diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java
index 47e0373..6f359c5 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java
@@ -83,6 +83,7 @@
 import org.apache.hyracks.algebricks.core.config.AlgebricksConfig;
 import org.apache.hyracks.algebricks.core.jobgen.impl.JobGenContext;
 import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
+import org.apache.hyracks.algebricks.core.rewriter.base.PhysicalOptimizationConfig;
 import org.apache.hyracks.algebricks.runtime.base.IEvaluatorContext;
 import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
 import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
@@ -146,7 +147,7 @@
                 BinaryIntegerInspector.FACTORY, ADMPrinterFactoryProvider.INSTANCE, MissingWriterFactory.INSTANCE, null,
                 new ExpressionRuntimeProvider(new QueryLogicalExpressionJobGen(metadataProvider.getFunctionManager())),
                 ExpressionTypeComputer.INSTANCE, null, null, null, null, GlobalConfig.DEFAULT_FRAME_SIZE, null,
-                NoOpWarningCollector.INSTANCE, 0);
+                NoOpWarningCollector.INSTANCE, 0, new PhysicalOptimizationConfig());
     }
 
     @Override
diff --git a/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/common/APIFramework.java b/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/common/APIFramework.java
index d573b52..c863080 100644
--- a/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/common/APIFramework.java
+++ b/asterixdb/asterix-app/src/main/java/org/apache/asterix/api/common/APIFramework.java
@@ -134,11 +134,12 @@
                     CompilerProperties.COMPILER_SORTMEMORY_KEY, CompilerProperties.COMPILER_WINDOWMEMORY_KEY,
                     CompilerProperties.COMPILER_TEXTSEARCHMEMORY_KEY, CompilerProperties.COMPILER_PARALLELISM_KEY,
                     CompilerProperties.COMPILER_SORT_PARALLEL_KEY, CompilerProperties.COMPILER_SORT_SAMPLES_KEY,
-                    FunctionUtil.IMPORT_PRIVATE_FUNCTIONS, FuzzyUtils.SIM_FUNCTION_PROP_NAME,
-                    FuzzyUtils.SIM_THRESHOLD_PROP_NAME, StartFeedStatement.WAIT_FOR_COMPLETION,
-                    FeedActivityDetails.FEED_POLICY_NAME, FeedActivityDetails.COLLECT_LOCATIONS,
-                    SqlppQueryRewriter.INLINE_WITH_OPTION, SqlppExpressionToPlanTranslator.REWRITE_IN_AS_OR_OPTION,
-                    "hash_merge", "output-record-type", AbstractIntroduceAccessMethodRule.NO_INDEX_ONLY_PLAN_OPTION,
+                    CompilerProperties.COMPILER_EXTERNALSCANMEMORY_KEY, FunctionUtil.IMPORT_PRIVATE_FUNCTIONS,
+                    FuzzyUtils.SIM_FUNCTION_PROP_NAME, FuzzyUtils.SIM_THRESHOLD_PROP_NAME,
+                    StartFeedStatement.WAIT_FOR_COMPLETION, FeedActivityDetails.FEED_POLICY_NAME,
+                    FeedActivityDetails.COLLECT_LOCATIONS, SqlppQueryRewriter.INLINE_WITH_OPTION,
+                    SqlppExpressionToPlanTranslator.REWRITE_IN_AS_OR_OPTION, "hash_merge", "output-record-type",
+                    AbstractIntroduceAccessMethodRule.NO_INDEX_ONLY_PLAN_OPTION,
                     DisjunctivePredicateToJoinRule.REWRITE_OR_AS_JOIN_OPTION);
 
