load --replace option, closes #6

Author: simonw

README.md

@@ -12,19 +12,25 @@ Tools for dumping/loading a SQLite database to diffable directory structure
 
 ## Dumping a database
 
-Given a SQLite database called `fixtures.db` containing a table `facetable`, the following will dump out that table to the `out/` directory:
+Given a SQLite database called `fixtures.db` containing a table `facetable`, the following will dump out that table to the `dump/` directory:
 
-    sqlite-diffable dump fixtures.db out/ facetable
+    sqlite-diffable dump fixtures.db dump/ facetable
 
 To dump out every table in that database, use `--all`:
 
-    sqlite-diffable dump fixtures.db out/ --all
+    sqlite-diffable dump fixtures.db dump/ --all
 
 ## Loading a database
 
 To load a previously dumped database, run the following:
 
-    sqlite-diffable load restored.db out/
+    sqlite-diffable load restored.db dump/
+
+This will show an error if any of the tables that are being restored already exist in the database file.
+
+You can replace those tables (dropping them before restoring them) using the `--replace` option:
+
+    sqlite-diffable load restored.db dump/ --replace
 
 ## Demo
 

sqlite_diffable/cli.py

@@ -2,6 +2,7 @@
 import json
 import pathlib
 import sqlite_utils
+import sqlite3
 
 
 @click.group()
@@ -72,13 +73,14 @@ def dump(dbpath, output, tables, all):
     "directory",
     type=click.Path(file_okay=False, dir_okay=True),
 )
-def load(dbpath, directory):
+@click.option("--replace", is_flag=True, help="Replace tables if they exist already")
+def load(dbpath, directory, replace):
     """
     Load flat files from a directory into a SQLite database
 
     Usage:
 
-        sqlite-diffable load my.db output/
+        sqlite-diffable load my.db dump-location/
     """
     db = sqlite_utils.Database(dbpath)
     directory = pathlib.Path(directory)
@@ -87,7 +89,15 @@ def load(dbpath, directory):
         info = json.loads(metadata.read_text())
         columns = info["columns"]
         schema = info["schema"]
-        db.execute(schema)
+        if db[info["name"]].exists() and replace:
+            db[info["name"]].drop()
+        try:
+            db.execute(schema)
+        except sqlite3.OperationalError as ex:
+            msg = str(ex)
+            if "already exists" in msg:
+                msg += "\n\nUse the --replace option to over-write existing tables"
+            raise click.ClickException(msg)
         # Now insert the rows
         ndjson = metadata.parent / metadata.stem.replace(".metadata", ".ndjson")
         rows = (

tests/test_dump.py

@@ -57,3 +57,22 @@ def test_load(two_tables_db, tmpdir):
     assert list(db["second_table"].rows) == [
         {"id": 1, "name": "Cleo"},
     ]
+    # Running load a second time should error
+    result3 = CliRunner().invoke(cli.cli, ["load", str(restore_db), str(output_dir)])
+    assert result3.exit_code == 1
+    assert result3.output == (
+        "Error: table [second_table] already exists\n\n"
+        "Use the --replace option to over-write existing tables\n"
+    )
+    # Using --replace should work correctly
+    (output_dir / "one_table.ndjson").write_text(
+        '[1, "Stacey"]\n[2, "Tilda"]\n', "utf-8"
+    )
+    result4 = CliRunner().invoke(
+        cli.cli, ["load", str(restore_db), str(output_dir), "--replace"]
+    )
+    assert result4.exit_code == 0
+    assert list(db["one_table"].rows) == [
+        {"id": 1, "name": "Stacey"},
+        {"id": 2, "name": "Tilda"},
+    ]