diff --git a/fe/src/main/java/org/apache/impala/planner/AggregationNode.java b/fe/src/main/java/org/apache/impala/planner/AggregationNode.java
index 2778a7f..c31f448 100644
--- a/fe/src/main/java/org/apache/impala/planner/AggregationNode.java
+++ b/fe/src/main/java/org/apache/impala/planner/AggregationNode.java
@@ -323,10 +323,12 @@
       if (useStreamingPreagg_) {
         // We can execute a streaming preagg without any buffers by passing through rows,
         // but that is a very low performance mode of execution if the aggregation reduces
-        // its input significantly. Instead reserve memory for one buffer and 64kb of hash
-        // tables per partition. We don't need to reserve memory for large rows since they
-        // can be passed through if needed.
-        perInstanceMinReservation = (bufferSize + 64 * 1024) * PARTITION_FANOUT;
+        // its input significantly. Instead reserve memory for one buffer per partition
+        // and at least 64kb for hash tables per partition. We must reserve at least one
+        // full buffer for hash tables for the suballocator to subdivide. We don't need to
+        // reserve memory for large rows since they can be passed through if needed.
+        perInstanceMinReservation = bufferSize * PARTITION_FANOUT +
+            Math.max(64 * 1024 * PARTITION_FANOUT, bufferSize);
       } else {
         long minBuffers = PARTITION_FANOUT + 1 + (aggInfo_.needsSerialize() ? 1 : 0);
         // Two of the buffers need to be buffers large enough to hold the maximum-sized
diff --git a/testdata/workloads/functional-planner/queries/PlannerTest/max-row-size.test b/testdata/workloads/functional-planner/queries/PlannerTest/max-row-size.test
index 5a0a76c..d563444 100644
--- a/testdata/workloads/functional-planner/queries/PlannerTest/max-row-size.test
+++ b/testdata/workloads/functional-planner/queries/PlannerTest/max-row-size.test
@@ -150,7 +150,7 @@
 group by 1, 2
 having count(*) = 1
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=110.00MB
+Max Per-Host Resource Reservation: Memory=111.00MB
 Per-Host Resource Estimates: Memory=251.12MB
 
 F04:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -176,11 +176,11 @@
 |  tuple-ids=2 row-size=33B cardinality=4690314
 |
 F02:PLAN FRAGMENT [HASH(l_orderkey)] hosts=3 instances=3
-Per-Host Resources: mem-estimate=85.12MB mem-reservation=64.00MB
+Per-Host Resources: mem-estimate=85.12MB mem-reservation=65.00MB
 03:AGGREGATE [STREAMING]
 |  output: count(*)
 |  group by: l_orderkey, o_orderstatus
-|  mem-estimate=54.12MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=54.12MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=2 row-size=33B cardinality=4690314
 |
 02:HASH JOIN [INNER JOIN, PARTITIONED]
@@ -224,7 +224,7 @@
 select distinct *
 from tpch_parquet.lineitem
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=79.00MB
+Max Per-Host Resource Reservation: Memory=80.00MB
 Per-Host Resource Estimates: Memory=3.31GB
 
 F02:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -248,10 +248,10 @@
 |  tuple-ids=1 row-size=263B cardinality=6001215
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=3
-Per-Host Resources: mem-estimate=1.69GB mem-reservation=33.00MB
+Per-Host Resources: mem-estimate=1.69GB mem-reservation=34.00MB
 01:AGGREGATE [STREAMING]
 |  group by: tpch_parquet.lineitem.l_orderkey, tpch_parquet.lineitem.l_partkey, tpch_parquet.lineitem.l_suppkey, tpch_parquet.lineitem.l_linenumber, tpch_parquet.lineitem.l_quantity, tpch_parquet.lineitem.l_extendedprice, tpch_parquet.lineitem.l_discount, tpch_parquet.lineitem.l_tax, tpch_parquet.lineitem.l_returnflag, tpch_parquet.lineitem.l_linestatus, tpch_parquet.lineitem.l_shipdate, tpch_parquet.lineitem.l_commitdate, tpch_parquet.lineitem.l_receiptdate, tpch_parquet.lineitem.l_shipinstruct, tpch_parquet.lineitem.l_shipmode, tpch_parquet.lineitem.l_comment
-|  mem-estimate=1.62GB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=1.62GB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=263B cardinality=6001215
 |
 00:SCAN HDFS [tpch_parquet.lineitem, RANDOM]
@@ -268,7 +268,7 @@
 from tpch_parquet.lineitem
 group by 1, 2
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=81.00MB
+Max Per-Host Resource Reservation: Memory=82.00MB
 Per-Host Resource Estimates: Memory=482.91MB
 
