Add lambda support for APPLY transformer on * and COLUMNS()

Adds support for lambda expressions in APPLY transformers:
- `* APPLY x -> toString(x)`
- `COLUMNS(...) APPLY x -> expr`

Previously only simple function names were supported (e.g., `* APPLY toString`).

This adds:
- ApplyLambda field to ast.ColumnTransformer struct
- Lambda detection and parsing in parseAsteriskApply and parseColumnsApply

Fixes 14 statements in 02378_analyzer_projection_names (16→2 pending) and
improves several other tests.

Author: claude

ast/ast.go

@@ -1215,11 +1215,12 @@ func (r *ReplaceExpr) End() token.Position { return r.Position }
 
 // ColumnTransformer represents a single transformer (APPLY, EXCEPT, or REPLACE) in order.
 type ColumnTransformer struct {
-	Position token.Position `json:"-"`
-	Type     string         `json:"type"`              // "apply", "except", "replace"
-	Apply    string         `json:"apply,omitempty"`   // function name for APPLY
-	Except   []string       `json:"except,omitempty"`  // column names for EXCEPT
-	Replaces []*ReplaceExpr `json:"replaces,omitempty"` // replacement expressions for REPLACE
+	Position    token.Position `json:"-"`
+	Type        string         `json:"type"`                   // "apply", "except", "replace"
+	Apply       string         `json:"apply,omitempty"`        // function name for APPLY
+	ApplyLambda Expression     `json:"apply_lambda,omitempty"` // lambda expression for APPLY x -> expr
+	Except      []string       `json:"except,omitempty"`       // column names for EXCEPT
+	Replaces    []*ReplaceExpr `json:"replaces,omitempty"`     // replacement expressions for REPLACE
 }
 
 // ColumnsMatcher represents COLUMNS('pattern') or COLUMNS(col1, col2) expression.

parser/expression.go

@@ -2557,8 +2557,17 @@ func (p *Parser) parseAsteriskApply(asterisk *ast.Asterisk) ast.Expression {
 		p.nextToken() // skip (
 	}
 
-	// Parse function name (can be IDENT or keyword like sum, avg, etc.)
-	if p.currentIs(token.IDENT) || p.current.Token.IsKeyword() {
+	// Check for lambda expression: x -> expr
+	if p.currentIs(token.IDENT) && p.peekIs(token.ARROW) {
+		// Parse lambda expression
+		lambda := p.parseExpression(LOWEST)
+		asterisk.Transformers = append(asterisk.Transformers, &ast.ColumnTransformer{
+			Position:     pos,
+			Type:         "apply",
+			ApplyLambda:  lambda,
+		})
+	} else if p.currentIs(token.IDENT) || p.current.Token.IsKeyword() {
+		// Parse function name (can be IDENT or keyword like sum, avg, etc.)
 		funcName := p.current.Value
 		asterisk.Apply = append(asterisk.Apply, funcName)
 		asterisk.Transformers = append(asterisk.Transformers, &ast.ColumnTransformer{
@@ -2586,8 +2595,17 @@ func (p *Parser) parseColumnsApply(matcher *ast.ColumnsMatcher) ast.Expression {
 		p.nextToken() // skip (
 	}
 
-	// Parse function name (can be IDENT or keyword like sum, avg, etc.)
-	if p.currentIs(token.IDENT) || p.current.Token.IsKeyword() {
+	// Check for lambda expression: x -> expr
+	if p.currentIs(token.IDENT) && p.peekIs(token.ARROW) {
+		// Parse lambda expression
+		lambda := p.parseExpression(LOWEST)
+		matcher.Transformers = append(matcher.Transformers, &ast.ColumnTransformer{
+			Position:    pos,
+			Type:        "apply",
+			ApplyLambda: lambda,
+		})
+	} else if p.currentIs(token.IDENT) || p.current.Token.IsKeyword() {
+		// Parse function name (can be IDENT or keyword like sum, avg, etc.)
 		funcName := p.current.Value
 		matcher.Apply = append(matcher.Apply, funcName)
 		matcher.Transformers = append(matcher.Transformers, &ast.ColumnTransformer{

parser/testdata/01470_columns_transformers2/metadata.json

@@ -1,7 +1,5 @@
 {
   "explain_todo": {
-    "stmt4": true,
-    "stmt6": true,
-    "stmt7": true
+    "stmt4": true
   }
 }

parser/testdata/02339_analyzer_matcher_basic/metadata.json

@@ -1,10 +1 @@
-{
-  "explain_todo": {
-    "stmt63": true,
-    "stmt64": true,
-    "stmt66": true,
-    "stmt67": true,
-    "stmt69": true,
-    "stmt70": true
-  }
-}
+{}

parser/testdata/02343_analyzer_lambdas/metadata.json

@@ -1,7 +1 @@
-{
-  "explain_todo": {
-    "stmt31": true,
-    "stmt32": true,
-    "stmt33": true
-  }
-}
+{}

parser/testdata/02378_analyzer_projection_names/metadata.json

@@ -1,20 +1,6 @@
 {
   "explain_todo": {
-    "stmt101": true,
-    "stmt105": true,
-    "stmt109": true,
     "stmt185": true,
-    "stmt207": true,
-    "stmt215": true,
-    "stmt227": true,
-    "stmt235": true,
-    "stmt33": true,
-    "stmt37": true,
-    "stmt41": true,
-    "stmt57": true,
-    "stmt67": true,
-    "stmt89": true,
-    "stmt93": true,
-    "stmt97": true
+    "stmt67": true
   }
 }

parser/testdata/02493_analyzer_table_functions_untuple/metadata.json

@@ -1,7 +1 @@
-{
-  "explain_todo": {
-    "stmt20": true,
-    "stmt22": true,
-    "stmt24": true
-  }
-}
+{}

parser/testdata/03144_invalid_filter/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true
-  }
-}
+{}

parser/testdata/03212_optimize_with_constraints_logical_error/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true
-  }
-}
+{}