fix: support expressions (dotted column refs) in DISTINCT ON

disq · disq · commit 60d421b71ed3 · 2026-03-16T14:19:37.000Z
parseDistinctOn() was calling parseIdent() which only handles simple
identifiers. Queries like DISTINCT ON (t.id, t.name) would fail because
the dot was not recognized. Changed to parseExpr() so that any valid
column expression (including table.column references) is accepted.
diff --git a/parser/ast.go b/parser/ast.go
@@ -5201,7 +5201,7 @@ func (s *SelectQuery) Accept(visitor ASTVisitor) error {
 }
 
 type DistinctOn struct {
-	Idents        []*Ident
+	Exprs         []Expr
 	DistinctOnPos Pos
 	DistinctOnEnd Pos
 }
@@ -5217,8 +5217,8 @@ func (s *DistinctOn) End() Pos {
 func (s *DistinctOn) Accept(visitor ASTVisitor) error {
 	visitor.Enter(s)
 	defer visitor.Leave(s)
-	for _, ident := range s.Idents {
-		if err := ident.Accept(visitor); err != nil {
+	for _, expr := range s.Exprs {
+		if err := expr.Accept(visitor); err != nil {
 			return err
 		}
 	}
diff --git a/parser/format.go b/parser/format.go
@@ -1344,11 +1344,11 @@ func (d *DictionarySourceClause) FormatSQL(formatter *Formatter) {
 
 func (s *DistinctOn) FormatSQL(formatter *Formatter) {
 	formatter.WriteString("ON (")
-	for i, ident := range s.Idents {
+	for i, expr := range s.Exprs {
 		if i > 0 {
 			formatter.WriteString(", ")
 		}
-		formatter.WriteExpr(ident)
+		formatter.WriteExpr(expr)
 	}
 	formatter.WriteByte(')')
 }
diff --git a/parser/parser_query.go b/parser/parser_query.go
@@ -89,28 +89,28 @@ func (p *Parser) parseDistinctOn(pos Pos) (*DistinctOn, error) {
 		return nil, err
 	}
 
-	ident, err := p.parseIdent()
+	expr, err := p.parseExpr(p.Pos())
 	if err != nil {
 		return nil, err
 	}
-	idents := []*Ident{ident}
+	exprs := []Expr{expr}
 
 	for p.matchTokenKind(TokenKindComma) {
 		_ = p.lexer.consumeToken()
 
-		ident, err = p.parseIdent()
+		expr, err = p.parseExpr(p.Pos())
 		if err != nil {
 			return nil, err
 		}
-		idents = append(idents, ident)
+		exprs = append(exprs, expr)
 	}
 
 	if err := p.expectTokenKind(TokenKindRParen); err != nil {
 		return nil, err
 	}
 
