Fix 16 todo tests: DESCRIBE TableExpression, window ORDER BY, SHOW SETTINGS

Key fixes:
- Wrap table functions in TableExpression for DESCRIBE queries
- Wrap window ORDER BY items in OrderByElement instead of plain Identifier
- Map SHOW SETTINGS to ShowTables in EXPLAIN AST output (ClickHouse quirk)

Tests now passing:
- 01293_show_settings
- 01568_window_functions_distributed
- 02245_s3_schema_desc
- 02383_schema_inference_hints
- 02409_url_format_detection
- 02410_csv_empty_fields_inference
- 02455_duplicate_column_names_in_schema_inference
- 02457_s3_cluster_schema_inference
- 02560_window_ntile
- 02587_csv_big_numbers_inference
- 02674_date_int_string_json_inference
- 02784_schema_inference_null_as_default
- 02874_parse_json_as_json_each_row_on_no_metadata
- 02876_s3_cluster_schema_inference_names_with_spaces
- 02922_respect_nulls_extensive
- 02982_dont_infer_exponent_floats

Author: claude

internal/explain/format.go

@@ -153,6 +153,21 @@ func formatTupleLiteral(val interface{}) string {
 	return fmt.Sprintf("Tuple_(%s)", strings.Join(parts, ", "))
 }
 
+// formatInListAsTuple formats an IN expression's value list as a tuple literal
+func formatInListAsTuple(list []ast.Expression) string {
+	var parts []string
+	for _, e := range list {
+		if lit, ok := e.(*ast.Literal); ok {
+			parts = append(parts, FormatLiteral(lit))
+		} else if ident, ok := e.(*ast.Identifier); ok {
+			parts = append(parts, ident.Name())
+		} else {
+			parts = append(parts, formatExprAsString(e))
+		}
+	}
+	return fmt.Sprintf("Tuple_(%s)", strings.Join(parts, ", "))
+}
+
 // FormatDataType formats a DataType for EXPLAIN AST output
 func FormatDataType(dt *ast.DataType) string {
 	if dt == nil {

internal/explain/functions.go

@@ -216,6 +216,18 @@ func explainArrayAccess(sb *strings.Builder, n *ast.ArrayAccess, indent string,
 	Node(sb, n.Index, depth+2)
 }
 
+func explainArrayAccessWithAlias(sb *strings.Builder, n *ast.ArrayAccess, alias string, indent string, depth int) {
+	// Array access is represented as Function arrayElement
+	if alias != "" {
+		fmt.Fprintf(sb, "%sFunction arrayElement (alias %s) (children %d)\n", indent, alias, 1)
+	} else {
+		fmt.Fprintf(sb, "%sFunction arrayElement (children %d)\n", indent, 1)
+	}
+	fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, 2)
+	Node(sb, n.Array, depth+2)
+	Node(sb, n.Index, depth+2)
+}
+
 func explainTupleAccess(sb *strings.Builder, n *ast.TupleAccess, indent string, depth int) {
 	// Tuple access is represented as Function tupleElement
 	fmt.Fprintf(sb, "%sFunction tupleElement (children %d)\n", indent, 1)
@@ -224,6 +236,18 @@ func explainTupleAccess(sb *strings.Builder, n *ast.TupleAccess, indent string,
 	Node(sb, n.Index, depth+2)
 }
 
+func explainTupleAccessWithAlias(sb *strings.Builder, n *ast.TupleAccess, alias string, indent string, depth int) {
+	// Tuple access is represented as Function tupleElement
+	if alias != "" {
+		fmt.Fprintf(sb, "%sFunction tupleElement (alias %s) (children %d)\n", indent, alias, 1)
+	} else {
+		fmt.Fprintf(sb, "%sFunction tupleElement (children %d)\n", indent, 1)
+	}
+	fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, 2)
+	Node(sb, n.Tuple, depth+2)
+	Node(sb, n.Index, depth+2)
+}
+
 func explainLikeExpr(sb *strings.Builder, n *ast.LikeExpr, indent string, depth int) {
 	// LIKE is represented as Function like
 	fnName := "like"
@@ -356,6 +380,7 @@ func explainExtractExpr(sb *strings.Builder, n *ast.ExtractExpr, indent string,
 func explainWindowSpec(sb *strings.Builder, n *ast.WindowSpec, indent string, depth int) {
 	// Window spec is represented as WindowDefinition
 	// For simple cases like OVER (), just output WindowDefinition without children
+	// Note: ClickHouse's EXPLAIN AST does not output frame info (ROWS BETWEEN etc)
 	children := 0
 	if n.Name != "" {
 		children++
@@ -366,9 +391,6 @@ func explainWindowSpec(sb *strings.Builder, n *ast.WindowSpec, indent string, de
 	if len(n.OrderBy) > 0 {
 		children++
 	}
-	if n.Frame != nil {
-		children++
-	}
 	if children > 0 {
 		fmt.Fprintf(sb, "%sWindowDefinition (children %d)\n", indent, children)
 		if n.Name != "" {
@@ -383,7 +405,7 @@ func explainWindowSpec(sb *strings.Builder, n *ast.WindowSpec, indent string, de
 		if len(n.OrderBy) > 0 {
 			fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, len(n.OrderBy))
 			for _, o := range n.OrderBy {
-				Node(sb, o.Expression, depth+2)
+				explainOrderByElement(sb, o, strings.Repeat(" ", depth+2), depth+2)
 			}
 		}
 		// Frame handling would go here if needed

internal/explain/statements.go

@@ -316,8 +316,12 @@ func explainExplainQuery(sb *strings.Builder, n *ast.ExplainQuery, indent string
 }
 
 func explainShowQuery(sb *strings.Builder, n *ast.ShowQuery, indent string) {
-	// Capitalize ShowType correctly for display
+	// ClickHouse maps certain SHOW types to ShowTables in EXPLAIN AST
 	showType := strings.Title(strings.ToLower(string(n.ShowType)))
+	// SHOW SETTINGS is displayed as ShowTables in ClickHouse
+	if showType == "Settings" {
+		showType = "Tables"
+	}
 	fmt.Fprintf(sb, "%sShow%s\n", indent, showType)
 }
 
@@ -327,13 +331,14 @@ func explainUseQuery(sb *strings.Builder, n *ast.UseQuery, indent string) {
 
 func explainDescribeQuery(sb *strings.Builder, n *ast.DescribeQuery, indent string) {
 	if n.TableFunction != nil {
-		// DESCRIBE on a table function
+		// DESCRIBE on a table function - wrap in TableExpression
 		children := 1
 		if len(n.Settings) > 0 {
 			children++
 		}
 		fmt.Fprintf(sb, "%sDescribeQuery (children %d)\n", indent, children)
-		explainFunctionCall(sb, n.TableFunction, indent+" ", 1)
+		fmt.Fprintf(sb, "%s TableExpression (children 1)\n", indent)
+		explainFunctionCall(sb, n.TableFunction, indent+"  ", 2)
 		if len(n.Settings) > 0 {
 			fmt.Fprintf(sb, "%s Set\n", indent)
 		}

parser/testdata/01293_show_settings/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/01568_window_functions_distributed/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/02245_s3_schema_desc/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/02383_schema_inference_hints/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/02409_url_format_detection/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/02410_csv_empty_fields_inference/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/02455_duplicate_column_names_in_schema_inference/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}