creation projection workinggg

.env.dist

@@ -0,0 +1,5 @@
+POSTGRES_HOST=localhost
+POSTGRES_PORT=5432
+POSTGRES_DB=rollup
+POSTGRES_USER=rollup
+POSTGRES_PASSWORD=rollup

.gitignore

@@ -0,0 +1,217 @@
+.env
+.venv/
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[codz]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# UV
+#   Similar to Pipfile.lock, it is generally recommended to include uv.lock in version control.
+#   This is especially recommended for binary packages to ensure reproducibility, and is more
+#   commonly ignored for libraries.
+#uv.lock
+
+# poetry
+#   Similar to Pipfile.lock, it is generally recommended to include poetry.lock in version control.
+#   This is especially recommended for binary packages to ensure reproducibility, and is more
+#   commonly ignored for libraries.
+#   https://python-poetry.org/docs/basic-usage/#commit-your-poetrylock-file-to-version-control
+#poetry.lock
+#poetry.toml
+
+# pdm
+#   Similar to Pipfile.lock, it is generally recommended to include pdm.lock in version control.
+#pdm.lock
+#   pdm stores project-wide configurations in .pdm.toml, but it is recommended to not include it
+#   in version control.
+#   https://pdm.fming.dev/latest/usage/project/#working-with-version-control
+.pdm.toml
+.pdm-python
+.pdm-build/
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.envrc
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+# PyCharm
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/
+
+# Abstra
+# Abstra is an AI-powered process automation framework.
+# Ignore directories containing user credentials, local state, and settings.
+# Learn more at https://abstra.io/docs
+.abstra/
+
+# Visual Studio Code
+#  Visual Studio Code specific template is maintained in a separate VisualStudioCode.gitignore 
+#  that can be found at https://github.com/github/gitignore/blob/main/Global/VisualStudioCode.gitignore
+#  and can be added to the global gitignore or merged into this file. However, if you prefer, 
+#  you could uncomment the following to ignore the entire vscode folder
+# .vscode/
+
+# Ruff stuff:
+.ruff_cache/
+
+# PyPI configuration file
+.pypirc
+
+# Cursor
+#  Cursor is an AI-powered code editor. `.cursorignore` specifies files/directories to
+#  exclude from AI features like autocomplete and code analysis. Recommended for sensitive data
+#  refer to https://docs.cursor.com/context/ignore-files
+.cursorignore
+.cursorindexingignore
+
+# Marimo
+marimo/_static/
+marimo/_lsp/
+__marimo__/

.vscode/settings.json

@@ -0,0 +1,6 @@
+{"[python]": {
+    "editor.formatOnSave": true,
+    "editor.defaultFormatter": "ms-python.black-formatter"
+},
+"python.experiments.enabled": false
+}

alembic.ini

@@ -0,0 +1,141 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts.
+# this is typically a path given in POSIX (e.g. forward slashes)
+# format, relative to the token %(here)s which refers to the location of this
+# ini file
+script_location = %(here)s/alembic
+
+# template used to generate migration file names; The default value is %%(rev)s_%%(slug)s
+# Uncomment the line below if you want the files to be prepended with date and time
+# see https://alembic.sqlalchemy.org/en/latest/tutorial.html#editing-the-ini-file
+# for all available tokens
+# file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(rev)s_%%(slug)s
+
+# sys.path path, will be prepended to sys.path if present.
+# defaults to the current working directory.  for multiple paths, the path separator
+# is defined by "path_separator" below.
+prepend_sys_path = .
+
+
+# timezone to use when rendering the date within the migration file
+# as well as the filename.
+# If specified, requires the python>=3.9 or backports.zoneinfo library and tzdata library.
+# Any required deps can installed by adding `alembic[tz]` to the pip requirements
+# string value is passed to ZoneInfo()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; This defaults
+# to <script_location>/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path.
+# The path separator used here should be the separator specified by "path_separator"
+# below.
+# version_locations = %(here)s/bar:%(here)s/bat:%(here)s/alembic/versions
+
+# path_separator; This indicates what character is used to split lists of file
+# paths, including version_locations and prepend_sys_path within configparser
+# files such as alembic.ini.
+# The default rendered in new alembic.ini files is "os", which uses os.pathsep
+# to provide os-dependent path splitting.
+#
+# Note that in order to support legacy alembic.ini files, this default does NOT
+# take place if path_separator is not present in alembic.ini.  If this
+# option is omitted entirely, fallback logic is as follows:
+#
+# 1. Parsing of the version_locations option falls back to using the legacy
+#    "version_path_separator" key, which if absent then falls back to the legacy
+#    behavior of splitting on spaces and/or commas.
+# 2. Parsing of the prepend_sys_path option falls back to the legacy
+#    behavior of splitting on spaces, commas, or colons.
+#
+# Valid values for path_separator are:
+#
+# path_separator = :
+# path_separator = ;
+# path_separator = space
+# path_separator = newline
+#
+# Use os.pathsep. Default configuration used for new projects.
+path_separator = os
+
+# set to 'true' to search source files recursively
+# in each "version_locations" directory
+# new in Alembic version 1.10
+# recursive_version_locations = false
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+# database URL.  This is consumed by the user-maintained env.py script only.
+# other means of configuring database URLs may be customized within the env.py
+# file.
+sqlalchemy.url = driver://user:pass@localhost/dbname
+
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "black" - use the console_scripts runner, against the "black" entrypoint
+# hooks = black
+# black.type = console_scripts
+# black.entrypoint = black
+# black.options = -l 79 REVISION_SCRIPT_FILENAME
+
+# lint with attempts to fix using "ruff" - use the exec runner, execute a binary
+# hooks = ruff
+# ruff.type = exec
+# ruff.executable = %(here)s/.venv/bin/ruff
+# ruff.options = check --fix REVISION_SCRIPT_FILENAME
+
+# Logging configuration.  This is also consumed by the user-maintained
+# env.py script only.
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARNING
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARNING
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

