fdwOutputPrecision

fdwOutputPrecision is a configuration option found in some foreign data wrappers (FDWs) used with PostgreSQL and other database systems. It controls how many decimal places are emitted for numeric values retrieved from a foreign server when they are returned to the local database session. The setting is typically per-foreign table or per-foreign server, depending on the FDW implementation, and is applied during the data fetch and type conversion process. The value is an integer representing the number of fractional digits to display; values are rounded to that precision. If the value is null or not specified, the FDW may use the remote type’s natural precision or the FDW’s default.

Pronounced effects: rounding may alter numerical results compared with the remote data, which can affect comparisons, aggregations, and ordering in queries using the retrieved data. It does not generally alter the data stored on the remote server; it only affects how results are presented locally.

Relation to other settings: fdwOutputPrecision is independent from input precision during INSERT or UPDATE; input conversions are handled by other options such as data type mappings. Some FDWs might allow a range of values or special tokens to request fixed precision vs. dynamic precision.

Security and compatibility: users should ensure that applying fixed precision does not hide meaningful data or violate precision requirements for business logic. Documentation for the specific FDW is required to understand supported values and placement (server/table) and interaction with casting.

In summary, fdwOutputPrecision provides a mechanism to standardize decimal output from foreign data sources, trading exact remote precision for a consistent local representation.