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Add LRU regex cache (#7587)

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Closes #7572 by adding a cache for compiled regexes of type
`Arc<Mutex<LruCache<String, Regex>>>` to `EngineState` .

The cache is limited to 100 entries (limit chosen arbitrarily) and
evicts least-recently-used items first.

This PR makes a noticeable difference when using regexes for
`color_config`, e.g.:
```bash
#first set string formatting in config.nu like:
string: { if $in =~ '^#\w{6}$' { $in } else { 'white' } }`

# then try displaying and exploring a table with many strings
# this is instant after the PR, but takes hundreds of milliseconds before
['#ff0033', '#0025ee', '#0087aa', 'string', '#4101ff', '#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff', '#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff', '#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff', '#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff','#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff','#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff','#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff','#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff','#ff0033', '#0025ee', '#0087aa', 'string', '#6103ff']
```

## New dependency (`lru`)
This uses [the popular `lru` crate](https://lib.rs/crates/lru). The new
dependency adds 19.8KB to a Linux release build of Nushell. I think this
is OK, especially since the crate can be useful elsewhere in Nu.
This commit is contained in:
Reilly Wood
2022-12-23 14:30:04 -08:00
committed by GitHub
parent 3be7996e79
commit a43e66ef92
5 changed files with 58 additions and 14 deletions
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11
crates/nu-protocol/src/engine/engine_state.rs
View File

@@ -1,3 +1,6 @@
use fancy_regex::Regex;
use lru::LruCache;
use super::{Command, EnvVars, OverlayFrame, ScopeFrame, Stack, Visibility, DEFAULT_OVERLAY_NAME};
use crate::Value;
use crate::{
@@ -6,6 +9,7 @@ use crate::{
};
use core::panic;
use std::borrow::Borrow;
use std::num::NonZeroUsize;
use std::path::Path;
use std::path::PathBuf;
use std::{
@@ -94,8 +98,12 @@ pub struct EngineState {
pub history_session_id: i64,
// If Nushell was started, e.g., with `nu spam.nu`, the file's parent is stored here
pub currently_parsed_cwd: Option<PathBuf>,
pub regex_cache: Arc<Mutex<LruCache<String, Regex>>>,
}
// The max number of compiled regexes to keep around in a LRU cache, arbitrarily chosen
const REGEX_CACHE_SIZE: usize = 100; // must be nonzero, otherwise will panic
pub const NU_VARIABLE_ID: usize = 0;
pub const IN_VARIABLE_ID: usize = 1;
pub const ENV_VARIABLE_ID: usize = 2;
@@ -137,6 +145,9 @@ impl EngineState {
config_path: HashMap::new(),
history_session_id: 0,
currently_parsed_cwd: None,
regex_cache: Arc::new(Mutex::new(LruCache::new(
NonZeroUsize::new(REGEX_CACHE_SIZE).expect("tried to create cache of size zero"),
))),
}
}