planner: add HasTiflash to avoid generating unnecessary mpp task | tidb-test=pr/2660

[hawkingrei]

What problem does this PR solve?

Issue Number: close #65335

Problem Summary:

What changed and how does it work?

checkCanPushDownToMPP will be called twice in the following code. The other problem is that if tables without tiflash replications are used in the query, we don't need to check the mpp task.

tidb/pkg/planner/core/operator/physicalop/physical_hash_agg.go

Lines 52 to 108 in 79ec3b6

	func getHashAggs(lp base.LogicalPlan, prop *property.PhysicalProperty) []base.PhysicalPlan {
	la := lp.(*logicalop.LogicalAggregation)
	if !prop.IsSortItemEmpty() {
	return nil
	}
	if prop.TaskTp == property.MppTaskType && !checkCanPushDownToMPP(la) {
	return nil
	}
	hashAggs := make([]base.PhysicalPlan, 0, len(prop.GetAllPossibleChildTaskTypes()))
	taskTypes := []property.TaskType{property.CopSingleReadTaskType, property.CopMultiReadTaskType, property.RootTaskType}
	// aggregation has a special case that it can be pushed down to TiKV which is indicated by the prop.NoCopPushDown
	if prop.NoCopPushDown {
	taskTypes = []property.TaskType{property.RootTaskType}
	}
	// lift the recursive check of canPushToCop(tiFlash)
	canPushDownToMPP := la.SCtx().GetSessionVars().IsMPPAllowed() && checkCanPushDownToMPP(la)
	if canPushDownToMPP {
	taskTypes = append(taskTypes, property.MppTaskType)
	} else {
	hasMppHints := false
	var errMsg string
	if la.PreferAggType&h.PreferMPP1PhaseAgg > 0 {
	errMsg = "The agg can not push down to the MPP side, the MPP_1PHASE_AGG() hint is invalid"
	hasMppHints = true
	}
	if la.PreferAggType&h.PreferMPP2PhaseAgg > 0 {
	errMsg = "The agg can not push down to the MPP side, the MPP_2PHASE_AGG() hint is invalid"
	hasMppHints = true
	}
	if hasMppHints {
	la.SCtx().GetSessionVars().StmtCtx.SetHintWarning(errMsg)
	}
	}
	if prop.IsFlashProp() {
	taskTypes = []property.TaskType{prop.TaskTp}
	}
	taskTypes = admitIndexJoinTypes(taskTypes, prop)
	for _, taskTp := range taskTypes {
	if taskTp == property.MppTaskType {
	mppAggs := tryToGetMppHashAggs(la, prop)
	if len(mppAggs) > 0 {
	hashAggs = append(hashAggs, mppAggs...)
	}
	} else {
	childProp := &property.PhysicalProperty{ExpectedCnt: math.MaxFloat64, TaskTp: taskTp, CTEProducerStatus: prop.CTEProducerStatus, NoCopPushDown: prop.NoCopPushDown}
	// mainly to fill indexJoinProp to childProp.
	childProp = admitIndexJoinProp(childProp, prop)
	if childProp == nil {
	continue
	}
	agg := NewPhysicalHashAgg(la, la.StatsInfo().ScaleByExpectCnt(la.SCtx().GetSessionVars(), prop.ExpectedCnt), childProp)
	agg.SetSchema(la.Schema().Clone())
	hashAggs = append(hashAggs, agg)
	}
	}
	return hashAggs
	}

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[codecov]

Codecov Report

❌ Patch coverage is 68.86228% with 52 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.5349%. Comparing base (6ff1adf) to head (d1e96df).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #65250         +/-   ##
=================================================
- Coverage   77.7600%   47.5349%   -30.2251%     
=================================================
  Files          2001       1780        -221     
  Lines        546165     464873      -81292     
=================================================
- Hits         424698     220977     -203721     
- Misses       119805     223075     +103270     
- Partials       1662      20821      +19159     

Flag	Coverage Δ
integration	47.5349% <68.8622%> (-0.6518%)	⬇️
tiprow_ft	?
unit	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	∅ <ø> (∅)
parser	∅ <ø> (∅)
br	47.0720% <ø> (-13.8998%)	⬇️

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[hawkingrei]

/retest

[hawkingrei]

/retest

[hawkingrei]

/retest

[hawkingrei]

/retest

[hawkingrei]

/retest

[hawkingrei]

/retest

[winoros]

I think we don't need to add this together in this pr.
Current physical optimization needs to generate the mpp task type first because we don't know whether its children can be converted to mpp plan.
If we want to do the pruning completely, we'll need to change the physical opt framework itself.

[hawkingrei]

But under the current circumstances, most users actually won't have TiFlash replicas. So when building the data source, it can quickly determine whether it contains TiFlash based on the table metadata.

[hawkingrei]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign d3hunter, time-and-fate, windtalker for approval. For more information see the Code Review Process.
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Details

Needs approval from an approver in each of these files:

• OWNERS
• pkg/expression/OWNERS
• pkg/infoschema/OWNERS
• pkg/planner/OWNERS
• pkg/statistics/OWNERS

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[ti-chi-bot]

@hawkingrei: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	d1e96df	link	true	/test unit-test
pull-unit-test-next-gen	d1e96df	link	true	/test pull-unit-test-next-gen
pull-integration-realcluster-test-next-gen	d1e96df	link	true	/test pull-integration-realcluster-test-next-gen
pull-mysql-client-test-next-gen	e80b918	link	true	/test pull-mysql-client-test-next-gen
idc-jenkins-ci-tidb/mysql-test	e80b918	link	true	/test mysql-test

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[tiprow]

@hawkingrei: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
fast_test_tiprow	e80b918	link	true	/test fast_test_tiprow

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