README.md

How to store OHLC time-series data: a SQL vs No-SQL vs Hybrid comparison

Complementary to the post at:

Dependencies

• Python 3.8.6+

• Install PostgreSQL 12. Then run start_and_setup_postgres.sh which should create a postgres database with a postgres user and start the service.

  Note: version 13 is not supported by TimescaleDB at the time of writing.

• MongoDB (installation page) with a performance database.

• TimescaleDB, just follow the installation page, and good luck.

Run

After installing dependencies, e.g. pip install -r requirements.txt or pipenv install, just:

python main.py

will take a few minutes.

You can tweak some settings, namely:

settings = {
    'num_prefill': 1000,
    'iterations': 100,
    'iterations_looped': 1,
    'records': 1000
}

where:

• num_prefill is the number of whole series to pre-fill the database in order to measure storage
• iterations is the number of operations to repeat an insert, read, delete, append
• iterations_looped is the number of times the group of same operations are repeated
• records is the number of records to append (other than 1)

The data

We download from Yahoo the OHLC data for Amazon on first run, then it's cached. The series has about 6000 daily records (or observations). Hence, when we insert a series, we add the whole 6000 records. When we append, we add some records to the bottom of an existing series.

The pre-fill generates random IDs but reuses the same Amazon series.

Contributing

To add tests, create a runner e.g. MySqlRunner taking inspiration from mongodb_runner.py or postgres_runner.py. The runner should:

• subclass the BaseRunner
• have an __enter__() method which creates the library/collection/table
• have an __exit__() method which removes the library/collection/table
• have a get_storage_size() method which measure the space on disk of the library/collection/table
• have the write_one(), read_one(), append_one(), delete_one() methods
• have a list_tickers() method

Then add the runner under the main() method in main.py.