feat: Add unbounded memory pool (#1386)

## Which issue does this PR close?

## Rationale for this change

DataFusion has an unbounded memory pool. I found it useful for experimental purpose.

## What changes are included in this PR?

Added an option for unbounded memory pool.

## How are these changes tested?

existing tests

common/src/main/scala/org/apache/comet/CometConf.scala

@@ -504,8 +504,8 @@ object CometConf extends ShimCometConf {
     .doc(
       "The type of memory pool to be used for Comet native execution. " +
         "Available memory pool types are 'greedy', 'fair_spill', 'greedy_task_shared', " +
-        "'fair_spill_task_shared', 'greedy_global' and 'fair_spill_global'. For off-heap " +
-        "types are 'unified' and `fair_unified`.")
+        "'fair_spill_task_shared', 'greedy_global', 'fair_spill_global', and `unbounded`. " +
+        "For off-heap types are 'unified' and `fair_unified`.")
     .stringConf
     .createWithDefault("greedy_task_shared")
 

docs/source/user-guide/configs.md

@@ -48,7 +48,7 @@ Comet provides the following configuration settings.
 | spark.comet.exec.hashJoin.enabled | Whether to enable hashJoin by default. | true |
 | spark.comet.exec.initCap.enabled | Whether to enable initCap by default. | false |
 | spark.comet.exec.localLimit.enabled | Whether to enable localLimit by default. | true |
-| spark.comet.exec.memoryPool | The type of memory pool to be used for Comet native execution. Available memory pool types are 'greedy', 'fair_spill', 'greedy_task_shared', 'fair_spill_task_shared', 'greedy_global' and 'fair_spill_global'. For off-heap types are 'unified' and `fair_unified`. | greedy_task_shared |
+| spark.comet.exec.memoryPool | The type of memory pool to be used for Comet native execution. Available memory pool types are 'greedy', 'fair_spill', 'greedy_task_shared', 'fair_spill_task_shared', 'greedy_global', 'fair_spill_global', and `unbounded`. For off-heap types are 'unified' and `fair_unified`. | greedy_task_shared |
 | spark.comet.exec.project.enabled | Whether to enable project by default. | true |
 | spark.comet.exec.replaceSortMergeJoin | Experimental feature to force Spark to replace SortMergeJoin with ShuffledHashJoin for improved performance. This feature is not stable yet. For more information, refer to the Comet Tuning Guide (https://datafusion.apache.org/comet/user-guide/tuning.html). | false |
 | spark.comet.exec.shuffle.compression.codec | The codec of Comet native shuffle used to compress shuffle data. lz4, zstd, and snappy are supported. Compression can be disabled by setting spark.shuffle.compress=false. | lz4 |

native/core/src/execution/jni_api.rs

@@ -26,7 +26,7 @@ use datafusion::{
     prelude::{SessionConfig, SessionContext},
 };
 use datafusion_execution::memory_pool::{
-    FairSpillPool, GreedyMemoryPool, MemoryPool, TrackConsumersPool,
+    FairSpillPool, GreedyMemoryPool, MemoryPool, TrackConsumersPool, UnboundedMemoryPool,
 };
 use futures::poll;
 use jni::{
@@ -118,6 +118,7 @@ enum MemoryPoolType {
     FairSpillTaskShared,
     GreedyGlobal,
     FairSpillGlobal,
+    Unbounded,
 }
 
 struct MemoryPoolConfig {
@@ -319,6 +320,7 @@ fn parse_memory_pool_config(
             "greedy_global" => MemoryPoolConfig::new(MemoryPoolType::GreedyGlobal, pool_size),
             "fair_spill" => MemoryPoolConfig::new(MemoryPoolType::FairSpill, pool_size_per_task),
             "greedy" => MemoryPoolConfig::new(MemoryPoolType::Greedy, pool_size_per_task),
+            "unbounded" => MemoryPoolConfig::new(MemoryPoolType::Unbounded, 0),
             _ => {
                 return Err(CometError::Config(format!(
                     "Unsupported memory pool type: {}",
@@ -397,6 +399,7 @@ fn create_memory_pool(
             per_task_memory_pool.num_plans += 1;
             Arc::clone(&per_task_memory_pool.memory_pool)
         }
+        MemoryPoolType::Unbounded => Arc::new(UnboundedMemoryPool::default()),
     }
 }