[GitHub] [arrow] westonpace commented on a diff in pull request #12845: ARROW-15718: [C++] Increase thread limit to work around thread issues

[GitBox <gi...@apache.org>]

westonpace commented on code in PR #12845:
URL: https://github.com/apache/arrow/pull/12845#discussion_r846429806


##########
cpp/src/arrow/compute/exec/hash_join.cc:
##########
@@ -103,7 +103,8 @@ class HashJoinBasicImpl : public HashJoinImpl {
     filter_ = std::move(filter);
     output_batch_callback_ = std::move(output_batch_callback);
     finished_callback_ = std::move(finished_callback);
-    local_states_.resize(num_threads + 1);  // +1 for calling thread + worker threads
+    // Adding ten, since each side of join might have an IO thread being called from.

Review Comment:
   Can you add `TODO(ARROW-15732)` to this comment so we know when to clean it up?



##########
cpp/src/arrow/compute/exec/hash_join.cc:
##########
@@ -103,7 +103,8 @@ class HashJoinBasicImpl : public HashJoinImpl {
     filter_ = std::move(filter);
     output_batch_callback_ = std::move(output_batch_callback);
     finished_callback_ = std::move(finished_callback);
-    local_states_.resize(num_threads + 1);  // +1 for calling thread + worker threads
+    // Adding ten, since each side of join might have an IO thread being called from.
+    local_states_.resize(num_threads + 10);

Review Comment:
   ```suggestion
       local_states_.resize(GetCpuThreadPoolCapacity() + io::GetIOThreadPoolCapacity() + 1);
   ```
   This is slightly less arbitrary than 10 and we'd have to be doing something truly weird to go over this value.



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