release-20.1: pgwire: de-strictify extended protocol handling #51249
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Previously, the protocol handler didn't permit simple queries during the extended protocol mode. I think this was done because the spec vaguely says that extended protocol commands must be ended with a SYNC command: https://www.postgresql.org/docs/9.3/protocol-flow.html#PROTOCOL-FLOW-EXT-QUERY However, an examination of the PostgreSQL source code shows that the extended protocol mode bit is only used for error recovery. If an error is encountered during extended protocol mode in Postgres, all commands are skipped until the next Sync. CockroachDB never implemented that behavior - instead, it used the extended protocol mode bit only to reject simple queries if they came before the Sync. This commit removes the extended protocol mode bit, as the use case we used it for was incorrect. It's unclear to me whether we need to re-add the bit for dealing with error cases, but we haven't needed it yet. Adding that might be follow-on work, and won't come in this PR. Release note (bug fix): prevent spurious "SimpleQuery not allowed while in extended protocol mode" errors.
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maddyblue
approved these changes
Jul 9, 2020
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Backport 1/1 commits from #51194.
/cc @cockroachdb/release
Fixes #33693.
Fixes #41511.
Previously, the protocol handler didn't permit simple queries during the
extended protocol mode. I think this was done because the spec vaguely
says that extended protocol commands must be ended with a SYNC command:
https://www.postgresql.org/docs/9.3/protocol-flow.html#PROTOCOL-FLOW-EXT-QUERY
However, an examination of the PostgreSQL source code shows that the
extended protocol mode bit is only used for error recovery. If an error
is encountered during extended protocol mode in Postgres, all commands
are skipped until the next Sync.
CockroachDB never implemented that behavior - instead, it used the
extended protocol mode bit only to reject simple queries if they came
before the Sync.
This commit removes the extended protocol mode bit, as the use case we
used it for was incorrect. It's unclear to me whether we need to re-add
the bit for dealing with error cases, but we haven't needed it yet.
Adding that might be follow-on work, and won't come in this PR.
Release note (bug fix): prevent spurious "SimpleQuery not allowed while
in extended protocol mode" errors.