mito2/

config.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.

//! Configurations.

use std::cmp;
use std::path::Path;
use std::time::Duration;

use common_base::memory_limit::MemoryLimit;
use common_base::readable_size::ReadableSize;
use common_memory_manager::OnExhaustedPolicy;
use common_stat::{get_total_cpu_cores, get_total_memory_readable};
use common_telemetry::warn;
use serde::{Deserialize, Serialize};
use serde_with::serde_as;

use crate::cache::file_cache::DEFAULT_INDEX_CACHE_PERCENT;
use crate::error::Result;
use crate::gc::GcConfig;
use crate::memtable::MemtableConfig;
use crate::sst::DEFAULT_WRITE_BUFFER_SIZE;

const MULTIPART_UPLOAD_MINIMUM_SIZE: ReadableSize = ReadableSize::mb(5);
/// Default channel size for parallel scan task.
pub(crate) const DEFAULT_SCAN_CHANNEL_SIZE: usize = 32;
/// Default maximum number of SST files to scan concurrently.
pub(crate) const DEFAULT_MAX_CONCURRENT_SCAN_FILES: usize = 384;

// Use `1/GLOBAL_WRITE_BUFFER_SIZE_FACTOR` of OS memory as global write buffer size in default mode
const GLOBAL_WRITE_BUFFER_SIZE_FACTOR: u64 = 8;
/// Use `1/SST_META_CACHE_SIZE_FACTOR` of OS memory size as SST meta cache size in default mode
const SST_META_CACHE_SIZE_FACTOR: u64 = 32;
/// Use `1/MEM_CACHE_SIZE_FACTOR` of OS memory size as mem cache size in default mode
const MEM_CACHE_SIZE_FACTOR: u64 = 16;
/// Use `1/PAGE_CACHE_SIZE_FACTOR` of OS memory size as page cache size in default mode
const PAGE_CACHE_SIZE_FACTOR: u64 = 8;
/// Use `1/INDEX_CREATE_MEM_THRESHOLD_FACTOR` of OS memory size as mem threshold for creating index
const INDEX_CREATE_MEM_THRESHOLD_FACTOR: u64 = 16;

/// Fetch option timeout
pub(crate) const FETCH_OPTION_TIMEOUT: Duration = Duration::from_secs(3);

/// Configuration for [MitoEngine](crate::engine::MitoEngine).
/// Before using the config, make sure to call `MitoConfig::validate()` to check if the config is valid.
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
#[serde(default)]
pub struct MitoConfig {
    // Worker configs:
    /// Number of region workers (default: 1/2 of cpu cores).
    /// Sets to 0 to use the default value.
    pub num_workers: usize,
    /// Request channel size of each worker (default 128).
    pub worker_channel_size: usize,
    /// Max batch size for a worker to handle requests (default 64).
    pub worker_request_batch_size: usize,

    // Manifest configs:
    /// Number of meta action updated to trigger a new checkpoint
    /// for the manifest (default 10).
    pub manifest_checkpoint_distance: u64,
    /// Number of removed files to keep in manifest's `removed_files` field before also
    /// remove them from `removed_files`. Mostly for debugging purpose.
    /// If set to 0, it will only use `keep_removed_file_ttl` to decide when to remove files
    /// from `removed_files` field.
    pub experimental_manifest_keep_removed_file_count: usize,
    /// How long to keep removed files in the `removed_files` field of manifest
    /// after they are removed from manifest.
    /// files will only be removed from `removed_files` field
    /// if both `keep_removed_file_count` and `keep_removed_file_ttl` is reached.
    #[serde(with = "humantime_serde")]
    pub experimental_manifest_keep_removed_file_ttl: Duration,
    /// Whether to compress manifest and checkpoint file by gzip (default false).
    pub compress_manifest: bool,

