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Apache Arrow and PyArrow for Data Scientists

bookMotivation: The Limits of Row-Based Data

As a data scientist, you often work with datasets that are not only large but also growing rapidly in both size and complexity. Traditional approaches to storing and processing data, such as those used in relational databases or CSV files, rely on row-based memory layouts. While these formats have served many use cases well, they introduce significant inefficiencies when you need to analyze or manipulate large volumes of data — especially when your workflow involves operations on entire columns, such as statistical analysis, aggregations, or machine learning feature engineering.

Note
Definition

A row-based memory layout stores all the fields (columns) for a single record (row) together in memory, one after another. In contrast, a columnar memory layout stores all the values for a single column together, followed by the next column, and so on.
Row-based: ['row1_col1', 'row1_col2', ..., 'row1_colN', 'row2_col1', ...]
Columnar: ['col1_row1', 'col1_row2', ..., 'col1_rowN', 'col2_row1', ...]

When you process data using a row-based layout, every time you access or operate on a particular column, the computer must skip over the data for all the other columns in each row. This pattern leads to poor use of the CPU cache, which is designed to speed up repeated access to contiguous memory. Additionally, modern CPUs and libraries like NumPy and pandas are optimized for vectorized operations — processing many values of the same type at once. Row-based layouts make such operations less efficient, since the data for a single column is scattered throughout memory rather than stored contiguously. As a result, performance suffers, especially with large datasets and analytical workloads that focus on columns rather than individual rows.

question mark

Which of the following scenarios is likely to be suboptimal when using a row-based memory layout?

Select the correct answer

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Comment pouvons-nous l'améliorer ?

Merci pour vos commentaires !

Section 1. Chapitre 1

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bookMotivation: The Limits of Row-Based Data

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As a data scientist, you often work with datasets that are not only large but also growing rapidly in both size and complexity. Traditional approaches to storing and processing data, such as those used in relational databases or CSV files, rely on row-based memory layouts. While these formats have served many use cases well, they introduce significant inefficiencies when you need to analyze or manipulate large volumes of data — especially when your workflow involves operations on entire columns, such as statistical analysis, aggregations, or machine learning feature engineering.

Note
Definition

A row-based memory layout stores all the fields (columns) for a single record (row) together in memory, one after another. In contrast, a columnar memory layout stores all the values for a single column together, followed by the next column, and so on.
Row-based: ['row1_col1', 'row1_col2', ..., 'row1_colN', 'row2_col1', ...]
Columnar: ['col1_row1', 'col1_row2', ..., 'col1_rowN', 'col2_row1', ...]

When you process data using a row-based layout, every time you access or operate on a particular column, the computer must skip over the data for all the other columns in each row. This pattern leads to poor use of the CPU cache, which is designed to speed up repeated access to contiguous memory. Additionally, modern CPUs and libraries like NumPy and pandas are optimized for vectorized operations — processing many values of the same type at once. Row-based layouts make such operations less efficient, since the data for a single column is scattered throughout memory rather than stored contiguously. As a result, performance suffers, especially with large datasets and analytical workloads that focus on columns rather than individual rows.

question mark

Which of the following scenarios is likely to be suboptimal when using a row-based memory layout?

Select the correct answer

Tout était clair ?

Comment pouvons-nous l'améliorer ?

Merci pour vos commentaires !

Section 1. Chapitre 1
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