = 5
// PreSplitRegions = 3
// ShardRowIDBits = 4
// PreSplitRegions = 2
//
// then will pre-split 2^(3-1) = 4 regions.
// then will pre-split 2^2 = 4 regions.
//
// in this code:
// max = 1 << (tblInfo.ShardRowIDBits - 1) = 1 << (5-1) = 16
// step := int64(1 << (tblInfo.ShardRowIDBits - tblInfo.PreSplitRegions)) = 1 << (5-3) = 4;
// max = 1 << tblInfo.ShardRowIDBits = 16
// step := int64(1 << (tblInfo.ShardRowIDBits - tblInfo.PreSplitRegions)) = 1 << (4-2) = 4;
//
// then split regionID is below:
// 4 << 59 = 2305843009213693952
Expand All @@ -68,13 +68,11 @@ func splitPreSplitedTable(store kv.SplitableStore, tbInfo *model.TableInfo, scat
// And the max _tidb_rowid is 9223372036854775807, it won't be negative number.

// Split table region.
regionIDs := make([]uint64, 0, 1<<(tbInfo.PreSplitRegions-1)+len(tbInfo.Indices))
regionIDs := make([]uint64, 0, 1<<(tbInfo.PreSplitRegions)+len(tbInfo.Indices))
step := int64(1 << (tbInfo.ShardRowIDBits - tbInfo.PreSplitRegions))
// The highest bit is the symbol bit,and alloc _tidb_rowid will always be positive number.
// So we only need to split the region for the positive number.
max := int64(1 << (tbInfo.ShardRowIDBits - 1))
max := int64(1 << tbInfo.ShardRowIDBits)
for p := int64(step); p < max; p += step {
recordID := p << (64 - tbInfo.ShardRowIDBits)
recordID := p << (64 - tbInfo.ShardRowIDBits - 1)
recordPrefix := tablecodec.GenTableRecordPrefix(tbInfo.ID)
key := tablecodec.EncodeRecordKey(recordPrefix, recordID)
regionID, err := store.SplitRegion(key, scatter)
Expand Down
16 changes: 13 additions & 3 deletions executor/executor_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4125,6 +4125,7 @@ func (s *testSuite) TestShowTableRegion(c *C) {
tk := testkit.NewTestKit(c, s.store)
tk.MustExec("use test")
tk.MustExec("drop table if exists t_regions1, t_regions")
atomic.StoreUint32(&ddl.EnableSplitTableRegion, 0)
tk.MustExec("create table t_regions1 (a int key, b int, index idx(b))")
tk.MustExec("create table t_regions (a int key, b int, index idx(b))")

Expand Down Expand Up @@ -4158,7 +4159,6 @@ func (s *testSuite) TestShowTableRegion(c *C) {

re = tk.MustQuery("show table t_regions regions")
rows = re.Rows()
// The index `idx` of table t_regions should have 4 regions now.
c.Assert(len(rows), Equals, 7)
// Check the region start key.
c.Assert(rows[0][1], Matches, fmt.Sprintf("t_%d_i_1_.*", tbl.Meta().ID))
Expand Down Expand Up @@ -4206,7 +4206,6 @@ func (s *testSuite) TestShowTableRegion(c *C) {
tk.MustExec("create table partition_t (a int, b int,index(a)) partition by hash (a) partitions 3")
re = tk.MustQuery("show table partition_t regions")
rows = re.Rows()
// Table t_regions should have 4 regions now.
c.Assert(len(rows), Equals, 1)
c.Assert(rows[0][1], Matches, "t_.*")

Expand All @@ -4217,13 +4216,24 @@ func (s *testSuite) TestShowTableRegion(c *C) {
tk.MustExec("create table partition_t (a int, b int,index(a)) partition by hash (a) partitions 3")
re = tk.MustQuery("show table partition_t regions")
rows = re.Rows()
// Table t_regions should have 4 regions now.
c.Assert(len(rows), Equals, 3)
tbl = testGetTableByName(c, tk.Se, "test", "partition_t")
partitionDef := tbl.Meta().GetPartitionInfo().Definitions
c.Assert(rows[0][1], Matches, fmt.Sprintf("t_%d_.*", partitionDef[0].ID))
c.Assert(rows[1][1], Matches, fmt.Sprintf("t_%d_.*", partitionDef[1].ID))
c.Assert(rows[2][1], Matches, fmt.Sprintf("t_%d_.*", partitionDef[2].ID))

// Test pre-split table region when create table.
tk.MustExec("drop table if exists t_pre")
tk.MustExec("create table t_pre (a int, b int) shard_row_id_bits = 2 pre_split_regions=2;")
re = tk.MustQuery("show table t_pre regions")
rows = re.Rows()
// Table t_regions should have 4 regions now.
c.Assert(len(rows), Equals, 4)
tbl = testGetTableByName(c, tk.Se, "test", "t_pre")
c.Assert(rows[1][1], Equals, fmt.Sprintf("t_%d_r_2305843009213693952", tbl.Meta().ID))
c.Assert(rows[2][1], Equals, fmt.Sprintf("t_%d_r_4611686018427387904", tbl.Meta().ID))
c.Assert(rows[3][1], Equals, fmt.Sprintf("t_%d_r_6917529027641081856", tbl.Meta().ID))
atomic.StoreUint32(&ddl.EnableSplitTableRegion, 0)
}

Expand Down