 F02:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -293,11 +293,11 @@
 |  tuple-ids=1 row-size=32B cardinality=6001215
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=3
-Per-Host Resources: mem-estimate=281.46MB mem-reservation=33.00MB
+Per-Host Resources: mem-estimate=281.46MB mem-reservation=34.00MB
 01:AGGREGATE [STREAMING]
 |  output: group_concat(l_linestatus, ',')
 |  group by: l_orderkey, l_partkey
-|  mem-estimate=201.46MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=201.46MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=32B cardinality=6001215
 |
 00:SCAN HDFS [tpch_parquet.lineitem, RANDOM]
diff --git a/testdata/workloads/functional-planner/queries/PlannerTest/mt-dop-validation.test b/testdata/workloads/functional-planner/queries/PlannerTest/mt-dop-validation.test
index 9f80785..dcebf07 100644
--- a/testdata/workloads/functional-planner/queries/PlannerTest/mt-dop-validation.test
+++ b/testdata/workloads/functional-planner/queries/PlannerTest/mt-dop-validation.test
@@ -95,11 +95,11 @@
 |  tuple-ids=1 row-size=16B cardinality=unavailable
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=9
-Per-Host Resources: mem-estimate=432.00MB mem-reservation=99.00MB
+Per-Host Resources: mem-estimate=432.00MB mem-reservation=102.00MB
 01:AGGREGATE [STREAMING]
 |  output: count(int_col)
 |  group by: bigint_col
-|  mem-estimate=128.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=128.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=16B cardinality=unavailable
 |
 00:SCAN HDFS [functional_parquet.alltypes, RANDOM]
diff --git a/testdata/workloads/functional-planner/queries/PlannerTest/resource-requirements.test b/testdata/workloads/functional-planner/queries/PlannerTest/resource-requirements.test
index 90035c1..fe3fd41 100644
--- a/testdata/workloads/functional-planner/queries/PlannerTest/resource-requirements.test
+++ b/testdata/workloads/functional-planner/queries/PlannerTest/resource-requirements.test
@@ -375,8 +375,8 @@
    mem-estimate=80.00MB mem-reservation=0B
    tuple-ids=0 row-size=8B cardinality=6001215
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=41.50MB
-Per-Host Resource Estimates: Memory=123.00MB
+Max Per-Host Resource Reservation: Memory=42.50MB
+Per-Host Resource Estimates: Memory=124.00MB
 
 F02:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
 |  Per-Host Resources: mem-estimate=0B mem-reservation=0B
@@ -400,11 +400,11 @@
 |  tuple-ids=1 row-size=16B cardinality=1563438
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=3
-Per-Host Resources: mem-estimate=113.00MB mem-reservation=33.00MB
+Per-Host Resources: mem-estimate=114.00MB mem-reservation=34.00MB
 01:AGGREGATE [STREAMING]
 |  output: count(*)
 |  group by: l_orderkey
-|  mem-estimate=33.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=34.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=16B cardinality=1563438
 |
 00:SCAN HDFS [tpch_parquet.lineitem, RANDOM]
@@ -415,8 +415,8 @@
    mem-estimate=80.00MB mem-reservation=0B
    tuple-ids=0 row-size=8B cardinality=6001215
 ---- PARALLELPLANS
-Max Per-Host Resource Reservation: Memory=75.50MB
-Per-Host Resource Estimates: Memory=246.00MB
+Max Per-Host Resource Reservation: Memory=77.50MB
+Per-Host Resource Estimates: Memory=248.00MB
 