     private final IRewriterFactory rewriterFactory;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.000.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.000.ddl.sqlpp
new file mode 100644
index 0000000..22a30ca
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.000.ddl.sqlpp
@@ -0,0 +1,66 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+drop dataverse test if exists;
+create dataverse test;
+use test;
+
+drop type test if exists;
+create type test as open {
+};
+
+drop dataset test1 if exists;
+create external dataset test1(test) using S3 (
+("accessKeyId"="dummyAccessKey"),
+("secretAccessKey"="dummySecretKey"),
+("region"="us-west-2"),
+("serviceEndpoint"="http://localhost:8001"),
+("container"="playground"),
+("definition"="json-data/reviews/single-line/json"),
+("format"="json"));
+
+drop dataset test2 if exists;
+create external dataset test2(test) using S3 (
+("accessKeyId"="dummyAccessKey"),
+("secretAccessKey"="dummySecretKey"),
+("region"="us-west-2"),
+("serviceEndpoint"="http://localhost:8001"),
+("container"="playground"),
+("definition"="json-data/reviews/multi-lines/json"),
+("format"="json"));
+
+drop dataset test3 if exists;
+create external dataset test3(test) using S3 (
+("accessKeyId"="dummyAccessKey"),
+("secretAccessKey"="dummySecretKey"),
+("region"="us-west-2"),
+("serviceEndpoint"="http://localhost:8001"),
+("container"="playground"),
+("definition"="json-data/reviews/multi-lines-with-arrays/json"),
+("format"="json"));
+
+drop dataset test4 if exists;
+create external dataset test4(test) using S3 (
+("accessKeyId"="dummyAccessKey"),
+("secretAccessKey"="dummySecretKey"),
+("region"="us-west-2"),
+("serviceEndpoint"="http://localhost:8001"),
+("container"="playground"),
+("definition"="json-data/reviews/multi-lines-with-nested-objects/json"),
+("format"="json"));
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.001.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.001.query.sqlpp
new file mode 100644
index 0000000..7c1708a
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.001.query.sqlpp
@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+set `compiler.externalscanmemory` "8KB";
+select count(*) `count` from test1;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.002.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.002.query.sqlpp
new file mode 100644
index 0000000..d122f42
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.002.query.sqlpp
@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+set `compiler.externalscanmemory` "16KB";
+select count(*) `count` from test2;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.003.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.003.query.sqlpp
new file mode 100644
index 0000000..552f943
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.003.query.sqlpp
@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+set `compiler.externalscanmemory` "32KB";
+select count(*) `count` from test3;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.004.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.004.query.sqlpp
new file mode 100644
index 0000000..f30af80
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.004.query.sqlpp
@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+set `compiler.externalscanmemory` "8KB";
+select value test3 from test3 order by id;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.005.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.005.query.sqlpp
new file mode 100644
index 0000000..af6aff0
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.005.query.sqlpp
@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+set `compiler.externalscanmemory` "16KB";
+select count(*) `count` from test4;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.006.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.006.query.sqlpp
new file mode 100644
index 0000000..854ac80
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.006.query.sqlpp
@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+use test;
+set `compiler.externalscanmemory` "10KB";
+select value test4 from test4 order by id;
+
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.999.ddl.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.999.ddl.sqlpp
new file mode 100644
index 0000000..548e632
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/external-dataset/aws/s3/custom-buffer-size/external_dataset.999.ddl.sqlpp
@@ -0,0 +1,20 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+drop dataverse test if exists;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.001.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.001.adm
new file mode 100644
index 0000000..187a8cb
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.001.adm
@@ -0,0 +1 @@
+{ "count": 100 }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.002.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.002.adm
new file mode 100644
index 0000000..187a8cb
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.002.adm
@@ -0,0 +1 @@
+{ "count": 100 }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.003.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.003.adm
new file mode 100644
index 0000000..5db606c
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.003.adm
@@ -0,0 +1 @@
+{ "count": 25 }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.004.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.004.adm
new file mode 100644
index 0000000..7660e7e
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.004.adm
