[codex] Fix ClickHouse quote escaping

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## 0.9.4 (2026-05-30)
 
+- Escape double quotes, backticks, and backslashes in quoted ClickHouse identifiers https://github.com/plausible/ecto_ch/pull/283
 - Support the `:comment` column option in migrations (`create`, `add`, and `modify`), which was previously silently ignored https://github.com/plausible/ecto_ch/pull/282
 
 ## 0.9.3 (2026-05-07)

lib/ecto/adapters/clickhouse/connection.ex

@@ -1024,6 +1024,7 @@ defmodule Ecto.Adapters.ClickHouse.Connection do
     names
     |> Enum.reject(&is_nil/1)
     |> intersperse_map(?., &quote_name(&1, nil))
+    |> escape_quoted(quoter)
     |> wrap_in(quoter)
   end
 
@@ -1032,7 +1033,9 @@ defmodule Ecto.Adapters.ClickHouse.Connection do
   end
 
   def quote_name(name, quoter) do
-    wrap_in(name, quoter)
+    name
+    |> escape_quoted(quoter)
+    |> wrap_in(quoter)
   end
 
   defp quote_qualified_name(name, sources, ix) do
@@ -1052,6 +1055,16 @@ defmodule Ecto.Adapters.ClickHouse.Connection do
   defp wrap_in(value, nil), do: value
   defp wrap_in(value, wrapper), do: [wrapper, value, wrapper]
 
+  defp escape_quoted(value, nil), do: value
+  defp escape_quoted(value, ?'), do: escape_string(IO.iodata_to_binary(value))
+
+  defp escape_quoted(value, quoter) when quoter in [?\", ?`] do
+    value
+    |> IO.iodata_to_binary()
+    |> :binary.replace("\\", "\\\\", [:global])
+    |> :binary.replace(<<quoter>>, "\\" <> <<quoter>>, [:global])
+  end
+
   @doc false
   # TODO faster?
   def escape_string(value) when is_binary(value) do

test/ecto/adapters/clickhouse/connection_test.exs

@@ -774,6 +774,24 @@ defmodule Ecto.Adapters.ClickHouse.ConnectionTest do
 
     query = "schema" |> where(foo: "'") |> select([], true)
     assert all(query) == ~s[SELECT true FROM "schema" AS s0 WHERE (s0."foo" = '''')]
+
+    query = "schema" |> select([], constant(^"let's \\ escape"))
+    assert all(query) == ~s[SELECT 'let''s \\\\ escape' FROM "schema" AS s0]
+  end
+
+  test "quoted identifier escape" do
+    assert Connection.quote_name(~s{has"quote}) |> IO.iodata_to_binary() ==
+             ~s{"has\\"quote"}
+
+    assert Connection.quote_name(~s{has\\slash}) |> IO.iodata_to_binary() ==
+             ~s{"has\\\\slash"}
+
+    assert Connection.quote_name(~s{has`tick}, ?`) |> IO.iodata_to_binary() ==
+             ~s{`has\\`tick`}
+
+    query = insert(nil, ~s{schema"quoted}, [~s{field"quoted}], [], :raise, [])
+
+    assert query == ~s{INSERT INTO "schema\\"quoted"("field\\"quoted")}
   end
 
   test "binary ops" do
@@ -2510,6 +2528,14 @@ defmodule Ecto.Adapters.ClickHouse.ConnectionTest do
     end
   end
 
+  test "create table with escaped table comment" do
+    create = {:create, table(:posts, comment: "owner's \\\\ table"), []}
+
+    assert execute_ddl(create) == [
+             ~s{CREATE TABLE "posts" () ENGINE=TinyLog COMMENT 'owner''s \\\\\\\\ table'}
+           ]
+  end
+
   test "create table with serial primary key" do
     create =
       {:create, table(:posts, engine: "MergeTree"),