    // Background job configs:
    /// Max number of running background index build jobs (default: 1/8 of cpu cores).
    pub max_background_index_builds: usize,
    /// Max number of running background flush jobs (default: 1/2 of cpu cores).
    pub max_background_flushes: usize,
    /// Max number of running background compaction jobs (default: 1/4 of cpu cores).
    pub max_background_compactions: usize,
    /// Max number of running background purge jobs (default: number of cpu cores).
    pub max_background_purges: usize,
    /// Memory budget for compaction tasks. Setting it to 0 or "unlimited" disables the limit.
    pub experimental_compaction_memory_limit: MemoryLimit,
    /// Behavior when compaction cannot acquire memory from the budget.
    pub experimental_compaction_on_exhausted: OnExhaustedPolicy,

    // Flush configs:
    /// Interval to auto flush a region if it has not flushed yet (default 30 min).
    #[serde(with = "humantime_serde")]
    pub auto_flush_interval: Duration,
    /// Global write buffer size threshold to trigger flush.
    pub global_write_buffer_size: ReadableSize,
    /// Global write buffer size threshold to reject write requests.
    pub global_write_buffer_reject_size: ReadableSize,

    // Cache configs:
    /// Cache size for SST metadata. Setting it to 0 to disable the cache.
    pub sst_meta_cache_size: ReadableSize,
    /// Cache size for vectors and arrow arrays. Setting it to 0 to disable the cache.
    pub vector_cache_size: ReadableSize,
    /// Cache size for pages of SST row groups. Setting it to 0 to disable the cache.
    pub page_cache_size: ReadableSize,
    /// Cache size for time series selector (e.g. `last_value()`). Setting it to 0 to disable the cache.
    pub selector_result_cache_size: ReadableSize,
    /// Whether to enable the write cache.
    pub enable_write_cache: bool,
    /// File system path for write cache dir's root, defaults to `{data_home}`.
    pub write_cache_path: String,
    /// Capacity for write cache.
    pub write_cache_size: ReadableSize,
    /// TTL for write cache.
    #[serde(with = "humantime_serde")]
    pub write_cache_ttl: Option<Duration>,
    /// Preload index (puffin) files into cache on region open (default: true).
    pub preload_index_cache: bool,
    /// Percentage of write cache capacity allocated for index (puffin) files (default: 20).
    /// The remaining capacity is used for data (parquet) files.
    /// Must be between 0 and 100 (exclusive).
    pub index_cache_percent: u8,
    /// Enable background downloading of files to the local cache when accessed during queries (default: true).
    /// When enabled, files will be asynchronously downloaded to improve performance for subsequent reads.
    pub enable_refill_cache_on_read: bool,
    /// Capacity for manifest cache (default: 256MB).
    pub manifest_cache_size: ReadableSize,

    // Other configs:
    /// Buffer size for SST writing.
    pub sst_write_buffer_size: ReadableSize,
    /// Capacity of the channel to send data from parallel scan tasks to the main task (default 32).
    pub parallel_scan_channel_size: usize,
    /// Maximum number of SST files to scan concurrently (default 384).
    pub max_concurrent_scan_files: usize,
    /// Whether to allow stale entries read during replay.
    pub allow_stale_entries: bool,
    /// Memory limit for table scans across all queries. Setting it to 0 disables the limit.
    /// Supports absolute size (e.g., "2GB") or percentage (e.g., "50%").
    pub scan_memory_limit: MemoryLimit,

    /// Index configs.
    pub index: IndexConfig,
    /// Inverted index configs.
    pub inverted_index: InvertedIndexConfig,
    /// Full-text index configs.
    pub fulltext_index: FulltextIndexConfig,
    /// Bloom filter index configs.
    pub bloom_filter_index: BloomFilterConfig,
    /// Vector index configs (HNSW).
    #[cfg(feature = "vector_index")]
    pub vector_index: VectorIndexConfig,

    /// Memtable config
    pub memtable: MemtableConfig,

    /// Minimum time interval between two compactions.
    /// To align with the old behavior, the default value is 0 (no restrictions).
    #[serde(with = "humantime_serde")]
    pub min_compaction_interval: Duration,