@@ -0,0 +1,25 @@
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3 ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3 ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3 ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3 ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3 ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3 ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3 ] }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.005.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.005.adm
new file mode 100644
index 0000000..5db606c
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.005.adm
@@ -0,0 +1 @@
+{ "count": 25 }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.006.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.006.adm
new file mode 100644
index 0000000..7643986
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/external-dataset/aws/s3/custom-buffer-size/external_dataset.006.adm
@@ -0,0 +1,25 @@
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ], "nested": { "id": 1 } }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ], "nested": { "id": 1 } }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ], "nested": { "id": 1 } }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ], "nested": { "id": 1 } }
+{ "id": 1, "year": null, "quarter": null, "review": "good", "array": [ 1, 2, 3 ], "nested": { "id": 1 } }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ], "nested": { "id": 1 }, "nested2": [ { "id": 1 } ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ], "nested": { "id": 1 }, "nested2": [ { "id": 1 } ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ], "nested": { "id": 1 }, "nested2": [ { "id": 1 } ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ], "nested": { "id": 1 }, "nested2": [ { "id": 1 } ] }
+{ "id": 2, "year": null, "quarter": null, "review": "good", "array": [ 1, [ 1, 2 ], [ 1 ] ], "nested": { "id": 1 }, "nested2": [ { "id": 1 } ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ { "nested": { "array": [ 1, 2 ] } } ] } } ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ { "nested": { "array": [ 1, 2 ] } } ] } } ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ { "nested": { "array": [ 1, 2 ] } } ] } } ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ { "nested": { "array": [ 1, 2 ] } } ] } } ] }
+{ "id": 3, "year": 2018, "quarter": null, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ { "nested": { "array": [ 1, 2 ] } } ] } } ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3, { "nested1": { "id": 1, "nested2": { "id": 2, "nested3": [ { "nested4": null } ] } } } ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3, { "nested1": { "id": 1, "nested2": { "id": 2, "nested3": [ { "nested4": null } ] } } } ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3, { "nested1": { "id": 1, "nested2": { "id": 2, "nested3": [ { "nested4": null } ] } } } ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3, { "nested1": { "id": 1, "nested2": { "id": 2, "nested3": [ { "nested4": null } ] } } } ] }
+{ "id": 4, "year": 2018, "quarter": null, "review": "bad", "array": [ 1, 2, 3, { "nested1": { "id": 1, "nested2": { "id": 2, "nested3": [ { "nested4": null } ] } } } ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ 1, 2 ] } } ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ 1, 2 ] } } ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ 1, 2 ] } } ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ 1, 2 ] } } ] }
+{ "id": 5, "year": 2018, "quarter": 1, "review": "good", "array": [ 1, 2, 3, { "nested": { "array": [ 1, 2 ] } } ] }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_external_dataset.xml b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_external_dataset.xml
index 9cded35..096e511 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_external_dataset.xml
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/testsuite_external_dataset.xml
@@ -19,6 +19,11 @@
  !-->
 <test-suite xmlns="urn:xml.testframework.asterix.apache.org" ResultOffsetPath="results" QueryOffsetPath="queries_sqlpp" QueryFileExtension=".sqlpp">
   <test-group name="external-dataset">
+    <test-case FilePath="external-dataset/aws/s3/">
+      <compilation-unit name="custom-buffer-size">
+        <output-dir compare="Text">custom-buffer-size</output-dir>
+      </compilation-unit>
+    </test-case>
     <test-case FilePath="external-dataset">
       <compilation-unit name="aws/s3/json/json">
         <output-dir compare="Text">aws/s3/json/json</output-dir>
diff --git a/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/CompilerProperties.java b/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/CompilerProperties.java
index 8860495..652f390 100644
--- a/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/CompilerProperties.java
+++ b/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/CompilerProperties.java
@@ -56,6 +56,10 @@
                 LONG_BYTE_UNIT,
                 StorageUtil.getLongSizeInBytes(32L, MEGABYTE),
                 "The memory budget (in bytes) for an inverted-index-search operator instance in a partition"),
+        COMPILER_EXTERNALSCANMEMORY(
+                INTEGER_BYTE_UNIT,
+                StorageUtil.getIntSizeInBytes(4, KILOBYTE),
+                "The memory budget (in bytes) for an external scan operator instance in a partition"),
         COMPILER_FRAMESIZE(
                 INTEGER_BYTE_UNIT,
                 StorageUtil.getIntSizeInBytes(32, KILOBYTE),
@@ -110,7 +114,7 @@
 
