TableDescriptor

TableDescriptor is a metadata construct used in database systems, data catalogs, and data processing frameworks to describe the structure and properties of a table. It serves as a canonical representation of a table’s schema, storage characteristics, and related metadata, enabling consistent interpretation by query planners, executors, and management tools.

A typical TableDescriptor includes several key elements. The table identifier usually consists of a name and an optional schema or database. The column definitions specify each column’s name, data type, and nullability, often accompanied by default values and descriptions. Constraints such as primary keys, unique constraints, and foreign keys may be included. Partitioning and distribution details describe how data is organized across files or nodes. Storage-related properties cover format (for example, CSV, Parquet, ORC), compression, location, and whether the table is external or managed. Additional metadata may provide ownership, description, creation and modification timestamps, statistics, and access controls.

TableDescriptors are used by the system’s catalog or metastore to validate queries, plan execution, enforce schema integrity, and support schema evolution. They are typically created or altered through DDL statements or programmatic APIs and may be versioned or cached for efficiency. In data lake and warehouse environments, TableDescriptor helps bridge logical schema with physical storage and drives features such as optimization, compatibility checks, and data governance.

In practice, TableDescriptor provides a stable, queryable view of a table’s structure and properties, enabling consistent interactions across tooling and pipelines.