Tambah Log Table sebagai backup

CHANGES.txt

+0.3 29-12-2020
+--------------
+- Helper untuk memasang pencatatan perubahan isi tabel.
+
 0.2 24-12-2020
 --------------
 - Jumlah backup bisa diatur di konfigurasi

MANIFEST.in

+include *.txt *.rst *.py
+recursive-include maintenance *.py
+recursive-include log_table *.py *.sql

README.rst

@@ -72,4 +72,25 @@ dilakukan. Contohnya di ``/etc/cron.d/maintenance`` berikut ini::
     MAILTO=""
     45 1 * * * root cd /home/sugiana/2020/08 && env/bin/maintenance maintenance.ini >/dev/null 2>&1
 
+
+Log Table
+---------
+
+Ini merupakan bagian dari skenario backup dimana setiap perubahan record akan
+dicatat di tabel `log_table` baik saat INSERT, UPDATE, maupun DELETE. Bekerja
+menggunakan trigger di setiap tabel yang akan dicatat.
+
+Buatlah file konfigurasi `live.ini`::
+
+    [main]
+    db_url = postgresql://user:pass@localhost/db
+
+Buat tabel beserta fungsi trigger::
+
+    $ ~/env/bin/log_table_init_db live.ini
+
+Tetapkanlah tabel yang akan dicatat perubahannya. Utamanya tabel terkait transaksi dan *user profile*::
+
+    $ ~/env/bin/log_table_trigger live.ini --schema=pbb --table=pembayaran_sppt
+
 Semoga berhasil.

log_table/func-rec-to-json.sql

+CREATE OR REPLACE FUNCTION rec_to_json(p_table_schema name, p_table_name name, p_rec record) RETURNS json LANGUAGE plpgsql AS $$
+DECLARE
+    v_val text;
+    v_one json;
+    v_all json;
+    v_field record;
+BEGIN
+    FOR v_field IN
+        SELECT column_name
+            FROM information_schema.columns
+            WHERE table_schema = p_table_schema
+                AND table_name = p_table_name 
+    LOOP
+        EXECUTE format('SELECT (($1).%I)::text', v_field.column_name)
+            USING p_rec 
+            INTO v_val;
+
+        v_one = json_build_object(v_field.column_name, v_val);
+
+        IF v_all IS NULL THEN
+            v_all = v_one;
+        ELSE
+            v_all = v_all::jsonb || v_one::jsonb;
+        END IF;
+    END LOOP;
+
+    RETURN v_all;
+END
+$$

log_table/func-trigger-after-delete.sql

+CREATE OR REPLACE FUNCTION log_table_after_delete() RETURNS trigger LANGUAGE plpgsql AS $$
+DECLARE
+    v_old json;
+BEGIN
+    v_old = rec_to_json(TG_TABLE_SCHEMA, TG_TABLE_NAME, OLD);
+
+    INSERT INTO log_table (table_schema, table_name, operation, old_values)
+        VALUES (TG_TABLE_SCHEMA, TG_TABLE_NAME, 'delete', v_old);
+
+    RETURN NEW;
+END
+$$

log_table/func-trigger-after-insert.sql

+CREATE OR REPLACE FUNCTION log_table_after_insert() RETURNS trigger LANGUAGE plpgsql AS $$
+DECLARE
+    v_new json;
+BEGIN
+    v_new = rec_to_json(TG_TABLE_SCHEMA, TG_TABLE_NAME, NEW);
+
+    INSERT INTO log_table (table_schema, table_name, operation, new_values)
+        VALUES (TG_TABLE_SCHEMA, TG_TABLE_NAME, 'insert', v_new);
+
+    RETURN NEW;
+END
+$$

