Major performance #4311.Rmd

---
title: 'Major performance drop of keyed := when index is present #4311'
author: "Doris Amoakohene"
date: "`r Sys.Date()`"
output: html_document
---


Major performance drop of keyed := when index is present #4311
https://github.com/Rdatatable/data.table/issues/4311
https://github.com/Rdatatable/data.table/issues/4311#issue-584883821

```{r}

```{r}
library(atime)
library(data.table)
library(ggplot2)
library(git2r)
```

```{r}
  tdir <- tempfile()
  dir.create(tdir)
  git2r::clone("https://github.com/Rdatatable/data.table", tdir)
  
```

```{r}

atime.list <- atime::atime_versions(
pkg.path=tdir,
pkg.edit.fun=function(old.Package, new.Package, sha, new.pkg.path){
      pkg_find_replace <- function(glob, FIND, REPLACE){
        atime::glob_find_replace(file.path(new.pkg.path, glob), FIND, REPLACE)
      }
      Package_regex <- gsub(".", "_?", old.Package, fixed=TRUE)
      Package_ <- gsub(".", "_", old.Package, fixed=TRUE)
      new.Package_ <- paste0(Package_, "_", sha)
      pkg_find_replace(
        "DESCRIPTION", 
        paste0("Package:\\s+", old.Package),
        paste("Package:", new.Package))
      pkg_find_replace(
        file.path("src","Makevars.*in"),
        Package_regex,
        new.Package_)
      pkg_find_replace(
        file.path("R", "onLoad.R"),
        Package_regex,
        new.Package_)
      pkg_find_replace(
        file.path("R", "onLoad.R"),
        sprintf('packageVersion\\("%s"\\)', old.Package),
        sprintf('packageVersion\\("%s"\\)', new.Package))
      pkg_find_replace(
        file.path("src", "init.c"),
        paste0("R_init_", Package_regex),
        paste0("R_init_", gsub("[.]", "_", new.Package_)))
      pkg_find_replace(
        "NAMESPACE",
        sprintf('useDynLib\\("?%s"?', Package_regex),
        paste0('useDynLib(', new.Package_))
    },
  N=10^seq(3,8),
  setup={ 
    n <- N/100
    set.seed(1L)
    dt <- data.table(
      g = sample(seq_len(n), N, TRUE),
      x = runif(N),
      key = "g")
    dt_mod <- copy(dt)
  },
  expr=data.table:::`[.data.table`(dt_mod, , N := .N, by = g)],
  "Before"="be2f72e6f5c90622fe72e1c315ca05769a9dc854",
  "Regression"="e793f53466d99f86e70fc2611b708ae8c601a451", #Before and Regression:https://github.com/Rdatatable/data.table/pull/4491/commits from this commits id in github. on(news items tweak and move items up)
  "Fixed"="58409197426ced4714af842650b0cc3b9e2cb842") #fixed:#https://github.com/Rdatatable/data.table/pull/5463/commits; taken from the last commits in here. for fixed.


```

```{r}
plot(atime.list)
```

```