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Implement metrics for HashJoinExec #664

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Jul 4, 2021
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Implement metrics for HashJoinExec #664

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103 changes: 66 additions & 37 deletions datafusion/src/physical_plan/hash_join.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ use super::{
SendableRecordBatchStream,
};
use crate::physical_plan::coalesce_batches::concat_batches;
use crate::physical_plan::PhysicalExpr;
use crate::physical_plan::{PhysicalExpr, SQLMetric};
use log::debug;

// Maps a `u64` hash value based on the left ["on" values] to a list of indices with this key's value.
Expand Down Expand Up @@ -102,6 +102,35 @@ pub struct HashJoinExec {
random_state: RandomState,
/// Partitioning mode to use
mode: PartitionMode,
/// Metrics
metrics: Arc<HashJoinMetrics>,
}

/// Metrics for HashJoinExec
#[derive(Debug)]
struct HashJoinMetrics {
/// Total time for joining probe-side batches to the build-side batches
join_time: Arc<SQLMetric>,
/// Number of batches consumed by this operator
input_batches: Arc<SQLMetric>,
/// Number of rows consumed by this operator
input_rows: Arc<SQLMetric>,
/// Number of batches produced by this operator
output_batches: Arc<SQLMetric>,
/// Number of rows produced by this operator
output_rows: Arc<SQLMetric>,
}

impl HashJoinMetrics {
fn new() -> Self {
Self {
join_time: SQLMetric::time_nanos(),
input_batches: SQLMetric::counter(),
input_rows: SQLMetric::counter(),
output_batches: SQLMetric::counter(),
output_rows: SQLMetric::counter(),
}
}
}

#[derive(Clone, Copy, Debug, PartialEq)]
Expand Down Expand Up @@ -154,6 +183,7 @@ impl HashJoinExec {
build_side: Arc::new(Mutex::new(None)),
random_state,
mode: partition_mode,
metrics: Arc::new(HashJoinMetrics::new()),
})
}

Expand Down Expand Up @@ -394,6 +424,7 @@ impl ExecutionPlan for HashJoinExec {
column_indices,
self.random_state.clone(),
visited_left_side,
self.metrics.clone(),
)))
}

Expand All @@ -412,6 +443,22 @@ impl ExecutionPlan for HashJoinExec {
}
}
}

fn metrics(&self) -> HashMap<String, SQLMetric> {
let mut metrics = HashMap::new();
metrics.insert("joinTime".to_owned(), (*self.metrics.join_time).clone());
metrics.insert(
"inputBatches".to_owned(),
(*self.metrics.input_batches).clone(),
);
metrics.insert("inputRows".to_owned(), (*self.metrics.input_rows).clone());
metrics.insert(
"outputBatches".to_owned(),
(*self.metrics.output_batches).clone(),
);
metrics.insert("outputRows".to_owned(), (*self.metrics.output_rows).clone());
metrics
}
}

/// Updates `hash` with new entries from [RecordBatch] evaluated against the expressions `on`,
Expand Down Expand Up @@ -467,22 +514,14 @@ struct HashJoinStream {
right: SendableRecordBatchStream,
/// Information of index and left / right placement of columns
column_indices: Vec<ColumnIndex>,
/// number of input batches
num_input_batches: usize,
/// number of input rows
num_input_rows: usize,
/// number of batches produced
num_output_batches: usize,
/// number of rows produced
num_output_rows: usize,
/// total time for joining probe-side batches to the build-side batches
join_time: usize,
/// Random state used for hashing initialization
random_state: RandomState,
/// Keeps track of the left side rows whether they are visited
visited_left_side: Vec<bool>, // TODO: use a more memory efficient data structure, https://github.com/apache/arrow-datafusion/issues/240
/// There is nothing to process anymore and left side is processed in case of left join
is_exhausted: bool,
/// Metrics
metrics: Arc<HashJoinMetrics>,
}

#[allow(clippy::too_many_arguments)]
Expand All @@ -497,6 +536,7 @@ impl HashJoinStream {
column_indices: Vec<ColumnIndex>,
random_state: RandomState,
visited_left_side: Vec<bool>,
metrics: Arc<HashJoinMetrics>,
) -> Self {
HashJoinStream {
schema,
Expand All @@ -506,14 +546,10 @@ impl HashJoinStream {
left_data,
right,
column_indices,
num_input_batches: 0,
num_input_rows: 0,
num_output_batches: 0,
num_output_rows: 0,
join_time: 0,
random_state,
visited_left_side,
is_exhausted: false,
metrics,
}
}
}
Expand Down Expand Up @@ -1215,12 +1251,14 @@ impl Stream for HashJoinStream {
&self.column_indices,
&self.random_state,
);
self.num_input_batches += 1;
self.num_input_rows += batch.num_rows();
self.metrics.input_batches.add(1);
self.metrics.input_rows.add(batch.num_rows());
if let Ok((ref batch, ref left_side)) = result {
self.join_time += start.elapsed().as_millis() as usize;
self.num_output_batches += 1;
self.num_output_rows += batch.num_rows();
self.metrics
.join_time
.add(start.elapsed().as_millis() as usize);
self.metrics.output_batches.add(1);
self.metrics.output_rows.add(batch.num_rows());

match self.join_type {
JoinType::Left
Expand Down Expand Up @@ -1254,13 +1292,14 @@ impl Stream for HashJoinStream {
self.join_type != JoinType::Semi,
);
if let Ok(ref batch) = result {
self.num_input_batches += 1;
self.num_input_rows += batch.num_rows();
self.metrics.input_batches.add(1);
self.metrics.input_rows.add(batch.num_rows());
if let Ok(ref batch) = result {
self.join_time +=
start.elapsed().as_millis() as usize;
self.num_output_batches += 1;
self.num_output_rows += batch.num_rows();
self.metrics
.join_time
.add(start.elapsed().as_millis() as usize);
self.metrics.output_batches.add(1);
self.metrics.output_rows.add(batch.num_rows());
}
}
self.is_exhausted = true;
Expand All @@ -1274,16 +1313,6 @@ impl Stream for HashJoinStream {
| JoinType::Right => {}
}

// End of right batch, print stats in debug mode
debug!(
"Processed {} probe-side input batches containing {} rows and \
produced {} output batches containing {} rows in {} ms",
self.num_input_batches,
self.num_input_rows,
self.num_output_batches,
self.num_output_rows,
self.join_time
);
other
}
})
Expand Down