sqlite-utils duplicate command, closes #454, refs #449

Also made it so .duplicate() raises new NoTable exception rather than raising
an AssertionError if the source table does not exist.

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, BadMultiValues, DescIndex
+from sqlite_utils.db import AlterError, BadMultiValues, DescIndex, NoTable
 from sqlite_utils.utils import maximize_csv_field_size_limit
 from sqlite_utils import recipes
 import textwrap
@@ -1465,6 +1465,27 @@ def create_table(
     )
 
 
+@cli.command(name="duplicate")
+@click.argument(
+    "path",
+    type=click.Path(file_okay=True, dir_okay=False, allow_dash=False),
+    required=True,
+)
+@click.argument("table")
+@click.argument("new_table")
+@load_extension_option
+def create_table(path, table, new_table, load_extension):
+    """
+    Create a duplicate of this table, copying across the schema and all row data.
+    """
+    db = sqlite_utils.Database(path)
+    _load_extensions(db, load_extension)
+    try:
+        db[table].duplicate(new_table)
+    except NoTable:
+        raise click.ClickException('Table "{}" does not exist'.format(table))
+
+
 @cli.command(name="drop-table")
 @click.argument(
     "path",

sqlite_utils/db.py

@@ -1,3 +1,4 @@
+from ast import Not
 from .utils import (
     chunks,
     hash_record,
@@ -224,6 +225,11 @@ class NoObviousTable(Exception):
     pass
 
 
+class NoTable(Exception):
+    "Specified table does not exist"
+    pass
+
+
 class BadPrimaryKey(Exception):
     "Table does not have a single obvious primary key"
     pass
@@ -1482,7 +1488,8 @@ class Table(Queryable):
 
         :param new_name: Name of the new table
         """
-        assert self.exists()
+        if not self.exists():
+            raise NoTable(f"Table {self.name} does not exist")
         with self.db.conn:
             sql = "CREATE TABLE [{new_table}] AS SELECT * FROM [{table}];".format(
                 new_table=new_name,