How to Cast PostgreSQL JSONB to Float for Arithmetic Operations?

Casting PostgreSQL's JSONB to Float

When attempting to perform arithmetic operations on a PostgreSQL JSONB type column containing numeric values, you may encounter errors due to type mismatches. This article demonstrates how to overcome this issue and successfully cast JSONB values to floats.

The root cause of the errors in the provided query is the attempt to add a numeric value (1.0) to a JSONB value, which results in the "operator does not exist" error. To address this, you can employ casting to convert the JSONB value to a float before performing the operation.

However, simply casting the JSONB value to float may not suffice, as PostgreSQL offers two options for accessing JSON values:

• json_data->'position': Returns a JSON value, which cannot be directly cast to a float.
• json_data->>'position': Returns a text value, which can be cast to a float using ::float.

In your specific case, since you know that the lat values are all JSON numbers, you can use the following query to cast them to floats:

SELECT (json_data->>'position'->>'lat')::float + 1.0 AS lat
FROM updates
LIMIT 5;

This revised query should successfully cast the JSONB lat values to floats, enabling you to perform the desired operations.

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