HV00R
PostgreSQLERRORNotableForeign Data Wrapper ErrorHIGH confidence

fdw_unable_to_create_reply

Production Risk

High — foreign table queries fail to return data; application may see empty or error results.

What this means

A foreign data wrapper failed to construct a reply to send back from the remote side, typically indicating a protocol or memory error during FDW communication.

Why it happens
  1. 1FDW implementation encountered an unexpected error while preparing a response tuple.
  2. 2Out-of-memory condition on the remote server while building the reply.
  3. 3Network-level or protocol mismatch between FDW versions.
  4. 4Bug in a custom FDW when constructing return values.
How to reproduce
trigger — this will error
trigger — this will error
SELECT * FROM my_foreign_table;  -- custom FDW with reply-construction bug

expected output

ERROR:  HV00R: fdw_unable_to_create_reply

Fix 1

Update the FDW extension to a newer version

Update the FDW extension to a newer version
ALTER EXTENSION my_fdw UPDATE;

Why this works

Replaces buggy reply-construction code in the FDW shared library.

Fix 2

Check remote server memory and logs

Check remote server memory and logs
-- Review remote server PostgreSQL log for OOM or protocol errors

Why this works

Identifies if a resource exhaustion on the remote side is causing the reply failure.

What not to do

Do not ignore this error silently in application code

It indicates the FDW could not return data; results may be incomplete or absent

Sources
Official documentation ↗

PostgreSQL 17 — HV00R fdw_unable_to_create_reply

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