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Add support for substr for static strings. #4350

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Merged
sougou merged 1 commit into from
Nov 9, 2018
Merged

Add support for substr for static strings. #4350

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24 changes: 17 additions & 7 deletions go/vt/sqlparser/ast.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2998,20 +2998,30 @@ func (node *ValuesFuncExpr) replace(from, to Expr) bool {
}

// SubstrExpr represents a call to SubstrExpr(column, value_expression) or SubstrExpr(column, value_expression,value_expression)
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@sougou sougou Nov 9, 2018

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Nit: column->column/val

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@kuba-- kuba-- Nov 9, 2018

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I thought about it, but if I reuse ColName , e.g.:

SUBSTR openb STRING ',' value_expression closeb
  {
    $$ = &SubstrExpr{Name: &ColName{Name: NewColIdent($3)}, From: $5, To: nil}
  }

How could I figure out later if it's a static string or column name? How could I stop walkSubtree in this case?
Maybe instead of having extra StrVal *SQLVal, I'll add some boolean member (static/resolved/...) to mark it's a static string expression.

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@sougou sougou Nov 9, 2018

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Oh. You misunderstood :). I just wanted the SubstrExpr comment to be updated to say that the input can be a column or a value, to reflect the code change.

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@kuba-- kuba-- Nov 9, 2018

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Ok, how about now - take a look.

// also supported syntax SubstrExpr(column from value_expression for value_expression)
// also supported syntax SubstrExpr(column from value_expression for value_expression).
// Additionally to column names, SubstrExpr is also supported for string values, e.g.:
// SubstrExpr('static string value', value_expression, value_expression)
// In this case StrVal will be set instead of Name.
type SubstrExpr struct {
Name *ColName
From Expr
To Expr
Name *ColName
StrVal *SQLVal
From Expr
To Expr
}

// Format formats the node.
func (node *SubstrExpr) Format(buf *TrackedBuffer) {
var val interface{}
if node.Name != nil {
val = node.Name
} else {
val = node.StrVal
}

if node.To == nil {
buf.Myprintf("substr(%v, %v)", node.Name, node.From)
buf.Myprintf("substr(%v, %v)", val, node.From)
} else {
buf.Myprintf("substr(%v, %v, %v)", node.Name, node.From, node.To)
buf.Myprintf("substr(%v, %v, %v)", val, node.From, node.To)
}
}

Expand All @@ -3020,7 +3030,7 @@ func (node *SubstrExpr) replace(from, to Expr) bool {
}

func (node *SubstrExpr) walkSubtree(visit Visit) error {
if node == nil {
if node == nil || node.Name == nil {
return nil
}
return Walk(
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8 changes: 7 additions & 1 deletion go/vt/sqlparser/parse_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1749,7 +1749,7 @@ func TestSubStr(t *testing.T) {
input string
output string
}{{
input: "select substr(a, 1) from t",
input: `select substr('foobar', 1) from t`,
}, {
input: "select substr(a, 1, 6) from t",
}, {
Expand All @@ -1764,6 +1764,12 @@ func TestSubStr(t *testing.T) {
}, {
input: "select substring(a from 1 for 6) from t",
output: "select substr(a, 1, 6) from t",
}, {
input: `select substr("foo" from 1 for 2) from t`,
output: `select substr('foo', 1, 2) from t`,
}, {
input: `select substring("foo", 1, 2) from t`,
output: `select substr('foo', 1, 2) from t`,
}}

for _, tcase := range validSQL {
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