Here is a summary of the text in 1 paragraph: PostgreSQL provides a built-in function called `generate_series()` that can be used to quickly create large datasets for testing and visualization. This function returns sequential numbers or dates between a start parameter and stop parameter, and can be modified to include step parameters to increment values by a certain amount. The function can also be used in conjunction with other SQL functions to add static and dynamic content to each row, and can be joined with multiple sets of data to create a Cartesian product. By understanding how to use `generate_series()` and date math, users can quickly generate large datasets for testing purposes, including time-series data with varying cardinalities and different lengths of time. The function can also be used to create more realistic-looking data by using custom user-defined functions and mathematical functions to add shape and trends to the generated data.