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*: add tidb_min_paging_size system variable #36107

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merged 7 commits into from
Jul 13, 2022
Merged

*: add tidb_min_paging_size system variable #36107

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7c243ec
*: add tidb_min_paging_size system variable
tiancaiamao Jul 11, 2022
c240ea9
fix CI
tiancaiamao Jul 12, 2022
05c431f
fix CI
tiancaiamao Jul 12, 2022
80b30c5
reset unrelated change so it get reviewed easier
tiancaiamao Jul 13, 2022
9363c5d
Merge branch 'master' into min-paging-size
tiancaiamao Jul 13, 2022
caff4d7
Merge branch 'master' into min-paging-size
tiancaiamao Jul 13, 2022
dbf7220
Merge branch 'master' into min-paging-size
ti-chi-bot Jul 13, 2022
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1 change: 1 addition & 0 deletions distsql/request_builder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,7 @@ func (builder *RequestBuilder) SetFromSessionVars(sv *variable.SessionVars) *Req
builder.SetResourceGroupTagger(sv.StmtCtx.GetResourceGroupTagger())
if sv.EnablePaging {
builder.SetPaging(true)
builder.Request.MinPagingSize = uint64(sv.MinPagingSize)
}
builder.RequestSource.RequestSourceInternal = sv.InRestrictedSQL
builder.RequestSource.RequestSourceType = sv.RequestSourceType
Expand Down
59 changes: 59 additions & 0 deletions executor/distsql_test.go
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Expand Up @@ -19,7 +19,9 @@ import (
"context"
"fmt"
"math/rand"
"regexp"
"runtime/pprof"
"strconv"
"strings"
"testing"
"time"
Expand All @@ -34,6 +36,7 @@ import (
"github.com/pingcap/tidb/testkit"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/mock"
"github.com/pingcap/tidb/util/paging"
"github.com/stretchr/testify/require"
"github.com/tikv/client-go/v2/testutils"
)
Expand Down Expand Up @@ -418,3 +421,59 @@ func TestPartitionTableIndexJoinIndexLookUp(t *testing.T) {
tk.MustQuery("select /*+ TIDB_INLJ(t1, t2) */ t1.* from t t1, t t2 use index(a) where t1.a=t2.b and " + cond).Sort().Check(result)
}
}

func TestCoprocessorPagingSize(t *testing.T) {
store, clean := testkit.CreateMockStore(t)
defer clean()
tk := testkit.NewTestKit(t, store)

tk.MustExec("use test")
tk.MustExec("create table t_paging (a int, b int, key(a), key(b))")
nRows := 512
values := make([]string, 0, nRows)
for i := 0; i < nRows; i++ {
values = append(values, fmt.Sprintf("(%v, %v)", rand.Intn(nRows), rand.Intn(nRows)))
}
tk.MustExec(fmt.Sprintf("insert into t_paging values %v", strings.Join(values, ", ")))
tk.MustQuery("select @@tidb_min_paging_size").Check(testkit.Rows(strconv.FormatUint(paging.MinPagingSize, 10)))

// When the min paging size is small, we need more RPC roundtrip!
// Check 'rpc_num' in the execution information
//
// mysql> explain analyze select * from t_paging;
// +--------------------+----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
// | id |task | execution info |
// +--------------------+----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
// | TableReader_5 |root | time:7.27ms, loops:2, cop_task: {num: 10, max: 1.57ms, min: 313.3µs, avg: 675.9µs, p95: 1.57ms, tot_proc: 2ms, rpc_num: 10, rpc_time: 6.69ms, copr_cache_hit_ratio: 0.00, distsql_concurrency: 15} |
// | └─TableFullScan_4 |cop[tikv] | tikv_task:{proc max:1.48ms, min:294µs, avg: 629µs, p80:1.21ms, p95:1.48ms, iters:0, tasks:10} |
// +--------------------+----------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
// 2 rows in set (0.01 sec)

getRPCNumFromExplain := func(rows [][]interface{}) (res uint64) {
re := regexp.MustCompile("rpc_num: ([0-9]+)")
for _, row := range rows {
buf := bytes.NewBufferString("")
_, _ = fmt.Fprintf(buf, "%s\n", row)
if matched := re.FindStringSubmatch(buf.String()); matched != nil {
require.Equal(t, len(matched), 2)
c, err := strconv.ParseUint(matched[1], 10, 64)
require.NoError(t, err)
return c
}
}
return res
}

