The FDW raised SQLSTATE HV009 because a required callback function or returned pointer was NULL.
fdw_invalid_use_of_null_pointer surfaces when a PostgreSQL foreign data wrapper (FDW) passes or returns a NULL pointer where the server expects a valid address. Remove or replace the NULL by implementing every required FDW callback and validating objects before access to resolve the error.
fdw_invalid_use_of_null_pointer
PostgreSQL throws SQLSTATE HV009 when an FDW extension tries to dereference a NULL pointer. The server core calls FDW callback hooks expecting valid memory addresses. If the FDW author leaves a required function unassigned or returns NULL instead of a valid Datum or struct, PostgreSQL aborts with this error.
Developers usually meet this error while writing custom FDWs, upgrading third-party wrappers, or running queries that push down scans to remote tables.
End users notice the failure as soon as the defective FDW path is planned or executed.
Missing callback implementations, such as GetForeignRelSize, IterateForeignScan, or BeginForeignModify, leave PostgreSQL with NULL pointers that it later dereferences.
Returning NULL instead of a tuple slot, path, or string from an implemented callback also triggers the condition.
Binary incompatibility between a compiled FDW and the current PostgreSQL server version can corrupt function pointers to NULL.
Incorrect memory context usage that frees objects too early can make previously valid pointers NULL or invalid.
First, identify which FDW raised the exception by checking the server log backtrace.
The shared library name often appears right before the error.
Recompile the FDW against the exact PostgreSQL header files for the running server version, then restart PostgreSQL.
Audit the FDW source code: ensure every required callback in the FdwRoutine struct is assigned.
Replace NULL with stubs that set an ERROR if the function is called unexpectedly.
Validate all return paths in callbacks so they never propagate NULL where PostgreSQL expects data.
Upgrading PostgreSQL without rebuilding an FDW commonly leads to incompatible struct sizes and NULL pointers. Rebuild the extension and run ALTER EXTENSION ... UPDATE.
Developers adding write support might forget to implement ExecForeignInsert.
Implement the function or set .ExecForeignInsert = NULL only if write operations are safely blocked.
Queries using IMPORT FOREIGN SCHEMA on an unmaintained FDW may hit a NULL pointer in the ImportForeignSchema callback.
Patch or disable that feature in the wrapper.
Always compile FDWs with the same major PostgreSQL version used in production, and automate rebuilds during upgrades.
Follow the official FDW API documentation and provide function stubs for every new callback introduced in newer versions.
Add ASSERTs inside the FDW to verify non-NULL pointers before returning to the server core.
fdw_dynamic_parameter_value_needed (HV00B) fires when an FDW cannot supply a parameter value during planning.
Implement the GetForeignRelParamInfo callback to fix it.
fdw_invalid_attribute_value (HV024) appears when the FDW returns an attribute outside the expected range. Double-check tuple mappings.
fdw_unable_to_create_execution (HV014) signals inability to build the plan. Ensure the FDW's PlannerInfo hooks succeed.
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No. Only sessions using a faulty FDW or foreign table encounter the error; local tables remain safe.
Yes. Drop or ALTER FOREIGN TABLE ... NO INHERIT to prevent planner selection of the FDW until it is fixed.
Minor upgrades usually preserve ABI stability, but rebuilding is safest when upgrading across major versions (e.g., 14 to 15).
Galaxy’s editor surfaces server logs next to your query, letting you pinpoint the failing FDW quickly and share the diagnosis with teammates.
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