From 9a8c6fa0205635a008515549df2f04aa89f86cc5 Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Fri, 28 May 2021 21:50:24 -0700
Subject: [PATCH] Ability to add desc indexes using CLI, closes #260

---
 docs/cli.rst        |  8 ++++++++
 sqlite_utils/cli.py | 16 +++++++++++++---
 tests/test_cli.py   | 11 +++++++++++
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/docs/cli.rst b/docs/cli.rst
index b314b2d..e5ffcfc 100644
--- a/docs/cli.rst
+++ b/docs/cli.rst
@@ -1033,6 +1033,14 @@ Use the ``--unique`` option to create a unique index.
 
 Use ``--if-not-exists`` to avoid attempting to create the index if one with that name already exists.
 
+To add an index on a column in descending order, prefix the column with a hyphen. Since this can be confused for a command-line option you need to construct that like this::
+
+    $ sqlite-utils create-index mydb.db mytable -- col1 -col2 col3
+
+This will create an index on that table on ``(col1, col2 desc, col3)``.
+
+If your column names are already prefixed with a hyphen you'll need to manually execute a ``CREATE INDEX`` SQL statement to add indexes to them rather than using this tool.
+
 .. _cli_fts:
 
 Configuring full-text search
diff --git a/sqlite_utils/cli.py b/sqlite_utils/cli.py
index 960d34c..52de64a 100644
--- a/sqlite_utils/cli.py
+++ b/sqlite_utils/cli.py
@@ -5,7 +5,7 @@ from datetime import datetime
 import hashlib
 import pathlib
 import sqlite_utils
-from sqlite_utils.db import AlterError
+from sqlite_utils.db import AlterError, DescIndex
 import textwrap
 import io
 import itertools
@@ -450,11 +450,21 @@ def index_foreign_keys(path, load_extension):
 )
 @load_extension_option
 def create_index(path, table, column, name, unique, if_not_exists, load_extension):
-    "Add an index to the specified table covering the specified columns"
+    """
+    Add an index to the specified table covering the specified columns.
+    Use "sqlite-utils create-index mydb -- -column" to specify descending
+    order for a column.
+    """
     db = sqlite_utils.Database(path)
     _load_extensions(db, load_extension)
+    # Treat -prefix as descending for columns
+    columns = []
+    for col in column:
+        if col.startswith("-"):
+            col = DescIndex(col[1:])
+        columns.append(col)
     db[table].create_index(
-        column, index_name=name, unique=unique, if_not_exists=if_not_exists
+        columns, index_name=name, unique=unique, if_not_exists=if_not_exists
     )
 
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 2e982dd..17ce27d 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -208,6 +208,17 @@ def test_create_index(db_path):
     )
 
 
+def test_create_index_desc(db_path):
+    db = Database(db_path)
+    assert [] == db["Gosh"].indexes
+    result = CliRunner().invoke(cli.cli, ["create-index", db_path, "Gosh", "--", "-c1"])
+    assert result.exit_code == 0
+    assert (
+        db.execute("select sql from sqlite_master where type='index'").fetchone()[0]
+        == "CREATE INDEX [idx_Gosh_c1]\n    ON [Gosh] ([c1] desc)"
+    )
+
+
 @pytest.mark.parametrize(
     "col_name,col_type,expected_schema",
     (