Support parameterized functions in APPLY column transformers

Add support for parsing APPLY(quantiles(0.5)) and similar parameterized
function calls within column transformers. Previously, the parser only
handled simple function names like APPLY(sum), but not functions with
parameters.

Changes:
- Add ApplyParams field to ColumnTransformer struct in AST
- Update parseColumnsApply and parseAsteriskApply to handle nested
  parentheses for parameterized functions
- Fixes 01470_columns_transformers stmt41, stmt42
- Also fixes 01710_projection_with_column_transformers

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

ast/ast.go

@@ -1428,6 +1428,7 @@ type ColumnTransformer struct {
 	Position    token.Position `json:"-"`
 	Type        string         `json:"type"`                   // "apply", "except", "replace"
 	Apply       string         `json:"apply,omitempty"`        // function name for APPLY
+	ApplyParams []Expression   `json:"apply_params,omitempty"` // parameters for parameterized APPLY functions like quantiles(0.5)
 	ApplyLambda Expression     `json:"apply_lambda,omitempty"` // lambda expression for APPLY x -> expr
 	Except      []string       `json:"except,omitempty"`       // column names for EXCEPT
 	Pattern     string         `json:"pattern,omitempty"`      // regex pattern for EXCEPT('pattern')

parser/expression.go

@@ -2957,20 +2957,40 @@ func (p *Parser) parseAsteriskApply(asterisk *ast.Asterisk) ast.Expression {
 		// Parse lambda expression
 		lambda := p.parseExpression(LOWEST)
 		asterisk.Transformers = append(asterisk.Transformers, &ast.ColumnTransformer{
-			Position:     pos,
-			Type:         "apply",
-			ApplyLambda:  lambda,
+			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
+		p.nextToken()
+
+		// Check for parameterized function: APPLY(quantiles(0.5))
+		var params []ast.Expression
+		if p.currentIs(token.LPAREN) {
+			p.nextToken() // skip (
+			for !p.currentIs(token.RPAREN) && !p.currentIs(token.EOF) {
+				expr := p.parseExpression(LOWEST)
+				if expr != nil {
+					params = append(params, expr)
+				}
+				if p.currentIs(token.COMMA) {
+					p.nextToken()
+				} else {
+					break
+				}
+			}
+			p.expect(token.RPAREN)
+		}
+
 		asterisk.Apply = append(asterisk.Apply, funcName)
 		asterisk.Transformers = append(asterisk.Transformers, &ast.ColumnTransformer{
-			Position: pos,
-			Type:     "apply",
-			Apply:    funcName,
+			Position:    pos,
+			Type:        "apply",
+			Apply:       funcName,
+			ApplyParams: params,
 		})
-		p.nextToken()
 	}
 
 	if hasParens {
@@ -3002,13 +3022,33 @@ func (p *Parser) parseColumnsApply(matcher *ast.ColumnsMatcher) ast.Expression {
 	} 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
+		p.nextToken()
+
+		// Check for parameterized function: APPLY(quantiles(0.5))
+		var params []ast.Expression
+		if p.currentIs(token.LPAREN) {
+			p.nextToken() // skip (
+			for !p.currentIs(token.RPAREN) && !p.currentIs(token.EOF) {
+				expr := p.parseExpression(LOWEST)
+				if expr != nil {
+					params = append(params, expr)
+				}
+				if p.currentIs(token.COMMA) {
+					p.nextToken()
+				} else {
+					break
+				}
+			}
+			p.expect(token.RPAREN)
+		}
+
 		matcher.Apply = append(matcher.Apply, funcName)
 		matcher.Transformers = append(matcher.Transformers, &ast.ColumnTransformer{
-			Position: pos,
-			Type:     "apply",
-			Apply:    funcName,
+			Position:    pos,
+			Type:        "apply",
+			Apply:       funcName,
+			ApplyParams: params,
 		})
-		p.nextToken()
 	}
 
 	if hasParens {

parser/testdata/01470_columns_transformers/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt41": true,
-    "stmt42": true
-  }
-}
+{}

parser/testdata/01710_projection_with_column_transformers/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt2": true
-  }
-}
+{}