 F02:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
 |  Per-Host Resources: mem-estimate=0B mem-reservation=0B
@@ -440,11 +440,11 @@
 |  tuple-ids=1 row-size=16B cardinality=1563438
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=6
-Per-Host Resources: mem-estimate=226.00MB mem-reservation=66.00MB
+Per-Host Resources: mem-estimate=228.00MB mem-reservation=68.00MB
 01:AGGREGATE [STREAMING]
 |  output: count(*)
 |  group by: l_orderkey
-|  mem-estimate=33.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=34.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=16B cardinality=1563438
 |
 00:SCAN HDFS [tpch_parquet.lineitem, RANDOM]
@@ -1548,7 +1548,7 @@
    mem-estimate=80.00MB mem-reservation=0B
    tuple-ids=0 row-size=78B cardinality=600122
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=71.75MB
+Max Per-Host Resource Reservation: Memory=72.75MB
 Per-Host Resource Estimates: Memory=344.33MB
 
 F09:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -1643,10 +1643,10 @@
 |  tuple-ids=2 row-size=70B cardinality=575772
 |
 F02:PLAN FRAGMENT [HASH(l_orderkey)] hosts=3 instances=3
-Per-Host Resources: mem-estimate=47.33MB mem-reservation=37.75MB
+Per-Host Resources: mem-estimate=47.33MB mem-reservation=38.75MB
 04:AGGREGATE [STREAMING]
 |  group by: l_orderkey, l_partkey, l_suppkey, l_linenumber, l_comment
-|  mem-estimate=42.58MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=42.58MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=2 row-size=70B cardinality=575772
 |
 03:HASH JOIN [INNER JOIN, PARTITIONED]
@@ -1688,7 +1688,7 @@
    mem-estimate=80.00MB mem-reservation=0B
    tuple-ids=0 row-size=78B cardinality=600122
 ---- PARALLELPLANS
-Max Per-Host Resource Reservation: Memory=139.75MB
+Max Per-Host Resource Reservation: Memory=141.75MB
 Per-Host Resource Estimates: Memory=684.91MB
 
 F09:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -1799,10 +1799,10 @@
 |  tuple-ids=2 row-size=70B cardinality=575772
 |
 F02:PLAN FRAGMENT [HASH(l_orderkey)] hosts=3 instances=6
-Per-Host Resources: mem-estimate=90.91MB mem-reservation=71.75MB
+Per-Host Resources: mem-estimate=90.91MB mem-reservation=73.75MB
 04:AGGREGATE [STREAMING]
 |  group by: l_orderkey, l_partkey, l_suppkey, l_linenumber, l_comment
-|  mem-estimate=42.58MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=42.58MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=2 row-size=70B cardinality=575772
 |
 03:HASH JOIN [INNER JOIN, PARTITIONED]
@@ -1968,7 +1968,7 @@
    mem-estimate=88.00MB mem-reservation=0B
    tuple-ids=2 row-size=16B cardinality=6001215
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=150.12MB
+Max Per-Host Resource Reservation: Memory=152.12MB
 Per-Host Resource Estimates: Memory=511.55MB
 