// This is required here because only the chunk encoding collect the execution information and contains 'rpc_num'.
tk.MustExec("set @@tidb_enable_chunk_rpc = on")

tk.MustExec("set @@tidb_min_paging_size = 1")
rows := tk.MustQuery("explain analyze select * from t_paging").Rows()
rpcNum := getRPCNumFromExplain(rows)
require.Greater(t, rpcNum, uint64(2))

tk.MustExec("set @@tidb_min_paging_size = 1000")
rows = tk.MustQuery("explain analyze select * from t_paging").Rows()
rpcNum = getRPCNumFromExplain(rows)
require.Equal(t, rpcNum, uint64(1))
}
2 changes: 2 additions & 0 deletions kv/kv.go
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Expand Up @@ -368,6 +368,8 @@ type Request struct {
ResourceGroupTagger tikvrpc.ResourceGroupTagger
// Paging indicates whether the request is a paging request.
Paging bool
// MinPagingSize is used when Paging is true.
MinPagingSize uint64
// RequestSource indicates whether the request is an internal request.
RequestSource util.RequestSource
}
Expand Down
4 changes: 4 additions & 0 deletions sessionctx/variable/session.go
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Expand Up @@ -1433,6 +1433,7 @@ func NewSessionVars() *SessionVars {
IndexLookupSize: DefIndexLookupSize,
InitChunkSize: DefInitChunkSize,
MaxChunkSize: DefMaxChunkSize,
MinPagingSize: DefMinPagingSize,
}
vars.DMLBatchSize = DefDMLBatchSize
vars.AllowBatchCop = DefTiDBAllowBatchCop
Expand Down Expand Up @@ -2173,6 +2174,9 @@ type BatchSize struct {

// MaxChunkSize defines max row count of a Chunk during query execution.
MaxChunkSize int

// MinPagingSize defines the min size used by the coprocessor paging protocol.
MinPagingSize int
}

const (
Expand Down
5 changes: 5 additions & 0 deletions sessionctx/variable/sysvar.go
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Expand Up @@ -35,6 +35,7 @@ import (
"github.com/pingcap/tidb/util/collate"
"github.com/pingcap/tidb/util/logutil"
"github.com/pingcap/tidb/util/mathutil"
"github.com/pingcap/tidb/util/paging"
"github.com/pingcap/tidb/util/stmtsummary"
"github.com/pingcap/tidb/util/tikvutil"
"github.com/pingcap/tidb/util/tls"
Expand Down Expand Up @@ -1667,6 +1668,10 @@ var defaultSysVars = []*SysVar{
metrics.ToggleSimplifiedMode(TiDBOptOn(s))
return nil
}},
{Scope: ScopeGlobal | ScopeSession, Name: TiDBMinPagingSize, Value: strconv.Itoa(DefMinPagingSize), Type: TypeUnsigned, MinValue: 1, MaxValue: paging.MaxPagingSize, SetSession: func(s *SessionVars, val string) error {
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If it is only for testing, is it necessary to be a global variable?

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I'm not sure, but I see some other variable use global | session, such as tidb_init_chunk_size, tidb_max_chunk_size

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If you can not come up with a scenario of set global, then no. TiDBInitChunkSize is historical.

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In the benchbot, we can test with this:

python3 main.py gen-benchbot-case --email "[email protected]" --token 'tcmsp_XXX' --testbed_size "2xl" \
--bench_type sysbench --bench_sub_types "select_random_ranges" \
--duration=30m --threads 100 \
--arch amd64 \
--versions nightly \
--tidb_urls "http://fileserver.pingcap.net/download/builds/pingcap/tidb-check/pr/80b30c51fb509e267d1fca9ed5122b70ded1a172/centos7/tidb-server.tar.gz" \
--testbed_size "2xl" \
--tidb_configs "{prepared-plan-cache: {enabled: true}}" \
--tidb_globals "set global tidb_enable_paging = 1; set global tidb_min_paging_size = 128;" \
--tidb_globals "set global tidb_enable_paging = 1; set global tidb_min_paging_size = 256;" \
--tidb_globals "set global tidb_enable_paging = 1; set global tidb_min_paging_size = 512;" \
--tidb_globals "set global tidb_enable_paging = 0;"