         @Override
         public boolean hidden() {
-            return this == COMPILER_STRINGOFFSET;
+            return this == COMPILER_STRINGOFFSET || this == COMPILER_EXTERNALSCANMEMORY;
         }
     }
 
@@ -130,6 +134,8 @@
 
     public static final String COMPILER_SORT_SAMPLES_KEY = Option.COMPILER_SORT_SAMPLES.ini();
 
+    public static final String COMPILER_EXTERNALSCANMEMORY_KEY = Option.COMPILER_EXTERNALSCANMEMORY.ini();
+
     public static final int COMPILER_PARALLELISM_AS_STORAGE = 0;
 
     public CompilerProperties(PropertiesAccessor accessor) {
@@ -176,4 +182,8 @@
     public int getSortSamples() {
         return accessor.getInt(Option.COMPILER_SORT_SAMPLES);
     }
+
+    public int getExternalScanMemorySize() {
+        return accessor.getInt(Option.COMPILER_EXTERNALSCANMEMORY);
+    }
 }
diff --git a/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/OptimizationConfUtil.java b/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/OptimizationConfUtil.java
index 23fdcac..22fb13b 100644
--- a/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/OptimizationConfUtil.java
+++ b/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/config/OptimizationConfUtil.java
@@ -59,6 +59,9 @@
         int textSearchFrameLimit = getTextSearchNumFrames(compilerProperties, querySpecificConfig, sourceLoc);
         int sortNumSamples = getSortSamples(compilerProperties, querySpecificConfig, sourceLoc);
         boolean fullParallelSort = getSortParallel(compilerProperties, querySpecificConfig);
+        int externalScanBufferSize = getExternalScanBufferSize(
+                (String) querySpecificConfig.get(CompilerProperties.COMPILER_EXTERNALSCANMEMORY_KEY),
+                compilerProperties.getExternalScanMemorySize(), sourceLoc);
 
         PhysicalOptimizationConfig physOptConf = new PhysicalOptimizationConfig();
         physOptConf.setFrameSize(frameSize);
@@ -69,10 +72,22 @@
         physOptConf.setMaxFramesForTextSearch(textSearchFrameLimit);
         physOptConf.setSortParallel(fullParallelSort);
         physOptConf.setSortSamples(sortNumSamples);
+        physOptConf.setExternalScanBufferSize(externalScanBufferSize);
 
         return physOptConf;
     }
 
+    private static int getExternalScanBufferSize(String externalScanMemorySizeParameter,
+            int compilerExternalScanMemorySize, SourceLocation sourceLoc) throws AsterixException {
+        IOptionType<Integer> intByteParser = OptionTypes.INTEGER_BYTE_UNIT;
+        try {
+            return externalScanMemorySizeParameter != null ? intByteParser.parse(externalScanMemorySizeParameter)
+                    : compilerExternalScanMemorySize;
+        } catch (IllegalArgumentException e) {
+            throw AsterixException.create(ErrorCode.COMPILATION_ERROR, sourceLoc, e.getMessage());
+        }
+    }
+
     public static int getSortNumFrames(CompilerProperties compilerProperties, Map<String, Object> querySpecificConfig,
             SourceLocation sourceLoc) throws AlgebricksException {
         return getFrameLimit(CompilerProperties.COMPILER_SORTMEMORY_KEY,
diff --git a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/aws/AwsS3InputStream.java b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/aws/AwsS3InputStream.java
index 9e10e6a..f558820 100644
--- a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/aws/AwsS3InputStream.java
+++ b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/aws/AwsS3InputStream.java
@@ -29,7 +29,6 @@
 import org.apache.asterix.common.exceptions.ErrorCode;
 import org.apache.asterix.common.exceptions.RuntimeDataException;
 import org.apache.asterix.external.input.stream.AbstractMultipleInputStream;
-import org.apache.asterix.external.util.ExternalDataConstants;
 import org.apache.asterix.external.util.ExternalDataUtils;
 import org.apache.hyracks.api.exceptions.HyracksDataException;
 import org.apache.hyracks.api.util.CleanupUtils;
@@ -48,6 +47,7 @@
 