 	return &DistinctOn{
-		Idents:        idents,
+		Exprs:         exprs,
 		DistinctOnPos: pos,
 		DistinctOnEnd: p.Pos(),
 	}, nil
diff --git a/parser/testdata/query/format/beautify/select_with_distinct_on_dotted_columns.sql b/parser/testdata/query/format/beautify/select_with_distinct_on_dotted_columns.sql
@@ -0,0 +1,10 @@
+-- Origin SQL:
+SELECT DISTINCT ON (t.id, t.name) t.id, t.name, t.value FROM test_table t
+
+-- Beautify SQL:
+SELECT DISTINCT ON (t.id, t.name)
+  t.id,
+  t.name,
+  t.value
+FROM
+  test_table AS t;
diff --git a/parser/testdata/query/format/select_with_distinct_on_dotted_columns.sql b/parser/testdata/query/format/select_with_distinct_on_dotted_columns.sql
@@ -0,0 +1,5 @@
+-- Origin SQL:
+SELECT DISTINCT ON (t.id, t.name) t.id, t.name, t.value FROM test_table t
+
+-- Format SQL:
+SELECT DISTINCT ON (t.id, t.name) t.id, t.name, t.value FROM test_table AS t;
diff --git a/parser/testdata/query/output/select_with_distinct_on_dotted_columns.sql.golden.json b/parser/testdata/query/output/select_with_distinct_on_dotted_columns.sql.golden.json
@@ -0,0 +1,155 @@
+[
+  {
+    "SelectPos": 0,
+    "StatementEnd": 73,
+    "With": null,
+    "Top": null,
+    "HasDistinct": true,
+    "DistinctOn": {
+      "Exprs": [
+        {
+          "Fields": [
+            {
+              "Name": "t",
+              "QuoteType": 1,
+              "NamePos": 20,
+              "NameEnd": 21
+            },
+            {
+              "Name": "id",
+              "QuoteType": 1,
+              "NamePos": 22,
+              "NameEnd": 24
+            }
+          ]
+        },
+        {
+          "Fields": [
+            {
+              "Name": "t",
+              "QuoteType": 1,
+              "NamePos": 26,
+              "NameEnd": 27
+            },
+            {
+              "Name": "name",
+              "QuoteType": 1,
+              "NamePos": 28,
+              "NameEnd": 32
+            }
+          ]
+        }
+      ],
+      "DistinctOnPos": 16,
+      "DistinctOnEnd": 34
+    },
+    "SelectItems": [
+      {
+        "Expr": {
+          "Fields": [
+            {
+              "Name": "t",
+              "QuoteType": 1,
+              "NamePos": 34,
+              "NameEnd": 35
+            },
+            {
+              "Name": "id",
+              "QuoteType": 1,
+              "NamePos": 36,
+              "NameEnd": 38
+            }
+          ]
+        },
+        "Modifiers": [],
+        "Alias": null
+      },
+      {
+        "Expr": {
+          "Fields": [
+            {
+              "Name": "t",
+              "QuoteType": 1,
+              "NamePos": 40,
+              "NameEnd": 41
+            },
+            {
+              "Name": "name",
+              "QuoteType": 1,
+              "NamePos": 42,
+              "NameEnd": 46
+            }
+          ]
+        },
+        "Modifiers": [],
+        "Alias": null
+      },
+      {
+        "Expr": {
+          "Fields": [
+            {
+              "Name": "t",
+              "QuoteType": 1,
+              "NamePos": 48,
+              "NameEnd": 49
+            },
+            {
+              "Name": "value",
+              "QuoteType": 1,
+              "NamePos": 50,
+              "NameEnd": 55
+            }
+          ]
+        },
+        "Modifiers": [],
+        "Alias": null
+      }
+    ],
+    "From": {
+      "FromPos": 56,
+      "Expr": {
+        "Table": {
+          "TablePos": 61,
+          "TableEnd": 73,
+          "Alias": null,
+          "Expr": {
+            "Expr": {
+              "Database": null,
+              "Table": {
+                "Name": "test_table",
+                "QuoteType": 1,
+                "NamePos": 61,
+                "NameEnd": 71
+              }
+            },
+            "AliasPos": 72,
+            "Alias": {
+              "Name": "t",
+              "QuoteType": 1,
+              "NamePos": 72,
+              "NameEnd": 73
+            }
+          },
+          "HasFinal": false
+        },
+        "StatementEnd": 73,
+        "SampleRatio": null,
+        "HasFinal": false
+      }
+    },
+    "Window": null,
+    "Prewhere": null,
+    "Where": null,
+    "GroupBy": null,
+    "WithTotal": false,
+    "Having": null,
+    "OrderBy": null,
+    "LimitBy": null,
+    "Limit": null,
+    "Settings": null,
+    "Format": null,
+    "UnionAll": null,
+    "UnionDistinct": null,
+    "Except": null
+  }
+]
diff --git a/parser/testdata/query/output/select_with_distinct_on_keyword.sql.golden.json b/parser/testdata/query/output/select_with_distinct_on_keyword.sql.golden.json
@@ -6,7 +6,7 @@
     "Top": null,
     "HasDistinct": true,
     "DistinctOn": {
-      "Idents": [
+      "Exprs": [
         {
           "Name": "album",
           "QuoteType": 1,
diff --git a/parser/testdata/query/select_with_distinct_on_dotted_columns.sql b/parser/testdata/query/select_with_distinct_on_dotted_columns.sql
@@ -0,0 +1 @@
+SELECT DISTINCT ON (t.id, t.name) t.id, t.name, t.value FROM test_table t
diff --git a/parser/walk.go b/parser/walk.go
@@ -1503,8 +1503,8 @@ func Walk(node Expr, fn WalkFunc) bool {
 			return false
 		}
 	case *DistinctOn:
-		for _, ident := range n.Idents {
-			if !Walk(ident, fn) {
+		for _, expr := range n.Exprs {
+			if !Walk(expr, fn) {
 				return false
 			}
 		}

