wip-limit-slab-allocated-tuple-size.diff

diff --git i/src/backend/replication/logical/reorderbuffer.c w/src/backend/replication/logical/reorderbuffer.c
index cd2a0111825..9a5b5530e75 100644
--- i/src/backend/replication/logical/reorderbuffer.c
+++ w/src/backend/replication/logical/reorderbuffer.c
@@ -421,6 +421,9 @@ ReorderBufferReturnChange(ReorderBuffer *rb, ReorderBufferChange *change)
 	pfree(change);
 }
 
+#define TUPLEBUF_MAX_SIZE 1024
+//MaxHeapTupleSize
+
 /*
  * Get a fresh ReorderBufferTupleBuf fitting at least a tuple of size
  * tuple_len (excluding header overhead).
@@ -434,22 +437,20 @@ ReorderBufferGetTupleBuf(ReorderBuffer *rb, Size tuple_len)
 	alloc_len = tuple_len + SizeofHeapTupleHeader;
 
 	/*
-	 * Most tuples are below MaxHeapTupleSize, so we use a slab allocator for
-	 * those. Thus always allocate at least MaxHeapTupleSize. Note that tuples
-	 * generated for oldtuples can be bigger, as they don't have out-of-line
-	 * toast columns.
+	 * Most tuples are below TUPLEBUF_MAX_SIZE, so we use a slab allocator for
+	 * those. Thus always allocate at least TUPLEBUF_MAX_SIZE.
 	 */
-	if (alloc_len < MaxHeapTupleSize)
-		alloc_len = MaxHeapTupleSize;
+	if (alloc_len < TUPLEBUF_MAX_SIZE)
+		alloc_len = TUPLEBUF_MAX_SIZE;
 
 
 	/* if small enough, check the slab cache */
-	if (alloc_len <= MaxHeapTupleSize && rb->nr_cached_tuplebufs)
+	if (alloc_len <= TUPLEBUF_MAX_SIZE && rb->nr_cached_tuplebufs)
 	{
 		rb->nr_cached_tuplebufs--;
 		tuple = slist_container(ReorderBufferTupleBuf, node,
 								slist_pop_head_node(&rb->cached_tuplebufs));
-		Assert(tuple->alloc_tuple_size == MaxHeapTupleSize);
+		Assert(tuple->alloc_tuple_size == TUPLEBUF_MAX_SIZE);
 #ifdef USE_ASSERT_CHECKING
 		memset(&tuple->tuple, 0xa9, sizeof(HeapTupleData));
 		VALGRIND_MAKE_MEM_UNDEFINED(&tuple->tuple, sizeof(HeapTupleData));
@@ -480,7 +481,7 @@ void
 ReorderBufferReturnTupleBuf(ReorderBuffer *rb, ReorderBufferTupleBuf *tuple)
 {
 	/* check whether to put into the slab cache, oversized tuples never are */
-	if (tuple->alloc_tuple_size == MaxHeapTupleSize &&
+	if (tuple->alloc_tuple_size == TUPLEBUF_MAX_SIZE &&
 		rb->nr_cached_tuplebufs < max_cached_tuplebufs)
 	{
 		rb->nr_cached_tuplebufs++;
@@ -2588,6 +2589,9 @@ ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
 		restored++;
 	}
 
+	elog(DEBUG5, "restored %zu changes in XID %u into memory",
+		 restored, txn->xid);
+
 	return restored;
 }