     // Configuration
     private final Map<String, String> configuration;
+    private final int bufferSize;
 
     private final S3Client s3Client;
 
@@ -59,6 +59,7 @@
         this.configuration = configuration;
         this.filePaths = filePaths;
         this.s3Client = buildAwsS3Client(configuration);
+        this.bufferSize = ExternalDataUtils.getOrDefaultBufferSize(configuration);
     }
 
     @Override
@@ -101,7 +102,7 @@
         // Use gzip stream if needed
         String filename = filePaths.get(nextFileIndex).toLowerCase();
         if (filename.endsWith(".gz") || filename.endsWith(".gzip")) {
-            in = new GZIPInputStream(s3Client.getObject(getObjectRequest), ExternalDataConstants.DEFAULT_BUFFER_SIZE);
+            in = new GZIPInputStream(s3Client.getObject(getObjectRequest), bufferSize);
         }
 
         // Current file ready, point to the next file
diff --git a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/stream/StreamRecordReader.java b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/stream/StreamRecordReader.java
index cb16de5..1e003a1 100644
--- a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/stream/StreamRecordReader.java
+++ b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/record/reader/stream/StreamRecordReader.java
@@ -33,7 +33,6 @@
 import org.apache.asterix.external.dataflow.AbstractFeedDataFlowController;
 import org.apache.asterix.external.input.record.CharArrayRecord;
 import org.apache.asterix.external.input.stream.AsterixInputStreamReader;
-import org.apache.asterix.external.util.ExternalDataConstants;
 import org.apache.asterix.external.util.ExternalDataUtils;
 import org.apache.asterix.external.util.FeedLogManager;
 import org.apache.hyracks.api.context.IHyracksTaskContext;
@@ -51,9 +50,10 @@
     private Supplier<String> previousDataSourceName = EMPTY_STRING;
 
     public void configure(AsterixInputStream inputStream, Map<String, String> config) {
-        this.reader = new AsterixInputStreamReader(inputStream);
+        int bufferSize = ExternalDataUtils.getOrDefaultBufferSize(config);
+        this.reader = new AsterixInputStreamReader(inputStream, bufferSize);
         record = new CharArrayRecord();
-        inputBuffer = new char[ExternalDataConstants.DEFAULT_BUFFER_SIZE];
+        inputBuffer = new char[bufferSize];
         if (!ExternalDataUtils.isTrue(config, KEY_REDACT_WARNINGS)) {
             this.dataSourceName = reader::getStreamName;
             this.previousDataSourceName = reader::getPreviousStreamName;
diff --git a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/stream/AsterixInputStreamReader.java b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/stream/AsterixInputStreamReader.java
index 4e963e4..ddbd350 100644
--- a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/stream/AsterixInputStreamReader.java
+++ b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/input/stream/AsterixInputStreamReader.java
@@ -27,21 +27,23 @@
 
 import org.apache.asterix.external.api.AsterixInputStream;
 import org.apache.asterix.external.dataflow.AbstractFeedDataFlowController;
-import org.apache.asterix.external.util.ExternalDataConstants;
 import org.apache.asterix.external.util.FeedLogManager;
 import org.apache.hyracks.api.exceptions.HyracksDataException;
 
 public class AsterixInputStreamReader extends Reader {
-    private AsterixInputStream in;
-    private byte[] bytes = new byte[ExternalDataConstants.DEFAULT_BUFFER_SIZE];
-    private ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
-    private CharBuffer charBuffer = CharBuffer.allocate(ExternalDataConstants.DEFAULT_BUFFER_SIZE);
-    private CharsetDecoder decoder;
+    private final AsterixInputStream in;
+    private final byte[] bytes;
+    private final ByteBuffer byteBuffer;
+    private final CharBuffer charBuffer;
+    private final CharsetDecoder decoder;
     private boolean done = false;
     private boolean remaining = false;
 
