greptimedb/src/mito2/src/read/prune.rs

// Copyright 2023 Greptime Team
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use common_time::Timestamp;
use datatypes::scalars::ScalarVectorBuilder;
use datatypes::vectors::BooleanVectorBuilder;

use crate::error::Result;
use crate::memtable::BoxedBatchIterator;
use crate::read::last_row::RowGroupLastRowCachedReader;
use crate::read::{Batch, BatchReader};
use crate::sst::file::FileTimeRange;
use crate::sst::parquet::file_range::FileRangeContextRef;
use crate::sst::parquet::reader::{ReaderMetrics, RowGroupReader};

pub enum Source {
    RowGroup(RowGroupReader),
    LastRow(RowGroupLastRowCachedReader),
}

impl Source {
    async fn next_batch(&mut self) -> Result<Option<Batch>> {
        match self {
            Source::RowGroup(r) => r.next_batch().await,
            Source::LastRow(r) => r.next_batch().await,
        }
    }
}

pub struct PruneReader {
    /// Context for file ranges.
    context: FileRangeContextRef,
    source: Source,
    metrics: ReaderMetrics,
}

impl PruneReader {
    pub(crate) fn new_with_row_group_reader(
        ctx: FileRangeContextRef,
        reader: RowGroupReader,
    ) -> Self {
        Self {
            context: ctx,
            source: Source::RowGroup(reader),
            metrics: Default::default(),
        }
    }

    pub(crate) fn new_with_last_row_reader(
        ctx: FileRangeContextRef,
        reader: RowGroupLastRowCachedReader,
    ) -> Self {
        Self {
            context: ctx,
            source: Source::LastRow(reader),
            metrics: Default::default(),
        }
    }

    pub(crate) fn reset_source(&mut self, source: Source) {
        self.source = source;
    }

    /// Merge metrics with the inner reader and return the merged metrics.
    pub(crate) fn metrics(&self) -> ReaderMetrics {
        let mut metrics = self.metrics.clone();
        match &self.source {
            Source::RowGroup(r) => {
                metrics.merge_from(r.metrics());
            }
            Source::LastRow(r) => {
                if let Some(inner_metrics) = r.metrics() {
                    metrics.merge_from(inner_metrics);
                }
            }
        }

        metrics
    }

    pub(crate) async fn next_batch(&mut self) -> Result<Option<Batch>> {
        while let Some(b) = self.source.next_batch().await? {
            match self.prune(b)? {
                Some(b) => {
                    return Ok(Some(b));
                }
                None => {
                    continue;
                }
            }
        }
        Ok(None)
    }

    /// Prunes batches by the pushed down predicate.
    fn prune(&mut self, batch: Batch) -> Result<Option<Batch>> {
        // fast path
        if self.context.filters().is_empty() {
            return Ok(Some(batch));
        }

        let num_rows_before_filter = batch.num_rows();
        let Some(batch_filtered) = self.context.precise_filter(batch)? else {
            // the entire batch is filtered out
            self.metrics.filter_metrics.num_rows_precise_filtered += num_rows_before_filter;
            return Ok(None);
        };

        // update metric
        let filtered_rows = num_rows_before_filter - batch_filtered.num_rows();
        self.metrics.filter_metrics.num_rows_precise_filtered += filtered_rows;

        if !batch_filtered.is_empty() {
            Ok(Some(batch_filtered))
        } else {
            Ok(None)
        }
    }
}

/// An iterator that prunes batches by time range.
pub(crate) struct PruneTimeIterator {
    iter: BoxedBatchIterator,
    time_range: FileTimeRange,
}

impl PruneTimeIterator {
    /// Creates a new `PruneTimeIterator` with the given iterator and time range.
    pub(crate) fn new(iter: BoxedBatchIterator, time_range: FileTimeRange) -> Self {
        Self { iter, time_range }
    }

    /// Prune batch by time range.
    fn prune(&self, mut batch: Batch) -> Result<Batch> {
        if batch.is_empty() {
            return Ok(batch);
        }

        // fast path, the batch is within the time range.
        // Note that the time range is inclusive.
        if self.time_range.0 <= batch.first_timestamp().unwrap()
            && batch.last_timestamp().unwrap() <= self.time_range.1
        {
            return Ok(batch);
        }

