mito2/read/
stream.rs

1// Copyright 2023 Greptime Team
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::pin::Pin;
16use std::sync::Arc;
17use std::task::{Context, Poll};
18use std::time::Instant;
19
20use common_error::ext::BoxedError;
21use common_recordbatch::error::{ArrowComputeSnafu, ExternalSnafu};
22use common_recordbatch::{DfRecordBatch, RecordBatch};
23use datatypes::compute;
24use futures::stream::BoxStream;
25use futures::{Stream, StreamExt};
26use snafu::ResultExt;
27
28use crate::cache::CacheStrategy;
29use crate::error::Result;
30use crate::read::projection::ProjectionMapper;
31use crate::read::scan_util::PartitionMetrics;
32use crate::read::series_scan::SeriesBatch;
33use crate::read::Batch;
34
35/// All kinds of [`Batch`]es to produce in scanner.
36pub enum ScanBatch {
37    Normal(Batch),
38    Series(SeriesBatch),
39}
40
41pub type ScanBatchStream = BoxStream<'static, Result<ScanBatch>>;
42
43/// A stream that takes [`ScanBatch`]es and produces (converts them to) [`RecordBatch`]es.
44pub(crate) struct ConvertBatchStream {
45    inner: ScanBatchStream,
46    projection_mapper: Arc<ProjectionMapper>,
47    cache_strategy: CacheStrategy,
48    partition_metrics: PartitionMetrics,
49    buffer: Vec<DfRecordBatch>,
50}
51
52impl ConvertBatchStream {
53    pub(crate) fn new(
54        inner: ScanBatchStream,
55        projection_mapper: Arc<ProjectionMapper>,
56        cache_strategy: CacheStrategy,
57        partition_metrics: PartitionMetrics,
58    ) -> Self {
59        Self {
60            inner,
61            projection_mapper,
62            cache_strategy,
63            partition_metrics,
64            buffer: Vec::new(),
65        }
66    }
67
68    fn convert(&mut self, batch: ScanBatch) -> common_recordbatch::error::Result<RecordBatch> {
69        match batch {
70            ScanBatch::Normal(batch) => {
71                if batch.is_empty() {
72                    Ok(self.projection_mapper.empty_record_batch())
73                } else {
74                    self.projection_mapper.convert(&batch, &self.cache_strategy)
75                }
76            }
77            ScanBatch::Series(series) => {
78                self.buffer.clear();
79                self.buffer.reserve(series.batches.len());
80
81                for batch in series.batches {
82                    let record_batch = self
83                        .projection_mapper
84                        .convert(&batch, &self.cache_strategy)?;
85                    self.buffer.push(record_batch.into_df_record_batch());
86                }
87
88                let output_schema = self.projection_mapper.output_schema();
89                let record_batch =
90                    compute::concat_batches(output_schema.arrow_schema(), &self.buffer)
91                        .context(ArrowComputeSnafu)?;
92
93                RecordBatch::try_from_df_record_batch(output_schema, record_batch)
94            }
95        }
96    }
97}
98
99impl Stream for ConvertBatchStream {
100    type Item = common_recordbatch::error::Result<RecordBatch>;
101
102    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
103        let batch = futures::ready!(self.inner.poll_next_unpin(cx));
104        let Some(batch) = batch else {
105            return Poll::Ready(None);
106        };
107
108        let record_batch = match batch {
109            Ok(batch) => {
110                let start = Instant::now();
111                let record_batch = self.convert(batch);
112                self.partition_metrics
113                    .inc_convert_batch_cost(start.elapsed());
114                record_batch
115            }
116            Err(e) => Err(BoxedError::new(e)).context(ExternalSnafu),
117        };
118        Poll::Ready(Some(record_batch))
119    }
120}
mito2/read/stream.rs

mito2/read/
stream.rs
