From aa40599e534aaed292e0e977bcd14584960547ea Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 14:16:04 -0400
Subject: [PATCH 01/37] Fast

---
 .ci/atime/tests.R | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 2d342ded67..701f21d268 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -331,6 +331,7 @@ test.list <- atime::atime_test_list(
     PR7401="0216983c51e03e3f61d5e6f08f4ba0c42cceb22c", # Merge commit (https://github.com/Rdatatable/data.table/commit/0216983c51e03e3f61d5e6f08f4ba0c42cceb22c) of a PR (https://github.com/Rdatatable/data.table/pull/7401) which increased speed and memory usage of this test (https://github.com/Rdatatable/data.table/issues/7687)
     Before = "7a9eaf62ede487625200981018d8692be8c6f134", # Parent of the first commit (https://github.com/Rdatatable/data.table/commit/515de90a6068911a148e54343a3503043b8bb87c) in the PR (https://github.com/Rdatatable/data.table/pull/4164/commits) that introduced the regression
     Regression = "c152ced0e5799acee1589910c69c1a2c6586b95d", # Parent of the first commit (https://github.com/Rdatatable/data.table/commit/15f0598b9828d3af2eb8ddc9b38e0356f42afe4f) in the PR (https://github.com/Rdatatable/data.table/pull/4558/commits) that fixes the regression
+    Fast="1.18.6",
     Fixed = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     expr = data.table:::`[.data.table`(d, , max(v1) - min(v2), by = id)),
 

From 657940ae9a29128c87d733118f505d93fa81ac86 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 14:33:15 -0400
Subject: [PATCH 02/37] rename commits

---
 .ci/atime/tests.R | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 701f21d268..7bf9cd13ce 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -328,11 +328,10 @@ test.list <- atime::atime_test_list(
         v2 = sample(5L, N, TRUE)
       )
     },
-    PR7401="0216983c51e03e3f61d5e6f08f4ba0c42cceb22c", # Merge commit (https://github.com/Rdatatable/data.table/commit/0216983c51e03e3f61d5e6f08f4ba0c42cceb22c) of a PR (https://github.com/Rdatatable/data.table/pull/7401) which increased speed and memory usage of this test (https://github.com/Rdatatable/data.table/issues/7687)
-    Before = "7a9eaf62ede487625200981018d8692be8c6f134", # Parent of the first commit (https://github.com/Rdatatable/data.table/commit/515de90a6068911a148e54343a3503043b8bb87c) in the PR (https://github.com/Rdatatable/data.table/pull/4164/commits) that introduced the regression
-    Regression = "c152ced0e5799acee1589910c69c1a2c6586b95d", # Parent of the first commit (https://github.com/Rdatatable/data.table/commit/15f0598b9828d3af2eb8ddc9b38e0356f42afe4f) in the PR (https://github.com/Rdatatable/data.table/pull/4558/commits) that fixes the regression
+    Before = "1.12.0",
+    Regression="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of Slow (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
+    Slow = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     Fast="1.18.6",
-    Fixed = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     expr = data.table:::`[.data.table`(d, , max(v1) - min(v2), by = id)),
 
   # Issue with sorting again when already sorted, as reported in https://github.com/Rdatatable/data.table/issues/4498

From 623bd2ff5ecfb97fcf89406970aa89ac1558df6f Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 14:41:44 -0400
Subject: [PATCH 03/37] 1.12.8

---
 .ci/atime/tests.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 7bf9cd13ce..c1dfee4636 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -328,7 +328,7 @@ test.list <- atime::atime_test_list(
         v2 = sample(5L, N, TRUE)
       )
     },
-    Before = "1.12.0",
+    Before = "1.12.8",
     Regression="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of Slow (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     Slow = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     Fast="1.18.6",

From 30885fd9a9e01c1e7c17d6c505a7fe783489f752 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 14:46:28 -0400
Subject: [PATCH 04/37] comment Before

---
 .ci/atime/tests.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index c1dfee4636..cd3a22a42a 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -328,7 +328,7 @@ test.list <- atime::atime_test_list(
         v2 = sample(5L, N, TRUE)
       )
     },
-    Before = "1.12.8",
+    #Before = "1.12.8",
     Regression="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of Slow (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     Slow = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     Fast="1.18.6",

From 66e1cded4e739e4e6eed8b1bb6c94bd54465074c Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 15:01:23 -0400
Subject: [PATCH 05/37] fast=master

---
 .ci/atime/tests.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index cd3a22a42a..f5fdbbe946 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -331,7 +331,7 @@ test.list <- atime::atime_test_list(
     #Before = "1.12.8",
     Regression="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of Slow (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     Slow = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
-    Fast="1.18.6",
+    Fast="master",
     expr = data.table:::`[.data.table`(d, , max(v1) - min(v2), by = id)),
 
   # Issue with sorting again when already sorted, as reported in https://github.com/Rdatatable/data.table/issues/4498

From 5dc14b864636294f5561c2356fbf680d56dc5a63 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 15:07:58 -0400
Subject: [PATCH 06/37] new Before

---
 .ci/atime/tests.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index f5fdbbe946..c95915297d 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -328,7 +328,7 @@ test.list <- atime::atime_test_list(
         v2 = sample(5L, N, TRUE)
       )
     },
-    #Before = "1.12.8",
+    Before = "166e0bab317e9d9f4f1844997a315e6482ab5fd9",#a few click of parent up from first commit in PR4164 gets to https://github.com/Rdatatable/data.table/commit/166e0bab317e9d9f4f1844997a315e6482ab5fd9
     Regression="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of Slow (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     Slow = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     Fast="master",

From 918be2c28862afc38e779fd9ba2c988334c41a60 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 15:14:42 -0400
Subject: [PATCH 07/37] bisect viz script

---
 .ci/atime/bisect-7687.R | 162 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 .ci/atime/bisect-7687.R

