mirror of
https://github.com/meilisearch/meilisearch.git
synced 2024-12-02 10:05:05 +08:00
495 lines
19 KiB
Rust
495 lines
19 KiB
Rust
use std::path::PathBuf;
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use std::sync::{Arc, RwLock};
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use std::time::Duration;
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use std::{fs, thread};
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use meilisearch_types::heed::types::{SerdeJson, Str};
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use meilisearch_types::heed::{Database, Env, RoTxn, RwTxn};
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use meilisearch_types::milli::update::IndexerConfig;
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use meilisearch_types::milli::{FieldDistribution, Index};
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use serde::{Deserialize, Serialize};
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use time::OffsetDateTime;
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use tracing::error;
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use uuid::Uuid;
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use self::index_map::IndexMap;
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use self::IndexStatus::{Available, BeingDeleted, Closing, Missing};
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use crate::uuid_codec::UuidCodec;
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use crate::{Error, Result};
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mod index_map;
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const INDEX_MAPPING: &str = "index-mapping";
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const INDEX_STATS: &str = "index-stats";
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/// Structure managing meilisearch's indexes.
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///
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/// It is responsible for:
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/// 1. Creating new indexes
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/// 2. Opening indexes and storing references to these opened indexes
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/// 3. Accessing indexes through their uuid
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/// 4. Mapping a user-defined name to each index uuid.
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///
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/// # Implementation notes
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///
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/// An index exists as 3 bits of data:
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/// 1. The index data on disk, that can exist in 3 states: Missing, Present, or BeingDeleted.
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/// 2. The persistent database containing the association between the index' name and its UUID,
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/// that can exist in 2 states: Missing or Present.
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/// 3. The state of the index in the in-memory `IndexMap`, that can exist in multiple states:
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/// - Missing
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/// - Available
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/// - Closing (because an index needs resizing or was evicted from the cache)
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/// - BeingDeleted
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///
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/// All of this data should be kept consistent between index operations, which is achieved by the `IndexMapper`
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/// with the use of the following primitives:
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/// - A RwLock on the `IndexMap`.
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/// - Transactions on the association database.
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/// - ClosingEvent signals emitted when closing an environment.
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#[derive(Clone)]
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pub struct IndexMapper {
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/// Keep track of the opened indexes. Used mainly by the index resolver.
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index_map: Arc<RwLock<IndexMap>>,
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/// Map an index name with an index uuid currently available on disk.
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pub(crate) index_mapping: Database<Str, UuidCodec>,
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/// Map an index UUID with the cached stats associated to the index.
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///
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/// Using an UUID forces to use the index_mapping table to recover the index behind a name, ensuring
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/// consistency wrt index swapping.
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pub(crate) index_stats: Database<UuidCodec, SerdeJson<IndexStats>>,
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/// Path to the folder where the LMDB environments of each index are.
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base_path: PathBuf,
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/// The map size an index is opened with on the first time.
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index_base_map_size: usize,
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/// The quantity by which the map size of an index is incremented upon reopening, in bytes.
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index_growth_amount: usize,
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/// Whether we open a meilisearch index with the MDB_WRITEMAP option or not.
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enable_mdb_writemap: bool,
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pub indexer_config: Arc<IndexerConfig>,
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/// A few types of long running batches of tasks that act on a single index set this field
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/// so that a handle to the index is available from other threads (search) in an optimized manner.
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currently_updating_index: Arc<RwLock<Option<(String, Index)>>>,
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}
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/// Whether the index is available for use or is forbidden to be inserted back in the index map
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#[allow(clippy::large_enum_variant)]
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#[derive(Clone)]
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pub enum IndexStatus {
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/// Not currently in the index map.
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Missing,
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/// Do not insert it back in the index map as it is currently being deleted.
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BeingDeleted,
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/// Temporarily do not insert the index in the index map as it is currently being resized/evicted from the map.
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Closing(index_map::ClosingIndex),
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/// You can use the index without worrying about anything.
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Available(Index),
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}
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/// The statistics that can be computed from an `Index` object.
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#[derive(Serialize, Deserialize, Debug)]
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pub struct IndexStats {
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/// Number of documents in the index.
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pub number_of_documents: u64,
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/// Size taken up by the index' DB, in bytes.
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///
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/// This includes the size taken by both the used and free pages of the DB, and as the free pages
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/// are not returned to the disk after a deletion, this number is typically larger than
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/// `used_database_size` that only includes the size of the used pages.