Original file line number	Diff line number	Diff line change
`@@ -5201,7 +5201,7 @@ func (s *SelectQuery) Accept(visitor ASTVisitor) error {`
`5201`	`5201`	`}`
`5202`	`5202`
`5203`	`5203`	`type DistinctOn struct {`
`5204`		`- Idents []*Ident`
	`5204`	`+ Exprs []Expr`
`5205`	`5205`	`DistinctOnPos Pos`
`5206`	`5206`	`DistinctOnEnd Pos`
`5207`	`5207`	`}`
`@@ -5217,8 +5217,8 @@ func (s *DistinctOn) End() Pos {`
`5217`	`5217`	`func (s *DistinctOn) Accept(visitor ASTVisitor) error {`
`5218`	`5218`	`visitor.Enter(s)`
`5219`	`5219`	`defer visitor.Leave(s)`
`5220`		`- for _, ident := range s.Idents {`
`5221`		`- if err := ident.Accept(visitor); err != nil {`
	`5220`	`+ for _, expr := range s.Exprs {`
	`5221`	`+ if err := expr.Accept(visitor); err != nil {`
`5222`	`5222`	`return err`
`5223`	`5223`	`}`
`5224`	`5224`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1344,11 +1344,11 @@ func (d DictionarySourceClause) FormatSQL(formatter Formatter) {`
`1344`	`1344`
`1345`	`1345`	`func (s DistinctOn) FormatSQL(formatter Formatter) {`
`1346`	`1346`	`formatter.WriteString("ON (")`
`1347`		`- for i, ident := range s.Idents {`
	`1347`	`+ for i, expr := range s.Exprs {`
`1348`	`1348`	`if i > 0 {`
`1349`	`1349`	`formatter.WriteString(", ")`
`1350`	`1350`	`}`
`1351`		`- formatter.WriteExpr(ident)`
	`1351`	`+ formatter.WriteExpr(expr)`
`1352`	`1352`	`}`
`1353`	`1353`	`formatter.WriteByte(')')`
`1354`	`1354`	`}`
Original file line number	Diff line number	Diff line change
`@@ -89,28 +89,28 @@ func (p Parser) parseDistinctOn(pos Pos) (DistinctOn, error) {`
`89`	`89`	`return nil, err`
`90`	`90`	`}`
`91`	`91`
`92`		`- ident, err := p.parseIdent()`
	`92`	`+ expr, err := p.parseExpr(p.Pos())`
`93`	`93`	`if err != nil {`
`94`	`94`	`return nil, err`
`95`	`95`	`}`
`96`		`- idents := []*Ident{ident}`
	`96`	`+ exprs := []Expr{expr}`
`97`	`97`
`98`	`98`	`for p.matchTokenKind(TokenKindComma) {`
`99`	`99`	`_ = p.lexer.consumeToken()`
`100`	`100`
`101`		`- ident, err = p.parseIdent()`
	`101`	`+ expr, err = p.parseExpr(p.Pos())`
`102`	`102`	`if err != nil {`
`103`	`103`	`return nil, err`
`104`	`104`	`}`
`105`		`- idents = append(idents, ident)`
	`105`	`+ exprs = append(exprs, expr)`
`106`	`106`	`}`
`107`	`107`
`108`	`108`	`if err := p.expectTokenKind(TokenKindRParen); err != nil {`
`109`	`109`	`return nil, err`
`110`	`110`	`}`
`111`	`111`
`112`	`112`	`return &DistinctOn{`
`113`		`- Idents: idents,`
	`113`	`+ Exprs: exprs,`
`114`	`114`	`DistinctOnPos: pos,`
`115`	`115`	`DistinctOnEnd: p.Pos(),`
`116`	`116`	`}, nil`
Original file line number	Diff line number	Diff line change
`@@ -6,7 +6,7 @@`
`6`	`6`	`"Top": null,`
`7`	`7`	`"HasDistinct": true,`
`8`	`8`	`"DistinctOn": {`
`9`		`- "Idents": [`
	`9`	`+ "Exprs": [`
`10`	`10`	`{`
`11`	`11`	`"Name": "album",`
`12`	`12`	`"QuoteType": 1,`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+SELECT DISTINCT ON (t.id, t.name) t.id, t.name, t.value FROM test_table t`
Original file line number	Diff line number	Diff line change
`@@ -1503,8 +1503,8 @@ func Walk(node Expr, fn WalkFunc) bool {`
`1503`	`1503`	`return false`
`1504`	`1504`	`}`
`1505`	`1505`	`case *DistinctOn:`
`1506`		`- for _, ident := range n.Idents {`
`1507`		`- if !Walk(ident, fn) {`
	`1506`	`+ for _, expr := range n.Exprs {`
	`1507`	`+ if !Walk(expr, fn) {`
`1508`	`1508`	`return false`
`1509`	`1509`	`}`
`1510`	`1510`	`}`