Fix compile warnings and update CI matrix for latest Elixir/OTP

Two unrelated maintenance changes:

1. Fix redundant execute_ddl/1 clauses in connection.ex

   The file had two duplicate sets of execute_ddl/1 clauses: a newer
   set (with @impl true markers) and an older set of duplicates. The
   newer Ecto type system flags the duplicates as redundant warnings
   that fail the build with --warnings-as-errors.

   Remove the older duplicate clauses, keeping the first (correct)
   set intact. Also remove one redundant {:drop_if_exists,
   %Index{concurrently: true}} clause that is fully covered by the
   wildcard {:_, %Index{concurrently: true}} clause which raises the
   same ArgumentError.

   Preserves the original non-duplicate clauses for Constraint and
   Index rename operations that only existed in the second set.

2. Update CI matrix to Elixir 1.18-1.20 / OTP 27-29

   Per the official Elixir/OTP compatibility table (June 2026):
     - Elixir 1.20: OTP 27-29 (latest)
     - Elixir 1.19: OTP 26-28
     - Elixir 1.18: OTP 25-27

   Drops Elixir 1.17 and OTP 26 (both EOL), adds Elixir 1.20 and
   OTP 29 (latest). Excludes 3 combinations that fall outside the
   official support ranges. Lint job runs on the latest (1.20+29).

   6 valid combinations remain, all within official support ranges.

Author: gilbertwong96

.github/workflows/ci.yml

@@ -15,8 +15,8 @@ jobs:
     strategy:
       matrix:
         os: ["ubuntu-latest"]
-        elixir: ["1.19"]
-        otp: ["28"]
+        elixir: ["1.20"]
+        otp: ["29"]
     steps:
       - uses: actions/checkout@v6
       - uses: erlef/setup-beam@v1
@@ -41,11 +41,15 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest"]
-        elixir: ["1.19", "1.18", "1.17"]
-        otp: ["28", "27", "26"]
+        elixir: ["1.20", "1.19", "1.18"]
+        otp: ["29", "28", "27"]
         exclude:
-          - elixir: "1.17"
+          - elixir: "1.18"
             otp: "28"
+          - elixir: "1.18"
+            otp: "29"
+          - elixir: "1.19"
+            otp: "29"
     steps:
       - uses: actions/checkout@v6
       - uses: erlef/setup-beam@v1

lib/ecto/adapters/sqlite3/connection.ex

@@ -550,11 +550,6 @@ defmodule Ecto.Adapters.SQLite3.Connection do
     execute_ddl({:drop, index})
   end
 
-  @impl true
-  def execute_ddl({:drop_if_exists, %Index{concurrently: true}}) do
-    raise ArgumentError, "`concurrently` is not supported with SQLite3"
-  end
-
   @impl true
   def execute_ddl({:drop_if_exists, %Index{} = index}) do
     [
@@ -604,77 +599,10 @@ defmodule Ecto.Adapters.SQLite3.Connection do
     raise ArgumentError, "SQLite3 adapter does not support keyword lists in execute"
   end
 
-  @impl true
-  def execute_ddl({:create, %Index{} = index}) do
-    fields = Enum.map_intersperse(index.columns, ", ", &index_expr/1)
-
-    [
-      [
-        "CREATE ",
-        if_do(index.unique, "UNIQUE "),
-        "INDEX",
-        ?\s,
-        quote_name(index.name),
-        " ON ",
-        quote_table(index.prefix, index.table),
-        " (",
-        fields,
-        ?),
-        if_do(index.where, [" WHERE ", to_string(index.where)])
-      ]
-    ]
-  end
-
-  def execute_ddl({:create_if_not_exists, %Index{} = index}) do
-    fields = Enum.map_intersperse(index.columns, ", ", &index_expr/1)
-
-    [
-      [
-        "CREATE ",
-        if_do(index.unique, "UNIQUE "),
-        "INDEX IF NOT EXISTS",
-        ?\s,
-        quote_name(index.name),
-        " ON ",
-        quote_table(index.prefix, index.table),
-        " (",
-        fields,
-        ?),
-        if_do(index.where, [" WHERE ", to_string(index.where)])
-      ]
-    ]
-  end
-
   def execute_ddl({:create, %Constraint{}}) do
     raise ArgumentError, "SQLite3 does not support ALTER TABLE ADD CONSTRAINT."
   end
 
-  def execute_ddl({:drop, %Index{} = index}) do
-    [
-      [
-        "DROP INDEX ",
-        quote_table(index.prefix, index.name)
-      ]
-    ]
-  end
-
-  def execute_ddl({:drop, %Index{} = index, _mode}) do
-    execute_ddl({:drop, index})
-  end
-
-  def execute_ddl({:drop_if_exists, %Index{} = index}) do
-    [
-      [
-        "DROP INDEX IF EXISTS ",
-        quote_table(index.prefix, index.name)
-      ]
-    ]
-  end
-
-  def execute_ddl({:drop_if_exists, %Index{} = index, _mode}) do
-    execute_ddl({:drop_if_exists, index})
-  end
-
   def execute_ddl({:drop, %Constraint{}, _mode}) do
     raise ArgumentError, "SQLite3 does not support ALTER TABLE DROP CONSTRAINT."
   end
@@ -683,43 +611,13 @@ defmodule Ecto.Adapters.SQLite3.Connection do
     raise ArgumentError, "SQLite3 does not support ALTER TABLE DROP CONSTRAINT."
   end
 
-  def execute_ddl({:rename, %Table{} = current_table, %Table{} = new_table}) do
-    [
-      [
-        "ALTER TABLE ",
-        quote_table(current_table.prefix, current_table.name),
-        " RENAME TO ",
-        quote_table(new_table.prefix, new_table.name)
-      ]
-    ]
-  end
-
-  def execute_ddl({:rename, %Table{} = table, current_column, new_column}) do
-    [
-      [
-        "ALTER TABLE ",
-        quote_table(table.prefix, table.name),
-        " RENAME COLUMN ",
-        quote_name(current_column),
-        " TO ",
-        quote_name(new_column)
-      ]
-    ]
-  end
-
   def execute_ddl({:rename, %Index{} = index, new_index}) do
     [
       execute_ddl({:drop, index}),
       execute_ddl({:create, %Index{index | name: new_index}})
     ]
   end
 
-  def execute_ddl(string) when is_binary(string), do: [string]
-
-  def execute_ddl(keyword) when is_list(keyword) do
-    raise ArgumentError, "SQLite3 adapter does not support keyword lists in execute"
-  end
-
   @impl true
   def ddl_logs(_), do: []