Tom Lane 1e22fad652 Further refine _SPI_execute_plan's rule for atomic execution.
Commit 2dc1deaea turns out to have been still a brick shy of a load,
because CALL statements executing within a plpgsql exception block
could still pass the wrong snapshot to stable functions within the
CALL's argument list.  That happened because standard_ProcessUtility
forces isAtomicContext to true if IsTransactionBlock is true, which
it always will be inside a subtransaction.  Then ExecuteCallStmt
would think it does not need to push a new snapshot --- but
_SPI_execute_plan didn't do so either, since it thought it was in
nonatomic mode.

The best fix for this seems to be for _SPI_execute_plan to operate
in atomic execution mode if IsSubTransaction() is true, even when the
SPI context as a whole is non-atomic.  This makes _SPI_execute_plan
have the same rules about when non-atomic execution is allowed as
_SPI_commit/_SPI_rollback have about when COMMIT/ROLLBACK are allowed,
which seems appropriately symmetric.  (If anyone ever tries to allow
COMMIT/ROLLBACK inside a subtransaction, this would all need to be
rethought ... but I'm unconvinced that such a thing could be logically
consistent at all.)

For further consistency, also check IsSubTransaction() in
SPI_inside_nonatomic_context.  That does not matter for its
one present-day caller StartTransaction, which can't be reached
inside a subtransaction.  But if any other callers ever arise,
they'd presumably want this definition.

Per bug #18656 from Alexander Alehin.  Back-patch to all
supported branches, like previous fixes in this area.

Discussion: https://postgr.es/m/18656-cade1780866ef66c@postgresql.org
2024-11-13 14:15:08 +05:00
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PostgreSQL Database Management System

This directory contains the source code distribution of the PostgreSQL database management system.

PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.

Copyright and license information can be found in the file COPYRIGHT.

General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/17/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/17/installation.html.

The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.

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