 F07:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -2000,11 +2000,11 @@
 |  tuple-ids=6 row-size=100B cardinality=575772
 |
 F02:PLAN FRAGMENT [HASH(l_orderkey)] hosts=3 instances=3
-Per-Host Resources: mem-estimate=115.78MB mem-reservation=83.12MB
+Per-Host Resources: mem-estimate=115.78MB mem-reservation=84.12MB
 08:AGGREGATE [STREAMING]
 |  output: sum(l_quantity)
 |  group by: c_name, c_custkey, o_orderkey, o_orderdate, o_totalprice
-|  mem-estimate=60.40MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=60.40MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=6 row-size=100B cardinality=575772
 |
 07:HASH JOIN [LEFT SEMI JOIN, PARTITIONED]
@@ -2025,11 +2025,11 @@
 |  |  tuple-ids=4 row-size=24B cardinality=1563438
 |  |
 |  F04:PLAN FRAGMENT [RANDOM] hosts=3 instances=3
-|  Per-Host Resources: mem-estimate=127.36MB mem-reservation=33.00MB
+|  Per-Host Resources: mem-estimate=127.36MB mem-reservation=34.00MB
 |  04:AGGREGATE [STREAMING]
 |  |  output: sum(l_quantity)
 |  |  group by: l_orderkey
-|  |  mem-estimate=39.36MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  |  mem-estimate=39.36MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  |  tuple-ids=4 row-size=24B cardinality=1563438
 |  |
 |  03:SCAN HDFS [tpch.lineitem, RANDOM]
@@ -2098,7 +2098,7 @@
    mem-estimate=88.00MB mem-reservation=0B
    tuple-ids=2 row-size=16B cardinality=6001215
 ---- PARALLELPLANS
-Max Per-Host Resource Reservation: Memory=254.88MB
+Max Per-Host Resource Reservation: Memory=258.88MB
 Per-Host Resource Estimates: Memory=967.22MB
 
 F07:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -2130,11 +2130,11 @@
 |  tuple-ids=6 row-size=100B cardinality=575772
 |
 F02:PLAN FRAGMENT [HASH(l_orderkey)] hosts=3 instances=6
-Per-Host Resources: mem-estimate=175.68MB mem-reservation=120.88MB
+Per-Host Resources: mem-estimate=175.68MB mem-reservation=122.88MB
 08:AGGREGATE [STREAMING]
 |  output: sum(l_quantity)
 |  group by: c_name, c_custkey, o_orderkey, o_orderdate, o_totalprice
-|  mem-estimate=60.40MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=60.40MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=6 row-size=100B cardinality=575772
 |
 07:HASH JOIN [LEFT SEMI JOIN, PARTITIONED]
@@ -2163,11 +2163,11 @@
 |  |  tuple-ids=4 row-size=24B cardinality=1563438
 |  |
 |  F04:PLAN FRAGMENT [RANDOM] hosts=3 instances=6
-|  Per-Host Resources: mem-estimate=254.73MB mem-reservation=66.00MB
+|  Per-Host Resources: mem-estimate=254.73MB mem-reservation=68.00MB
 |  04:AGGREGATE [STREAMING]
 |  |  output: sum(l_quantity)
 |  |  group by: l_orderkey
-|  |  mem-estimate=39.36MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  |  mem-estimate=39.36MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  |  tuple-ids=4 row-size=24B cardinality=1563438
 |  |
 |  03:SCAN HDFS [tpch.lineitem, RANDOM]
@@ -2452,7 +2452,7 @@
    mem-estimate=88.00MB mem-reservation=0B
    tuple-ids=0 row-size=66B cardinality=150000
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=102.94MB
+Max Per-Host Resource Reservation: Memory=103.94MB
 Per-Host Resource Estimates: Memory=473.94MB
 WARNING: The following tables are missing relevant table and/or column statistics.
 tpch_nested_parquet.customer
@@ -2478,10 +2478,10 @@
 |  tuple-ids=6 row-size=58B cardinality=1500000
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=3
-Per-Host Resources: mem-estimate=345.94MB mem-reservation=68.94MB
+Per-Host Resources: mem-estimate=345.94MB mem-reservation=69.94MB
 09:AGGREGATE [STREAMING]
 |  group by: c_name, o1.o_orderkey, o2.o_orderstatus
-|  mem-estimate=128.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=128.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=6 row-size=58B cardinality=1500000
 |
 01:SUBPLAN
@@ -2531,7 +2531,7 @@
    mem-estimate=88.00MB mem-reservation=0B
    tuple-ids=0 row-size=66B cardinality=150000
 ---- PARALLELPLANS
-Max Per-Host Resource Reservation: Memory=205.88MB
+Max Per-Host Resource Reservation: Memory=207.88MB
 Per-Host Resource Estimates: Memory=947.88MB
 WARNING: The following tables are missing relevant table and/or column statistics.
 tpch_nested_parquet.customer
@@ -2557,10 +2557,10 @@
 |  tuple-ids=6 row-size=58B cardinality=1500000
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=6
-Per-Host Resources: mem-estimate=691.88MB mem-reservation=137.88MB
+Per-Host Resources: mem-estimate=691.88MB mem-reservation=139.88MB
 09:AGGREGATE [STREAMING]
 |  group by: c_name, o1.o_orderkey, o2.o_orderstatus
-|  mem-estimate=128.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=128.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=6 row-size=58B cardinality=1500000
 |
 01:SUBPLAN
diff --git a/testdata/workloads/functional-planner/queries/PlannerTest/spillable-buffer-sizing.test b/testdata/workloads/functional-planner/queries/PlannerTest/spillable-buffer-sizing.test
index 115a8bd..719b07d 100644
--- a/testdata/workloads/functional-planner/queries/PlannerTest/spillable-buffer-sizing.test
+++ b/testdata/workloads/functional-planner/queries/PlannerTest/spillable-buffer-sizing.test
@@ -603,7 +603,7 @@
 group by 1, 2
 having count(*) = 1
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=84.00MB
+Max Per-Host Resource Reservation: Memory=85.00MB
 Per-Host Resource Estimates: Memory=225.12MB
 
