Hi team,
I am evaluating an approach to change the scale of a numeric column from numeric(18,2) to numeric(18,4) in a large table, aiming to avoid the cost of a full table rewrite.
The proposed approach involves directly updating the PostgreSQL system catalog:
UPDATE pg_attribute
SET atttypmod = (18 << 16 | 4) + 4
WHERE attrelid = 'table'::regclass AND attname = 'column';
Before considering this in practice, I would like to validate a few points:
- Is this approach considered safe from a data integrity perspective?
- Is there a risk of inconsistencies in the internal representation of the
numeric type (especially regarding scale)? - Could this impact indexes, functions, or aggregation operations?
- Is there any official recommendation or prior experience using this approach in production environments?
- Are there additional risks related to rollback, maintenance, or future operations (e.g., dump/restore, upgrades)?
The goal is to determine whether this alternative is viable, or if we should stick with more standard approaches (e.g., shadow column, incremental migration, etc.).
If anyone has experience with a similar scenario, your insights would be appreciated.
Thanks.