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
new file mode 100644
index 0000000000..1563b6dd93
--- /dev/null
+++ b/.ci/atime/bisect-7687.R
@@ -0,0 +1,162 @@
+remotes::install_github("tdhock/atime@bisect")
+pkg.path <- "~/R/data.table"
+Test <- "DT[by] fixed in #4558"
+atime::bisect(pkg.path, Test, "Before", "Regression")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
+atime::bisect(pkg.path, Test, "Slow", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
+
+Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Slow_Fast"
+Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Before_Regression"
+library(data.table)
+(results.wide <- data.table(
+  csv=Sys.glob(file.path(Test.dir, "csv", "*"))
+)[
+, fread(csv), by=csv
+][
+, rank := rank(time)
+][order(rank)][, let(
+  Rank = factor(rank, labels=format(time)),
+  Status = factor(status)
+)][])
+(results.long <- melt(
+  results.wide,
+  measure.vars=measure(variable, version, sep=".")))
+
+show.versions <- unique(results.long$version)
+details.dt.list <- list()
+dot.dt.list <- list()
+common.dt.list <- list()
+for(result.RData in Sys.glob(file.path(Test.dir, "RData", "*"))){
+  (objs <- load(result.RData))
+  commit <- sub(".RData", "", basename(result.RData))
+  details <- tres.or.status$measurements[
+    show.versions,
+    on="version",
+    data.table(commit, expr.name, version, N, median, min, max)
+  ]
+  common.dt.list[[commit]] <- details[, .(
+    versions=.N
+  ), by=N][
+    versions==max(versions)
+  ][.N, data.table(commit, N)]
+  evers <- unique(details[, .(expr.name, version)])
+  details.dt.list[[commit]] <- details
+  dot.dt.list[[commit]] <- data.table(
+    commit,
+    tpred$prediction[evers, on="expr.name"])
+}
+(details.dt <- rbindlist(details.dt.list))
+(dot.dt <- rbindlist(dot.dt.list))
+(common.dt <- rbindlist(common.dt.list))
+
+limit.dt <- data.table(seconds=tpred$seconds.limit)
+library(animint2)
+(version.colors <- atime:::default.version.colors)
+version.colors[setdiff(unique(dot.dt$version), names(version.colors))] <- "black"
+animint(
+  overview=ggplot()+
+    ggtitle("Overview, select commit")+
+    theme_bw()+
+    geom_tallrect(aes(
+      xmin=rank-0.5, xmax=rank+0.5,
+      key=rank,
+      fill=Status),
+      color=NA,
+      data=results.wide)+
+    geom_line(aes(
+      rank, value, color=version, group=version),
+      data=results.long)+
+    facet_grid(variable ~ ., scales="free")+
+    theme(axis.text.x=element_text(angle=30, hjust=1))+
+    geom_label_aligned(aes(
+      rank, value, label=version, color=version),
+      data=results.long[rank==max(rank)],
+      hjust=0,
+      alignment="vertical")+
+    scale_fill_manual(values=c(
+      "0"="grey",
+      "1"="white"))+
+    scale_color_manual(values=version.colors)+
+    scale_y_continuous("")+
+    scale_x_continuous("commit rank over time")+
+    geom_tallrect(aes(
+      xmin=rank-0.5, xmax=rank+0.5),
+      clickSelects="commit",
+      alpha=1,
+      alpha_off=0,
+      color="black",
+      color_off=NA,
+      fill=NA,
+      data=results.wide),
+  details=ggplot()+
+    ggtitle("Details for selected commit")+
+    theme_bw()+
+    theme(legend.position="none")+
+    theme_animint(width=1000)+
+    geom_hline(aes(
+      yintercept=seconds),
+      color="grey",
+      data=limit.dt)+
+    geom_text(aes(
+      0, seconds*1.1,
+      label=sprintf(
+        "time limit = %s seconds",
+        paste(seconds)
+      )),
+      hjust=0,
+      color="grey50",
+      data=limit.dt)+
+    geom_vline(aes(
+      xintercept=N,
+      key=1),
+      data=common.dt,
+      color="grey",
+      showSelected="commit")+
+    geom_text(aes(
+      N, 0, label=sprintf("largest common N=%s", paste(N)),
+      key=1),
+      data=common.dt,
+      hjust=1,
+      color="grey50",
+      showSelected="commit")+
+    geom_text(aes(
+      0, 0, label=commit,
+      href=paste0("https://github.com/Rdatatable/data.table/commit/", commit),
+      key=1),
+      hjust=0,
+      vjust=0,
+      data=common.dt,
+      showSelected="commit")+
+    geom_ribbon(aes(
+      N, ymin=min, ymax=max,
+      key=version, fill=version, group=version),
+      showSelected=c("version","commit"),
+      alpha=0.5,
+      color=NA,
+      data=details.dt)+
+    geom_line(aes(
+      N, median,
+      key=version, color=version, group=version),
+      showSelected=c("version","commit"),
+      data=details.dt)+
+    geom_point(aes(
+      N, unit.value,
+      key=version, color=version),
+      showSelected=c("version","commit"),
+      fill="white",
+      data=dot.dt)+
+    geom_label_aligned(aes(
+      N, unit.value, label=version,
+      key=version, color=version),
+      showSelected=c("version","commit"),
+      alignment="horizontal",
+      vjust=-0.1,
+      alpha=0.5,
+      data=dot.dt)+
+    scale_color_manual(values=version.colors)+
+    scale_fill_manual(values=version.colors)+
+    scale_x_log10()+
+    scale_y_log10("seconds"),
+  duration=list(
+    commit=1000)
+)
+

From 50e7c3232cf2ef00baafec0d2c5dd0b6c49dcfec Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Fri, 9 Oct 2026 15:35:58 -0400
Subject: [PATCH 08/37] publish

---
 .ci/atime/bisect-7687.R | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 1563b6dd93..bf8c3c5262 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -50,9 +50,15 @@ for(result.RData in Sys.glob(file.path(Test.dir, "RData", "*"))){
 
 limit.dt <- data.table(seconds=tpred$seconds.limit)
 library(animint2)
-(version.colors <- atime:::default.version.colors)
-version.colors[setdiff(unique(dot.dt$version), names(version.colors))] <- "black"
-animint(
+version.colors <- c(
+  Slow="violet",
+  Fast="red",
+  Regression="violet",
+  Before="red",
+  HEAD= "blue")
+viz <- animint(
+  title=paste("Performance testing with git bisect in data.table", basename(Test.dir)),
+  source="https://github.com/Rdatatable/data.table/pull/7912/files#diff-e7f10716f0ff9f29e3186a43cfed95d970b167dc4d6a92c00b9e0736bf4b05ae",
   overview=ggplot()+
     ggtitle("Overview, select commit")+
     theme_bw()+
@@ -66,7 +72,6 @@ animint(
       rank, value, color=version, group=version),
       data=results.long)+
     facet_grid(variable ~ ., scales="free")+
-    theme(axis.text.x=element_text(angle=30, hjust=1))+
     geom_label_aligned(aes(
       rank, value, label=version, color=version),
       data=results.long[rank==max(rank)],
@@ -77,7 +82,9 @@ animint(
       "1"="white"))+
     scale_color_manual(values=version.colors)+
     scale_y_continuous("")+
-    scale_x_continuous("commit rank over time")+
+    scale_x_continuous(
+      "commit rank over time",
+      breaks=results.wide$rank)+
     geom_tallrect(aes(
       xmin=rank-0.5, xmax=rank+0.5),
       clickSelects="commit",
@@ -91,7 +98,7 @@ animint(
     ggtitle("Details for selected commit")+
     theme_bw()+
     theme(legend.position="none")+
-    theme_animint(width=1000)+
+    theme_animint(width=500, last_in_row=TRUE)+
     geom_hline(aes(
       yintercept=seconds),
       color="grey",
@@ -119,7 +126,7 @@ animint(
       color="grey50",
       showSelected="commit")+
     geom_text(aes(
-      0, 0, label=commit,
+      0, 0, label=substring(commit, 1, 10),
       href=paste0("https://github.com/Rdatatable/data.table/commit/", commit),
       key=1),
       hjust=0,
@@ -130,7 +137,7 @@ animint(
       N, ymin=min, ymax=max,
       key=version, fill=version, group=version),
       showSelected=c("version","commit"),
-      alpha=0.5,
+      alpha=0.2,
       color=NA,
       data=details.dt)+
     geom_line(aes(
@@ -154,9 +161,13 @@ animint(
       data=dot.dt)+
     scale_color_manual(values=version.colors)+
     scale_fill_manual(values=version.colors)+
-    scale_x_log10()+
+    scale_x_log10("N = number of data")+
     scale_y_log10("seconds"),
   duration=list(
     commit=1000)
 )
+viz
 
+if(FALSE){
+  animint2::animint2pages(viz, paste0("2026-10-09-performance-bisect-", basename(Test.dir)), chromote_sleep_seconds=3)
+}

From 305810afff97738d030e312989637471404912f8 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 04:44:30 -0400
Subject: [PATCH 09/37] PR4164

---
 .ci/atime/bisect-7687.R | 2 +-
 .ci/atime/tests.R       | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index bf8c3c5262..41cfc9593d 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -4,8 +4,8 @@ Test <- "DT[by] fixed in #4558"
 atime::bisect(pkg.path, Test, "Before", "Regression")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
 atime::bisect(pkg.path, Test, "Slow", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
 
-Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Slow_Fast"
 Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Before_Regression"
+Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Slow_Fast"
 library(data.table)
 (results.wide <- data.table(
   csv=Sys.glob(file.path(Test.dir, "csv", "*"))
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index c95915297d..096929cb3e 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -330,6 +330,7 @@ test.list <- atime::atime_test_list(
     },
     Before = "166e0bab317e9d9f4f1844997a315e6482ab5fd9",#a few click of parent up from first commit in PR4164 gets to https://github.com/Rdatatable/data.table/commit/166e0bab317e9d9f4f1844997a315e6482ab5fd9
     Regression="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of Slow (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
+    PR4164="4aadde8f5a51cd7c8f3889964e7280432ec65bbc", # Merge commit of the PR that causes the regression.
     Slow = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     Fast="master",
     expr = data.table:::`[.data.table`(d, , max(v1) - min(v2), by = id)),

From fd435f572b1d3831a304bb5bc76f60d94c43ef5e Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 04:46:02 -0400
Subject: [PATCH 10/37] PR4164

---
 .ci/atime/bisect-7687.R | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 41cfc9593d..72a9f2389b 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -3,6 +3,7 @@ pkg.path <- "~/R/data.table"
 Test <- "DT[by] fixed in #4558"
 atime::bisect(pkg.path, Test, "Before", "Regression")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
 atime::bisect(pkg.path, Test, "Slow", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
+atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits.
 
 Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Before_Regression"
 Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Slow_Fast"

From 43bbdf4f6079197fc7a7528040285b831f659827 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 05:21:33 -0400
Subject: [PATCH 11/37] no change bisects

---
 .ci/atime/bisect-7687.R | 16 +++++++++-------
 .ci/atime/tests.R       |  6 ++++--
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 72a9f2389b..76c87a8175 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -1,12 +1,15 @@
 remotes::install_github("tdhock/atime@bisect")
 pkg.path <- "~/R/data.table"
 Test <- "DT[by] fixed in #4558"
-atime::bisect(pkg.path, Test, "Before", "Regression")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
-atime::bisect(pkg.path, Test, "Slow", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
-atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits.
+atime::bisect(pkg.path, Test, "Before", "PR4164")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
+atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
+atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
+atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#two speed increases between these two commits, bisect finds the larger one: PR7401.
+atime::bisect(pkg.path, Test, "PR7401", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
 
 Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Before_Regression"
 Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Slow_Fast"
+Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_PR4164_Fast"
 library(data.table)
 (results.wide <- data.table(
   csv=Sys.glob(file.path(Test.dir, "csv", "*"))
@@ -52,14 +55,13 @@ for(result.RData in Sys.glob(file.path(Test.dir, "RData", "*"))){
 limit.dt <- data.table(seconds=tpred$seconds.limit)
 library(animint2)
 version.colors <- c(
-  Slow="violet",
-  Fast="red",
-  Regression="violet",
-  Before="red",
   HEAD= "blue")
+version.colors[c("Slow", "Regression", "PR4164")] <- "violet"
+version.colors[c("Fast", "Before")] <- "red"
 viz <- animint(
   title=paste("Performance testing with git bisect in data.table", basename(Test.dir)),
   source="https://github.com/Rdatatable/data.table/pull/7912/files#diff-e7f10716f0ff9f29e3186a43cfed95d970b167dc4d6a92c00b9e0736bf4b05ae",
+  out.dir=file.path("bisect-viz", basename(Test.dir)),
   overview=ggplot()+
     ggtitle("Overview, select commit")+
     theme_bw()+
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 096929cb3e..41be26d82d 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -329,9 +329,11 @@ test.list <- atime::atime_test_list(
       )
     },
     Before = "166e0bab317e9d9f4f1844997a315e6482ab5fd9",#a few click of parent up from first commit in PR4164 gets to https://github.com/Rdatatable/data.table/commit/166e0bab317e9d9f4f1844997a315e6482ab5fd9
-    Regression="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of Slow (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     PR4164="4aadde8f5a51cd7c8f3889964e7280432ec65bbc", # Merge commit of the PR that causes the regression.
-    Slow = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
+    Parent4558="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of PR4558 (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
+    PR4558 = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
+    Parent7401="20b463c9592c07d05ad2e89a25f84f0b998d6154", # master parent of the PR7401 which caused the recent speedup.
+    PR7401="0216983c51e03e3f61d5e6f08f4ba0c42cceb22c",
     Fast="master",
     expr = data.table:::`[.data.table`(d, , max(v1) - min(v2), by = id)),
 

From d9800534288038bbf886d3893382d9ed9e9b809d Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 05:47:47 -0400
Subject: [PATCH 12/37] viz

---
 .ci/atime/bisect-7687.R | 171 +---------------------------------------
 .ci/atime/bisect-viz.R  | 168 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 170 insertions(+), 169 deletions(-)
 create mode 100644 .ci/atime/bisect-viz.R

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 76c87a8175..eca812b103 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -4,173 +4,6 @@ Test <- "DT[by] fixed in #4558"
 atime::bisect(pkg.path, Test, "Before", "PR4164")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
 atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
 atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
-atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#two speed increases between these two commits, bisect finds the larger one: PR7401.
-atime::bisect(pkg.path, Test, "PR7401", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
+atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558.
+atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes.
 
-Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Before_Regression"
-Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_Slow_Fast"
-Test.dir <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_PR4164_Fast"
-library(data.table)
-(results.wide <- data.table(
-  csv=Sys.glob(file.path(Test.dir, "csv", "*"))
-)[
-, fread(csv), by=csv
-][
-, rank := rank(time)
-][order(rank)][, let(
-  Rank = factor(rank, labels=format(time)),
-  Status = factor(status)
-)][])
-(results.long <- melt(
-  results.wide,
-  measure.vars=measure(variable, version, sep=".")))
-
-show.versions <- unique(results.long$version)
-details.dt.list <- list()
-dot.dt.list <- list()
-common.dt.list <- list()
-for(result.RData in Sys.glob(file.path(Test.dir, "RData", "*"))){
-  (objs <- load(result.RData))
-  commit <- sub(".RData", "", basename(result.RData))
-  details <- tres.or.status$measurements[
-    show.versions,
-    on="version",
-    data.table(commit, expr.name, version, N, median, min, max)
-  ]
-  common.dt.list[[commit]] <- details[, .(
-    versions=.N
-  ), by=N][
-    versions==max(versions)
-  ][.N, data.table(commit, N)]
-  evers <- unique(details[, .(expr.name, version)])
-  details.dt.list[[commit]] <- details
-  dot.dt.list[[commit]] <- data.table(
-    commit,
-    tpred$prediction[evers, on="expr.name"])
-}
-(details.dt <- rbindlist(details.dt.list))
-(dot.dt <- rbindlist(dot.dt.list))
-(common.dt <- rbindlist(common.dt.list))
-
-limit.dt <- data.table(seconds=tpred$seconds.limit)
-library(animint2)
-version.colors <- c(
-  HEAD= "blue")
-version.colors[c("Slow", "Regression", "PR4164")] <- "violet"
-version.colors[c("Fast", "Before")] <- "red"
-viz <- animint(
-  title=paste("Performance testing with git bisect in data.table", basename(Test.dir)),
-  source="https://github.com/Rdatatable/data.table/pull/7912/files#diff-e7f10716f0ff9f29e3186a43cfed95d970b167dc4d6a92c00b9e0736bf4b05ae",
-  out.dir=file.path("bisect-viz", basename(Test.dir)),
-  overview=ggplot()+
-    ggtitle("Overview, select commit")+
-    theme_bw()+
-    geom_tallrect(aes(
-      xmin=rank-0.5, xmax=rank+0.5,
-      key=rank,
-      fill=Status),
-      color=NA,
-      data=results.wide)+
-    geom_line(aes(
-      rank, value, color=version, group=version),
-      data=results.long)+
-    facet_grid(variable ~ ., scales="free")+
-    geom_label_aligned(aes(
-      rank, value, label=version, color=version),
-      data=results.long[rank==max(rank)],
-      hjust=0,
-      alignment="vertical")+
-    scale_fill_manual(values=c(
-      "0"="grey",
-      "1"="white"))+
-    scale_color_manual(values=version.colors)+
-    scale_y_continuous("")+
-    scale_x_continuous(
-      "commit rank over time",
-      breaks=results.wide$rank)+
-    geom_tallrect(aes(
-      xmin=rank-0.5, xmax=rank+0.5),
-      clickSelects="commit",
-      alpha=1,
-      alpha_off=0,
-      color="black",
-      color_off=NA,
-      fill=NA,
-      data=results.wide),
-  details=ggplot()+
-    ggtitle("Details for selected commit")+
-    theme_bw()+
-    theme(legend.position="none")+
-    theme_animint(width=500, last_in_row=TRUE)+
-    geom_hline(aes(
-      yintercept=seconds),
-      color="grey",
-      data=limit.dt)+
-    geom_text(aes(
-      0, seconds*1.1,
-      label=sprintf(
-        "time limit = %s seconds",
-        paste(seconds)
-      )),
-      hjust=0,
-      color="grey50",
-      data=limit.dt)+
-    geom_vline(aes(
-      xintercept=N,
-      key=1),
-      data=common.dt,
-      color="grey",
-      showSelected="commit")+
-    geom_text(aes(
-      N, 0, label=sprintf("largest common N=%s", paste(N)),
-      key=1),
-      data=common.dt,
-      hjust=1,
-      color="grey50",
-      showSelected="commit")+
-    geom_text(aes(
-      0, 0, label=substring(commit, 1, 10),
-      href=paste0("https://github.com/Rdatatable/data.table/commit/", commit),
-      key=1),
-      hjust=0,
-      vjust=0,
-      data=common.dt,
-      showSelected="commit")+
-    geom_ribbon(aes(
-      N, ymin=min, ymax=max,
-      key=version, fill=version, group=version),
-      showSelected=c("version","commit"),
-      alpha=0.2,
-      color=NA,
-      data=details.dt)+
-    geom_line(aes(
-      N, median,
-      key=version, color=version, group=version),
-      showSelected=c("version","commit"),
-      data=details.dt)+
-    geom_point(aes(
-      N, unit.value,
-      key=version, color=version),
-      showSelected=c("version","commit"),
-      fill="white",
-      data=dot.dt)+
-    geom_label_aligned(aes(
-      N, unit.value, label=version,
-      key=version, color=version),
-      showSelected=c("version","commit"),
-      alignment="horizontal",
-      vjust=-0.1,
-      alpha=0.5,
-      data=dot.dt)+
-    scale_color_manual(values=version.colors)+
-    scale_fill_manual(values=version.colors)+
-    scale_x_log10("N = number of data")+
-    scale_y_log10("seconds"),
-  duration=list(
-    commit=1000)
-)
-viz
-
-if(FALSE){
-  animint2::animint2pages(viz, paste0("2026-10-09-performance-bisect-", basename(Test.dir)), chromote_sleep_seconds=3)
-}
diff --git a/.ci/atime/bisect-viz.R b/.ci/atime/bisect-viz.R
new file mode 100644
index 0000000000..0b8d8d2a8f
--- /dev/null
+++ b/.ci/atime/bisect-viz.R
@@ -0,0 +1,168 @@
+library(animint2)
+library(data.table)
+Test.dir.vec <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_PR4164_Fast"
+Test.dir.vec <- Sys.glob("bisect/*")
+for(Test.dir in Test.dir.vec){
+  print(Test.dir)
+  (results.wide <- data.table(
+    csv=Sys.glob(file.path(Test.dir, "csv", "*"))
+  )[
+  , fread(csv), by=csv
+  ][
+  , rank := rank(time)
+  ][order(rank)][, let(
+    Rank = factor(rank, labels=format(time)),
+    Status = factor(status)
+  )][])
+  (results.long <- melt(
+    results.wide,
+    measure.vars=measure(variable, version, sep=".")))
+  show.versions <- unique(results.long$version)
+  details.dt.list <- list()
+  dot.dt.list <- list()
+  common.dt.list <- list()
+  for(result.RData in Sys.glob(file.path(Test.dir, "RData", "*"))){
+    (objs <- load(result.RData))
+    commit <- sub(".RData", "", basename(result.RData))
+    details <- tres.or.status$measurements[
+      show.versions,
+      on="version",
+      data.table(commit, expr.name, version, N, median, min, max)
+    ]
+    common.dt.list[[commit]] <- details[, .(
+      versions=.N
+    ), by=N][
+      versions==max(versions)
+    ][.N, data.table(commit, N)]
+    evers <- unique(details[, .(expr.name, version)])
+    details.dt.list[[commit]] <- details
+    dot.dt.list[[commit]] <- data.table(
+      commit,
+      tpred$prediction[evers, on="expr.name"])
+  }
+  (details.dt <- rbindlist(details.dt.list))
+  (dot.dt <- rbindlist(dot.dt.list))
+  (common.dt <- rbindlist(common.dt.list))
+  limit.dt <- data.table(seconds=tpred$seconds.limit)
+  version.colors <- c(
+    HEAD= "blue")
+  vers.dt <- nc::capture_first_vec(Test.dir, ".*_", old="[^_]+", "_", new="[^_]+")
+  version.colors[vers.dt$old] <- "violet"
+  version.colors[vers.dt$new] <- "red"
+  viz <- animint(
+    title=paste("Performance testing with git bisect in data.table", basename(Test.dir)),
+    source="https://github.com/Rdatatable/data.table/pull/7912/files#diff-e7f10716f0ff9f29e3186a43cfed95d970b167dc4d6a92c00b9e0736bf4b05ae",
+    out.dir=file.path("bisect-viz", basename(Test.dir)),
+    overview=ggplot()+
+      ggtitle("Overview, select commit")+
+      theme_bw()+
+      geom_tallrect(aes(
+        xmin=rank-0.5, xmax=rank+0.5,
+        key=rank,
+        fill=Status),
+        color=NA,
+        data=results.wide)+
+      geom_line(aes(
+        rank, value, color=version, group=version),
+        data=results.long)+
+      facet_grid(variable ~ ., scales="free")+
+      geom_label_aligned(aes(
+        rank, value, label=version, color=version),
+        data=results.long[rank==max(rank)],
+        hjust=0,
+        alignment="vertical")+
+      scale_fill_manual(values=c(
+        "0"="grey",
+        "1"="white"))+
+      scale_color_manual(values=version.colors)+
+      scale_y_log10("")+
+      scale_x_continuous(
+        "commit rank over time",
+        breaks=results.wide$rank)+
+      geom_tallrect(aes(
+        xmin=rank-0.5, xmax=rank+0.5),
+        clickSelects="commit",
+        alpha=1,
+        alpha_off=0,
+        color="black",
+        color_off=NA,
+        fill=NA,
+        data=results.wide),
+    details=ggplot()+
+      ggtitle("Details for selected commit")+
+      theme_bw()+
+      theme(legend.position="none")+
+      theme_animint(width=500, last_in_row=TRUE)+
+      geom_hline(aes(
+        yintercept=seconds),
+        color="grey",
+        data=limit.dt)+
+      geom_text(aes(
+        0, seconds*1.1,
+        label=sprintf(
+          "time limit = %s seconds",
+          paste(seconds)
+        )),
+        hjust=0,
+        color="grey50",
+        data=limit.dt)+
+      geom_vline(aes(
+        xintercept=N,
+        key=1),
+        data=common.dt,
+        color="grey",
+        showSelected="commit")+
+      geom_text(aes(
+        N, 0, label=sprintf("largest common N=%s", paste(N)),
+        key=1),
+        data=common.dt,
+        hjust=1,
+        color="grey50",
+        showSelected="commit")+
+      geom_text(aes(
+        0, 0, label=substring(commit, 1, 10),
+        href=paste0("https://github.com/Rdatatable/data.table/commit/", commit),
+        key=1),
+        hjust=0,
+        vjust=0,
+        data=common.dt,
+        showSelected="commit")+
+      geom_ribbon(aes(
+        N, ymin=min, ymax=max,
+        key=version, fill=version, group=version),
+        showSelected=c("version","commit"),
+        alpha=0.2,
+        color=NA,
+        data=details.dt)+
+      geom_line(aes(
+        N, median,
+        key=version, color=version, group=version),
+        showSelected=c("version","commit"),
+        data=details.dt)+
+      geom_point(aes(
+        N, unit.value,
+        key=version, color=version),
+        showSelected=c("version","commit"),
+        fill="white",
+        data=dot.dt)+
+      geom_label_aligned(aes(
+        N, unit.value, label=version,
+        key=version, color=version),
+        showSelected=c("version","commit"),
+        alignment="horizontal",
+        vjust=-0.1,
+        alpha=0.5,
+        data=dot.dt)+
+      scale_color_manual(values=version.colors)+
+      scale_fill_manual(values=version.colors)+
+      scale_x_log10("N = number of data")+
+      scale_y_log10("seconds"),
+    duration=list(
+      commit=1000)
+  )
+  print(viz)
+}
+
+if(FALSE){
+  animint2::animint2pages(viz, paste0("2026-10-09-performance-bisect-", basename(Test.dir)), chromote_sleep_seconds=3)
+}

