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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