perf: Reduce peak memory usage of NLJ by 2X using segmented batch layout

datafusion/core/tests/memory_limit/memory_limit_validation/mod.rs

@@ -18,6 +18,7 @@
 //! Validates query's actual memory usage is consistent with the specified memory
 //! limit.
 
+mod nlj_mem_validation;
 mod smj_mem_validation;
 mod sort_mem_validation;
 mod utils;

datafusion/core/tests/memory_limit/memory_limit_validation/nlj_mem_validation.rs

@@ -0,0 +1,57 @@
+// 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.
+
+//! Memory validation for the nested loop join's buffered build side.
+
+use datafusion::prelude::SessionConfig;
+
+use crate::memory_limit::memory_limit_validation::utils;
+
+#[test]
+fn nlj_no_mem_limit_runner() {
+    utils::spawn_test_process("nlj_mem_validation", "nlj_no_mem_limit");
+}
+
+// NLJ buffers the entire build side and uses a small, constant amount of memory
+// to stream the probe side.
+//
+// This test verifies that an NLJ without a memory limit follows this estimate.
+#[tokio::test]
+async fn nlj_no_mem_limit() {
+    let config = SessionConfig::new()
+        .with_target_partitions(1)
+        .with_batch_size(8192)
+        // Keep the large input on the build side, as written in the query.
+        .set_bool("datafusion.optimizer.join_reordering", false);
+
+    utils::validate_query_with_memory_limits_and_config(
+        90_000_000, // 80 MB for the build side + 10 MB of extra room.
+        None,
+        "SELECT count(*), sum(l.value)
+         FROM generate_series(1, 10000000) AS l
+         JOIN generate_series(1, 1) AS r
+             ON (l.value + r.value) % 2 = 0",
+        "SELECT count(*), sum(l.value)
+         FROM generate_series(1, 1000000) AS l
+         JOIN generate_series(1, 1) AS r
+             ON (l.value + r.value) % 2 = 0",
+        config,
+        Some("NestedLoopJoinExec"),
+        Some(false),
+    )
+    .await;
+}