From 6190108c0e24757f094b602827fbaae1745b2af7 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 05:49:41 -0400
Subject: [PATCH 13/37] comment

---
 .ci/atime/bisect-7687.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index eca812b103..195432a627 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -4,6 +4,6 @@ Test <- "DT[by] fixed in #4558"
 atime::bisect(pkg.path, Test, "Before", "PR4164")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
 atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
 atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
-atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558.
+atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558? Finds PR5463??
 atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes.
 

From c6b88bd401e322017be03205f9393783888dd124 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 06:13:05 -0400
Subject: [PATCH 14/37] Parent5463

---
 .ci/atime/bisect-7687.R | 3 ++-
 .ci/atime/tests.R       | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 195432a627..6c6a4e45b7 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -5,5 +5,6 @@ atime::bisect(pkg.path, Test, "Before", "PR4164")#returns PR4164, consistent wit
 atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
 atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
 atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558? Finds PR5463??
-atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes.
+atime::bisect(pkg.path, Test, "PR4164", "Parent5463")#should find one small speed increase?
+atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes, returns PR7650, but atime plot clearly shows no real change.
 
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 41be26d82d..4962b2bd7e 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -332,6 +332,7 @@ test.list <- atime::atime_test_list(
     PR4164="4aadde8f5a51cd7c8f3889964e7280432ec65bbc", # Merge commit of the PR that causes the regression.
     Parent4558="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of PR4558 (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     PR4558 = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
+    Parent5463="052f8da6", # PR5463 is bisect result of PR4164 and Parent7401.
     Parent7401="20b463c9592c07d05ad2e89a25f84f0b998d6154", # master parent of the PR7401 which caused the recent speedup.
     PR7401="0216983c51e03e3f61d5e6f08f4ba0c42cceb22c",
     Fast="master",

From a595e5d28c807957e8f527b832c5ecf640352099 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 06:36:53 -0400
Subject: [PATCH 15/37] 4491

---
 .ci/atime/bisect-7687.R | 3 ++-
 .ci/atime/bisect-viz.R  | 2 +-
 .ci/atime/tests.R       | 1 +
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 6c6a4e45b7..850e66a6a7 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -5,6 +5,7 @@ atime::bisect(pkg.path, Test, "Before", "PR4164")#returns PR4164, consistent wit
 atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
 atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
 atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558? Finds PR5463??
-atime::bisect(pkg.path, Test, "PR4164", "Parent5463")#should find one small speed increase?
+atime::bisect(pkg.path, Test, "PR4164", "Parent5463")#expected speed increase, found PR4491.
+atime::bisect(pkg.path, Test, "PR4164", "Parent4491")#expected speed increase, 
 atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes, returns PR7650, but atime plot clearly shows no real change.
 
diff --git a/.ci/atime/bisect-viz.R b/.ci/atime/bisect-viz.R
index 0b8d8d2a8f..bfa02727a4 100644
--- a/.ci/atime/bisect-viz.R
+++ b/.ci/atime/bisect-viz.R
@@ -1,7 +1,7 @@
 library(animint2)
 library(data.table)
-Test.dir.vec <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_PR4164_Fast"
 Test.dir.vec <- Sys.glob("bisect/*")
+Test.dir.vec <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_PR4164_Parent5463"
 for(Test.dir in Test.dir.vec){
   print(Test.dir)
   (results.wide <- data.table(
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 4962b2bd7e..e1a56f97b6 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -332,6 +332,7 @@ test.list <- atime::atime_test_list(
     PR4164="4aadde8f5a51cd7c8f3889964e7280432ec65bbc", # Merge commit of the PR that causes the regression.
     Parent4558="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of PR4558 (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     PR4558 = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
+    Parent4491="3fa8b20435d33b3d4b5c26fd9b0ac14c10b98800", # PR4491 is bisect result of PR4164 and Parent5463.
     Parent5463="052f8da6", # PR5463 is bisect result of PR4164 and Parent7401.
     Parent7401="20b463c9592c07d05ad2e89a25f84f0b998d6154", # master parent of the PR7401 which caused the recent speedup.
     PR7401="0216983c51e03e3f61d5e6f08f4ba0c42cceb22c",

From fcbbd99d13cf8640e56958fa0082b0b78cace823 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 06:58:53 -0400
Subject: [PATCH 16/37] DONE

---
 .ci/atime/bisect-7687.R | 2 +-
 .ci/atime/bisect-viz.R  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 850e66a6a7..8d22369bdf 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -6,6 +6,6 @@ atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with
 atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
 atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558? Finds PR5463??
 atime::bisect(pkg.path, Test, "PR4164", "Parent5463")#expected speed increase, found PR4491.
-atime::bisect(pkg.path, Test, "PR4164", "Parent4491")#expected speed increase, 
+atime::bisect(pkg.path, Test, "PR4164", "Parent4491")#expected speed increase, found PR4558. DONE.
 atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes, returns PR7650, but atime plot clearly shows no real change.
 