        // slow path, prune the batch by time range.
        // Note that the timestamp precision may be different from the time range.
        // Safety: We know this is the timestamp type.
        let unit = batch
            .timestamps()
            .data_type()
            .as_timestamp()
            .unwrap()
            .unit();
        let mut filter_builder = BooleanVectorBuilder::with_capacity(batch.timestamps().len());
        let timestamps = batch.timestamps_native().unwrap();
        for ts in timestamps {
            let ts = Timestamp::new(*ts, unit);
            if self.time_range.0 <= ts && ts <= self.time_range.1 {
                filter_builder.push(Some(true));
            } else {
                filter_builder.push(Some(false));
            }
        }
        let filter = filter_builder.finish();

        batch.filter(&filter)?;
        Ok(batch)
    }

    // Prune and return the next non-empty batch.
    fn next_non_empty_batch(&mut self) -> Result<Option<Batch>> {
        while let Some(batch) = self.iter.next() {
            let batch = batch?;
            let pruned_batch = self.prune(batch)?;
            if !pruned_batch.is_empty() {
                return Ok(Some(pruned_batch));
            }
        }
        Ok(None)
    }
}

impl Iterator for PruneTimeIterator {
    type Item = Result<Batch>;

    fn next(&mut self) -> Option<Self::Item> {
        self.next_non_empty_batch().transpose()
    }
}

#[cfg(test)]
mod tests {
    use api::v1::OpType;

    use super::*;
    use crate::test_util::new_batch;

    #[test]
    fn test_prune_time_iter_empty() {
        let input = [];
        let iter = input.into_iter().map(Ok);
        let iter = PruneTimeIterator::new(
            Box::new(iter),
            (
                Timestamp::new_millisecond(0),
                Timestamp::new_millisecond(1000),
            ),
        );
        let actual: Vec<_> = iter.map(|batch| batch.unwrap()).collect();
        assert!(actual.is_empty());
    }

    #[test]
    fn test_prune_time_iter_filter() {
        let input = [
            new_batch(
                b"k1",
                &[10, 11],
                &[20, 20],
                &[OpType::Put, OpType::Put],
                &[110, 111],
            ),
            new_batch(
                b"k1",
                &[15, 16],
                &[20, 20],
                &[OpType::Put, OpType::Put],
                &[115, 116],
            ),
            new_batch(
                b"k1",
                &[17, 18],
                &[20, 20],
                &[OpType::Put, OpType::Put],
                &[117, 118],
            ),
        ];

        let iter = input.clone().into_iter().map(Ok);
        let iter = PruneTimeIterator::new(
            Box::new(iter),
            (
                Timestamp::new_millisecond(10),
                Timestamp::new_millisecond(15),
            ),
        );
        let actual: Vec<_> = iter.map(|batch| batch.unwrap()).collect();
        assert_eq!(
            actual,
            [
                new_batch(
                    b"k1",
                    &[10, 11],
                    &[20, 20],
                    &[OpType::Put, OpType::Put],
                    &[110, 111],
                ),
                new_batch(b"k1", &[15], &[20], &[OpType::Put], &[115],),
            ]
        );

        let iter = input.clone().into_iter().map(Ok);
        let iter = PruneTimeIterator::new(
            Box::new(iter),
            (
                Timestamp::new_millisecond(11),
                Timestamp::new_millisecond(20),
            ),
        );
        let actual: Vec<_> = iter.map(|batch| batch.unwrap()).collect();
        assert_eq!(
            actual,
            [
                new_batch(b"k1", &[11], &[20], &[OpType::Put], &[111],),
                new_batch(
                    b"k1",
                    &[15, 16],
                    &[20, 20],
                    &[OpType::Put, OpType::Put],
                    &[115, 116],
                ),
                new_batch(
                    b"k1",
                    &[17, 18],
                    &[20, 20],
                    &[OpType::Put, OpType::Put],
                    &[117, 118],
                ),
            ]
        );

        let iter = input.into_iter().map(Ok);
        let iter = PruneTimeIterator::new(
            Box::new(iter),
            (
                Timestamp::new_millisecond(10),
                Timestamp::new_millisecond(18),
            ),
        );
        let actual: Vec<_> = iter.map(|batch| batch.unwrap()).collect();
        assert_eq!(
            actual,
            [
                new_batch(
                    b"k1",
                    &[10, 11],
                    &[20, 20],
                    &[OpType::Put, OpType::Put],
                    &[110, 111],
                ),
                new_batch(
                    b"k1",
                    &[15, 16],
                    &[20, 20],
                    &[OpType::Put, OpType::Put],
                    &[115, 116],
                ),
                new_batch(
                    b"k1",
                    &[17, 18],
                    &[20, 20],
                    &[OpType::Put, OpType::Put],
                    &[117, 118],
                ),
            ]
        );
    }
}