mirror of
https://github.com/neondatabase/neon.git
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abb114decd
- Add comments - Handle members multixact wraparoud - Extract WAL segment creation (pg_resetwal) to postgres_ffi - Fix adding prepared 2PC files to basebackup
89 lines
3.0 KiB
Rust
89 lines
3.0 KiB
Rust
//! Low-level key-value storage abstraction.
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//!
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use crate::repository::{ObjectTag, RelTag};
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use crate::ZTimelineId;
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use anyhow::Result;
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use serde::{Deserialize, Serialize};
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use std::collections::HashSet;
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use std::iter::Iterator;
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use zenith_utils::lsn::Lsn;
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#[derive(Debug, Clone, Serialize, Deserialize)]
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pub struct ObjectKey {
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pub timeline: ZTimelineId,
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pub tag: ObjectTag,
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}
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///
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/// Low-level storage abstraction.
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///
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/// All the data in the repository is stored in a key-value store. This trait
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/// abstracts the details of the key-value store.
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///
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/// A simple key-value store would support just GET and PUT operations with
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/// a key, but the upper layer needs slightly complicated read operations
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///
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/// The most frequently used function is 'object_versions'. It is used
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/// to look up a page version. It is LSN aware, in that the caller
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/// specifies an LSN, and the function returns all values for that
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/// block with the same or older LSN.
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///
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pub trait ObjectStore: Send + Sync {
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///
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/// Store a value with given key.
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///
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fn put(&self, key: &ObjectKey, lsn: Lsn, value: &[u8]) -> Result<()>;
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/// Read entry with the exact given key.
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///
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/// This is used for retrieving metadata with special key that doesn't
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/// correspond to any real relation.
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fn get(&self, key: &ObjectKey, lsn: Lsn) -> Result<Vec<u8>>;
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/// Iterate through all page versions of one object.
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///
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/// Returns all page versions in descending LSN order, along with the LSN
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/// of each page version.
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fn object_versions<'a>(
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&'a self,
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key: &ObjectKey,
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lsn: Lsn,
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) -> Result<Box<dyn Iterator<Item = (Lsn, Vec<u8>)> + 'a>>;
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/// Iterate through versions of all objects in a timeline.
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///
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/// Returns objects in increasing key-version order.
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/// Returns all versions up to and including the specified LSN.
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fn objects<'a>(
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&'a self,
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timeline: ZTimelineId,
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lsn: Lsn,
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) -> Result<Box<dyn Iterator<Item = Result<(ObjectTag, Lsn, Vec<u8>)>> + 'a>>;
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/// Iterate through all keys with given tablespace and database ID, and LSN <= 'lsn'.
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/// Both dbnode and spcnode can be InvalidId (0) which means get all relations in tablespace/cluster
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///
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/// This is used to implement 'create database'
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fn list_rels(
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&self,
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timelineid: ZTimelineId,
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spcnode: u32,
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dbnode: u32,
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lsn: Lsn,
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) -> Result<HashSet<RelTag>>;
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/// Iterate through objects tags. If nonrel_only, then only non-relationa data is iterated.
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///
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/// This is used to implement GC and preparing tarball for new node startup
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/// Returns objects in increasing key-version order.
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fn list_objects<'a>(
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&'a self,
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timelineid: ZTimelineId,
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nonrel_only: bool,
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lsn: Lsn,
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) -> Result<Box<dyn Iterator<Item = ObjectTag> + 'a>>;
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/// Unlink object (used by GC). This mehod may actually delete object or just mark it for deletion.
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fn unlink(&self, key: &ObjectKey, lsn: Lsn) -> Result<()>;
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}
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