alembic/README

@@ -0,0 +1 @@
+Generic single-database configuration.

alembic/env.py

@@ -0,0 +1,85 @@
+import os
+from logging.config import fileConfig
+from dotenv import load_dotenv
+from sqlalchemy import engine_from_config, pool
+from alembic import context
+
+
+load_dotenv()
+
+
+db_url = f"postgresql://{os.getenv('POSTGRES_USER')}:{os.getenv('POSTGRES_PASSWORD')}@{os.getenv('POSTGRES_HOST')}:{os.getenv('POSTGRES_PORT')}/{os.getenv('POSTGRES_DB')}"
+
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+config.set_main_option("sqlalchemy.url", db_url)
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+target_metadata = None
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

alembic/script.py.mako

@@ -0,0 +1,28 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}

alembic/versions/394542f24f6c_add_projection_table.py

@@ -0,0 +1,106 @@
+"""add projection table
+
+Revision ID: 394542f24f6c
+Revises: abfbb3d96037
+Create Date: 2025-06-14 23:57:39.301255
+
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = "394542f24f6c"
+down_revision: Union[str, None] = "abfbb3d96037"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    op.create_table(
+        "users",
+        sa.Column(
+            "id",
+            sa.UUID(as_uuid=True),
+            nullable=False,
+        ),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("deleted_at", sa.DateTime(timezone=True)),
+        sa.Column("last_event_id", sa.UUID(as_uuid=True), nullable=False, unique=True),
+        sa.Column(
+            "last_event_sequence",
+            sa.Integer(),
+            nullable=False,
+            autoincrement=True,
+            unique=True,
+        ),
+        sa.Column("name", sa.String(), nullable=False),
+        sa.Column("age", sa.Integer(), nullable=False),
+        sa.Column("hair_color", sa.String(), nullable=False),
+        sa.PrimaryKeyConstraint("id"),
+    )
+
+    op.execute(
+        """
+        create or replace function fn_project_user_created(event_id uuid, event_sequence integer, event_timestamp timestamptz, event jsonb) returns uuid
+            security definer
+            language plpgsql as $$
+            declare result uuid;
+            begin
+                insert into users(
+                    id, 
+                    created_at, 
+                    updated_at, 
+                    last_event_id, 
+                    last_event_sequence,
+                    name,
+                    age,
+                    hair_color
+                )
+                values(
+                    cast(event->'event_payload'->>'id' as UUID), 
+                    event_timestamp,
+                    event_timestamp,
+                    event_id,
+                    event_sequence,
+                    event->'event_payload'->>'name',
+                    cast(event->'event_payload'->>'age' as INTEGER),
+                    event->'event_payload'->>'hair_color'
+                )
+                returning id into result;
+                return result;
+            end;
+        $$;
+
+        create or replace function fn_trigger_user_created() returns trigger
+            security definer
+            language plpgsql
+        as $$
+        begin
+            perform fn_project_user_created(
+                new.id,
+                new.sequence,
+                new.created_at,
+                new.event_payload
+                );
+            return new;
+        end;
+        $$;
+
+        create trigger event_insert_user_created
+        after insert on user_events
+        for each row
+        when ((new.event_payload->>'event_type') = 'user_created')
+        execute procedure fn_trigger_user_created();
+        """
+    )
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    op.drop_table("users")

alembic/versions/abfbb3d96037_create_user_event_table.py

@@ -0,0 +1,49 @@
+"""create user event table
+
+Revision ID: abfbb3d96037
+Revises:
+Create Date: 2025-06-14 22:22:48.407239
+
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+import sqlalchemy.dialects.postgresql as psql
+
+# revision identifiers, used by Alembic.
+revision: str = "abfbb3d96037"
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+
+    op.execute("CREATE EXTENSION IF NOT EXISTS pgcrypto;")
+
+    op.create_table(
+        "user_events",
+        sa.Column(
+            "id",
+            sa.UUID(as_uuid=True),
+            nullable=False,
+            server_default=sa.text("gen_random_uuid()"),
+        ),
+        sa.Column("sequence", sa.Integer(), nullable=False, autoincrement=True),
+        sa.Column("event_payload", psql.JSONB, nullable=False),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            nullable=False,
+            server_default=sa.text("NOW()"),
+        ),
+        sa.PrimaryKeyConstraint("id", "sequence"),
+    )
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    op.drop_table("user_events")