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pub database_size: u64,
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/// Size taken by the used pages of the index' DB, in bytes.
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///
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/// As the DB backend does not return to the disk the pages that are not currently used by the DB,
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/// this value is typically smaller than `database_size`.
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pub used_database_size: u64,
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/// Association of every field name with the number of times it occurs in the documents.
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pub field_distribution: FieldDistribution,
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/// Creation date of the index.
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pub created_at: OffsetDateTime,
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/// Date of the last update of the index.
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pub updated_at: OffsetDateTime,
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}
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impl IndexStats {
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/// Compute the stats of an index
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///
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/// # Parameters
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///
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/// - rtxn: a RO transaction for the index, obtained from `Index::read_txn()`.
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pub fn new(index: &Index, rtxn: &RoTxn) -> Result<Self> {
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Ok(IndexStats {
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number_of_documents: index.number_of_documents(rtxn)?,
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database_size: index.on_disk_size()?,
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used_database_size: index.used_size()?,
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field_distribution: index.field_distribution(rtxn)?,
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created_at: index.created_at(rtxn)?,
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updated_at: index.updated_at(rtxn)?,
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})
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}
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}
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impl IndexMapper {
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pub fn new(
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env: &Env,
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base_path: PathBuf,
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index_base_map_size: usize,
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index_growth_amount: usize,
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index_count: usize,
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enable_mdb_writemap: bool,
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indexer_config: IndexerConfig,
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) -> Result<Self> {
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let mut wtxn = env.write_txn()?;
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let index_mapping = env.create_database(&mut wtxn, Some(INDEX_MAPPING))?;
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let index_stats = env.create_database(&mut wtxn, Some(INDEX_STATS))?;
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wtxn.commit()?;
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Ok(Self {
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index_map: Arc::new(RwLock::new(IndexMap::new(index_count))),
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index_mapping,
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index_stats,
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base_path,
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index_base_map_size,
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index_growth_amount,
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enable_mdb_writemap,
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indexer_config: Arc::new(indexer_config),
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currently_updating_index: Default::default(),
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})
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}
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/// Get or create the index.
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pub fn create_index(
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&self,
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mut wtxn: RwTxn,
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name: &str,
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date: Option<(OffsetDateTime, OffsetDateTime)>,
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) -> Result<Index> {
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match self.index(&wtxn, name) {
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Ok(index) => {
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wtxn.commit()?;
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Ok(index)
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}
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Err(Error::IndexNotFound(_)) => {
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let uuid = Uuid::new_v4();
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self.index_mapping.put(&mut wtxn, name, &uuid)?;
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let index_path = self.base_path.join(uuid.to_string());
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fs::create_dir_all(&index_path)?;
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// Error if the UUIDv4 somehow already exists in the map, since it should be fresh.
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// This is very unlikely to happen in practice.
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// TODO: it would be better to lazily create the index. But we need an Index::open function for milli.
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let index = self.index_map.write().unwrap().create(
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&uuid,
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&index_path,
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date,
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self.enable_mdb_writemap,
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self.index_base_map_size,
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)?;
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wtxn.commit()?;
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Ok(index)
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}
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error => error,
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}
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}
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/// Removes the index from the mapping table and the in-memory index map
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/// but keeps the associated tasks.
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pub fn delete_index(&self, mut wtxn: RwTxn, name: &str) -> Result<()> {
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let uuid = self
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.index_mapping
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.get(&wtxn, name)?
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.ok_or_else(|| Error::IndexNotFound(name.to_string()))?;
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// Not an error if the index had no stats in cache.
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self.index_stats.delete(&mut wtxn, &uuid)?;
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// Once we retrieved the UUID of the index we remove it from the mapping table.
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assert!(self.index_mapping.delete(&mut wtxn, name)?);
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wtxn.commit()?;
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let mut tries = 0;
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// Attempts to remove the index from the in-memory index map in a loop.
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//
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// If the index is currently being closed, we will wait for it to be closed and retry getting it in a subsequent
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// loop iteration.
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//
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// We make 100 attempts before giving up.
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// This could happen in the following situations:
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//
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// 1. There is a bug preventing the index from being correctly closed, or us from detecting this.
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// 2. A user of the index is keeping it open for more than 600 seconds. This could happen e.g. during a pathological search.
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// This can not be caused by indexation because deleting an index happens in the scheduler itself, so cannot be concurrent with indexation.
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//
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// In these situations, reporting the error through a panic is in order.