 F04:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -629,11 +629,11 @@
 |  tuple-ids=2 row-size=33B cardinality=4690314
 |
 F02:PLAN FRAGMENT [HASH(l_orderkey)] hosts=3 instances=3
-Per-Host Resources: mem-estimate=71.12MB mem-reservation=50.00MB
+Per-Host Resources: mem-estimate=71.12MB mem-reservation=51.00MB
 03:AGGREGATE [STREAMING]
 |  output: count(*)
 |  group by: l_orderkey, o_orderstatus
-|  mem-estimate=54.12MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=54.12MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=2 row-size=33B cardinality=4690314
 |
 02:HASH JOIN [INNER JOIN, PARTITIONED]
@@ -672,8 +672,8 @@
    mem-estimate=80.00MB mem-reservation=0B
    tuple-ids=0 row-size=8B cardinality=6001215
 ---- PARALLELPLANS
-Max Per-Host Resource Reservation: Memory=117.00MB
-Per-Host Resource Estimates: Memory=357.00MB
+Max Per-Host Resource Reservation: Memory=119.00MB
+Per-Host Resource Estimates: Memory=359.00MB
 
 F04:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
 |  Per-Host Resources: mem-estimate=0B mem-reservation=0B
@@ -698,11 +698,11 @@
 |  tuple-ids=2 row-size=33B cardinality=4690314
 |
 F02:PLAN FRAGMENT [HASH(l_orderkey)] hosts=3 instances=6
-Per-Host Resources: mem-estimate=83.00MB mem-reservation=83.00MB
+Per-Host Resources: mem-estimate=85.00MB mem-reservation=85.00MB
 03:AGGREGATE [STREAMING]
 |  output: count(*)
 |  group by: l_orderkey, o_orderstatus
-|  mem-estimate=33.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=34.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=2 row-size=33B cardinality=4690314
 |
 02:HASH JOIN [INNER JOIN, PARTITIONED]
@@ -753,7 +753,7 @@
 select distinct *
 from tpch_parquet.lineitem
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=67.00MB
+Max Per-Host Resource Reservation: Memory=68.00MB
 Per-Host Resource Estimates: Memory=3.31GB
 