create_events.py

@@ -0,0 +1,147 @@
+import os
+from dotenv import load_dotenv
+import psycopg2
+import uuid
+import json
+
+load_dotenv()
+
+conn_params = {
+    "host": os.getenv("POSTGRES_HOST"),
+    "port": os.getenv("POSTGRES_PORT"),
+    "dbname": os.getenv("POSTGRES_DB"),
+    "user": os.getenv("POSTGRES_USER"),
+    "password": os.getenv("POSTGRES_PASSWORD"),
+}
+
+
+class User:
+
+    def __init__(self, cursor, name, age, hair_color):
+        self.cursor = cursor
+        self.id = uuid.uuid4()
+        self.name = name
+        self.age = age
+        self.hair_color = hair_color
+
+        self._fire_created_user_event()
+
+    def update_user_details(self, name=None, age=None, hair_color=None):
+        if name:
+            self.name = name
+        if age:
+            self.age = age
+        if hair_color:
+            self.hair_color = hair_color
+
+        self._fire_updated_user_event()
+
+    def delete_user(self):
+        self._fire_deleted_user_event()
+
+    def _fire_created_user_event(self):
+        event = CreateUserEvent(self)
+        self._fire_event(event)
+
+    def _fire_updated_user_event(self):
+        event = UpdateUserEvent(self)
+        self._fire_event(event)
+
+    def _fire_deleted_user_event(self):
+        event = DeleteUserEvent(self)
+        self._fire_event(event)
+
+    def _fire_event(self, event):
+        query = f"INSERT INTO user_events (event_payload) VALUES ('{event.to_json()}')"
+        self.cursor.execute(query)
+
+
+class CreateUserEvent:
+
+    def __init__(self, user):
+        self._user = user
+
+    def to_json(self):
+        return json.dumps(
+            {
+                "event_type": "user_created",
+                "event_payload": {
+                    "id": self._user.id,
+                    "name": self._user.name,
+                    "age": self._user.age,
+                    "hair_color": self._user.hair_color,
+                },
+            },
+            default=str,
+        )
+
+
+class UpdateUserEvent:
+    def __init__(self, user):
+        self._user = user
+
+    def to_json(self):
+        return json.dumps(
+            {
+                "event_type": "user_updated",
+                "event_payload": {
+                    "id": self._user.id,
+                    "name": self._user.name,
+                    "age": self._user.age,
+                    "hair_color": self._user.hair_color,
+                },
+            },
+            default=str,
+        )
+
+
+class DeleteUserEvent:
+    def __init__(self, user):
+        self._user = user
+
+    def to_json(self):
+        return json.dumps(
+            {
+                "event_type": "user_deleted",
+                "event_payload": {"id": self._user.id},
+            },
+            default=str,
+        )
+
+
+def main():
+
+    try:
+        # Connect to PostgreSQL
+        conn = psycopg2.connect(**conn_params)
+        cur = conn.cursor()
+
+        my_user = User(cursor=cur, name="John", age=95, hair_color="Gray")
+        my_user.update_user_details(age=96)
+        my_user.delete_user()
+
+        my_other_user = User(cursor=cur, name="Jane", age=3, hair_color="Fire Red")
+        my_other_user.update_user_details(age=15, hair_color="Golden Blonde")
+        my_other_user.update_user_details(age=35, hair_color="Touches of gray")
+
+        my_immutable_user = User(
+            cursor=cur, name="The Dude", age=33, hair_color="Muffin Orange"
+        )
+
+        # Commit the transaction
+        conn.commit()
+
+        print("Done")
+
+    except Exception as e:
+        print("Error:", e)
+
+    finally:
+        if cur:
+            cur.close()
+        if conn:
+            conn.close()
+
+
+if __name__ == "__main__":
+    main()

docker-compose.yml

@@ -0,0 +1,11 @@
+version: '3.8'
+
+services:
+  postgres:
+    image: postgres:17
+    environment:
+      POSTGRES_DB: ${POSTGRES_DB}
+      POSTGRES_USER: ${POSTGRES_USER}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+    ports:
+      - "${POSTGRES_PORT}:${POSTGRES_PORT}"

requirements.txt

@@ -0,0 +1,3 @@
+alembic
+python-dotenv
+psycopg2-binary

run_show.sh

@@ -0,0 +1,7 @@
+docker compose down
+docker compose up -d
+sleep 2s
+echo "Running migrations"
+alembic upgrade head
+echo "Creating events"
+python3 create_events.py