-    public AsterixInputStreamReader(AsterixInputStream in) {
+    public AsterixInputStreamReader(AsterixInputStream in, int bufferSize) {
         this.in = in;
+        this.bytes = new byte[bufferSize];
+        this.byteBuffer = ByteBuffer.wrap(bytes);
+        this.charBuffer = CharBuffer.allocate(bufferSize);
         this.decoder = StandardCharsets.UTF_8.newDecoder();
         this.byteBuffer.flip();
     }
diff --git a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataConstants.java b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataConstants.java
index 53306c5..1911083 100644
--- a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataConstants.java
+++ b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataConstants.java
@@ -117,6 +117,7 @@
     // a string representing the NULL value
     public static final String KEY_NULL_STR = "null";
     public static final String KEY_REDACT_WARNINGS = "redact-warnings";
+    public static final String KEY_EXTERNAL_SCAN_BUFFER_SIZE = "external-scan-buffer-size";
 
     /**
      *  Keys for adapter name
diff --git a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataUtils.java b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataUtils.java
index c0a7a4d..bc9a038 100644
--- a/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataUtils.java
+++ b/asterixdb/asterix-external-data/src/main/java/org/apache/asterix/external/util/ExternalDataUtils.java
@@ -20,6 +20,7 @@
 
 import static org.apache.asterix.external.util.ExternalDataConstants.KEY_DELIMITER;
 import static org.apache.asterix.external.util.ExternalDataConstants.KEY_ESCAPE;
+import static org.apache.asterix.external.util.ExternalDataConstants.KEY_EXTERNAL_SCAN_BUFFER_SIZE;
 import static org.apache.asterix.external.util.ExternalDataConstants.KEY_QUOTE;
 import static org.apache.asterix.external.util.ExternalDataConstants.KEY_RECORD_END;
 import static org.apache.asterix.external.util.ExternalDataConstants.KEY_RECORD_START;
@@ -90,6 +91,11 @@
     private ExternalDataUtils() {
     }
 
+    public static int getOrDefaultBufferSize(Map<String, String> configuration) {
+        String bufferSize = configuration.get(KEY_EXTERNAL_SCAN_BUFFER_SIZE);
+        return bufferSize != null ? Integer.parseInt(bufferSize) : ExternalDataConstants.DEFAULT_BUFFER_SIZE;
+    }
+
     // Get a delimiter from the given configuration
     public static char validateGetDelimiter(Map<String, String> configuration) throws HyracksDataException {
         return validateCharOrDefault(configuration, KEY_DELIMITER, ExternalDataConstants.DEFAULT_DELIMITER.charAt(0));
diff --git a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/declared/DatasetDataSource.java b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/declared/DatasetDataSource.java
index 71d389e..715092a 100644
--- a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/declared/DatasetDataSource.java
+++ b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/declared/DatasetDataSource.java
@@ -18,7 +18,10 @@
  */
 package org.apache.asterix.metadata.declared;
 
+import static org.apache.asterix.external.util.ExternalDataConstants.KEY_EXTERNAL_SCAN_BUFFER_SIZE;
+
 import java.util.List;
+import java.util.Map;
 
 import org.apache.asterix.common.config.DatasetConfig.DatasetType;
 import org.apache.asterix.common.exceptions.CompilationException;
@@ -42,6 +45,7 @@
 import org.apache.hyracks.algebricks.core.algebra.operators.logical.IOperatorSchema;
 import org.apache.hyracks.algebricks.core.algebra.properties.INodeDomain;
 import org.apache.hyracks.algebricks.core.jobgen.impl.JobGenContext;
+import org.apache.hyracks.algebricks.core.rewriter.base.PhysicalOptimizationConfig;
 import org.apache.hyracks.api.dataflow.IOperatorDescriptor;
 import org.apache.hyracks.api.job.JobSpecification;
 import org.apache.hyracks.storage.am.common.api.ITupleFilterFactory;
@@ -111,9 +115,12 @@
                         externalDataset.getItemTypeDataverseName(), itemTypeName).getDatatype();
 