    /// Whether to enable experimental flat format as the default format.
    /// When enabled, forces using BulkMemtable and BulkMemtableBuilder.
    pub default_experimental_flat_format: bool,

    pub gc: GcConfig,
}

impl Default for MitoConfig {
    fn default() -> Self {
        let mut mito_config = MitoConfig {
            num_workers: divide_num_cpus(2),
            worker_channel_size: 128,
            worker_request_batch_size: 64,
            manifest_checkpoint_distance: 10,
            experimental_manifest_keep_removed_file_count: 256,
            experimental_manifest_keep_removed_file_ttl: Duration::from_secs(60 * 60),
            compress_manifest: false,
            max_background_index_builds: divide_num_cpus(8),
            max_background_flushes: divide_num_cpus(2),
            max_background_compactions: divide_num_cpus(4),
            max_background_purges: get_total_cpu_cores(),
            experimental_compaction_memory_limit: MemoryLimit::Unlimited,
            experimental_compaction_on_exhausted: OnExhaustedPolicy::default(),
            auto_flush_interval: Duration::from_secs(30 * 60),
            global_write_buffer_size: ReadableSize::gb(1),
            global_write_buffer_reject_size: ReadableSize::gb(2),
            sst_meta_cache_size: ReadableSize::mb(128),
            vector_cache_size: ReadableSize::mb(512),
            page_cache_size: ReadableSize::mb(512),
            selector_result_cache_size: ReadableSize::mb(512),
            enable_write_cache: false,
            write_cache_path: String::new(),
            write_cache_size: ReadableSize::gb(5),
            write_cache_ttl: None,
            preload_index_cache: true,
            index_cache_percent: DEFAULT_INDEX_CACHE_PERCENT,
            enable_refill_cache_on_read: true,
            manifest_cache_size: ReadableSize::mb(256),
            sst_write_buffer_size: DEFAULT_WRITE_BUFFER_SIZE,
            parallel_scan_channel_size: DEFAULT_SCAN_CHANNEL_SIZE,
            max_concurrent_scan_files: DEFAULT_MAX_CONCURRENT_SCAN_FILES,
            allow_stale_entries: false,
            scan_memory_limit: MemoryLimit::default(),
            index: IndexConfig::default(),
            inverted_index: InvertedIndexConfig::default(),
            fulltext_index: FulltextIndexConfig::default(),
            bloom_filter_index: BloomFilterConfig::default(),
            #[cfg(feature = "vector_index")]
            vector_index: VectorIndexConfig::default(),
            memtable: MemtableConfig::default(),
            min_compaction_interval: Duration::from_secs(0),
            default_experimental_flat_format: false,
            gc: GcConfig::default(),
        };

        // Adjust buffer and cache size according to system memory if we can.
        if let Some(sys_memory) = get_total_memory_readable() {
            mito_config.adjust_buffer_and_cache_size(sys_memory);
        }

        mito_config
    }
}

impl MitoConfig {
    /// Sanitize incorrect configurations.
    ///
    /// Returns an error if there is a configuration that unable to sanitize.
    pub fn sanitize(&mut self, data_home: &str) -> Result<()> {
        // Use default value if `num_workers` is 0.
        if self.num_workers == 0 {
            self.num_workers = divide_num_cpus(2);
        }

