From 068ab52b0d6331f3ed23abdeaa35ed056b4a180b Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Thu, 25 Dec 2025 04:19:07 +0000
Subject: [PATCH] Fix EXPLAIN AST output for single tuple in IN expression

When an IN expression contains a single tuple literal, ClickHouse wraps
it in a Function tuple node. This matches ClickHouse's behavior for
queries like `SELECT (1, '') IN ((1, ''));`.
---
 internal/explain/functions.go                 | 25 ++++++++++++++++++-
 .../testdata/00131_set_hashed/metadata.json   |  2 +-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/internal/explain/functions.go b/internal/explain/functions.go
index 71a9e391b..9e5f83d87 100644
--- a/internal/explain/functions.go
+++ b/internal/explain/functions.go
@@ -184,7 +184,17 @@ func explainInExpr(sb *strings.Builder, n *ast.InExpr, indent string, depth int)
 	if n.Query != nil {
 		argCount++
 	} else {
-		argCount += len(n.List)
+		// Check if we have a single tuple literal that should be wrapped in Function tuple
+		if len(n.List) == 1 {
+			if lit, ok := n.List[0].(*ast.Literal); ok && lit.Type == ast.LiteralTuple {
+				// Single tuple literal gets wrapped in Function tuple, so count as 1
+				argCount++
+			} else {
+				argCount += len(n.List)
+			}
+		} else {
+			argCount += len(n.List)
+		}
 	}
 	fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, argCount)
 	Node(sb, n.Expr, depth+2)
@@ -192,6 +202,19 @@ func explainInExpr(sb *strings.Builder, n *ast.InExpr, indent string, depth int)
 		// Subqueries in IN should be wrapped in Subquery node
 		fmt.Fprintf(sb, "%s  Subquery (children %d)\n", indent, 1)
 		Node(sb, n.Query, depth+3)
+	} else if len(n.List) == 1 {
+		// Single element in the list
+		// If it's a tuple literal, wrap it in Function tuple
+		// Otherwise, output the element directly
+		if lit, ok := n.List[0].(*ast.Literal); ok && lit.Type == ast.LiteralTuple {
+			// Wrap tuple literal in Function tuple
+			fmt.Fprintf(sb, "%s  Function tuple (children %d)\n", indent, 1)
+			fmt.Fprintf(sb, "%s   ExpressionList (children %d)\n", indent, 1)
+			Node(sb, n.List[0], depth+4)
+		} else {
+			// Single non-tuple element - output directly
+			Node(sb, n.List[0], depth+2)
+		}
 	} else {
 		for _, item := range n.List {
 			Node(sb, item, depth+2)
diff --git a/parser/testdata/00131_set_hashed/metadata.json b/parser/testdata/00131_set_hashed/metadata.json
index ef120d978..0967ef424 100644
--- a/parser/testdata/00131_set_hashed/metadata.json
+++ b/parser/testdata/00131_set_hashed/metadata.json
@@ -1 +1 @@
-{"todo": true}
+{}