Columnfirst

Columnfirst is a concept used in computer science to describe a data processing approach in which the primary unit of access and computation is a column rather than a row. The term is often used to discuss memory layout, algorithm design, and data storage strategies that favor column-wise organization. In practice, columnfirst encompasses both column-major storage, where elements of the same column are stored contiguously, and column-oriented processing patterns that operate on entire columns before moving to others.

In memory, column-first or column-major layouts are exemplified by languages such as Fortran and MATLAB, where column vectors are aligned in memory to maximize spatial locality during column operations. This arrangement aligns well with vectorized operations and can improve cache utilization when computations repeatedly touch a limited set of columns.

In data analytics and databases, columnfirst refers to columnar storage and query execution that process data column by column. Columnar formats such as Parquet or ORC enable reading only the needed columns, reducing I/O and improving compression. Column-first processing is particularly effective for analytic workloads that aggregate or scan a small subset of attributes across many records.

Benefits of columnfirst include improved cache locality for column operations, better data compression, and opportunities for vectorization. Trade-offs include suboptimal performance for row-wise or object-oriented workloads, potential fragmentation when mixing column-first with row-oriented structures, and increased complexity in algorithms that must bridge column and row perspectives.

See also: row-major order, column-major order, columnar database, data layout, vectorization.