        // Sanitize channel size.
        if self.worker_channel_size == 0 {
            warn!("Sanitize channel size 0 to 1");
            self.worker_channel_size = 1;
        }

        if self.max_background_flushes == 0 {
            warn!(
                "Sanitize max background flushes 0 to {}",
                divide_num_cpus(2)
            );
            self.max_background_flushes = divide_num_cpus(2);
        }
        if self.max_background_compactions == 0 {
            warn!(
                "Sanitize max background compactions 0 to {}",
                divide_num_cpus(4)
            );
            self.max_background_compactions = divide_num_cpus(4);
        }
        if self.max_background_purges == 0 {
            let cpu_cores = get_total_cpu_cores();
            warn!("Sanitize max background purges 0 to {}", cpu_cores);
            self.max_background_purges = cpu_cores;
        }

        if self.global_write_buffer_reject_size <= self.global_write_buffer_size {
            self.global_write_buffer_reject_size = self.global_write_buffer_size * 2;
            warn!(
                "Sanitize global write buffer reject size to {}",
                self.global_write_buffer_reject_size
            );
        }

        if self.sst_write_buffer_size < MULTIPART_UPLOAD_MINIMUM_SIZE {
            self.sst_write_buffer_size = MULTIPART_UPLOAD_MINIMUM_SIZE;
            warn!(
                "Sanitize sst write buffer size to {}",
                self.sst_write_buffer_size
            );
        }

        if self.parallel_scan_channel_size < 1 {
            self.parallel_scan_channel_size = DEFAULT_SCAN_CHANNEL_SIZE;
            warn!(
                "Sanitize scan channel size to {}",
                self.parallel_scan_channel_size
            );
        }

        // Sets write cache path if it is empty.
        if self.write_cache_path.trim().is_empty() {
            self.write_cache_path = data_home.to_string();
        }

        // Validate index_cache_percent is within valid range (0, 100)
        if self.index_cache_percent == 0 || self.index_cache_percent >= 100 {
            warn!(
                "Invalid index_cache_percent {}, resetting to default {}",
                self.index_cache_percent, DEFAULT_INDEX_CACHE_PERCENT
            );
            self.index_cache_percent = DEFAULT_INDEX_CACHE_PERCENT;
        }

        self.index.sanitize(data_home, &self.inverted_index)?;

        Ok(())
    }

    fn adjust_buffer_and_cache_size(&mut self, sys_memory: ReadableSize) {
        // shouldn't be greater than 1G in default mode.
        let global_write_buffer_size = cmp::min(
            sys_memory / GLOBAL_WRITE_BUFFER_SIZE_FACTOR,
            ReadableSize::gb(1),
        );
        // Use 2x of global write buffer size as global write buffer reject size.
        let global_write_buffer_reject_size = global_write_buffer_size * 2;
        // shouldn't be greater than 128MB in default mode.
        let sst_meta_cache_size = cmp::min(
            sys_memory / SST_META_CACHE_SIZE_FACTOR,
            ReadableSize::mb(128),
        );
        // shouldn't be greater than 512MB in default mode.
        let mem_cache_size = cmp::min(sys_memory / MEM_CACHE_SIZE_FACTOR, ReadableSize::mb(512));
        let page_cache_size = sys_memory / PAGE_CACHE_SIZE_FACTOR;

        self.global_write_buffer_size = global_write_buffer_size;
        self.global_write_buffer_reject_size = global_write_buffer_reject_size;
        self.sst_meta_cache_size = sst_meta_cache_size;
        self.vector_cache_size = mem_cache_size;
        self.page_cache_size = page_cache_size;
        self.selector_result_cache_size = mem_cache_size;

        self.index.adjust_buffer_and_cache_size(sys_memory);
    }

    /// Enable write cache.
    #[cfg(test)]
    pub fn enable_write_cache(
        mut self,
        path: String,
        size: ReadableSize,
        ttl: Option<Duration>,
    ) -> Self {
        self.enable_write_cache = true;
        self.write_cache_path = path;
        self.write_cache_size = size;
        self.write_cache_ttl = ttl;
        self
    }
}

/// Index build mode.
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq, Default)]
#[serde(rename_all = "snake_case")]
pub enum IndexBuildMode {
    /// Build index synchronously.
    #[default]
    Sync,
    /// Build index asynchronously.
    Async,
}

