planner/cascades: Add the transformation rule PushSelDownWindow

[jiangyuzhao]

What problem does this PR solve?

This PR adds Transformation rule PushSelDownWindow which is a part of predicate push down in cascades planner(#13709).

What is changed and how it works?

The logic is the same with planner/core/rule_predicate_push_down.go/LogicalWindow.PredicatePushdown.

Check List

Tests

• Unit test

Code changes

• Has exported function/method change

[claassistantio]

All committers have signed the CLA.

[winoros]

@jiangyuzhao Oh, there's one more thing you need to modify:

func (s *testTransformationRuleSuite) SetUpSuite(c *C) {
	s.is = infoschema.MockInfoSchema([]*model.TableInfo{plannercore.MockSignedTable()})
	s.sctx = plannercore.MockContext()
	s.Parser = parser.New()
	s.optimizer = NewOptimizer()
	var err error
	s.testData, err = testutil.LoadTestSuiteData("testdata", "transformation_rules_suite")
	c.Assert(err, IsNil)
}

After s.Parser = parser.New(). We need to set p.EnableWindowFunc(true) to enable window function in test.

[jiangyuzhao]

@jiangyuzhao Oh, there's one more thing you need to modify:

func (s *testTransformationRuleSuite) SetUpSuite(c *C) {
	s.is = infoschema.MockInfoSchema([]*model.TableInfo{plannercore.MockSignedTable()})
	s.sctx = plannercore.MockContext()
	s.Parser = parser.New()
	s.optimizer = NewOptimizer()
	var err error
	s.testData, err = testutil.LoadTestSuiteData("testdata", "transformation_rules_suite")
	c.Assert(err, IsNil)
}

After s.Parser = parser.New(). We need to set p.EnableWindowFunc(true) to enable window function in test.

I think it will be better if I use

s.Parser.EnableWindowFunc(true)
defer func() {
	s.Parser.EnableWindowFunc(false)
}()

in TestPredicatePushDown?

[winoros]

@jiangyuzhao Oh, there's one more thing you need to modify:

```

func (s *testTransformationRuleSuite) SetUpSuite(c *C) {
s.is = infoschema.MockInfoSchema([]*model.TableInfo{plannercore.MockSignedTable()})
s.sctx = plannercore.MockContext()
s.Parser = parser.New()
s.optimizer = NewOptimizer()
var err error
s.testData, err = testutil.LoadTestSuiteData("testdata", "transformation_rules_suite")
c.Assert(err, IsNil)
}

After `s.Parser = parser.New()`. We need to set `p.EnableWindowFunc(true)` to enable window function in test.

I think it will be better if I use

s.Parser.EnableWindowFunc(true)
defer func() {
	s.Parser.EnableWindowFunc(false)
}()

in TestPredicatePushDown?

It's ok to open it in SetUpSuite.

[francis0407]

Thanks for you contribution.
LGTM after address this comment.

[jiangyuzhao]

I'm not sure whether it's right. For the Projection_3 may be unexpected.
And I wonder why we can only push b > 10 down to window, that is why we can only push col in partition by down to window?

[winoros]

Let me explain the second one first.
Push the filters which contain the column not in partition by clause would cause wrong result.
Take the given case as example. There're two rows a=-1 and b = 11 and a = 10 and b = 11. If we push the filter a < 10 down to the window. a=-1 and b=11 will be filtered. Then the partition b=11's min(a) would become 10 instead of -1.

[winoros]

And for the first one.
Though windown is in the select field but it's calculated at last.
For a SQL pattern select normal_field, window_field from tables where filters:
The tables in FROM CLAUSE is calcualted first, then is the normal_field, then filters, then window_field. So some redundant project may be added when build plans. We'll use the EliminateProjection rule to eliminate the unnecessary ones.
@jingyugao

[jiangyuzhao]

OK, Thank you for the awesome explanation. But my github name is @jiangyuzhao , hhh.

[codecov]

Codecov Report

Merging #14068 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master    #14068   +/-   ##
=========================================
  Coverage   80.449%   80.449%           
=========================================
  Files          483       483           
  Lines       123452    123452           
=========================================
  Hits         99316     99316           
  Misses       16355     16355           
  Partials      7781      7781

[winoros]

Thanks, please sign the CLA. See @claassistantio 's comment

[francis0407]

LGTM

[jiangyuzhao]

@lzmhhh123

[lzmhhh123]

LGTM

[sre-bot]

/run-all-tests