Thread: BUG #17565: Extended query protocol incorrectly sets TBLOCK_STARTED even though multiple queries can be executed
BUG #17565: Extended query protocol incorrectly sets TBLOCK_STARTED even though multiple queries can be executed
From
PG Bug reporting form
Date:
The following bug has been logged on the website: Bug reference: 17565 Logged by: Matt Jibson Email address: matt.jibson@gmail.com PostgreSQL version: 14.4 Operating system: linux Description: The extended query protocol is most often used with the 4 messages in the sequence: Parse, Bind, Execute, Sync. Parse, Bind, and Execute all call start_xact_command, which will change blockState to TBLOCK_STARTED. However it is within the protocol spec to instead do: Parse, Bind, Execute, Parse, Bind, Execute, Sync. That is: issue two query executions and then a Sync. The Npgsql driver does exactly this at its startup. The doc comment for TBLOCK_STARTED says "running single-query transaction", but this is a case where a driver can escape that restriction which is assumed by the rest of the code. For example, there are various things differentiate between STARTED and INPROGRESS or IMPLICIT_INPROGRESS: PreventInTransactionBlock, IsInTransactionBlock. Some statements (VACUUM, DISCARD ALL) use those functions to prevent their execution in a multi statement context, but those can be escaped using the extended protocol. The protocol docs have an excellent section on how to handle multiple statements in a simple query. Assuming that this is indeed a bug and is fixed somehow, the extended protocol may need its docs changed to similarly describe what happens in this case.
Re: BUG #17565: Extended query protocol incorrectly sets TBLOCK_STARTED even though multiple queries can be executed
From
Tom Lane
Date:
PG Bug reporting form <noreply@postgresql.org> writes: > The extended query protocol is most often used with the 4 messages in the > sequence: Parse, Bind, Execute, Sync. Parse, Bind, and Execute all call > start_xact_command, which will change blockState to TBLOCK_STARTED. However > it is within the protocol spec to instead do: Parse, Bind, Execute, Parse, > Bind, Execute, Sync. That is: issue two query executions and then a Sync. > The Npgsql driver does exactly this at its startup. > The doc comment for TBLOCK_STARTED says "running single-query transaction", > but this is a case where a driver can escape that restriction which is > assumed by the rest of the code. For example, there are various things > differentiate between STARTED and INPROGRESS or IMPLICIT_INPROGRESS: > PreventInTransactionBlock, IsInTransactionBlock. Some statements (VACUUM, > DISCARD ALL) use those functions to prevent their execution in a multi > statement context, but those can be escaped using the extended protocol. Hmmm ... I think this is a duplicate of a bug that we just fixed last week. Please see https://www.postgresql.org/message-id/flat/17434-d9f7a064ce2a88a3%40postgresql.org https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=f92944137 and let us know (preferably on that thread) if you think there's still more to do. regards, tom lane