#[serde_as]
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
#[serde(default)]
pub struct IndexConfig {
    /// Auxiliary directory path for the index in filesystem, used to
    /// store intermediate files for creating the index and staging files
    /// for searching the index, defaults to `{data_home}/index_intermediate`.
    ///
    /// This path contains two subdirectories:
    /// - `__intm`: for storing intermediate files used during creating index.
    /// - `staging`: for storing staging files used during searching index.
    ///
    /// The default name for this directory is `index_intermediate` for backward compatibility.
    pub aux_path: String,

    /// The max capacity of the staging directory.
    pub staging_size: ReadableSize,
    /// The TTL of the staging directory.
    /// Defaults to 7 days.
    /// Setting it to "0s" to disable TTL.
    #[serde(with = "humantime_serde")]
    pub staging_ttl: Option<Duration>,

    /// Index Build Mode
    pub build_mode: IndexBuildMode,

    /// Write buffer size for creating the index.
    pub write_buffer_size: ReadableSize,

    /// Cache size for metadata of puffin files. Setting it to 0 to disable the cache.
    pub metadata_cache_size: ReadableSize,
    /// Cache size for inverted index content. Setting it to 0 to disable the cache.
    pub content_cache_size: ReadableSize,
    /// Page size for inverted index content.
    pub content_cache_page_size: ReadableSize,
    /// Cache size for index result. Setting it to 0 to disable the cache.
    pub result_cache_size: ReadableSize,
}

impl Default for IndexConfig {
    fn default() -> Self {
        Self {
            aux_path: String::new(),
            staging_size: ReadableSize::gb(2),
            staging_ttl: Some(Duration::from_secs(7 * 24 * 60 * 60)),
            build_mode: IndexBuildMode::default(),
            write_buffer_size: ReadableSize::mb(8),
            metadata_cache_size: ReadableSize::mb(64),
            content_cache_size: ReadableSize::mb(128),
            content_cache_page_size: ReadableSize::kb(64),
            result_cache_size: ReadableSize::mb(128),
        }
    }
}

impl IndexConfig {
    pub fn sanitize(
        &mut self,
        data_home: &str,
        inverted_index: &InvertedIndexConfig,
    ) -> Result<()> {
        #[allow(deprecated)]
        if self.aux_path.is_empty() && !inverted_index.intermediate_path.is_empty() {
            self.aux_path.clone_from(&inverted_index.intermediate_path);
            warn!(
                "`inverted_index.intermediate_path` is deprecated, use
                 `index.aux_path` instead. Set `index.aux_path` to {}",
                &inverted_index.intermediate_path
            )
        }
        if self.aux_path.is_empty() {
            let path = Path::new(data_home).join("index_intermediate");
            self.aux_path = path.as_os_str().to_string_lossy().to_string();
        }

        if self.write_buffer_size < MULTIPART_UPLOAD_MINIMUM_SIZE {
            self.write_buffer_size = MULTIPART_UPLOAD_MINIMUM_SIZE;
            warn!(
                "Sanitize index write buffer size to {}",
                self.write_buffer_size
            );
        }

        if self.staging_ttl.map(|ttl| ttl.is_zero()).unwrap_or(false) {
            self.staging_ttl = None;
        }

        Ok(())
    }

    pub fn adjust_buffer_and_cache_size(&mut self, sys_memory: ReadableSize) {
        let cache_size = cmp::min(sys_memory / MEM_CACHE_SIZE_FACTOR, ReadableSize::mb(128));
        self.result_cache_size = cmp::min(self.result_cache_size, cache_size);
        self.content_cache_size = cmp::min(self.content_cache_size, cache_size);

        let metadata_cache_size = cmp::min(
            sys_memory / SST_META_CACHE_SIZE_FACTOR,
            ReadableSize::mb(64),
        );
        self.metadata_cache_size = cmp::min(self.metadata_cache_size, metadata_cache_size);
    }
}