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let closing_event = loop {
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let mut lock = self.index_map.write().unwrap();
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match lock.start_deletion(&uuid) {
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Ok(env_closing) => break env_closing,
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Err(Some(reopen)) => {
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// drop the lock here so that we don't synchronously wait for the index to close.
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drop(lock);
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tries += 1;
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if tries >= 100 {
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panic!("Too many attempts to close index {name} prior to deletion.")
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}
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let reopen = if let Some(reopen) = reopen.wait_timeout(Duration::from_secs(6)) {
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reopen
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} else {
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continue;
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};
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reopen.close(&mut self.index_map.write().unwrap());
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continue;
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}
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Err(None) => return Ok(()),
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}
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};
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let index_map = self.index_map.clone();
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let index_path = self.base_path.join(uuid.to_string());
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let index_name = name.to_string();
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thread::Builder::new()
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.name(String::from("index_deleter"))
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.spawn(move || {
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// We first wait to be sure that the previously opened index is effectively closed.
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// This can take a lot of time, this is why we do that in a separate thread.
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if let Some(closing_event) = closing_event {
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closing_event.wait();
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}
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// Then we remove the content from disk.
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if let Err(e) = fs::remove_dir_all(&index_path) {
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error!(
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"An error happened when deleting the index {} ({}): {}",
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index_name, uuid, e
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);
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}
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// Finally we remove the entry from the index map.
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index_map.write().unwrap().end_deletion(&uuid);
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})
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.unwrap();
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Ok(())
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}
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pub fn exists(&self, rtxn: &RoTxn, name: &str) -> Result<bool> {
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Ok(self.index_mapping.get(rtxn, name)?.is_some())
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}
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/// Resizes the maximum size of the specified index to the double of its current maximum size.
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///
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/// This operation involves closing the underlying environment and so can take a long time to complete.
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///
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/// # Panics
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///
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/// - If the Index corresponding to the passed name is concurrently being deleted/resized or cannot be found in the
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/// in memory hash map.
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pub fn resize_index(&self, rtxn: &RoTxn, name: &str) -> Result<()> {
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let uuid = self
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.index_mapping
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.get(rtxn, name)?
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.ok_or_else(|| Error::IndexNotFound(name.to_string()))?;
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// We remove the index from the in-memory index map.
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self.index_map.write().unwrap().close_for_resize(
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&uuid,
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self.enable_mdb_writemap,
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self.index_growth_amount,
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);
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Ok(())
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}
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/// Return an index, may open it if it wasn't already opened.
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pub fn index(&self, rtxn: &RoTxn, name: &str) -> Result<Index> {
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if let Some((current_name, current_index)) =
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self.currently_updating_index.read().unwrap().as_ref()
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{
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if current_name == name {
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return Ok(current_index.clone());
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}
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}
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let uuid = self
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.index_mapping
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.get(rtxn, name)?
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.ok_or_else(|| Error::IndexNotFound(name.to_string()))?;
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let mut tries = 0;
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// attempts to open the index in a loop.
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//
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// If the index is currently being closed, we will wait for it to be closed and retry getting it in a subsequent
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// loop iteration.
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//
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// We make 100 attempts before giving up.
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// This could happen in the following situations:
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//
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// 1. There is a bug preventing the index from being correctly closed, or us from detecting it was.
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// 2. A user of the index is keeping it open for more than 600 seconds. This could happen e.g. during a long indexation,
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// a pathological search, and so on.
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//
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// In these situations, reporting the error through a panic is in order.
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let index = loop {
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tries += 1;
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if tries > 100 {
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panic!("Too many spurious wake ups while trying to open the index {name}");
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}
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// we get the index here to drop the lock before entering the match
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let index = self.index_map.read().unwrap().get(&uuid);
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match index {
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Available(index) => break index,
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Closing(reopen) => {
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// Avoiding deadlocks: no lock taken while doing this operation.
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let reopen = if let Some(reopen) = reopen.wait_timeout(Duration::from_secs(6)) {
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reopen
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} else {
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continue;
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};
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let index_path = self.base_path.join(uuid.to_string());
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// take the lock to reopen the environment.
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reopen.reopen(&mut self.index_map.write().unwrap(), &index_path)?;
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continue;
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}
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BeingDeleted => return Err(Error::IndexNotFound(name.to_string())),
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// since we're lazy, it's possible that the index has not been opened yet.
