sqlite-utils create-index command, closes #14

docs/cli.rst

@@ -221,6 +221,23 @@ After running the above ``dogs.json`` example, try running this::
 
 This will replace the record for id=2 (Pancakes) with a new record with an updated age.
 
+.. _cli_create_index:
+
+Creating indexes
+================
+
+You can add an index to an existing table using the ``create-index`` subcommand::
+
+    $ sqlite-utils create-index mydb.db mytable col1 [col2...]
+
+This can be used to create indexes against a single column or multiple columns.
+
+The name of the index will be automatically derived from the table and columns. To specify a different name, use ``--name=name_of_index``.
+
+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.
+
 .. _cli_fts:
 
 Configuring full-text search

sqlite_utils/cli.py

@@ -134,6 +134,30 @@ def optimize(path, no_vacuum):
         db.vacuum()
 
 
+@cli.command(name="create-index")
+@click.argument(
+    "path",
+    type=click.Path(exists=True, file_okay=True, dir_okay=False, allow_dash=False),
+    required=True,
+)
+@click.argument("table")
+@click.argument("column", nargs=-1, required=True)
+@click.option("--name", help="Explicit name for the new index")
+@click.option("--unique", help="Make this a unique index", default=False, is_flag=True)
+@click.option(
+    "--if-not-exists",
+    help="Ignore if index already exists",
+    default=False,
+    is_flag=True,
+)
+def create_index(path, table, column, name, unique, if_not_exists):
+    "Add an index to the specified table covering the specified columns"
+    db = sqlite_utils.Database(path)
+    db[table].create_index(
+        column, index_name=name, unique=unique, if_not_exists=if_not_exists
+    )
+
+
 @cli.command(name="enable-fts")
 @click.argument(
     "path",

tests/test_cli.py

@@ -1,4 +1,5 @@
 from sqlite_utils import cli, Database
+from sqlite_utils.db import Index
 from click.testing import CliRunner
 import json
 import os
@@ -116,6 +117,59 @@ def test_output_table(db_path, fmt, expected):
     assert expected == result.output.strip()
 
 
+def test_create_index(db_path):
+    db = Database(db_path)
+    assert [] == db["Gosh"].indexes
+    result = CliRunner().invoke(cli.cli, ["create-index", db_path, "Gosh", "c1"])
+    assert 0 == result.exit_code
+    assert [
+        Index(
+            seq=0, name="idx_Gosh_c1", unique=0, origin="c", partial=0, columns=["c1"]
+        )
+    ] == db["Gosh"].indexes
+    # Try with a custom name
+    result = CliRunner().invoke(
+        cli.cli, ["create-index", db_path, "Gosh", "c2", "--name", "blah"]
+    )
+    assert 0 == result.exit_code
+    assert [
+        Index(seq=0, name="blah", unique=0, origin="c", partial=0, columns=["c2"]),
+        Index(
+            seq=1, name="idx_Gosh_c1", unique=0, origin="c", partial=0, columns=["c1"]
+        ),
+    ] == db["Gosh"].indexes
+    # Try a two-column unique index
+    create_index_unique_args = [
+        "create-index",
+        db_path,
+        "Gosh2",
+        "c1",
+        "c2",
+        "--unique",
+    ]
+    result = CliRunner().invoke(cli.cli, create_index_unique_args)
+    assert 0 == result.exit_code
+    assert [
+        Index(
+            seq=0,
+            name="idx_Gosh2_c1_c2",
+            unique=1,
+            origin="c",
+            partial=0,
+            columns=["c1", "c2"],
+        )
+    ] == db["Gosh2"].indexes
+    # Trying to create the same index should fail
+    assert -1 == CliRunner().invoke(cli.cli, create_index_unique_args).exit_code
+    # ... unless we use --if-not-exists
+    assert (
+        0
+        == CliRunner()
+        .invoke(cli.cli, create_index_unique_args + ["--if-not-exists"])
+        .exit_code
+    )
+
+
 def test_enable_fts(db_path):
     assert None == Database(db_path)["Gosh"].detect_fts()
     result = CliRunner().invoke(