diff --git a/.ci/atime/bisect-viz.R b/.ci/atime/bisect-viz.R
index bfa02727a4..f52a169ef1 100644
--- a/.ci/atime/bisect-viz.R
+++ b/.ci/atime/bisect-viz.R
@@ -1,7 +1,7 @@
 library(animint2)
 library(data.table)
 Test.dir.vec <- Sys.glob("bisect/*")
-Test.dir.vec <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_PR4164_Parent5463"
+Test.dir.vec <- "~/R/data.table/.ci/atime/bisect/DT_by__fixed_in__4558_PR4164_Parent4491"
 for(Test.dir in Test.dir.vec){
   print(Test.dir)
   (results.wide <- data.table(

From d61d44e5352f7bfa1d02448cc5cf6a2874f53382 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 12:07:00 -0400
Subject: [PATCH 17/37] FALSE

---
 .ci/atime/bisect-7687.R | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 8d22369bdf..776c573779 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -1,4 +1,6 @@
-remotes::install_github("tdhock/atime@bisect")
+if(FALSE){
+  remotes::install_github("tdhock/atime@bisect")
+}
 pkg.path <- "~/R/data.table"
 Test <- "DT[by] fixed in #4558"
 atime::bisect(pkg.path, Test, "Before", "PR4164")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420

From 0eaee4e32ddb73a9b374621e9240f8fd2c3b8f5f Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 14:01:40 -0400
Subject: [PATCH 18/37] Parent4558

---
 .ci/atime/bisect-7687.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 776c573779..00eaa193c6 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -3,7 +3,7 @@ if(FALSE){
 }
 pkg.path <- "~/R/data.table"
 Test <- "DT[by] fixed in #4558"
-atime::bisect(pkg.path, Test, "Before", "PR4164")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
+atime::bisect(pkg.path, Test, "Before", "Parent4558")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
 atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
 atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
 atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558? Finds PR5463??

From ac0e49f12e172d308a158a9244f09d233a258311 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sat, 10 Oct 2026 15:20:08 -0400
Subject: [PATCH 19/37] bisect 5463_parent7401

---
 .ci/atime/bisect-7687.R | 1 +
 .ci/atime/tests.R       | 1 +
 2 files changed, 2 insertions(+)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 00eaa193c6..efb22de067 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -10,4 +10,5 @@ atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small spee
 atime::bisect(pkg.path, Test, "PR4164", "Parent5463")#expected speed increase, found PR4491.
 atime::bisect(pkg.path, Test, "PR4164", "Parent4491")#expected speed increase, found PR4558. DONE.
 atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes, returns PR7650, but atime plot clearly shows no real change.
+atime::bisect(pkg.path, Test, "PR5463", "Parent7401")#slight speed decrease.
 
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index e1a56f97b6..be78301bb7 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -334,6 +334,7 @@ test.list <- atime::atime_test_list(
     PR4558 = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     Parent4491="3fa8b20435d33b3d4b5c26fd9b0ac14c10b98800", # PR4491 is bisect result of PR4164 and Parent5463.
     Parent5463="052f8da6", # PR5463 is bisect result of PR4164 and Parent7401.
+    PR5463="19b7866112614db53eb3e909c097407d91cd6738",
     Parent7401="20b463c9592c07d05ad2e89a25f84f0b998d6154", # master parent of the PR7401 which caused the recent speedup.
     PR7401="0216983c51e03e3f61d5e6f08f4ba0c42cceb22c",
     Fast="master",

From 37b0ce5c7b3dc6ddf7186c3902d349c38e9d2bdc Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Sun, 11 Oct 2026 10:22:28 -0400
Subject: [PATCH 20/37] 2

---
 .ci/atime/tests.R | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index be78301bb7..696cfe4cea 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -453,6 +453,7 @@ test.list <- atime::atime_test_list(
 
   # Regression introduced by https://github.com/Rdatatable/data.table/pull/6890 and discussed in https://github.com/Rdatatable/data.table/issues/7404 (grouped by factor).
   "DT[by] max regression fixed in #7480" = atime::atime_test(
+    N=2^seq(1, 20),
     setup = {
       dt = data.table(
         id = as.factor(rep(seq_len(N), each = 100L)),

From c19e9f3acfad9bd723ec915d57e6b058897dab36 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Mon, 12 Oct 2026 12:27:46 -0400
Subject: [PATCH 21/37] rowwiseDT

---
 .ci/atime/bisect-7687.R | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index efb22de067..130adf061b 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -3,12 +3,26 @@ if(FALSE){
 }
 pkg.path <- "~/R/data.table"
 Test <- "DT[by] fixed in #4558"
-atime::bisect(pkg.path, Test, "Before", "Parent4558")#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
-atime::bisect(pkg.path, Test, "PR4558", "Fast")#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
-atime::bisect(pkg.path, Test, "PR4164", "Fast")#two speed increases between these two commits, bisect finds the larger one: PR7401.
-atime::bisect(pkg.path, Test, "PR4164", "Parent7401")#should find one small speed increase in PR4558? Finds PR5463??
-atime::bisect(pkg.path, Test, "PR4164", "Parent5463")#expected speed increase, found PR4491.
-atime::bisect(pkg.path, Test, "PR4164", "Parent4491")#expected speed increase, found PR4558. DONE.
-atime::bisect(pkg.path, Test, "PR7401", "Fast")#no speed changes, returns PR7650, but atime plot clearly shows no real change.
-atime::bisect(pkg.path, Test, "PR5463", "Parent7401")#slight speed decrease.
-
+library(data.table)
+(bisect.dt <- rowwiseDT(
+  old=, new=, label=,
+  "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
+  "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
+  "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
+  "PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
+  "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
+  "PR4164", "Parent4491", "PR4558",#expected speed increase, found PR4558. DONE.
+  "PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
+  "PR5463", "Parent7401", "TODO"))#slight speed decrease.
+for(bisect.i in 1:nrow(bisect.dt)){
+  bisect.row <- bisect.dt[bisect.i]
+  done <- FALSE
+  while(!done){
+    done <- tryCatch({
+      bisect.row[, atime::bisect(pkg.path, Test, old, new)]
+      TRUE
+    }, error=function(e){
+      FALSE
+    })
+  }
+}

From 3d63649956ef92d04f6429481ffbc877fdd20448 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Mon, 12 Oct 2026 12:29:13 -0400
Subject: [PATCH 22/37] comment-neg

---
 .ci/atime/bisect-7687.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 130adf061b..999ea29f32 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -12,7 +12,7 @@ library(data.table)
   "PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
   "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
   "PR4164", "Parent4491", "PR4558",#expected speed increase, found PR4558. DONE.
-  "PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
+  #"PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
   "PR5463", "Parent7401", "TODO"))#slight speed decrease.
 for(bisect.i in 1:nrow(bisect.dt)){
   bisect.row <- bisect.dt[bisect.i]

From 72b254ad610de7f534ea39c84c0add727b81e761 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Mon, 12 Oct 2026 14:04:57 -0400
Subject: [PATCH 23/37] comment

---
 .ci/atime/bisect-7687.R | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 999ea29f32..ae8088c11f 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -9,11 +9,11 @@ library(data.table)
   "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
-  "PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
-  "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
-  "PR4164", "Parent4491", "PR4558",#expected speed increase, found PR4558. DONE.
+  #"PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
   #"PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
-  "PR5463", "Parent7401", "TODO"))#slight speed decrease.
+  #"PR5463", "Parent7401", "TODO",#slight speed decrease.
+  "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
+  "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.
 for(bisect.i in 1:nrow(bisect.dt)){
   bisect.row <- bisect.dt[bisect.i]
   done <- FALSE
@@ -26,3 +26,4 @@ for(bisect.i in 1:nrow(bisect.dt)){
     })
   }
 }
+

