From 7523f037a4d2bfe843ac9b4c4236f500666da360 Mon Sep 17 00:00:00 2001
From: ybai08 <271969568+ybai08@users.noreply.github.com>
Date: Sat, 17 Oct 2026 08:05:00 -0500
Subject: [PATCH] Escape backslashes in MySQL JSON path keys

json_extract_path keys were only escaped for the SQL string literal, so
a backslash in a key reached MySQL's JSON path parser as an escape
character. A key such as "a\\b" matched nothing, "a\\nb" matched the key
containing a newline, and a key ending in a backslash raised a syntax
error.

Escape backslashes and double quotes for the JSON path first, then
escape the result for the SQL string literal.
---
 lib/ecto/adapters/myxql/connection.ex | 3 ++-
 test/ecto/adapters/myxql_test.exs     | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/ecto/adapters/myxql/connection.ex b/lib/ecto/adapters/myxql/connection.ex
index c3c45359..c609cd16 100644
--- a/lib/ecto/adapters/myxql/connection.ex
+++ b/lib/ecto/adapters/myxql/connection.ex
@@ -1626,8 +1626,9 @@ if Code.ensure_loaded?(MyXQL) do
 
     defp escape_json_key(value) when is_binary(value) do
       value
+      |> :binary.replace("\\", "\\\\", [:global])
+      |> :binary.replace("\"", "\\\"", [:global])
       |> escape_string()
-      |> :binary.replace("\"", "\\\\\"", [:global])
     end
 
     defp ecto_cast_to_db(:id, _query), do: "unsigned"
diff --git a/test/ecto/adapters/myxql_test.exs b/test/ecto/adapters/myxql_test.exs
index 373bb6e4..6b5f71da 100644
--- a/test/ecto/adapters/myxql_test.exs
+++ b/test/ecto/adapters/myxql_test.exs
@@ -824,6 +824,12 @@ defmodule Ecto.Adapters.MyXQLTest do
 
     query = Schema |> select([s], json_extract_path(s.meta, ["\"a"])) |> plan()
     assert all(query) == ~s{SELECT json_extract(s0.`meta`, '$."\\\\"a"') FROM `schema` AS s0}
+
+    query = Schema |> select([s], json_extract_path(s.meta, ["a\\b"])) |> plan()
+    assert all(query) == ~S{SELECT json_extract(s0.`meta`, '$."a\\\\b"') FROM `schema` AS s0}
+
+    query = Schema |> select([s], json_extract_path(s.meta, ["a\\"])) |> plan()
+    assert all(query) == ~S{SELECT json_extract(s0.`meta`, '$."a\\\\"') FROM `schema` AS s0}
   end
 
   test "nested expressions" do