What is the Maximum Number of Columns Allowed in a PostgreSQL SELECT Query?

Maximum number of columns in PostgreSQL SELECT query

When starting a PostgreSQL project, it is crucial to understand the limitations of the platform. One such limit is the maximum number of columns allowed in a SELECT query.

Answer:

According to PostgreSQL limitations, the maximum number of columns in a SELECT query is between 250 and 1600, depending on the data type used.

Explanation:

This limitation stems from the maximum PostgreSQL row width of 8kB (one page). Therefore, rows cannot span multiple pages. Although TOAST handles large column values, the number of columns that can fit within this limit depends on the size of the data type used.

Consequences and recommendations:

Approaching or exceeding the column limit can cause performance issues. If you anticipate encountering a large number of columns, consider using other data management techniques such as arrays, composite types, or JSON.

In summary, the maximum number of columns in a PostgreSQL SELECT query is affected by the data type and ranges from 250 to 1600. Understanding this limit is critical to avoid performance bottlenecks and ensure optimal database performance.

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