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Ensure the row count is preserved when coalescing over empty records #3439

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Sep 12, 2022
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Ensure the row count is preserved when coalescing over empty records #3439

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8b2b1e4
Ensure the row count is preserved when coalescing over empty records
isidentical Sep 10, 2022
928eb9a
Explain the reasoning for not using optimized_plan in tests
isidentical Sep 12, 2022
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8 changes: 6 additions & 2 deletions datafusion/core/src/physical_plan/coalesce_batches.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ use crate::execution::context::TaskContext;
use arrow::compute::kernels::concat::concat;
use arrow::datatypes::SchemaRef;
use arrow::error::Result as ArrowResult;
use arrow::record_batch::RecordBatch;
use arrow::record_batch::{RecordBatch, RecordBatchOptions};
use futures::stream::{Stream, StreamExt};
use log::trace;

Expand Down Expand Up @@ -291,7 +291,11 @@ pub fn concat_batches(
batches.len(),
row_count
);
RecordBatch::try_new(schema.clone(), arrays)

let mut options = RecordBatchOptions::default();
options.row_count = Some(row_count);
Comment on lines +295 to +296
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As an FYI (not important) you can write this same pattern in what is likely more idiomatic rust (avoid mut) like:

Suggested change
let mut options = RecordBatchOptions::default();
options.row_count = Some(row_count);
let options = RecordBatchOptions{
row_count:Some(row_count),
..Default::default()
};

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This seems to fail since RecordBatchOptions is non-exhaustive and comes directly from arrow-rs. I am not really familiar with this part of Rust semantics, but there seems to be an existing issue about it.

error[E0639]: cannot create non-exhaustive struct using struct expression
   --> /home/isidentical/projects/arrow-datafusion/datafusion/core/src/physical_plan/coalesce_batches.rs:295:19
    |
295 |       let options = RecordBatchOptions {
    |  ___________________^
296 | |         row_count: Some(row_count),
297 | |         ..Default::default()
298 | |     };
    | |_____^

For more information about this error, try `rustc --explain E0639`.

Is there any way to achieve it? The only other example of RecordBatchOptions construction present in DF is the following which uses the same pattern as the code present in this PR but I'd be happy to refactor both if there is a more idiomatic way.
https://github.com/apache/arrow-datafusion/blob/9956f80f197550051db7debae15d5c706afc22a3/datafusion/core/src/physical_plan/file_format/mod.rs#L286-L288

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Thanks for trying @isidentical -- I will file a follow on in arrow-rs to make this API more ergonomic

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Filed apache/arrow-rs#2728 as a follow on (I also hit the same thing in #3454 FWIW)

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FYI apache/arrow-rs#2729 fixed this issue and #3483 includes using the new API.


RecordBatch::try_new_with_options(schema.clone(), arrays, &options)
}

#[cfg(test)]
Expand Down
14 changes: 11 additions & 3 deletions datafusion/core/tests/sql/mod.rs
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Expand Up @@ -765,14 +765,22 @@ async fn execute_to_batches(ctx: &SessionContext, sql: &str) -> Vec<RecordBatch>
.unwrap();
let logical_schema = plan.schema();

// We are not really interested in the direct output of optimized_logical_plan
// since the physical plan construction already optimizes the given logical plan
// and we want to avoid double-optimization as a consequence. So we just construct
// it here to make sure that it doesn't fail at this step and get the optimized
// schema (to assert later that the logical and optimized schemas are the same).
let msg = format!("Optimizing logical plan for '{}': {:?}", sql, plan);
let plan = ctx
let optimized_logical_plan = ctx
.optimize(&plan)
.map_err(|e| format!("{:?} at {}", e, msg))
.unwrap();
let optimized_logical_schema = plan.schema();
let optimized_logical_schema = optimized_logical_plan.schema();

let msg = format!("Creating physical plan for '{}': {:?}", sql, plan);
let msg = format!(
"Creating physical plan for '{}': {:?}",
sql, optimized_logical_plan
);
let plan = ctx
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.create_physical_plan(&plan)
.await
Expand Down