risinglight 0.2.0

An OLAP database system for educational purpose
Documentation 
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// Copyright 2022 RisingLight Project Authors. Licensed under Apache-2.0.

use std::path::{Path, PathBuf};

use bytes::Bytes;
use tokio::fs::{File, OpenOptions};
use tokio::io::{AsyncWriteExt, BufWriter};

use crate::catalog::ColumnCatalog;
use crate::storage::secondary::rowset::EncodedRowset;
use crate::storage::secondary::IOBackend;
use crate::storage::StorageResult;

pub fn path_of_data_column(base: impl AsRef<Path>, column_info: &ColumnCatalog) -> PathBuf {
    path_of_column(base, column_info, ".col")
}

pub fn path_of_index_column(base: impl AsRef<Path>, column_info: &ColumnCatalog) -> PathBuf {
    path_of_column(base, column_info, ".idx")
}

pub fn path_of_column(
    base: impl AsRef<Path>,
    column_info: &ColumnCatalog,
    suffix: &str,
) -> PathBuf {
    base.as_ref()
        .join(format!("{}{}", column_info.id(), suffix))
}

/// Rowset writer.
pub struct RowsetWriter {
    /// Directory of the rowset.
    directory: PathBuf,

    /// The backend used to write the rowset
    io_backend: IOBackend,
}

impl RowsetWriter {
    pub fn new(directory: impl AsRef<Path>, io_backend: IOBackend) -> Self {
        Self {
            directory: directory.as_ref().to_path_buf(),
            io_backend,
        }
    }

    pub async fn create_dir(&self) -> StorageResult<()> {
        if !self.io_backend.is_in_memory() {
            tokio::fs::create_dir(&self.directory)
                .await
                .map_err(|err| err.into())
        } else {
            Ok(())
        }
    }

    async fn pipe_to_file(
        io_backend: &IOBackend,
        path: impl AsRef<Path>,
        data: Vec<u8>,
    ) -> StorageResult<()> {
        match io_backend {
            IOBackend::InMemory(map) => {
                let mut guard = map.lock();
                guard.insert(path.as_ref().to_path_buf(), Bytes::from(data));
            }
            _ => {
                let file = OpenOptions::new()
                    .write(true)
                    .create_new(true)
                    .open(path.as_ref())
                    .await?;

                let mut writer = BufWriter::new(file);
                writer.write_all(&data).await?;
                writer.flush().await?;

                let file = writer.into_inner();
                file.sync_data().await?;
            }
        }

        Ok(())
    }

    async fn sync_dir(io_backend: &IOBackend, path: &impl AsRef<Path>) -> StorageResult<()> {
        if !io_backend.is_in_memory() {
            File::open(path.as_ref()).await?.sync_data().await?;
        }
        Ok(())
    }

    /// Flush rows in an encoded rowset. Create files if not exists.
    /// Panics if the rowset is empty.
    pub async fn flush(self, rowset: EncodedRowset) -> StorageResult<()> {
        // Panic on empty flush.
        if rowset.is_empty() {
            panic!("empty rowset")
        }

        for (column_info, column) in rowset.columns_info.iter().zip(rowset.columns) {
            Self::pipe_to_file(
                &self.io_backend,
                path_of_data_column(&self.directory, column_info),
                column.data,
            )
            .await?;
            Self::pipe_to_file(
                &self.io_backend,
                path_of_index_column(&self.directory, column_info),
                column.index,
            )
            .await?;
        }

        Self::sync_dir(&self.io_backend, &self.directory).await?;

        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::array::ArrayImpl;
    use crate::storage::secondary::rowset::RowsetBuilder;
    use crate::storage::secondary::ColumnBuilderOptions;
    use crate::types::DataTypeKind;

    #[tokio::test]
    async fn test_rowset_flush() {
        let tempdir = tempfile::tempdir().unwrap();

        let mut builder = RowsetBuilder::new(
            vec![ColumnCatalog::new(
                0,
                DataTypeKind::Int32.nullable().to_column("v1".to_string()),
            )]
            .into(),
            ColumnBuilderOptions::default_for_test(),
        );

        for _ in 0..1000 {
            builder.append(
                [ArrayImpl::new_int32(
                    [1, 2, 3].into_iter().cycle().take(1000).collect(),
                )]
                .into_iter()
                .collect(),
            )
        }
        let backend = IOBackend::in_memory();
        let writer = RowsetWriter::new(tempdir.path(), backend);
        writer.flush(builder.finish()).await.unwrap();
    }
}