From 1f48059043bc7026dd6d96cf275fc8d2fb2e4f67 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Mon, 12 Oct 2026 18:57:18 -0400
Subject: [PATCH 24/37] lim0.1

---
 .ci/atime/bisect-7687.R | 2 +-
 .ci/atime/tests.R       | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index ae8088c11f..cdcf3ebe9f 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -19,7 +19,7 @@ for(bisect.i in 1:nrow(bisect.dt)){
   done <- FALSE
   while(!done){
     done <- tryCatch({
-      bisect.row[, atime::bisect(pkg.path, Test, old, new)]
+      bisect.row[, atime::bisect(pkg.path, Test, old, new, reps=1)]
       TRUE
     }, error=function(e){
       FALSE
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 696cfe4cea..968539a186 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -320,6 +320,8 @@ test.list <- atime::atime_test_list(
   # Test case adapted from https://github.com/Rdatatable/data.table/issues/4200#issuecomment-645980224 which is where the issue was reported.
   # Fixed in https://github.com/Rdatatable/data.table/pull/4558
   "DT[by] fixed in #4558" = atime::atime_test(
+    N=2^seq(1, 20),
+    seconds.limit=0.1,
     setup = {
       N9 <- as.integer(N * 0.9)
       d <- data.table(
@@ -453,7 +455,6 @@ test.list <- atime::atime_test_list(
 
   # Regression introduced by https://github.com/Rdatatable/data.table/pull/6890 and discussed in https://github.com/Rdatatable/data.table/issues/7404 (grouped by factor).
   "DT[by] max regression fixed in #7480" = atime::atime_test(
-    N=2^seq(1, 20),
     setup = {
       dt = data.table(
         id = as.factor(rep(seq_len(N), each = 100L)),

From 030ff5ec349b444852792a0ed2e7c5e80a124582 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Mon, 12 Oct 2026 18:57:18 -0400
Subject: [PATCH 25/37] lim0.1

---
 .ci/atime/bisect-7687.R | 8 ++++----
 .ci/atime/tests.R       | 3 ++-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index ae8088c11f..777ad3c8bb 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -9,9 +9,9 @@ library(data.table)
   "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
-  #"PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
-  #"PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
-  #"PR5463", "Parent7401", "TODO",#slight speed decrease.
+  "PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
+  "PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
+  "PR5463", "Parent7401", "TODO",#slight speed decrease.
   "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
   "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.
 for(bisect.i in 1:nrow(bisect.dt)){
@@ -19,7 +19,7 @@ for(bisect.i in 1:nrow(bisect.dt)){
   done <- FALSE
   while(!done){
     done <- tryCatch({
-      bisect.row[, atime::bisect(pkg.path, Test, old, new)]
+      bisect.row[, atime::bisect(pkg.path, Test, old, new, reps=1)]
       TRUE
     }, error=function(e){
       FALSE
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 696cfe4cea..968539a186 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -320,6 +320,8 @@ test.list <- atime::atime_test_list(
   # Test case adapted from https://github.com/Rdatatable/data.table/issues/4200#issuecomment-645980224 which is where the issue was reported.
   # Fixed in https://github.com/Rdatatable/data.table/pull/4558
   "DT[by] fixed in #4558" = atime::atime_test(
+    N=2^seq(1, 20),
+    seconds.limit=0.1,
     setup = {
       N9 <- as.integer(N * 0.9)
       d <- data.table(
@@ -453,7 +455,6 @@ test.list <- atime::atime_test_list(
 
   # Regression introduced by https://github.com/Rdatatable/data.table/pull/6890 and discussed in https://github.com/Rdatatable/data.table/issues/7404 (grouped by factor).
   "DT[by] max regression fixed in #7480" = atime::atime_test(
-    N=2^seq(1, 20),
     setup = {
       dt = data.table(
         id = as.factor(rep(seq_len(N), each = 100L)),

From 38fa2599b5d2b3cb392b716e71f258b3ca929931 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 03:16:53 -0400
Subject: [PATCH 26/37] commint

---
 .ci/atime/bisect-7687.R | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 777ad3c8bb..f9bd608a9a 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -10,20 +10,12 @@ library(data.table)
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
   "PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
-  "PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
-  "PR5463", "Parent7401", "TODO",#slight speed decrease.
+  ## "PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
+  ## "PR5463", "Parent7401", "TODO",#slight speed decrease.
   "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
   "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.
 for(bisect.i in 1:nrow(bisect.dt)){
   bisect.row <- bisect.dt[bisect.i]
-  done <- FALSE
-  while(!done){
-    done <- tryCatch({
-      bisect.row[, atime::bisect(pkg.path, Test, old, new, reps=1)]
-      TRUE
-    }, error=function(e){
-      FALSE
-    })
-  }
+  bisect.row[, atime::bisect(pkg.path, Test, old, new, reps=1)]
 }
 

From c78b6473ace141b7295268109884e16a56ae1f6e Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 03:17:11 -0400
Subject: [PATCH 27/37] print

---
 .ci/atime/bisect-7687.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index f9bd608a9a..a98413b4eb 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -15,7 +15,7 @@ library(data.table)
   "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
   "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.
 for(bisect.i in 1:nrow(bisect.dt)){
-  bisect.row <- bisect.dt[bisect.i]
+  print(bisect.row <- bisect.dt[bisect.i])
   bisect.row[, atime::bisect(pkg.path, Test, old, new, reps=1)]
 }
 

From 0b8b7f126b7ce0b7a2b6b4c55366683cd7d16513 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 05:17:34 -0400
Subject: [PATCH 28/37] neg

---
 .ci/atime/bisect-7687.R | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index a98413b4eb..11a4281c4e 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -1,9 +1,11 @@
-if(FALSE){
-  remotes::install_github("tdhock/atime@bisect")
-}
 pkg.path <- "~/R/data.table"
 Test <- "DT[by] fixed in #4558"
 library(data.table)
+if(FALSE){
+  remotes::install_github("tdhock/atime@bisect")
+  atime::bisect(pkg.path, Test, "PR7401", "Fast")
+}
+
 (bisect.dt <- rowwiseDT(
   old=, new=, label=,
   "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
@@ -16,6 +18,6 @@ library(data.table)
   "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.
 for(bisect.i in 1:nrow(bisect.dt)){
   print(bisect.row <- bisect.dt[bisect.i])
-  bisect.row[, atime::bisect(pkg.path, Test, old, new, reps=1)]
+  bisect.row[, atime::bisect(pkg.path, Test, old, new)]
 }
 

From a8e75d2eb6c28b7468f2883844faa47a2b8112ed Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 06:24:46 -0400
Subject: [PATCH 29/37] PR4491

---
 .ci/atime/bisect-7687.R | 2 +-
 .ci/atime/tests.R       | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 11a4281c4e..6e868284fe 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -11,7 +11,7 @@ if(FALSE){
   "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
-  "PR4164", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
+  "PR4491", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
   ## "PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
   ## "PR5463", "Parent7401", "TODO",#slight speed decrease.
   "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 968539a186..2c9df7a193 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -335,6 +335,7 @@ test.list <- atime::atime_test_list(
     Parent4558="6f360be0b2a6cf425f6df751ca9a99ec5d35ed93", #parent of PR4558 (https://github.com/Rdatatable/data.table/commit/ba32f3cba38ec270587e395f6e6c26a80be36be6)
     PR4558 = "ba32f3cba38ec270587e395f6e6c26a80be36be6", # Merge commit of the PR (https://github.com/Rdatatable/data.table/pull/4558) that fixes the regression
     Parent4491="3fa8b20435d33b3d4b5c26fd9b0ac14c10b98800", # PR4491 is bisect result of PR4164 and Parent5463.
+    PR4491="85adf09e3463838d547977ae9bc75e3b37f9cbaf",
     Parent5463="052f8da6", # PR5463 is bisect result of PR4164 and Parent7401.
     PR5463="19b7866112614db53eb3e909c097407d91cd6738",
     Parent7401="20b463c9592c07d05ad2e89a25f84f0b998d6154", # master parent of the PR7401 which caused the recent speedup.

