08006

At a glance

SQLSTATE 08006 is connection_failure in Class 08. 08006 names failure of an established connection. The fixed paths include postgres_fdw cancel/connection-loss handling and COPY failure handling; they do not define one universal primary or severity, and this batch intentionally has no generic socket run.

Meaning

The fixed source paths show why this class cannot have one universal message. In postgres_fdw, a failed cancel request reports a WARNING while the established foreign connection is being handled; this warning is a diagnostic from the cancel path, not by itself proof that the client session was terminated. In the COPY paths, an open-transaction client EOF is reported as an ERROR, while the older COPY-to-stdout path reports FATAL when the output connection is lost. The severity and phase are part of the meaning: these branches must not be collapsed into “the socket broke”.

An ERROR branch can leave a still-connected session in INERROR when it occurs inside an explicit transaction, so the caller must recover with ROLLBACK or an appropriate savepoint before issuing unrelated SQL. A FATAL branch ends the backend connection; there is no session on which to send ROLLBACK. A client socket that has already reached EOF can also leave the client with no SQLSTATE at all. The evidence here confirms these source branches, but does not claim that every ordinary network disconnect emits 08006.

Branch guide

Diagnosis

Correlate backend PID, operation, server log fields, and the client exception. A client-side broken socket can expose SQLSTATE null, while a server-side FDW or COPY path may emit 08006 with path-specific text. Distinguish it from 08001 (no connection was established), 08007/40003 (completion uncertainty), and a normal statement error before deciding whether work may have completed.

Check severity and lifecycle together. WARNING means the FDW cancel branch may still have a live local session; ERROR means inspect INERROR versus IDLE and recover the transaction if needed; FATAL means the backend is gone. If the client saw EOF before an ErrorResponse, the absence of a SQLSTATE is expected evidence of a lost protocol exchange, not proof of 08006.

Response

Discard a connection the pool marks broken, reconcile remote or non-idempotent work, and retry only a complete operation under an explicit idempotency policy. The fixed source paths are useful boundaries here; no artificial RAISE, timeout, or ordinary socket close is counted as observed 08006.

For an independently still-connected ERROR case, roll back the failed explicit transaction (or roll back to a savepoint intentionally established around the operation), then decide whether the complete operation can be retried. That generic transaction rule does not prove that the COPY client-EOF socket is reusable: the source branch has already detected EOF on that client connection. For FATAL or an already-lost socket, establish a fresh session and reconcile the outcome before replaying anything. Autocommit does not make a remote or COPY operation idempotent; it only changes the local transaction boundary.

Messages

The fixed branches include these distinct diagnostics:

• WARNING could not send cancel request: %s from the postgres_fdw cancel path; the libpq error text is dynamic.
• WARNING could not get result of cancel request: %s from the same FDW path; the returned connection error text is dynamic.
• FATAL connection lost during COPY to stdout in the fixed 10.23 COPY path.
• ERROR unexpected EOF on client connection with an open transaction in the fixed 18.6/10.23 COPY client-EOF paths.

The evidence keeps these as separate variants and does not turn an ordinary client-side null SQLSTATE into 08006.

The ERROR and FATAL variants have different recovery contracts even when their text mentions a connection. The COPY client-EOF ERROR branch detects that the client socket is already gone; it does not establish a reusable socket or a path for sending ROLLBACK. The FATAL variant closes the backend as part of the COPY-to-stdout path. The selected batch has no natural 08006 run, so these distinctions come from fixed source paths and the documented transaction boundary rather than a synthetic socket experiment.

Representative case

This page has no selected natural SQL run. The structured evidence records a source or definition boundary; a client-side RAISE would not represent a backend mechanism.

Versions

The generated facts table records the locked catalogue snapshots and earliest observed definition. This page has no selected natural SQL run; its fixed REL_18_6/REL_10_23 source boundary must not be read as an observed runtime result or as a claim about every intermediate release.

Related

• 08001 — sqlclient_unable_to_establish_sqlconnection
• 08007 — transaction_resolution_unknown
• 40003 — related condition

Sources

• src.fdw-connection-failure.18.6 — contrib/postgres_fdw/connection.c at REL_18_6 commit 724edf9bde9d356724ad384a2e196edc3c9f80f7; fixed blob SHA-256 67fc002657f2c7df6d93cbf99c933cbc103907d1857ed77aedbb85099ea4dda0 (source).
• src.copy-connection-failure.10.23 — src/backend/commands/copy.c at REL_10_23 commit 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; fixed blob SHA-256 0edb032be1ce8d8c90efc28e504aa9e298a2cd26cd374c85da6da0e33ed0915c (source).
• src.copy-client-eof.18.6 — src/backend/commands/copyfromparse.c at REL_18_6 commit 724edf9bde9d356724ad384a2e196edc3c9f80f7; fixed blob SHA-256 bc42754023579cd782a3cb3f144ad2c2c3d3aa46119eb7567fcdb05f2d445571 (source).
• src.copy-client-eof.10.23 — src/backend/commands/copy.c at REL_10_23 commit 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; fixed blob SHA-256 0edb032be1ce8d8c90efc28e504aa9e298a2cd26cd374c85da6da0e33ed0915c (source).
• src.calls.REL_18_6 / src.calls.REL_10_23 — fixed local call scans, SHA-256 9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf / 00d16d3eb01b71ccf1b245c8f3102f9d0ec9f36fb02777b8dd1b99fcb263040c; these scans preserve the resolved call context used by the claims.