feat: Add 'native_partitioned_output_eager_flush' session property

[spershin]

Description

The news session property would allow Partitioned Output Velox operators to flush (return) data eagerly, as soon as it arrives.
This would match default Presto Java behavior of returning results eagerly to the caller, while the query is still running (scanning).

Motivation and Context

For "needle in a haystack" type of queries running in various UIs this early return functionality is crucial.

Test Plan

Existing session property test.
Ran the custom build in a Prestissimo cluster to ensure session property changes query behavior accordingly.

== NO RELEASE NOTE ==

Summary by Sourcery

Add a native session property to control eager flushing behavior of partitioned output operators.

New Features:

• Introduce the native_partitioned_output_eager_flush session property to enable eager flushing of PartitionedOutput operator rows in native execution.

Documentation:

• Document the native_partitioned_output_eager_flush session property in the Presto native session properties reference.

Tests:

• Extend session property mapping tests to cover the new native_partitioned_output_eager_flush property.

[sourcery-ai]

Reviewer's Guide

Adds a new native session property native_partitioned_output_eager_flush that controls whether the PartitionedOutput operator flushes rows eagerly, wires it through native C++ session properties, Java native worker session property provider, and updates the session property mapping test.

Sequence diagram for native_partitioned_output_eager_flush propagation

sequenceDiagram
    actor User
    participant Coordinator as CoordinatorSession
    participant Java as NativeWorkerSessionPropertyProvider
    participant Cpp as CppSessionProperties
    participant Exec as PartitionedOutputOperator

    User->>Coordinator: Set session native_partitioned_output_eager_flush=true
    Coordinator->>Java: Build native worker session properties
    Java->>Java: booleanProperty(NATIVE_PARTITIONED_OUTPUT_EAGER_FLUSH,...)
    Java-->>Coordinator: Session property map
    Coordinator->>Cpp: Start native query with session properties
    Cpp->>Cpp: SessionProperties::addSessionProperty(kPartitionedOutputEagerFlush,...)
    Cpp-->>Exec: Construct with partitionedOutputEagerFlush=true
    Exec->>Exec: Use eager flush behavior when producing pages

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Class diagram for new native_partitioned_output_eager_flush session property

classDiagram
    class NativeWorkerSessionPropertyProvider {
        +String NATIVE_MAX_EXTENDED_PARTIAL_AGGREGATION_MEMORY
        +String NATIVE_MAX_SPILL_BYTES
        +String NATIVE_MAX_PAGE_PARTITIONING_BUFFER_SIZE
        +String NATIVE_PARTITIONED_OUTPUT_EAGER_FLUSH
        +String NATIVE_MAX_OUTPUT_BUFFER_SIZE
        +String NATIVE_QUERY_TRACE_ENABLED
        +String NATIVE_QUERY_TRACE_DIR
        +NativeWorkerSessionPropertyProvider(FeaturesConfig featuresConfig)
        -booleanProperty(String name, String description, boolean defaultValue, boolean hidden)
        -integerProperty(String name, String description, int defaultValue, boolean hidden)
    }

    class SessionProperties {
        +const char* kMaxPartitionedOutputBufferSize
        +const char* kPartitionedOutputEagerFlush
        +const char* kMaxLocalExchangePartitionCount
        +SessionProperties()
        -void addSessionProperty(const char* name, const char* description, Type type, bool defaultValue, const char* configKey, const char* defaultConfigValue)
    }

    class QueryConfig {
        +const char* kMaxPartitionedOutputBufferSize
        +const char* kPartitionedOutputEagerFlush
    }

    NativeWorkerSessionPropertyProvider --> SessionProperties : defines Java property
    SessionProperties --> QueryConfig : uses config keys for mapping