                 ExternalDatasetDetails edd = (ExternalDatasetDetails) externalDataset.getDatasetDetails();
-                ITypedAdapterFactory adapterFactory =
-                        metadataProvider.getConfiguredAdapterFactory(externalDataset, edd.getAdapter(),
-                                edd.getProperties(), (ARecordType) itemType, null, context.getWarningCollector());
+                PhysicalOptimizationConfig physicalOptimizationConfig = context.getPhysicalOptimizationConfig();
+                int externalScanBufferSize = physicalOptimizationConfig.getExternalScanBufferSize();
+                Map<String, String> properties = edd.getProperties();
+                properties.put(KEY_EXTERNAL_SCAN_BUFFER_SIZE, String.valueOf(externalScanBufferSize));
+                ITypedAdapterFactory adapterFactory = metadataProvider.getConfiguredAdapterFactory(externalDataset,
+                        edd.getAdapter(), properties, (ARecordType) itemType, null, context.getWarningCollector());
                 return metadataProvider.buildExternalDatasetDataScannerRuntime(jobSpec, itemType, adapterFactory);
             case INTERNAL:
                 DataSourceId id = getId();
diff --git a/hyracks-fullstack/algebricks/algebricks-compiler/src/main/java/org/apache/hyracks/algebricks/compiler/api/HeuristicCompilerFactoryBuilder.java b/hyracks-fullstack/algebricks/algebricks-compiler/src/main/java/org/apache/hyracks/algebricks/compiler/api/HeuristicCompilerFactoryBuilder.java
index 0fd107f..b96d657 100644
--- a/hyracks-fullstack/algebricks/algebricks-compiler/src/main/java/org/apache/hyracks/algebricks/compiler/api/HeuristicCompilerFactoryBuilder.java
+++ b/hyracks-fullstack/algebricks/algebricks-compiler/src/main/java/org/apache/hyracks/algebricks/compiler/api/HeuristicCompilerFactoryBuilder.java
@@ -105,7 +105,7 @@
                                 normalizedKeyComputerFactoryProvider, expressionRuntimeProvider, expressionTypeComputer,
                                 oc, expressionEvalSizeComputer, partialAggregationTypeComputer,
                                 predEvaluatorFactoryProvider, physicalOptimizationConfig.getFrameSize(),
-                                clusterLocations, warningCollector, maxWarnings);
+                                clusterLocations, warningCollector, maxWarnings, physicalOptimizationConfig);
 
                         PlanCompiler pc = new PlanCompiler(context);
                         return pc.compilePlan(plan, jobEventListenerFactory);
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/config/AlgebricksConfig.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/config/AlgebricksConfig.java
index 15bb54b..7630a13 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/config/AlgebricksConfig.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/config/AlgebricksConfig.java
@@ -18,6 +18,7 @@
  */
 package org.apache.hyracks.algebricks.core.config;
 
