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expression: support ConstItem() for expression #10004

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merged 6 commits into from
Apr 15, 2019
Merged

expression: support ConstItem() for expression #10004

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c1ea2e9
support ReferTable
wjhuang2016 Apr 2, 2019
a5f5029
rename
wjhuang2016 Apr 5, 2019
6ea2ec8
Fix comment
wjhuang2016 Apr 5, 2019
fde3a79
Use unfoldablefunc to simplification
wjhuang2016 Apr 12, 2019
6ae2af4
Merge branch 'master' into suppot-refertable
wjhuang2016 Apr 12, 2019
5a0f944
Merge branch 'master' into suppot-refertable
alivxxx Apr 15, 2019
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10 changes: 10 additions & 0 deletions expression/column.go
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,11 @@ func (col *CorrelatedColumn) IsCorrelated() bool {
return true
}

// ConstItem implements Expression interface.
func (col *CorrelatedColumn) ConstItem() bool {
return false
}

// Decorrelate implements Expression interface.
func (col *CorrelatedColumn) Decorrelate(schema *Schema) Expression {
if !schema.Contains(&col.Column) {
Expand Down Expand Up @@ -297,6 +302,11 @@ func (col *Column) IsCorrelated() bool {
return false
}

// ConstItem implements Expression interface.
func (col *Column) ConstItem() bool {
return false
}

// Decorrelate implements Expression interface.
func (col *Column) Decorrelate(_ *Schema) Expression {
return col
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1 change: 1 addition & 0 deletions expression/column_test.go
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Expand Up @@ -43,6 +43,7 @@ func (s *testEvaluatorSuite) TestColumn(c *C) {
c.Assert(corCol.Equal(nil, corCol), IsTrue)
c.Assert(corCol.Equal(nil, invalidCorCol), IsFalse)
c.Assert(corCol.IsCorrelated(), IsTrue)
c.Assert(corCol.ConstItem(), IsFalse)
c.Assert(corCol.Decorrelate(schema).Equal(nil, col), IsTrue)
c.Assert(invalidCorCol.Decorrelate(schema).Equal(nil, invalidCorCol), IsTrue)

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5 changes: 5 additions & 0 deletions expression/constant.go
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Expand Up @@ -311,6 +311,11 @@ func (c *Constant) IsCorrelated() bool {
return false
}

// ConstItem implements Expression interface.
func (c *Constant) ConstItem() bool {
return true
}

// Decorrelate implements Expression interface.
func (c *Constant) Decorrelate(_ *Schema) Expression {
return c
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8 changes: 8 additions & 0 deletions expression/expression.go
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Expand Up @@ -79,6 +79,14 @@ type Expression interface {
// IsCorrelated checks if this expression has correlated key.
IsCorrelated() bool

// ConstItem checks if this expression is constant item, regardless of query evaluation state.
// An expression is constant item if it:
// refers no tables.
// refers no subqueries that refers any tables.
// refers no non-deterministic functions.
// refers no statement parameters.
ConstItem() bool

// Decorrelate try to decorrelate the expression by schema.
Decorrelate(schema *Schema) Expression

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14 changes: 14 additions & 0 deletions expression/expression_test.go
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Expand Up @@ -61,6 +61,7 @@ func (s *testEvaluatorSuite) TestConstant(c *C) {

sc := &stmtctx.StatementContext{TimeZone: time.Local}
c.Assert(Zero.IsCorrelated(), IsFalse)
c.Assert(Zero.ConstItem(), IsTrue)
c.Assert(Zero.Decorrelate(nil).Equal(s.ctx, Zero), IsTrue)
c.Assert(Zero.HashCode(sc), DeepEquals, []byte{0x0, 0x8, 0x0})
c.Assert(Zero.Equal(s.ctx, One), IsFalse)
Expand All @@ -85,6 +86,19 @@ func (s *testEvaluatorSuite) TestIsBinaryLiteral(c *C) {
c.Assert(IsBinaryLiteral(con), IsFalse)
}

func (s *testEvaluatorSuite) TestConstItem(c *C) {
defer testleak.AfterTest(c)()

sf := newFunction(ast.Rand)
c.Assert(sf.ConstItem(), Equals, false)
sf = newFunction(ast.UUID)
c.Assert(sf.ConstItem(), Equals, false)
sf = newFunction(ast.GetParam, One)
c.Assert(sf.ConstItem(), Equals, false)
sf = newFunction(ast.Abs, One)
c.Assert(sf.ConstItem(), Equals, true)
}

type testTableBuilder struct {
tableName string
columnNames []string
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14 changes: 14 additions & 0 deletions expression/scalar_function.go
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Expand Up @@ -165,6 +165,20 @@ func (sf *ScalarFunction) IsCorrelated() bool {
return false
}

// ConstItem implements Expression interface.
func (sf *ScalarFunction) ConstItem() bool {
// Note: some unfoldable functions are deterministic, we use unFoldableFunctions here for simplification.
if _, ok := unFoldableFunctions[sf.FuncName.L]; ok {
return false
}
for _, arg := range sf.GetArgs() {
if !arg.ConstItem() {
return false
}
}
return true
}

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Seems ExtractColumns can provide what you want? CorrelatedColumn should be treated as constant actually?

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Oh, my fault. We need to check also non-deterministic functions and statement parameters

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Oh from this comment, you need to check if the expression is "purely" constant, i.e, CorrelatedColumn should not be treated as constant because we are not in executor, so ExtractColumns cannot work, sorry for the misleading.

Why would non-deterministic functions matter here? though their return value is non-deterministic, the return type is deterministic?

What does statement parameters mean?

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For non-deterministic functions, their return value is non-deterministic, so you can't use its value to computer the frac part or somethings else.
I believe statement parameters is the parameters used in prepare statement.

// Decorrelate implements Expression interface.
func (sf *ScalarFunction) Decorrelate(schema *Schema) Expression {
for i, arg := range sf.GetArgs() {
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1 change: 1 addition & 0 deletions expression/scalar_function_test.go
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Expand Up @@ -40,6 +40,7 @@ func (s *testEvaluatorSuite) TestScalarFunction(c *C) {
c.Assert(err, IsNil)
c.Assert(res, DeepEquals, []byte{0x22, 0x6c, 0x74, 0x28, 0x66, 0x65, 0x69, 0x2e, 0x68, 0x61, 0x6e, 0x2c, 0x20, 0x31, 0x29, 0x22})
c.Assert(sf.IsCorrelated(), IsFalse)
c.Assert(sf.ConstItem(), IsFalse)
c.Assert(sf.Decorrelate(nil).Equal(s.ctx, sf), IsTrue)
c.Assert(sf.HashCode(sc), DeepEquals, []byte{0x3, 0x4, 0x6c, 0x74, 0x1, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x0, 0x5, 0xbf, 0xf0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0})

Expand Down