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feat: support IS UNKNOWN expressions #399

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feat: support IS UNKNOWN expressions #399

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14 changes: 14 additions & 0 deletions ast/ast.go
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Original file line number Diff line number Diff line change
Expand Up @@ -212,6 +212,7 @@ func (UnaryExpr) isExpr() {}
func (InExpr) isExpr() {}
func (IsNullExpr) isExpr() {}
func (IsBoolExpr) isExpr() {}
func (IsUnknownExpr) isExpr() {}
func (IsSourceExpr) isExpr() {}
func (IsDestinationExpr) isExpr() {}
func (IsLabeledExpr) isExpr() {}
Expand Down Expand Up @@ -1438,6 +1439,19 @@ type IsBoolExpr struct {
Right bool
}

// IsUnknownExpr is IS UNKNOWN expression node.
//
// {{.Left | sql}} IS {{if .Not}}NOT{{end}} UNKNOWN

@makenowjust makenowjust Aug 15, 2026

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Is this better?

Suggested change
// {{.Left | sql}} IS {{if .Not}}NOT{{end}} UNKNOWN
// {{.Left | sql}} IS{{if .Not}} NOT{{end}} UNKNOWN

@apstndb apstndb Aug 15, 2026

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I think the current form is preferable as documentation. These templates are not intended to specify whitespace exactly, and keeping spaces outside the template actions makes the SQL token boundaries easier to read. Tight adjacency is useful when tokens are intentionally concatenated, such as SAFE_ and CAST, but that is not the case here. This also matches the nearby IsNullExpr and IsBoolExpr templates.

type IsUnknownExpr struct {
// pos = Left.pos
// end = Unknown + 7

Unknown token.Pos // position of "UNKNOWN"

Not bool
Left Expr
}

// IsSourceExpr is IS SOURCE [OF] expression node.
//
// {{.Left | sql}} IS {{if .Not}}NOT {{end}}SOURCE{{if .Of.Invalid | not}} OF{{end}} {{.Right | sql}}
Expand Down
1 change: 1 addition & 0 deletions ast/expr_impls_test.go
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8 changes: 8 additions & 0 deletions ast/pos.go
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7 changes: 6 additions & 1 deletion ast/sql.go
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Expand Up @@ -113,7 +113,7 @@ func exprPrec(e Expr) prec {
return precLit
case *IndexExpr, *SelectorExpr:
return precSelector
case *InExpr, *IsNullExpr, *IsBoolExpr, *IsSourceExpr, *IsDestinationExpr, *IsLabeledExpr, *BetweenExpr:
case *InExpr, *IsNullExpr, *IsBoolExpr, *IsUnknownExpr, *IsSourceExpr, *IsDestinationExpr, *IsLabeledExpr, *BetweenExpr:
return precComparison
case *BinaryExpr:
switch e.Op {
Expand Down Expand Up @@ -449,6 +449,11 @@ func (i *IsBoolExpr) SQL() string {
return paren(p, i.Left) + " IS " + strOpt(i.Not, "NOT ") + formatBoolUpper(i.Right)
}

func (i *IsUnknownExpr) SQL() string {
p := exprPrec(i)
return paren(p, i.Left) + " IS " + strOpt(i.Not, "NOT ") + "UNKNOWN"
}

func (i *IsSourceExpr) SQL() string {
p := exprPrec(i)
return paren(p, i.Left) + " IS " + strOpt(i.Not, "NOT ") + "SOURCE" + strOpt(!i.Of.Invalid(), " OF") + " " + paren(p, i.Right)
Expand Down
3 changes: 3 additions & 0 deletions ast/walk_internal.go
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9 changes: 8 additions & 1 deletion parser.go
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Expand Up @@ -1679,6 +1679,13 @@ func (p *Parser) parseComparison() ast.Expr {
}
case token.TokenIdent:
switch {
case p.Token.IsKeywordLike("UNKNOWN"):
p.nextToken()
return &ast.IsUnknownExpr{
Unknown: pos,
Left: expr,
Not: not,
}
case p.Token.IsKeywordLike("SOURCE") || p.Token.IsKeywordLike("DESTINATION"):
isSource := p.Token.IsKeywordLike("SOURCE")
p.nextToken()
Expand Down Expand Up @@ -1711,7 +1718,7 @@ func (p *Parser) parseComparison() ast.Expr {
}
}
}
p.panicfAtToken(&p.Token, "expected token: NULL, TRUE, FALSE, SOURCE, DESTINATION, LABELED, but: %s", p.Token.Kind)
p.panicfAtToken(&p.Token, "expected token: NULL, TRUE, FALSE, UNKNOWN, SOURCE, DESTINATION, LABELED, but: %s", p.Token.Kind)
default:
return expr
}
Expand Down
1 change: 1 addition & 0 deletions testdata/input/query/select_is_unknown.sql
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
SELECT true IS UNKNOWN, true IS NOT UNKNOWN
32 changes: 32 additions & 0 deletions testdata/result/query/select_is_unknown.sql.txt
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@@ -0,0 +1,32 @@
--- select_is_unknown.sql
SELECT true IS UNKNOWN, true IS NOT UNKNOWN

--- AST
&ast.QueryStatement{
Query: &ast.Select{
Results: []ast.SelectItem{
&ast.ExprSelectItem{
Expr: &ast.IsUnknownExpr{
Unknown: 15,
Left: &ast.BoolLiteral{
ValuePos: 7,
Value: true,
},
},
},
&ast.ExprSelectItem{
Expr: &ast.IsUnknownExpr{
Unknown: 36,
Not: true,
Left: &ast.BoolLiteral{
ValuePos: 24,
Value: true,
},
},
},
},
},
}

--- SQL
SELECT TRUE IS UNKNOWN, TRUE IS NOT UNKNOWN
32 changes: 32 additions & 0 deletions testdata/result/statement/select_is_unknown.sql.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
--- select_is_unknown.sql
SELECT true IS UNKNOWN, true IS NOT UNKNOWN

--- AST
&ast.QueryStatement{
Query: &ast.Select{
Results: []ast.SelectItem{
&ast.ExprSelectItem{
Expr: &ast.IsUnknownExpr{
Unknown: 15,
Left: &ast.BoolLiteral{
ValuePos: 7,
Value: true,
},
},
},
&ast.ExprSelectItem{
Expr: &ast.IsUnknownExpr{
Unknown: 36,
Not: true,
Left: &ast.BoolLiteral{
ValuePos: 24,
Value: true,
},
},
},
},
},
}

--- SQL
SELECT TRUE IS UNKNOWN, TRUE IS NOT UNKNOWN
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