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LazyRecord (#7619)
This is an attempt to implement a new `Value::LazyRecord` variant for performance reasons. `LazyRecord` is like a regular `Record`, but it's possible to access individual columns without evaluating other columns. I've implemented `LazyRecord` for the special `$nu` variable; accessing `$nu` is relatively slow because of all the information in `scope`, and [`$nu` accounts for about 2/3 of Nu's startup time on Linux](https://github.com/nushell/nushell/issues/6677#issuecomment-1364618122). ### Benchmarks I ran some benchmarks on my desktop (Linux, 12900K) and the results are very pleasing. Nu's time to start up and run a command (`cargo build --release; hyperfine 'target/release/nu -c "echo \"Hello, world!\""' --shell=none --warmup 10`) goes from **8.8ms to 3.2ms, about 2.8x faster**. Tests are also much faster! Running `cargo nextest` (with our very slow `proptest` tests disabled) goes from **7.2s to 4.4s (1.6x faster)**, because most tests involve launching a new instance of Nu. ### Design (updated) I've added a new `LazyRecord` trait and added a `Value` variant wrapping those trait objects, much like `CustomValue`. `LazyRecord` implementations must implement these 2 functions: ```rust // All column names fn column_names(&self) -> Vec<&'static str>; // Get 1 specific column value fn get_column_value(&self, column: &str) -> Result<Value, ShellError>; ``` ### Serializability `Value` variants must implement `Serializable` and `Deserializable`, which poses some problems because I want to use unserializable things like `EngineState` in `LazyRecord`s. To work around this, I basically lie to the type system: 1. Add `#[typetag::serde(tag = "type")]` to `LazyRecord` to make it serializable 2. Any unserializable fields in `LazyRecord` implementations get marked with `#[serde(skip)]` 3. At the point where a `LazyRecord` normally would get serialized and sent to a plugin, I instead collect it into a regular `Value::Record` (which can be serialized)
This commit is contained in:
Reilly Wood
GitHub
@ -1,4 +1,4 @@
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use crate::{current_dir_str, get_full_help, scope::create_scope};
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use crate::{current_dir_str, get_full_help, nu_variable::NuVariable};
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use nu_path::expand_path_with;
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use nu_protocol::{
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ast::{
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@ -6,12 +6,11 @@ use nu_protocol::{
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Operator, PathMember, PipelineElement, Redirection,
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},
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engine::{EngineState, Stack},
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Config, HistoryFileFormat, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
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Range, ShellError, Span, Spanned, Unit, Value, VarId, ENV_VARIABLE_ID,
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Config, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, Range, ShellError, Span,
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Spanned, Unit, Value, VarId, ENV_VARIABLE_ID,
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};
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use nu_utils::stdout_write_all_and_flush;
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use std::collections::HashMap;
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use sysinfo::SystemExt;
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pub fn eval_operator(op: &Expression) -> Result<Operator, ShellError> {
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match op {
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@ -1120,146 +1119,15 @@ pub fn eval_variable(
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span: Span,
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) -> Result<Value, ShellError> {
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match var_id {
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nu_protocol::NU_VARIABLE_ID => {
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// $nu
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let mut output_cols = vec![];
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let mut output_vals = vec![];
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if let Some(path) = engine_state.get_config_path("config-path") {
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output_cols.push("config-path".into());
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output_vals.push(Value::String {
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val: path.to_string_lossy().to_string(),
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span,
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});
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}
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if let Some(path) = engine_state.get_config_path("env-path") {
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output_cols.push("env-path".into());
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output_vals.push(Value::String {
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val: path.to_string_lossy().to_string(),
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span,
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});
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}
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if let Some(mut config_path) = nu_path::config_dir() {
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config_path.push("nushell");
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let mut env_config_path = config_path.clone();
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let mut loginshell_path = config_path.clone();
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let mut history_path = config_path.clone();
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match engine_state.config.history_file_format {
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HistoryFileFormat::Sqlite => {
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history_path.push("history.sqlite3");
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}
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HistoryFileFormat::PlainText => {
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history_path.push("history.txt");
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}
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}
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// let mut history_path = config_files::get_history_path(); // todo: this should use the get_history_path method but idk where to put that function
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output_cols.push("history-path".into());
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output_vals.push(Value::String {
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val: history_path.to_string_lossy().to_string(),
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span,
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});
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if engine_state.get_config_path("config-path").is_none() {
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config_path.push("config.nu");
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output_cols.push("config-path".into());
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output_vals.push(Value::String {
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val: config_path.to_string_lossy().to_string(),
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span,
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});
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}
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if engine_state.get_config_path("env-path").is_none() {
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env_config_path.push("env.nu");
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output_cols.push("env-path".into());
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output_vals.push(Value::String {
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val: env_config_path.to_string_lossy().to_string(),
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span,
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});
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}
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loginshell_path.push("login.nu");
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output_cols.push("loginshell-path".into());
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output_vals.push(Value::String {
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val: loginshell_path.to_string_lossy().to_string(),
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span,
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});
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}
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#[cfg(feature = "plugin")]
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if let Some(path) = &engine_state.plugin_signatures {
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if let Some(path_str) = path.to_str() {
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output_cols.push("plugin-path".into());
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output_vals.push(Value::String {
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val: path_str.into(),
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span,
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});
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}
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}
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output_cols.push("scope".into());
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output_vals.push(create_scope(engine_state, stack, span)?);
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if let Some(home_path) = nu_path::home_dir() {
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if let Some(home_path_str) = home_path.to_str() {
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output_cols.push("home-path".into());
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output_vals.push(Value::String {
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val: home_path_str.into(),
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span,
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})
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}
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}
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let temp = std::env::temp_dir();
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if let Some(temp_path) = temp.to_str() {
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output_cols.push("temp-path".into());
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output_vals.push(Value::String {
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val: temp_path.into(),
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span,
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})
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}
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let pid = std::process::id();
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output_cols.push("pid".into());
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output_vals.push(Value::int(pid as i64, span));
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let sys = sysinfo::System::new();
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let ver = match sys.kernel_version() {
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Some(v) => v,
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None => "unknown".into(),
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};
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let os_record = Value::Record {
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cols: vec![
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"name".into(),
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"arch".into(),
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"family".into(),
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"kernel_version".into(),
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],
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vals: vec![
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Value::string(std::env::consts::OS, span),
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Value::string(std::env::consts::ARCH, span),
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Value::string(std::env::consts::FAMILY, span),
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Value::string(ver, span),
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],
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// $nu
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nu_protocol::NU_VARIABLE_ID => Ok(Value::LazyRecord {
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val: Box::new(NuVariable {
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engine_state: engine_state.clone(),
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stack: stack.clone(),
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span,
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};
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output_cols.push("os-info".into());
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output_vals.push(os_record);
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Ok(Value::Record {
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cols: output_cols,
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vals: output_vals,
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span,
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})
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}
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}),
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span,
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}),
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ENV_VARIABLE_ID => {
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let env_vars = stack.get_env_vars(engine_state);
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let env_columns = env_vars.keys();
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