Revert "Fix race in Parallel Hash Join batch cleanup."

This reverts commit 378802e.
This reverts commit 3b8981b.

Discussion: https://postgr.es/m/CA%2BhUKGJmcqAE3MZeDCLLXa62cWM0AJbKmp2JrJYaJ86bz36LFA%40mail.gmail.com

Author: macdice

src/backend/executor/nodeHash.c

@@ -246,10 +246,10 @@ MultiExecParallelHash(HashState *node)
 	 */
 	pstate = hashtable->parallel_state;
 	build_barrier = &pstate->build_barrier;
-	Assert(BarrierPhase(build_barrier) >= PHJ_BUILD_ALLOCATE);
+	Assert(BarrierPhase(build_barrier) >= PHJ_BUILD_ALLOCATING);
 	switch (BarrierPhase(build_barrier))
 	{
-		case PHJ_BUILD_ALLOCATE:
+		case PHJ_BUILD_ALLOCATING:
 
 			/*
 			 * Either I just allocated the initial hash table in
@@ -259,7 +259,7 @@ MultiExecParallelHash(HashState *node)
 			BarrierArriveAndWait(build_barrier, WAIT_EVENT_HASH_BUILD_ALLOCATE);
 			/* Fall through. */
 
-		case PHJ_BUILD_HASH_INNER:
+		case PHJ_BUILD_HASHING_INNER:
 
 			/*
 			 * It's time to begin hashing, or if we just arrived here then
@@ -271,10 +271,10 @@ MultiExecParallelHash(HashState *node)
 			 * below.
 			 */
 			if (PHJ_GROW_BATCHES_PHASE(BarrierAttach(&pstate->grow_batches_barrier)) !=
-				PHJ_GROW_BATCHES_ELECT)
+				PHJ_GROW_BATCHES_ELECTING)
 				ExecParallelHashIncreaseNumBatches(hashtable);
 			if (PHJ_GROW_BUCKETS_PHASE(BarrierAttach(&pstate->grow_buckets_barrier)) !=
-				PHJ_GROW_BUCKETS_ELECT)
+				PHJ_GROW_BUCKETS_ELECTING)
 				ExecParallelHashIncreaseNumBuckets(hashtable);
 			ExecParallelHashEnsureBatchAccessors(hashtable);
 			ExecParallelHashTableSetCurrentBatch(hashtable, 0);
@@ -333,22 +333,15 @@ MultiExecParallelHash(HashState *node)
 	hashtable->nbuckets = pstate->nbuckets;
 	hashtable->log2_nbuckets = my_log2(hashtable->nbuckets);
 	hashtable->totalTuples = pstate->total_tuples;
-
-	/*
-	 * Unless we're completely done and the batch state has been freed, make
-	 * sure we have accessors.
-	 */
-	if (BarrierPhase(build_barrier) < PHJ_BUILD_FREE)
-		ExecParallelHashEnsureBatchAccessors(hashtable);
+	ExecParallelHashEnsureBatchAccessors(hashtable);
 
 	/*
 	 * The next synchronization point is in ExecHashJoin's HJ_BUILD_HASHTABLE
-	 * case, which will bring the build phase to PHJ_BUILD_RUN (if it isn't
+	 * case, which will bring the build phase to PHJ_BUILD_DONE (if it isn't
 	 * there already).
 	 */
-	Assert(BarrierPhase(build_barrier) == PHJ_BUILD_HASH_OUTER ||
-		   BarrierPhase(build_barrier) == PHJ_BUILD_RUN ||
-		   BarrierPhase(build_barrier) == PHJ_BUILD_FREE);
+	Assert(BarrierPhase(build_barrier) == PHJ_BUILD_HASHING_OUTER ||
+		   BarrierPhase(build_barrier) == PHJ_BUILD_DONE);
 }
 
 /* ----------------------------------------------------------------
@@ -596,8 +589,8 @@ ExecHashTableCreate(HashState *state, List *hashOperators, List *hashCollations,
 		 * Attach to the build barrier.  The corresponding detach operation is
 		 * in ExecHashTableDetach.  Note that we won't attach to the
 		 * batch_barrier for batch 0 yet.  We'll attach later and start it out
-		 * in PHJ_BATCH_PROBE phase, because batch 0 is allocated up front and
-		 * then loaded while hashing (the standard hybrid hash join
+		 * in PHJ_BATCH_PROBING phase, because batch 0 is allocated up front
+		 * and then loaded while hashing (the standard hybrid hash join
 		 * algorithm), and we'll coordinate that using build_barrier.
 		 */
 		build_barrier = &pstate->build_barrier;
@@ -610,7 +603,7 @@ ExecHashTableCreate(HashState *state, List *hashOperators, List *hashCollations,
 		 * SharedHashJoinBatch objects and the hash table for batch 0.  One
 		 * backend will be elected to do that now if necessary.
 		 */
-		if (BarrierPhase(build_barrier) == PHJ_BUILD_ELECT &&
+		if (BarrierPhase(build_barrier) == PHJ_BUILD_ELECTING &&
 			BarrierArriveAndWait(build_barrier, WAIT_EVENT_HASH_BUILD_ELECT))
 		{
 			pstate->nbatch = nbatch;
@@ -631,7 +624,7 @@ ExecHashTableCreate(HashState *state, List *hashOperators, List *hashCollations,
 		/*
 		 * The next Parallel Hash synchronization point is in
 		 * MultiExecParallelHash(), which will progress it all the way to
-		 * PHJ_BUILD_RUN.  The caller must not return control from this
+		 * PHJ_BUILD_DONE.  The caller must not return control from this
 		 * executor node between now and then.
 		 */
 	}
@@ -1067,7 +1060,7 @@ ExecParallelHashIncreaseNumBatches(HashJoinTable hashtable)
 	ParallelHashJoinState *pstate = hashtable->parallel_state;
 	int			i;
 
