Update error handling

docs/demo_on_conflict.py

@@ -0,0 +1,33 @@
+"""ETL Helper script to load records to a database table."""
+import sqlite3
+import etlhelper as etl
+
+db_file = "igneous_rocks.db"
+create_sql = """
+    CREATE TABLE IF NOT EXISTS igneous_rock (
+        id INTEGER PRIMARY KEY,
+        name TEXT UNIQUE,
+        grain_size TEXT
+    )"""
+insert_sql = """
+    INSERT INTO igneous_rock (id, name, grain_size)
+    VALUES (:id, :name, :grain_size)
+    ON CONFLICT DO NOTHING
+"""
+
+igneous_rocks = [
+    {"id": 1, "name": "basalt", "grain_size": "fine"},
+    {"id": 1, "name": "basalt", "grain_size": "fine"}  # duplicate row
+]
+
+
+with sqlite3.connect(db_file) as conn:
+    # Create table
+    etl.execute(create_sql, conn)
+
+    # Insert rows
+    etl.executemany(insert_sql, conn, rows=igneous_rocks)
+
+    # Confirm selection
+    for row in etl.fetchall('SELECT * FROM igneous_rock', conn):
+        print(row)

docs/etl_functions/error_handling.rst

@@ -106,4 +106,15 @@ By customising an INSERT query (which can be programmatically generated with
 :func:`generate_insert_query() <etlhelper.generate_insert_query>`) the database
 can be instructed how to process such rows.
 
-TODO: example script of ON CONFLICT ignore
+The following example for SQLite will ignore duplicate rows.
+Different databases have different syntax and capabilities, including
+``upsert`` and ``merge``.
+
+.. literalinclude:: ../demo_on_conflict.py
+   :language: python
+
+The output is:
+
+.. code:: bash
+
+   {'id': 1, 'name': 'basalt', 'grain_size': 'fine'}

docs/etl_functions/extract.rst

@@ -114,7 +114,7 @@ Row factories control the output format of returned rows.
 The default row factory for ETL Helper is a dictionary, but this can be
 changed with the ``row_factory`` argument.
 
-.. literalinclude:: demo_named_tuple.py
+.. literalinclude:: ../demo_namedtuple.py
    :language: python
 
 The output is:

etlhelper/db_helpers/__init__.py

@@ -4,13 +4,6 @@
 They are not normally called directly.
 
 For more details, see the source code in each module.
-
-.. autoclass:: DbHelper
-.. autoclass:: SQLiteDbHelper
-.. autoclass:: PostgresDbHelper
-.. autoclass:: OracleDbHelper
-.. autoclass:: MSSQLDbHelper
-
 """
 # flake8: noqa
 from etlhelper.db_helpers.db_helper import DbHelper

etlhelper/exceptions.py

@@ -1,5 +1,6 @@
 """
-ETL Helper Exception classes
+ETLHelper exceptions are derived from the ETLHelperError base class.
+
 """