+import org.apache.hyracks.util.StorageUtil;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
@@ -26,5 +27,7 @@
     public static final String ALGEBRICKS_LOGGER_NAME = "org.apache.hyracks.algebricks";
     public static final Logger ALGEBRICKS_LOGGER = LogManager.getLogger(ALGEBRICKS_LOGGER_NAME);
     public static final int SORT_SAMPLES = 100;
+    public static final int EXTERNAL_SCAN_BUFFER_SIZE =
+            StorageUtil.getIntSizeInBytes(4, StorageUtil.StorageUnit.KILOBYTE);
     public static final boolean SORT_PARALLEL = true;
 }
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/jobgen/impl/JobGenContext.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/jobgen/impl/JobGenContext.java
index 4bc5689..3c03b18 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/jobgen/impl/JobGenContext.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/jobgen/impl/JobGenContext.java
@@ -34,6 +34,7 @@
 import org.apache.hyracks.algebricks.core.algebra.metadata.IMetadataProvider;
 import org.apache.hyracks.algebricks.core.algebra.operators.logical.IOperatorSchema;
 import org.apache.hyracks.algebricks.core.algebra.typing.ITypingContext;
+import org.apache.hyracks.algebricks.core.rewriter.base.PhysicalOptimizationConfig;
 import org.apache.hyracks.algebricks.data.IBinaryBooleanInspectorFactory;
 import org.apache.hyracks.algebricks.data.IBinaryComparatorFactoryProvider;
 import org.apache.hyracks.algebricks.data.IBinaryHashFunctionFactoryProvider;
@@ -68,6 +69,7 @@
     private final IPartialAggregationTypeComputer partialAggregationTypeComputer;
     private final IPredicateEvaluatorFactoryProvider predEvaluatorFactoryProvider;
     private final int frameSize;
+    private final PhysicalOptimizationConfig physicalOptimizationConfig;
     private AlgebricksAbsolutePartitionConstraint clusterLocations;
     private int varCounter;
     private final ITypingContext typingContext;
@@ -88,7 +90,7 @@
             IPartialAggregationTypeComputer partialAggregationTypeComputer,
             IPredicateEvaluatorFactoryProvider predEvaluatorFactoryProvider, int frameSize,
             AlgebricksAbsolutePartitionConstraint clusterLocations, IWarningCollector warningCollector,
-            long maxWarnings) {
+            long maxWarnings, PhysicalOptimizationConfig physicalOptimizationConfig) {
         this.outerFlowSchema = outerFlowSchema;
         this.metadataProvider = metadataProvider;
         this.appContext = appContext;
@@ -110,6 +112,7 @@
         this.partialAggregationTypeComputer = partialAggregationTypeComputer;
         this.predEvaluatorFactoryProvider = predEvaluatorFactoryProvider;
         this.frameSize = frameSize;
+        this.physicalOptimizationConfig = physicalOptimizationConfig;
         this.varCounter = 0;
         this.warningCollector = warningCollector;
         this.maxWarnings = maxWarnings;
@@ -220,4 +223,8 @@
     public long getMaxWarnings() {
         return maxWarnings;
     }
+
+    public PhysicalOptimizationConfig getPhysicalOptimizationConfig() {
+        return physicalOptimizationConfig;
+    }
 }
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/rewriter/base/PhysicalOptimizationConfig.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/rewriter/base/PhysicalOptimizationConfig.java
index 598497c..93f5d74 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/rewriter/base/PhysicalOptimizationConfig.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/rewriter/base/PhysicalOptimizationConfig.java
@@ -39,6 +39,7 @@
     private static final String DEFAULT_IN_MEM_HASH_JOIN_TABLE_SIZE = "DEFAULT_IN_MEM_HASH_JOIN_TABLE_SIZE";
     private static final String SORT_PARALLEL = "SORT_PARALLEL";
     private static final String SORT_SAMPLES = "SORT_SAMPLES";
+    private static final String EXTERNAL_SCAN_BUFFER_SIZE = "EXTERNAL_SCAN_BUFFER_SIZE";
 
     private Properties properties = new Properties();
 
@@ -172,6 +173,14 @@
         setInt(SORT_SAMPLES, sortSamples);
     }
 
+    public int getExternalScanBufferSize() {
+        return getInt(EXTERNAL_SCAN_BUFFER_SIZE, AlgebricksConfig.EXTERNAL_SCAN_BUFFER_SIZE);
+    }
+
+    public void setExternalScanBufferSize(int bufferSize) {
+        setInt(EXTERNAL_SCAN_BUFFER_SIZE, bufferSize);
+    }
+
     private void setInt(String property, int value) {
         properties.setProperty(property, Integer.toString(value));
     }