log_table/func-trigger-after-update.sql

+CREATE OR REPLACE FUNCTION log_table_after_update() RETURNS trigger LANGUAGE plpgsql AS $$
+DECLARE
+    v_old json;
+    v_new json;
+BEGIN
+    v_old = rec_to_json(TG_TABLE_SCHEMA, TG_TABLE_NAME, OLD);
+    v_new = rec_to_json(TG_TABLE_SCHEMA, TG_TABLE_NAME, NEW);
+
+    INSERT INTO log_table (table_schema, table_name, operation, old_values, new_values)
+        VALUES (TG_TABLE_SCHEMA, TG_TABLE_NAME, 'update', v_old, v_new);
+
+    RETURN NEW;
+END
+$$

log_table/init_db.py

+import sys
+import os
+from configparser import ConfigParser
+from sqlalchemy import engine_from_config
+from sqlalchemy.sql.expression import text
+from .models import Base
+
+
+t = os.path.split(__file__)
+current_dir = t[0]
+
+
+def execute(engine, filename):
+    fullpath = os.path.join(current_dir, filename)
+    with open(fullpath) as f:
+        sql = f.read()
+    engine.execute(text(sql))
+
+
+def main(argv=sys.argv[1:]):
+    conf_file = argv[0]
+    conf = ConfigParser()
+    conf.read(conf_file)
+    engine = engine_from_config(conf['main'], 'db_')
+    engine.echo = True
+    Base.metadata.create_all(engine)
+    execute(engine, 'func-rec-to-json.sql')
+    for operation in ('insert', 'update', 'delete'):
+        filename = f'func-trigger-after-{operation}.sql'
+        execute(engine, filename)

log_table/models.py

+from sqlalchemy import (
+    Column,
+    Integer,
+    String,
+    DateTime,
+    JSON,
+    CheckConstraint,
+    func,
+    )
+from sqlalchemy.ext.declarative import declarative_base
+
+
+Base = declarative_base()
+
+
+class Log(Base):
+    __tablename__ = 'log_table'
+    id = Column(Integer, primary_key=True)
+    created = Column(
+            DateTime(timezone=True), nullable=False,
+            server_default=func.now())
+    table_schema = Column(String(32))
+    table_name = Column(String(32), nullable=False)
+    operation = Column(
+        String(6),
+        CheckConstraint("operation IN ('insert', 'update', 'delete')"),
+        nullable=False)
+    old_values = Column(JSON)
+    new_values = Column(JSON)

log_table/requirements.txt

+sqlalchemy
+psycopg2-binary

log_table/set_trigger.py

+import sys
+from configparser import ConfigParser
+from argparse import ArgumentParser
+from sqlalchemy import (
+    engine_from_config,
+    exc,
+    )
+from sqlalchemy.sql.expression import text
+
+
+def get_option(argv):
+    default_schema = 'public'
+    help_schema = 'default ' + default_schema
+    pars = ArgumentParser()
+    pars.add_argument('conf')
+    pars.add_argument('--table', required=True)
+    pars.add_argument('--schema', default=default_schema, help=help_schema)
+    return pars.parse_args(argv)
+
+
+def main(argv=sys.argv[1:]):
+    option = get_option(argv)
+    conf_file = option.conf
+    conf = ConfigParser()
+    conf.read(conf_file)
+    engine = engine_from_config(conf['main'], 'db_')
+    engine.echo = True
+    table_name = option.table
+    table_schema = option.schema
+    for operation in ('insert', 'update', 'delete'):
+        trigger_name = f'log_table_{operation}'
+        sql = f'DROP TRIGGER {trigger_name} ON {table_name}'
+        try:
+            engine.execute(text(sql))
+        except exc.ProgrammingError as e:
+            s = str(e)
+            if s.find('does not exist') == -1:
+                raise e
+        sql = f'CREATE TRIGGER {trigger_name} '\
+              f'AFTER {operation} ON {table_name} '\
+              f'FOR EACH ROW EXECUTE PROCEDURE log_table_after_{operation}()'
+        engine.execute(text(sql))

setup.py

@@ -32,6 +32,8 @@ setup(
     entry_points={
         'console_scripts': [
             'maintenance = maintenance:main',
+            'log_table_init_db = log_table.init_db:main',
+            'log_table_trigger = log_table.set_trigger:main',
         ]
     },
 )