0001-Vacuum-allow-using-more-than-1GB-work-mem.patch

From 7b47b59d89bf3edaeb11c4ffe3660f3d5b7b86de Mon Sep 17 00:00:00 2001
From: Claudio Freire <klaussfreire@gmail.com>
Date: Fri, 2 Sep 2016 23:21:01 -0300
Subject: [PATCH 1/2] Vacuum: allow using more than 1GB work mem

Turns the palloc for dead_tuples into a huge allocation to allow
using more than 1GB worth of dead_tuples, saving index scans on
heavily bloated tables
---
 src/backend/commands/vacuumlazy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 231e92d..2c98da4 100644
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -1952,7 +1952,7 @@ lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks)
 	{
 		maxtuples = (vac_work_mem * 1024L) / sizeof(ItemPointerData);
 		maxtuples = Min(maxtuples, INT_MAX);
-		maxtuples = Min(maxtuples, MaxAllocSize / sizeof(ItemPointerData));
+		maxtuples = Min(maxtuples, MaxAllocHugeSize / sizeof(ItemPointerData));
 
 		/* curious coding here to ensure the multiplication can't overflow */
 		if ((BlockNumber) (maxtuples / LAZY_ALLOC_TUPLES) > relblocks)
@@ -1969,7 +1969,7 @@ lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks)
 	vacrelstats->num_dead_tuples = 0;
 	vacrelstats->max_dead_tuples = (int) maxtuples;
 	vacrelstats->dead_tuples = (ItemPointer)
-		palloc(maxtuples * sizeof(ItemPointerData));
+		MemoryContextAllocHuge(CurrentMemoryContext, maxtuples * sizeof(ItemPointerData));
 }
 
 /*
-- 
2.6.6