PostgreSQL raises fdw_function_sequence_error (SQLSTATE HV010) when an FDW callback is called out of the required order.
fdw_function_sequence_error occurs when PostgreSQL detects that a foreign-data wrapper (FDW) calls its callback functions in the wrong order. Update or patch the FDW, then reload or recreate the foreign table to restore normal query execution.
fdw_function_sequence_error
PostgreSQL returns SQLSTATE HV010 with the message fdw_function_sequence_error when a foreign-data wrapper violates the expected order of its callback functions. The executor checks that BeginForeignScan, IterateForeignScan, ReScanForeignScan, and EndForeignScan run in the documented sequence. Any deviation triggers this error.
The issue surfaces while running SELECT, INSERT, UPDATE, or DELETE statements against a foreign table.
Although the error appears to end-users, the root cause usually lives in the FDW extension code, version mismatch, or an unexpected backend crash that left stale state.
PostgreSQL raises the error if IterateForeignScan is invoked after EndForeignScan, or if ReScanForeignScan is skipped when needed.
A mismatched server and client FDW version, an unclean extension upgrade, or a buggy driver can all corrupt the call sequence.
Operational issues such as abrupt backend termination, out-of-order parallel workers, or cancelled queries that leave orphaned plan state may also provoke the sequence check on the next access.
Most users should first upgrade the offending FDW extension to the latest compatible version. Use ALTER EXTENSION … UPDATE to apply bug fixes.
Restart the backend or reload the extension with LOAD if the library was rebuilt in place.
If the error persists, drop and recreate the foreign table to reset cached callback pointers. As a temporary workaround, disable the foreign table with ALTER FOREIGN TABLE … DISABLE TRIGGER USER; then re-enable it after validation.
Upgrading PostgreSQL without rebuilding community FDWs often triggers the error.
Recompile the extension against the new server headers to align callback signatures.
If using postgres_fdw and hitting the error after altering a remote table, run ANALYZE LOCAL; then REFRESH PUBLICATION on the remote to refresh cached descriptors.
Pin extension versions in your deployment scripts and rebuild them during every PostgreSQL major upgrade.
Monitor server logs for HV010 entries to catch sequence violations early.
In Galaxy, store your FDW management SQL in an endorsed Collection so every engineer runs the same, vetted upgrade commands, preventing drift.
invalid_cursor_state (34000) appears when application cursors violate protocol, while fdw_unable_to_create_execution (HV014) points to setup failures before the scan begins. Both may stem from the same buggy FDW and can be resolved by upgrading or patching the extension.
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An older foreign-data wrapper library may not honor the new callback contract introduced by a later PostgreSQL version.
Backend termination or statement cancellation can leave the FDW in an inconsistent state that surfaces on the next call.
Upgrading the core server without recompiling third-party FDWs breaks symbol alignment and callback sequencing.
Developers of in-house FDWs sometimes omit a required ReScanForeignScan or call EndForeignScan too early.
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No. fdw_function_sequence_error reflects a control-flow issue inside the FDW, not data corruption. Updating or recompiling the extension usually resolves it without data loss.
Ignoring is risky. The server will keep throwing the error until the FDW sequence issue is fixed. Apply the patch to restore stable queries.
Galaxy lets teams version their FDW maintenance scripts in shared Collections, ensuring consistent upgrades across environments and preventing sequence mismatches.
A restart clears in-memory state and may temporarily hide the error, but you should still upgrade or patch the FDW to prevent recurrence.
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