On Tue, Jul 31, 2018 at 01:39:07PM +0900, Kyotaro HORIGUCHI wrote: > "int backendID" is left in autovacuum.c as an unused variable.
Fixed. > "Even if this is *not* an atomic operation" ? Yeah, I am reworking this comment a bit more to map with the other PGPROC fields. > + * Mark the proc entry as owning this namespace which autovacuum uses to > + * decide if a temporary file entry can be marked as orphaned or not. Even > + * if this is an atomic operation, this can be safely done lock-less as no > + * temporary relations associated to it can be seen yet by autovacuum when > + * scanning pg_class. > + */ > + MyProc->tempNamespaceId = namespaceId; > > The comment looks wrong. After a crash having temp tables, > pg_class has orphaned temp relations and the namespace can be of > reconnected backends especially for low-numbered backends I don't quite understand your comment. InitProcess() initializes the field, so if a backend reconnects and uses the same proc slot as a backend which had a temporary namespace, then you would discard orphaned tables. Anyway, I have reworked it as such: + /* + * Mark MyProc as owning this namespace which other processes can use to + * decide if a temporary namespace is in use or not. We assume that + * assignment of namespaceId is an atomic operation. Even if it is not, + * there is as no temporary relations associated to it and the temporary + * namespace creation is not committed yet, so none of its contents can + * be seen yet if scanning pg_class or pg_namespace. + */ As new minor versions have been tagged, I am planning to commit this patch soon with some tweaks for the comments. As this introduces a new field to PGPROC, so back-patching the thing as-is would cause an ABI breakage. Are folks here fine with the new field added to the bottom of the structure for the backpatched versions, including v11? I have found about commit 13752743 which has also added a new field called isBackgroundWorker in the middle of PGPROC in a released branch, which looks to me like an ABI breakage... -- Michael
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