-	Assert(BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_HASH_INNER);
+	Assert(BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_HASHING_INNER);
 
 	/*
 	 * It's unlikely, but we need to be prepared for new participants to show
@@ -1076,7 +1069,7 @@ ExecParallelHashIncreaseNumBatches(HashJoinTable hashtable)
 	 */
 	switch (PHJ_GROW_BATCHES_PHASE(BarrierPhase(&pstate->grow_batches_barrier)))
 	{
-		case PHJ_GROW_BATCHES_ELECT:
+		case PHJ_GROW_BATCHES_ELECTING:
 
 			/*
 			 * Elect one participant to prepare to grow the number of batches.
@@ -1194,13 +1187,13 @@ ExecParallelHashIncreaseNumBatches(HashJoinTable hashtable)
 			}
 			/* Fall through. */
 
-		case PHJ_GROW_BATCHES_REALLOCATE:
+		case PHJ_GROW_BATCHES_ALLOCATING:
 			/* Wait for the above to be finished. */
 			BarrierArriveAndWait(&pstate->grow_batches_barrier,
-								 WAIT_EVENT_HASH_GROW_BATCHES_REALLOCATE);
+								 WAIT_EVENT_HASH_GROW_BATCHES_ALLOCATE);
 			/* Fall through. */
 
-		case PHJ_GROW_BATCHES_REPARTITION:
+		case PHJ_GROW_BATCHES_REPARTITIONING:
 			/* Make sure that we have the current dimensions and buckets. */
 			ExecParallelHashEnsureBatchAccessors(hashtable);
 			ExecParallelHashTableSetCurrentBatch(hashtable, 0);
@@ -1213,7 +1206,7 @@ ExecParallelHashIncreaseNumBatches(HashJoinTable hashtable)
 								 WAIT_EVENT_HASH_GROW_BATCHES_REPARTITION);
 			/* Fall through. */
 
-		case PHJ_GROW_BATCHES_DECIDE:
+		case PHJ_GROW_BATCHES_DECIDING:
 
 			/*
 			 * Elect one participant to clean up and decide whether further
@@ -1268,7 +1261,7 @@ ExecParallelHashIncreaseNumBatches(HashJoinTable hashtable)
 			}
 			/* Fall through. */
 
-		case PHJ_GROW_BATCHES_FINISH:
+		case PHJ_GROW_BATCHES_FINISHING:
 			/* Wait for the above to complete. */
 			BarrierArriveAndWait(&pstate->grow_batches_barrier,
 								 WAIT_EVENT_HASH_GROW_BATCHES_FINISH);
@@ -1508,7 +1501,7 @@ ExecParallelHashIncreaseNumBuckets(HashJoinTable hashtable)
 	HashMemoryChunk chunk;
 	dsa_pointer chunk_s;
 
-	Assert(BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_HASH_INNER);
+	Assert(BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_HASHING_INNER);
 
 	/*
 	 * It's unlikely, but we need to be prepared for new participants to show
@@ -1517,7 +1510,7 @@ ExecParallelHashIncreaseNumBuckets(HashJoinTable hashtable)
 	 */
 	switch (PHJ_GROW_BUCKETS_PHASE(BarrierPhase(&pstate->grow_buckets_barrier)))
 	{
-		case PHJ_GROW_BUCKETS_ELECT:
+		case PHJ_GROW_BUCKETS_ELECTING:
 			/* Elect one participant to prepare to increase nbuckets. */
 			if (BarrierArriveAndWait(&pstate->grow_buckets_barrier,
 									 WAIT_EVENT_HASH_GROW_BUCKETS_ELECT))
@@ -1546,13 +1539,13 @@ ExecParallelHashIncreaseNumBuckets(HashJoinTable hashtable)
 			}
 			/* Fall through. */
 
-		case PHJ_GROW_BUCKETS_REALLOCATE:
+		case PHJ_GROW_BUCKETS_ALLOCATING:
 			/* Wait for the above to complete. */
 			BarrierArriveAndWait(&pstate->grow_buckets_barrier,
-								 WAIT_EVENT_HASH_GROW_BUCKETS_REALLOCATE);
+								 WAIT_EVENT_HASH_GROW_BUCKETS_ALLOCATE);
 			/* Fall through. */
 