/// Operational mode for certain actions.
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq, Default)]
#[serde(rename_all = "snake_case")]
pub enum Mode {
    /// The action is performed automatically based on internal criteria.
    #[default]
    Auto,
    /// The action is explicitly disabled.
    Disable,
}

impl Mode {
    /// Whether the action is disabled.
    pub fn disabled(&self) -> bool {
        matches!(self, Mode::Disable)
    }

    /// Whether the action is automatic.
    pub fn auto(&self) -> bool {
        matches!(self, Mode::Auto)
    }
}

/// Memory threshold for performing certain actions.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Default)]
#[serde(rename_all = "snake_case")]
pub enum MemoryThreshold {
    /// Automatically determine the threshold based on internal criteria.
    #[default]
    Auto,
    /// Unlimited memory.
    Unlimited,
    /// Fixed memory threshold.
    #[serde(untagged)]
    Size(ReadableSize),
}

/// Configuration options for the inverted index.
#[serde_as]
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
#[serde(default)]
pub struct InvertedIndexConfig {
    /// Whether to create the index on flush: automatically or never.
    pub create_on_flush: Mode,
    /// Whether to create the index on compaction: automatically or never.
    pub create_on_compaction: Mode,
    /// Whether to apply the index on query: automatically or never.
    pub apply_on_query: Mode,

    /// Memory threshold for performing an external sort during index creation.
    pub mem_threshold_on_create: MemoryThreshold,

    #[deprecated = "use [IndexConfig::aux_path] instead"]
    #[serde(skip_serializing)]
    pub intermediate_path: String,

    #[deprecated = "use [IndexConfig::write_buffer_size] instead"]
    #[serde(skip_serializing)]
    pub write_buffer_size: ReadableSize,
}

impl Default for InvertedIndexConfig {
    #[allow(deprecated)]
    fn default() -> Self {
        Self {
            create_on_flush: Mode::Auto,
            create_on_compaction: Mode::Auto,
            apply_on_query: Mode::Auto,
            mem_threshold_on_create: MemoryThreshold::Auto,
            write_buffer_size: ReadableSize::mb(8),
            intermediate_path: String::new(),
        }
    }
}

impl InvertedIndexConfig {
    pub fn mem_threshold_on_create(&self) -> Option<usize> {
        match self.mem_threshold_on_create {
            MemoryThreshold::Auto => {
                if let Some(sys_memory) = get_total_memory_readable() {
                    Some((sys_memory / INDEX_CREATE_MEM_THRESHOLD_FACTOR).as_bytes() as usize)
                } else {
                    Some(ReadableSize::mb(64).as_bytes() as usize)
                }
            }
            MemoryThreshold::Unlimited => None,
            MemoryThreshold::Size(size) => Some(size.as_bytes() as usize),
        }
    }
}

/// Configuration options for the full-text index.
#[serde_as]
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
#[serde(default)]
pub struct FulltextIndexConfig {
    /// Whether to create the index on flush: automatically or never.
    pub create_on_flush: Mode,
    /// Whether to create the index on compaction: automatically or never.
    pub create_on_compaction: Mode,
    /// Whether to apply the index on query: automatically or never.
    pub apply_on_query: Mode,
    /// Memory threshold for creating the index.
    pub mem_threshold_on_create: MemoryThreshold,
    /// Whether to compress the index data.
    pub compress: bool,
}

impl Default for FulltextIndexConfig {
    fn default() -> Self {
        Self {
            create_on_flush: Mode::Auto,
            create_on_compaction: Mode::Auto,
            apply_on_query: Mode::Auto,
            mem_threshold_on_create: MemoryThreshold::Auto,
            compress: true,
        }
    }
}

impl FulltextIndexConfig {
    pub fn mem_threshold_on_create(&self) -> usize {
        match self.mem_threshold_on_create {
            MemoryThreshold::Auto => {
                if let Some(sys_memory) = get_total_memory_readable() {
                    (sys_memory / INDEX_CREATE_MEM_THRESHOLD_FACTOR).as_bytes() as _
                } else {
                    ReadableSize::mb(64).as_bytes() as _
                }
            }
            MemoryThreshold::Unlimited => usize::MAX,
            MemoryThreshold::Size(size) => size.as_bytes() as _,
        }
    }
}