From 95b8f69befdfbfb1e43783d54f5fa655aecde155 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 06:43:54 -0400
Subject: [PATCH 30/37] pos

---
 .ci/atime/bisect-7687.R | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 6e868284fe..dd4734c11e 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -3,7 +3,8 @@ Test <- "DT[by] fixed in #4558"
 library(data.table)
 if(FALSE){
   remotes::install_github("tdhock/atime@bisect")
-  atime::bisect(pkg.path, Test, "PR7401", "Fast")
+  atime::bisect(pkg.path, Test, "PR7401", "Fast") #should error
+  atime::bisect(pkg.path, Test, "PR4491", "Parent7401") #should find PR5463
 }
 
 (bisect.dt <- rowwiseDT(
@@ -12,7 +13,6 @@ if(FALSE){
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
   "PR4491", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
-  ## "PR7401", "Fast", "",#no speed changes, returns PR7650, but atime plot clearly shows no real change.
   ## "PR5463", "Parent7401", "TODO",#slight speed decrease.
   "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
   "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.

From 7b8475522d1510ba9814d0501fe820d1e52e0d9a Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 07:09:40 -0400
Subject: [PATCH 31/37] finding PR5463

---
 .ci/atime/bisect-7687.R | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index dd4734c11e..1cf65a691e 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -12,6 +12,7 @@ if(FALSE){
   "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
+  "PR4164", "Parent7401", "PR5463",
   "PR4491", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
   ## "PR5463", "Parent7401", "TODO",#slight speed decrease.
   "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.

From b87d894857b3bb72f7b84b832a46d7ddc75dd0c3 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 12:18:12 -0400
Subject: [PATCH 32/37] comment

---
 .ci/atime/bisect-7687.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 1cf65a691e..b1c6d664a6 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -15,7 +15,7 @@ if(FALSE){
   "PR4164", "Parent7401", "PR5463",
   "PR4491", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
   ## "PR5463", "Parent7401", "TODO",#slight speed decrease.
-  "PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
+  ##"PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
   "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.
 for(bisect.i in 1:nrow(bisect.dt)){
   print(bisect.row <- bisect.dt[bisect.i])

From 86537fc1c9e13e84e6858ac5b19e29f27453fb85 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 13:13:27 -0400
Subject: [PATCH 33/37] largerN

---
 .ci/atime/tests.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 2c9df7a193..09df807c2a 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -320,7 +320,7 @@ test.list <- atime::atime_test_list(
   # Test case adapted from https://github.com/Rdatatable/data.table/issues/4200#issuecomment-645980224 which is where the issue was reported.
   # Fixed in https://github.com/Rdatatable/data.table/pull/4558
   "DT[by] fixed in #4558" = atime::atime_test(
-    N=2^seq(1, 20),
+    N=2^seq(1, 30),
     seconds.limit=0.1,
     setup = {
       N9 <- as.integer(N * 0.9)

From 22d5e1b665fb7712acb26b23ae145e0de8d3c6d8 Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 15:37:35 -0400
Subject: [PATCH 34/37] move up

---
 .ci/atime/bisect-7687.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index b1c6d664a6..1c9fe778a7 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -9,10 +9,10 @@ if(FALSE){
 
 (bisect.dt <- rowwiseDT(
   old=, new=, label=,
+  "PR4164", "Parent7401", "PR5463",
   "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
-  "PR4164", "Parent7401", "PR5463",
   "PR4491", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
   ## "PR5463", "Parent7401", "TODO",#slight speed decrease.
   ##"PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.

From 79d563bffd613a9f452aae31204d2f169ae4a0cd Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Tue, 13 Oct 2026 16:19:37 -0400
Subject: [PATCH 35/37] fix Fast

---
 .ci/atime/tests.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/tests.R b/.ci/atime/tests.R
index 09df807c2a..f6b974f292 100644
--- a/.ci/atime/tests.R
+++ b/.ci/atime/tests.R
@@ -340,7 +340,7 @@ test.list <- atime::atime_test_list(
     PR5463="19b7866112614db53eb3e909c097407d91cd6738",
     Parent7401="20b463c9592c07d05ad2e89a25f84f0b998d6154", # master parent of the PR7401 which caused the recent speedup.
     PR7401="0216983c51e03e3f61d5e6f08f4ba0c42cceb22c",
-    Fast="master",
+    Fast="a3eeb4c0caec51afd66bdf9bbc16817e12a47a40", #master 10 Sept 2026
     expr = data.table:::`[.data.table`(d, , max(v1) - min(v2), by = id)),
 
   # Issue with sorting again when already sorted, as reported in https://github.com/Rdatatable/data.table/issues/4498

From 958d1c431730f36dcd580ef217f2081b744cd7ac Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Wed, 14 Oct 2026 07:16:24 -0400
Subject: [PATCH 36/37] find PR4491

---
 .ci/atime/bisect-7687.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 1c9fe778a7..1e038e92de 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -9,12 +9,12 @@ if(FALSE){
 
 (bisect.dt <- rowwiseDT(
   old=, new=, label=,
+  "PR4558", "Parent5463", "PR4491",
   "PR4164", "Parent7401", "PR5463",
   "Before", "Parent4558", "PR4164",#returns PR4164, consistent with https://github.com/Rdatatable/data.table/issues/4200#issuecomment-646111420
   "PR4558", "Fast", "PR7401",#returns PR7401, consistent with https://github.com/Rdatatable/data.table/issues/7687#issuecomment-4162931822
   "PR4164", "Fast", "PR7401",#two speed increases between these two commits, bisect finds the larger one: PR7401.
   "PR4491", "Parent7401", "PR5463",#should find one small speed increase in PR4558? Finds PR5463??
-  ## "PR5463", "Parent7401", "TODO",#slight speed decrease.
   ##"PR4164", "Parent5463", "PR4491",#expected speed increase, found PR4491.
   "PR4164", "Parent4491", "PR4558"))#expected speed increase, found PR4558. DONE.
 for(bisect.i in 1:nrow(bisect.dt)){

From 9ce58b0489cca9b8133098002202384adafcc59e Mon Sep 17 00:00:00 2001
From: Toby Dylan Hocking <toby.hocking@r-project.org>
Date: Wed, 14 Oct 2026 11:10:03 -0400
Subject: [PATCH 37/37] removedt

---
 .ci/atime/bisect-7687.R | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.ci/atime/bisect-7687.R b/.ci/atime/bisect-7687.R
index 1e038e92de..125a985353 100644
--- a/.ci/atime/bisect-7687.R
+++ b/.ci/atime/bisect-7687.R
@@ -3,6 +3,7 @@ Test <- "DT[by] fixed in #4558"
 library(data.table)
 if(FALSE){
   remotes::install_github("tdhock/atime@bisect")
+  atime::atime_versions_remove("data.table")
   atime::bisect(pkg.path, Test, "PR7401", "Fast") #should error
   atime::bisect(pkg.path, Test, "PR4491", "Parent7401") #should find PR5463
 }