-		case PHJ_GROW_BUCKETS_REINSERT:
+		case PHJ_GROW_BUCKETS_REINSERTING:
 			/* Reinsert all tuples into the hash table. */
 			ExecParallelHashEnsureBatchAccessors(hashtable);
 			ExecParallelHashTableSetCurrentBatch(hashtable, 0);
@@ -1708,7 +1701,7 @@ ExecParallelHashTableInsert(HashJoinTable hashtable,
 
 		/* Try to load it into memory. */
 		Assert(BarrierPhase(&hashtable->parallel_state->build_barrier) ==
-			   PHJ_BUILD_HASH_INNER);
+			   PHJ_BUILD_HASHING_INNER);
 		hashTuple = ExecParallelHashTupleAlloc(hashtable,
 											   HJTUPLE_OVERHEAD + tuple->t_len,
 											   &shared);
@@ -2862,7 +2855,7 @@ ExecParallelHashTupleAlloc(HashJoinTable hashtable, size_t size,
 	if (pstate->growth != PHJ_GROWTH_DISABLED)
 	{
 		Assert(curbatch == 0);
-		Assert(BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_HASH_INNER);
+		Assert(BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_HASHING_INNER);
 
 		/*
 		 * Check if our space limit would be exceeded.  To avoid choking on
@@ -2982,7 +2975,7 @@ ExecParallelHashJoinSetUpBatches(HashJoinTable hashtable, int nbatch)
 		{
 			/* Batch 0 doesn't need to be loaded. */
 			BarrierAttach(&shared->batch_barrier);
-			while (BarrierPhase(&shared->batch_barrier) < PHJ_BATCH_PROBE)
+			while (BarrierPhase(&shared->batch_barrier) < PHJ_BATCH_PROBING)
 				BarrierArriveAndWait(&shared->batch_barrier, 0);
 			BarrierDetach(&shared->batch_barrier);
 		}
@@ -3055,11 +3048,14 @@ ExecParallelHashEnsureBatchAccessors(HashJoinTable hashtable)
 	}
 
 	/*
-	 * We should never see a state where the batch-tracking array is freed,
-	 * because we should have given up sooner if we join when the build
-	 * barrier has reached the PHJ_BUILD_FREE phase.
+	 * It's possible for a backend to start up very late so that the whole
+	 * join is finished and the shm state for tracking batches has already
+	 * been freed by ExecHashTableDetach().  In that case we'll just leave
+	 * hashtable->batches as NULL so that ExecParallelHashJoinNewBatch() gives
+	 * up early.
 	 */
-	Assert(DsaPointerIsValid(pstate->batches));
+	if (!DsaPointerIsValid(pstate->batches))
+		return;
 
 	/* Use hash join memory context. */
 	oldcxt = MemoryContextSwitchTo(hashtable->hashCxt);
@@ -3140,7 +3136,7 @@ ExecHashTableDetachBatch(HashJoinTable hashtable)
 			 * longer attached, but since there is no way it's moving after
 			 * this point it seems safe to make the following assertion.
 			 */
-			Assert(BarrierPhase(&batch->batch_barrier) == PHJ_BATCH_FREE);
+			Assert(BarrierPhase(&batch->batch_barrier) == PHJ_BATCH_DONE);
 
 			/* Free shared chunks and buckets. */
 			while (DsaPointerIsValid(batch->chunks))
@@ -3179,17 +3175,9 @@ ExecHashTableDetachBatch(HashJoinTable hashtable)
 void
 ExecHashTableDetach(HashJoinTable hashtable)
 {
-	ParallelHashJoinState *pstate = hashtable->parallel_state;
-
-	/*
-	 * If we're involved in a parallel query, we must either have got all the
-	 * way to PHJ_BUILD_RUN, or joined too late and be in PHJ_BUILD_FREE.
-	 */
-	Assert(!pstate ||
-		   BarrierPhase(&pstate->build_barrier) >= PHJ_BUILD_RUN);
-
-	if (pstate && BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_RUN)
+	if (hashtable->parallel_state)
 	{
+		ParallelHashJoinState *pstate = hashtable->parallel_state;
 		int			i;
 
 		/* Make sure any temporary files are closed. */
@@ -3205,22 +3193,17 @@ ExecHashTableDetach(HashJoinTable hashtable)
 		}
 
 		/* If we're last to detach, clean up shared memory. */
-		if (BarrierArriveAndDetach(&pstate->build_barrier))
+		if (BarrierDetach(&pstate->build_barrier))
 		{
-			/*
-			 * Late joining processes will see this state and give up
-			 * immediately.
-			 */
-			Assert(BarrierPhase(&pstate->build_barrier) == PHJ_BUILD_FREE);
-
 			if (DsaPointerIsValid(pstate->batches))
 			{
 				dsa_free(hashtable->area, pstate->batches);
 				pstate->batches = InvalidDsaPointer;
 			}
 		}
+
+		hashtable->parallel_state = NULL;
 	}
-	hashtable->parallel_state = NULL;
 }
 
 /*