table.enable_counts() method, closes #212

tests/test_enable_counts.py

@@ -0,0 +1,27 @@
+def test_enable_counts(fresh_db):
+    foo = fresh_db["foo"]
+    assert fresh_db.table_names() == []
+    for i in range(10):
+        foo.insert({"name": "item {}".format(i)})
+    assert fresh_db.table_names() == ["foo"]
+    assert foo.count == 10
+    # Now enable counts
+    foo.enable_counts()
+    assert foo.triggers_dict == {
+        "foo_counts_insert": "CREATE TRIGGER [foo_counts_insert] AFTER INSERT ON [foo]\nBEGIN\n    INSERT OR REPLACE INTO [_counts]\n    VALUES (\n        'foo',\n        COALESCE(\n            (SELECT count FROM [_counts] WHERE [table] = 'foo'),\n        0\n        ) + 1\n    );\nEND",
+        "foo_counts_delete": "CREATE TRIGGER [foo_counts_delete] AFTER DELETE ON [foo]\nBEGIN\n    INSERT OR REPLACE INTO [_counts]\n    VALUES (\n        'foo',\n        COALESCE(\n            (SELECT count FROM [_counts] WHERE [table] = 'foo'),\n        0\n        ) - 1\n    );\nEND",
+    }
+    assert fresh_db.table_names() == ["foo", "_counts"]
+    assert list(fresh_db["_counts"].rows) == [{"count": 10, "table": "foo"}]
+    # Add some items to test the triggers
+    for i in range(5):
+        foo.insert({"name": "item {}".format(10 + i)})
+    assert foo.count == 15
+    assert list(fresh_db["_counts"].rows) == [{"count": 15, "table": "foo"}]
+    # Delete some items
+    foo.delete_where("rowid < 7")
+    assert foo.count == 9
+    assert list(fresh_db["_counts"].rows) == [{"count": 9, "table": "foo"}]
+    foo.delete_where()
+    assert foo.count == 0
+    assert list(fresh_db["_counts"].rows) == [{"count": 0, "table": "foo"}]