/// Configuration options for the bloom filter.
#[serde_as]
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
#[serde(default)]
pub struct BloomFilterConfig {
    /// Whether to create the index on flush: automatically or never.
    pub create_on_flush: Mode,
    /// Whether to create the index on compaction: automatically or never.
    pub create_on_compaction: Mode,
    /// Whether to apply the index on query: automatically or never.
    pub apply_on_query: Mode,
    /// Memory threshold for creating the index.
    pub mem_threshold_on_create: MemoryThreshold,
}

impl Default for BloomFilterConfig {
    fn default() -> Self {
        Self {
            create_on_flush: Mode::Auto,
            create_on_compaction: Mode::Auto,
            apply_on_query: Mode::Auto,
            mem_threshold_on_create: MemoryThreshold::Auto,
        }
    }
}

impl BloomFilterConfig {
    pub fn mem_threshold_on_create(&self) -> Option<usize> {
        match self.mem_threshold_on_create {
            MemoryThreshold::Auto => {
                if let Some(sys_memory) = get_total_memory_readable() {
                    Some((sys_memory / INDEX_CREATE_MEM_THRESHOLD_FACTOR).as_bytes() as usize)
                } else {
                    Some(ReadableSize::mb(64).as_bytes() as usize)
                }
            }
            MemoryThreshold::Unlimited => None,
            MemoryThreshold::Size(size) => Some(size.as_bytes() as usize),
        }
    }
}

/// Configuration options for the vector index (HNSW).
#[cfg(feature = "vector_index")]
#[serde_as]
#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
#[serde(default)]
pub struct VectorIndexConfig {
    /// Whether to create the index on flush: automatically or never.
    pub create_on_flush: Mode,
    /// Whether to create the index on compaction: automatically or never.
    pub create_on_compaction: Mode,
    /// Whether to apply the index on query: automatically or never.
    pub apply_on_query: Mode,
    /// Memory threshold for creating the index.
    pub mem_threshold_on_create: MemoryThreshold,
}

#[cfg(feature = "vector_index")]
impl Default for VectorIndexConfig {
    fn default() -> Self {
        Self {
            create_on_flush: Mode::Auto,
            create_on_compaction: Mode::Auto,
            apply_on_query: Mode::Auto,
            mem_threshold_on_create: MemoryThreshold::Auto,
        }
    }
}

#[cfg(feature = "vector_index")]
impl VectorIndexConfig {
    pub fn mem_threshold_on_create(&self) -> Option<usize> {
        match self.mem_threshold_on_create {
            MemoryThreshold::Auto => {
                if let Some(sys_memory) = get_total_memory_readable() {
                    Some((sys_memory / INDEX_CREATE_MEM_THRESHOLD_FACTOR).as_bytes() as usize)
                } else {
                    Some(ReadableSize::mb(64).as_bytes() as usize)
                }
            }
            MemoryThreshold::Unlimited => None,
            MemoryThreshold::Size(size) => Some(size.as_bytes() as usize),
        }
    }
}

/// Divide cpu num by a non-zero `divisor` and returns at least 1.
fn divide_num_cpus(divisor: usize) -> usize {
    debug_assert!(divisor > 0);
    let cores = get_total_cpu_cores();
    debug_assert!(cores > 0);

    cores.div_ceil(divisor)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_deserialize_config() {
        let s = r#"
[memtable]
type = "partition_tree"
index_max_keys_per_shard = 8192
data_freeze_threshold = 1024
dedup = true
fork_dictionary_bytes = "512MiB"
"#;
        let config: MitoConfig = toml::from_str(s).unwrap();
        let MemtableConfig::PartitionTree(config) = &config.memtable else {
            unreachable!()
        };
        assert_eq!(1024, config.data_freeze_threshold);
    }
}