--tidb_globals requires global variables @xhebox

s.MinPagingSize = tidbOptPositiveInt32(val, DefMinPagingSize)
return nil
}},
{Scope: ScopeSession, Name: TiDBMemoryDebugModeMinHeapInUse, Value: strconv.Itoa(0), Type: TypeInt, MinValue: math.MinInt64, MaxValue: math.MaxInt64, SetSession: func(s *SessionVars, val string) error {
s.MemoryDebugModeMinHeapInUse = TidbOptInt64(val, 0)
return nil
Expand Down
5 changes: 5 additions & 0 deletions sessionctx/variable/tidb_vars.go
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Expand Up @@ -19,6 +19,7 @@ import (

"github.com/pingcap/tidb/config"
"github.com/pingcap/tidb/parser/mysql"
"github.com/pingcap/tidb/util/paging"
"go.uber.org/atomic"
)

Expand Down Expand Up @@ -363,6 +364,9 @@ const (
// TiDBInitChunkSize is used to control the init chunk size during query execution.
TiDBInitChunkSize = "tidb_init_chunk_size"

// TiDBMinPagingSize is used to control the min paging size in the coprocessor paging protocol.
TiDBMinPagingSize = "tidb_min_paging_size"

// TiDBEnableCascadesPlanner is used to control whether to enable the cascades planner.
TiDBEnableCascadesPlanner = "tidb_enable_cascades_planner"

Expand Down Expand Up @@ -818,6 +822,7 @@ const (
DefBatchCommit = false
DefCurretTS = 0
DefInitChunkSize = 32
DefMinPagingSize = int(paging.MinPagingSize)
DefMaxChunkSize = 1024
DefDMLBatchSize = 0
DefMaxPreparedStmtCount = -1
Expand Down
8 changes: 8 additions & 0 deletions sessionctx/variable/varsutil_test.go
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Expand Up @@ -432,6 +432,14 @@ func TestVarsutil(t *testing.T) {
err = SetSessionSystemVar(v, TiDBTableCacheLease, "123")
require.Error(t, err)
require.Regexp(t, "'tidb_table_cache_lease' is a GLOBAL variable and should be set with SET GLOBAL", err.Error())

val, err = GetSessionOrGlobalSystemVar(v, TiDBMinPagingSize)
require.NoError(t, err)
require.Equal(t, strconv.Itoa(DefMinPagingSize), val)

err = SetSessionSystemVar(v, TiDBMinPagingSize, "123")
require.NoError(t, err)
require.Equal(t, v.MinPagingSize, 123)
}

func TestValidate(t *testing.T) {
Expand Down
3 changes: 2 additions & 1 deletion store/copr/coprocessor.go
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Expand Up @@ -211,7 +211,7 @@ func buildCopTasks(bo *Backoffer, cache *RegionCache, ranges *KeyRanges, req *kv
// the size will grow every round.
pagingSize := uint64(0)
if req.Paging {
pagingSize = paging.MinPagingSize
pagingSize = req.MinPagingSize
}
tasks = append(tasks, &copTask{
region: loc.Location.Region,
Expand Down Expand Up @@ -868,6 +868,7 @@ func (worker *copIteratorWorker) handleCopPagingResult(bo *Backoffer, rpcCtx *ti
// So we finish here.
return nil, nil
}

// calculate next ranges and grow the paging size
task.ranges = worker.calculateRemain(task.ranges, pagingRange, worker.req.Desc)
if task.ranges.Len() == 0 {
Expand Down
1 change: 1 addition & 0 deletions store/copr/coprocessor_test.go
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Expand Up @@ -509,6 +509,7 @@ func TestBuildPagingTasks(t *testing.T) {

req := &kv.Request{}
req.Paging = true
req.MinPagingSize = paging.MinPagingSize
flashReq := &kv.Request{}
flashReq.StoreType = kv.TiFlash
tasks, err := buildCopTasks(bo, cache, buildCopRanges("a", "c"), req, nil)
Expand Down