Propagate parallel VACUUM's buffer access strategy.

petergeoghegan · petergeoghegan · commit 49f49defe7c0 · 2021-04-05T14:56:56.000-07:00
Parallel VACUUM relied on global variable state from the leader process being propagated to workers on fork(). Commit b4af70c removed most uses of global variables inside vacuumlazy.c, but did not account for the buffer access strategy state. To fix, propagate the state through shared memory instead. Per buildfarm failures on elver, curculio, and morepork. Many thanks to Thomas Munro for off-list assistance with this issue.
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
@@ -194,6 +194,11 @@ typedef struct LVShared
 	Oid			relid;
 	int			elevel;
 
+	/*
+	 * Buffer access strategy from leader
+	 */
+	BufferAccessStrategy bstrategy;
+
 	/*
 	 * An indication for vacuum workers to perform either index vacuum or
 	 * index cleanup.  first_time is true only if for_cleanup is true and
@@ -3480,6 +3485,7 @@ begin_parallel_vacuum(LVRelState *vacrel, BlockNumber nblocks,
 	MemSet(shared, 0, est_shared);
 	shared->relid = RelationGetRelid(vacrel->rel);
 	shared->elevel = elevel;
+	shared->bstrategy = vacrel->bstrategy;
 	shared->maintenance_work_mem_worker =
 		(nindexes_mwm > 0) ?
 		maintenance_work_mem / Min(parallel_workers, nindexes_mwm) :
@@ -3720,6 +3726,7 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
 	vacrel.rel = rel;
 	vacrel.indrels = indrels;
 	vacrel.nindexes = nindexes;
+	vacrel.bstrategy = lvshared->bstrategy;
 	vacrel.indstats = (IndexBulkDeleteResult **)
 		palloc0(nindexes * sizeof(IndexBulkDeleteResult *));
 