 F02:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -777,10 +777,10 @@
 |  tuple-ids=1 row-size=263B cardinality=6001215
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=3
-Per-Host Resources: mem-estimate=1.69GB mem-reservation=33.00MB
+Per-Host Resources: mem-estimate=1.69GB mem-reservation=34.00MB
 01:AGGREGATE [STREAMING]
 |  group by: tpch_parquet.lineitem.l_orderkey, tpch_parquet.lineitem.l_partkey, tpch_parquet.lineitem.l_suppkey, tpch_parquet.lineitem.l_linenumber, tpch_parquet.lineitem.l_quantity, tpch_parquet.lineitem.l_extendedprice, tpch_parquet.lineitem.l_discount, tpch_parquet.lineitem.l_tax, tpch_parquet.lineitem.l_returnflag, tpch_parquet.lineitem.l_linestatus, tpch_parquet.lineitem.l_shipdate, tpch_parquet.lineitem.l_commitdate, tpch_parquet.lineitem.l_receiptdate, tpch_parquet.lineitem.l_shipinstruct, tpch_parquet.lineitem.l_shipmode, tpch_parquet.lineitem.l_comment
-|  mem-estimate=1.62GB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=1.62GB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=263B cardinality=6001215
 |
 00:SCAN HDFS [tpch_parquet.lineitem, RANDOM]
@@ -791,7 +791,7 @@
    mem-estimate=80.00MB mem-reservation=0B
    tuple-ids=0 row-size=263B cardinality=6001215
 ---- PARALLELPLANS
-Max Per-Host Resource Reservation: Memory=134.00MB
+Max Per-Host Resource Reservation: Memory=136.00MB
 Per-Host Resource Estimates: Memory=6.62GB
 