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File-Level Changes

Change	Details	Files
Introduce native session property to control eager flushing behavior of PartitionedOutput operator and wire it to query config.	Define kPartitionedOutputEagerFlush session property key in native C++ session properties header. Register the new boolean session property in SessionProperties::SessionProperties() with default false and link it to QueryConfig::kPartitionedOutputEagerFlush. Extend the session properties mapping test to validate the mapping from the new session property key to the corresponding QueryConfig key.	presto-native-execution/presto_cpp/main/SessionProperties.h presto-native-execution/presto_cpp/main/SessionProperties.cpp presto-native-execution/presto_cpp/main/tests/SessionPropertiesTest.cpp
Expose the eager flush behavior as a Java-level native worker session property for configuration.	Add the NATIVE_PARTITIONED_OUTPUT_EAGER_FLUSH constant in NativeWorkerSessionPropertyProvider. Register a new boolean session property, documented as native-execution-only, with default false and disabled when nativeExecution is false.	presto-main-base/src/main/java/com/facebook/presto/sessionpropertyproviders/NativeWorkerSessionPropertyProvider.java

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[sourcery-ai]

Hey - I've found 2 issues, and left some high level feedback:

• In SessionProperties.h/SessionProperties.cpp, consider aligning the description text with the Java NativeWorkerSessionPropertyProvider (e.g., explicitly mentioning it is Native Execution only) so that users see a consistent explanation of native_partitioned_output_eager_flush across codepaths.
• If there are still any minimum batching constraints or other conditions under which rows might not be flushed immediately, consider tightening the property description (both Java and C++) so that "flush rows eagerly" doesn’t oversell semantics that depend on internal buffering.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `SessionProperties.h`/`SessionProperties.cpp`, consider aligning the description text with the Java `NativeWorkerSessionPropertyProvider` (e.g., explicitly mentioning it is Native Execution only) so that users see a consistent explanation of `native_partitioned_output_eager_flush` across codepaths.
- If there are still any minimum batching constraints or other conditions under which rows might not be flushed immediately, consider tightening the property description (both Java and C++) so that "flush rows eagerly" doesn’t oversell semantics that depend on internal buffering.

## Individual Comments

### Comment 1
<location> `presto-native-execution/presto_cpp/main/SessionProperties.cpp:354-361` </location>
<code_context>

+  addSessionProperty(
+      kPartitionedOutputEagerFlush,
+      "If true, the PartitionedOutput operator will flush rows eagerly, without"
+      "waiting until buffers reach certain size. Default is false.",
+      BOOLEAN(),
+      false,
</code_context>

<issue_to_address>
**issue (typo):** Add a space at the join between the two string literals so the description doesn’t render as 'withoutwaiting'.

Since C++ concatenates adjacent string literals directly, the current two-literal form produces "withoutwaiting" in the output; adding a space to either literal avoids this.

```suggestion
  addSessionProperty(
      kPartitionedOutputEagerFlush,
      "If true, the PartitionedOutput operator will flush rows eagerly, without "
      "waiting until buffers reach certain size. Default is false.",
      BOOLEAN(),
      false,
      QueryConfig::kPartitionedOutputEagerFlush,
      "false");
```
</issue_to_address>

### Comment 2
<location> `presto-docs/src/main/sphinx/presto_cpp/properties-session.rst:309-310` </location>
<code_context>
+* **Default value:** ``false``
+
+Native Execution only. If true, the PartitionedOutput operator will flush rows eagerly, without
+waiting until buffers reach certain size. Default is false.
+
 ``native_max_local_exchange_partition_count``
</code_context>

<issue_to_address>
**issue (typo):** Consider adding an article: "waiting until buffers reach a certain size."

```suggestion
Native Execution only. If true, the PartitionedOutput operator will flush rows eagerly, without
waiting until buffers reach a certain size. Default is false.
```
</issue_to_address>

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[steveburnett]

Thanks for the doc! Just a single nit of formatting.

[steveburnett]

LGTM! (docs)

Pull updated branch, new local doc build, looks good. Thanks!

[steveburnett]

When you have time, edit the PR title to pass the required failing test.

Maybe something like:

feat(native): Add 'native_partitioned_output_eager_flush' session property

[kaikalur]

LGTM

[amitkdutta]

Thanks @spershin