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::{OptionExt, ResultExt};
27
28use crate::cache::CacheStrategy;
29use crate::error::{Result, UnexpectedSnafu};
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    RecordBatch(DfRecordBatch),
40}
41
42pub type ScanBatchStream = BoxStream<'static, Result<ScanBatch>>;
43
44/// A stream that takes [`ScanBatch`]es and produces (converts them to) [`RecordBatch`]es.
45pub(crate) struct ConvertBatchStream {
46    inner: ScanBatchStream,
47    projection_mapper: Arc<ProjectionMapper>,
48    cache_strategy: CacheStrategy,
49    partition_metrics: PartitionMetrics,
50    buffer: Vec<DfRecordBatch>,
51}
52
53impl ConvertBatchStream {
54    pub(crate) fn new(
55        inner: ScanBatchStream,
56        projection_mapper: Arc<ProjectionMapper>,
57        cache_strategy: CacheStrategy,
58        partition_metrics: PartitionMetrics,
59    ) -> Self {
60        Self {
61            inner,
62            projection_mapper,
63            cache_strategy,
64            partition_metrics,
65            buffer: Vec::new(),
66        }
67    }
68
69    fn convert(&mut self, batch: ScanBatch) -> common_recordbatch::error::Result<RecordBatch> {
70        let mapper = self
71            .projection_mapper
72            .as_primary_key()
73            .context(UnexpectedSnafu {
74                reason: "Unexpected format",
75            })
76            .map_err(|e| BoxedError::new(e) as _)
77            .context(ExternalSnafu)?;
78
79        match batch {
80            ScanBatch::Normal(batch) => {
81                if batch.is_empty() {
82                    Ok(mapper.empty_record_batch())
83                } else {
84                    mapper.convert(&batch, &self.cache_strategy)
85                }
86            }
87            ScanBatch::Series(series) => {
88                self.buffer.clear();
89                self.buffer.reserve(series.batches.len());
90
91                for batch in series.batches {
92                    let record_batch = mapper.convert(&batch, &self.cache_strategy)?;
93                    self.buffer.push(record_batch.into_df_record_batch());
94                }
95
96                let output_schema = mapper.output_schema();
97                let record_batch =
98                    compute::concat_batches(output_schema.arrow_schema(), &self.buffer)
99                        .context(ArrowComputeSnafu)?;
100
101                RecordBatch::try_from_df_record_batch(output_schema, record_batch)
102            }
103            ScanBatch::RecordBatch(df_record_batch) => {
104                // Safety: Only flat format returns this batch.
105                let mapper = self.projection_mapper.as_flat().unwrap();
106
107                mapper.convert(&df_record_batch)
108            }
109        }
110    }
111}
112
113impl Stream for ConvertBatchStream {
114    type Item = common_recordbatch::error::Result<RecordBatch>;
115
116    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
117        let batch = futures::ready!(self.inner.poll_next_unpin(cx));
118        let Some(batch) = batch else {
119            return Poll::Ready(None);
120        };
121
122        let record_batch = match batch {
123            Ok(batch) => {
124                let start = Instant::now();
125                let record_batch = self.convert(batch);
126                self.partition_metrics
127                    .inc_convert_batch_cost(start.elapsed());
128                record_batch
129            }
130            Err(e) => Err(BoxedError::new(e)).context(ExternalSnafu),
131        };
132        Poll::Ready(Some(record_batch))
133    }
134}
mito2/read/stream.rs

mito2/read/
stream.rs