 F02:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
@@ -815,10 +815,10 @@
 |  tuple-ids=1 row-size=263B cardinality=6001215
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=6
-Per-Host Resources: mem-estimate=3.39GB mem-reservation=66.00MB
+Per-Host Resources: mem-estimate=3.39GB mem-reservation=68.00MB
 01:AGGREGATE [STREAMING]
 |  group by: tpch_parquet.lineitem.l_orderkey, tpch_parquet.lineitem.l_partkey, tpch_parquet.lineitem.l_suppkey, tpch_parquet.lineitem.l_linenumber, tpch_parquet.lineitem.l_quantity, tpch_parquet.lineitem.l_extendedprice, tpch_parquet.lineitem.l_discount, tpch_parquet.lineitem.l_tax, tpch_parquet.lineitem.l_returnflag, tpch_parquet.lineitem.l_linestatus, tpch_parquet.lineitem.l_shipdate, tpch_parquet.lineitem.l_commitdate, tpch_parquet.lineitem.l_receiptdate, tpch_parquet.lineitem.l_shipinstruct, tpch_parquet.lineitem.l_shipmode, tpch_parquet.lineitem.l_comment
-|  mem-estimate=1.62GB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=1.62GB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=263B cardinality=6001215
 |
 00:SCAN HDFS [tpch_parquet.lineitem, RANDOM]
@@ -834,7 +834,7 @@
 from functional_parquet.alltypestiny
 group by string_col
 ---- DISTRIBUTEDPLAN
-Max Per-Host Resource Reservation: Memory=67.00MB
+Max Per-Host Resource Reservation: Memory=68.00MB
 Per-Host Resource Estimates: Memory=272.00MB
 WARNING: The following tables are missing relevant table and/or column statistics.
 functional_parquet.alltypestiny
@@ -861,11 +861,11 @@
 |  tuple-ids=1 row-size=24B cardinality=unavailable
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=3
-Per-Host Resources: mem-estimate=144.00MB mem-reservation=33.00MB
+Per-Host Resources: mem-estimate=144.00MB mem-reservation=34.00MB
 01:AGGREGATE [STREAMING]
 |  output: count(*)
 |  group by: string_col
-|  mem-estimate=128.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=128.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=24B cardinality=unavailable
 |
 00:SCAN HDFS [functional_parquet.alltypestiny, RANDOM]
@@ -876,7 +876,7 @@
    mem-estimate=16.00MB mem-reservation=0B
    tuple-ids=0 row-size=16B cardinality=unavailable
 ---- PARALLELPLANS
-Max Per-Host Resource Reservation: Memory=134.00MB
+Max Per-Host Resource Reservation: Memory=136.00MB
 Per-Host Resource Estimates: Memory=544.00MB
 WARNING: The following tables are missing relevant table and/or column statistics.
 functional_parquet.alltypestiny
@@ -903,11 +903,11 @@
 |  tuple-ids=1 row-size=24B cardinality=unavailable
 |
 F00:PLAN FRAGMENT [RANDOM] hosts=3 instances=6
-Per-Host Resources: mem-estimate=288.00MB mem-reservation=66.00MB
+Per-Host Resources: mem-estimate=288.00MB mem-reservation=68.00MB
 01:AGGREGATE [STREAMING]
 |  output: count(*)
 |  group by: string_col
-|  mem-estimate=128.00MB mem-reservation=33.00MB spill-buffer=2.00MB
+|  mem-estimate=128.00MB mem-reservation=34.00MB spill-buffer=2.00MB
 |  tuple-ids=1 row-size=24B cardinality=unavailable
 |
 00:SCAN HDFS [functional_parquet.alltypestiny, RANDOM]
diff --git a/testdata/workloads/functional-query/queries/QueryTest/admission-reject-min-reservation.test b/testdata/workloads/functional-query/queries/QueryTest/admission-reject-min-reservation.test
index 940fd6e..a84ec34 100644
--- a/testdata/workloads/functional-query/queries/QueryTest/admission-reject-min-reservation.test
+++ b/testdata/workloads/functional-query/queries/QueryTest/admission-reject-min-reservation.test
@@ -5,7 +5,7 @@
 ---- CATCH
 minimum memory reservation is greater than memory available to the
  query for buffer reservations. Memory reservation needed given the
- current plan: 67.00 MB. Set mem_limit to at least 142.00 MB.
+ current plan: 68.00 MB. Set mem_limit to at least 143.00 MB.
 ====
 ---- QUERY
 set mem_limit=150mb;
@@ -13,14 +13,14 @@
 ---- CATCH
 minimum memory reservation needed is greater than pool max mem resources.
  Pool max mem resources: 10.00 MB.
- Cluster-wide memory reservation needed: 201.00 MB
+ Cluster-wide memory reservation needed: 204.00 MB
 ====
 ---- QUERY
 set buffer_pool_limit=10mb;
 select distinct * from functional_parquet.alltypesagg
 ---- CATCH
 minimum memory reservation is greater than memory available to the query
- for buffer reservations. Increase the buffer_pool_limit to 67.00 MB.
+ for buffer reservations. Increase the buffer_pool_limit to 68.00 MB.
 ====
 ---- QUERY
 set mem_limit=1024;
diff --git a/testdata/workloads/functional-query/queries/QueryTest/aggregation.test b/testdata/workloads/functional-query/queries/QueryTest/aggregation.test
index de1c507..3cc2f20 100644
--- a/testdata/workloads/functional-query/queries/QueryTest/aggregation.test
+++ b/testdata/workloads/functional-query/queries/QueryTest/aggregation.test
@@ -1319,3 +1319,15 @@
 ---- TYPES
 tinyint
 ====
+---- QUERY
+# IMPALA-5855: pre-aggregation does not reserve enough memory with 2MB buffers.
+# The pre-aggregation in this query is estimated to consume enough memory for the planner
+# to use 2MB buffers.
+set debug_action="-1:PREPARE:SET_DENY_RESERVATION_PROBABILITY@1.0";
+select count(*) from (
+    select distinct l_orderkey, l_comment from tpch_parquet.lineitem) v
+---- RESULTS
+6001198
+---- TYPES
+bigint
+====