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Missing => {
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let mut index_map = self.index_map.write().unwrap();
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// between the read lock and the write lock it's not impossible
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// that someone already opened the index (eg if two searches happen
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// at the same time), thus before opening it we check a second time
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// if it's not already there.
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match index_map.get(&uuid) {
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Missing => {
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let index_path = self.base_path.join(uuid.to_string());
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break index_map.create(
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&uuid,
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&index_path,
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None,
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self.enable_mdb_writemap,
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self.index_base_map_size,
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)?;
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}
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Available(index) => break index,
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Closing(_) => {
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// the reopening will be handled in the next loop operation
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continue;
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}
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BeingDeleted => return Err(Error::IndexNotFound(name.to_string())),
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}
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}
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}
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};
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Ok(index)
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}
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/// Attempts `f` for each index that exists in the index mapper.
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///
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/// It is preferable to use this function rather than a loop that opens all indexes, as a way to avoid having all indexes opened,
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/// which is unsupported in general.
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///
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/// Since `f` is allowed to return a result, and `Index` is cloneable, it is still possible to wrongly build e.g. a vector of
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/// all the indexes, but this function makes it harder and so less likely to do accidentally.
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pub fn try_for_each_index<U, V>(
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&self,
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rtxn: &RoTxn,
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mut f: impl FnMut(&str, &Index) -> Result<U>,
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) -> Result<V>
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where
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V: FromIterator<U>,
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{
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self.index_mapping
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.iter(rtxn)?
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.map(|res| {
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res.map_err(Error::from)
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.and_then(|(name, _)| self.index(rtxn, name).and_then(|index| f(name, &index)))
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})
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.collect()
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}
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/// Return the name of all indexes without opening them.
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pub fn index_names(&self, rtxn: &RoTxn) -> Result<Vec<String>> {
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self.index_mapping
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.iter(rtxn)?
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.map(|res| res.map_err(Error::from).map(|(name, _)| name.to_string()))
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.collect()
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}
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/// Swap two index names.
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pub fn swap(&self, wtxn: &mut RwTxn, lhs: &str, rhs: &str) -> Result<()> {
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let lhs_uuid = self
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.index_mapping
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.get(wtxn, lhs)?
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.ok_or_else(|| Error::IndexNotFound(lhs.to_string()))?;
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let rhs_uuid = self
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.index_mapping
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.get(wtxn, rhs)?
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.ok_or_else(|| Error::IndexNotFound(rhs.to_string()))?;
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self.index_mapping.put(wtxn, lhs, &rhs_uuid)?;
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self.index_mapping.put(wtxn, rhs, &lhs_uuid)?;
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Ok(())
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}
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/// The stats of an index.
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///
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/// If available in the cache, they are directly returned.
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/// Otherwise, the `Index` is opened to compute the stats on the fly (the result is not cached).
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/// The stats for an index are cached after each `Index` update.
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pub fn stats_of(&self, rtxn: &RoTxn, index_uid: &str) -> Result<IndexStats> {
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let uuid = self
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.index_mapping
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.get(rtxn, index_uid)?
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.ok_or_else(|| Error::IndexNotFound(index_uid.to_string()))?;
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match self.index_stats.get(rtxn, &uuid)? {
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Some(stats) => Ok(stats),
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None => {
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let index = self.index(rtxn, index_uid)?;
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let index_rtxn = index.read_txn()?;
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IndexStats::new(&index, &index_rtxn)
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}
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}
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}
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|
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/// Stores the new stats for an index.
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///
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/// Expected usage is to compute the stats the index using `IndexStats::new`, the pass it to this function.
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pub fn store_stats_of(
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&self,
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wtxn: &mut RwTxn,
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index_uid: &str,
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stats: &IndexStats,
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) -> Result<()> {
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let uuid = self
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.index_mapping
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.get(wtxn, index_uid)?
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.ok_or_else(|| Error::IndexNotFound(index_uid.to_string()))?;
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self.index_stats.put(wtxn, &uuid, stats)?;
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Ok(())
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}
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pub fn index_exists(&self, rtxn: &RoTxn, name: &str) -> Result<bool> {
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Ok(self.index_mapping.get(rtxn, name)?.is_some())
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}
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pub fn indexer_config(&self) -> &IndexerConfig {
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&self.indexer_config
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}
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pub fn set_currently_updating_index(&self, index: Option<(String, Index)>) {
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*self.currently_updating_index.write().unwrap() = index;
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|
}
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|
}
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