#!/usr/bin/env bash
# CTR empirical test A: client-visible ROLLBACK latency vs undo-chain length N.
#
# The design (README.undo:20-25, 105-112) claims ROLLBACK returns in O(1) to
# the client for "sparse" transactions: physical undo is deferred to background
# workers above undo_instant_abort_threshold, and applied INLINE (in the
# aborting backend, before ROLLBACK returns) below it.
#
# We measure the client-visible ROLLBACK latency as N (number of undo-generating
# file ops in one transaction) grows, at three settings of the threshold
# (session-local SET; the GUC is PGC_USERSET), to separate the two regimes and
# prove the knee is caused by the threshold (calibration), not something else.
#
# Metric: wall time of the ROLLBACK statement only (psql \timing), median of R
# repeats. The N chmods hit one pre-created file; each records one undo record
# (prior mode). Nothing commits, so filesystem state is trivial and the only
# thing that scales is the undo chain length.
set -u
PORT=${PORT:-5467}
BIN=$HOME/undo-v2-inst/bin
PSQL="$BIN/psql -p $PORT -U postgres -X -q -t -A"
REPEATS=${REPEATS:-5}
NS=${NS:-"100 300 1000 3000 10000 30000 100000"}
# threshold regimes: default, forced-inline (huge), forced-deferred (tiny)
THRS=${THRS:-"65536 1000000000 1"}
OUT=${OUT:-/home/manu/Proyectos/yggdrasil/aportes/postgres-undo-ctr/logs_v2/ctr_rollback_latency.tsv}
mkdir -p "$(dirname "$OUT")"

$PSQL -c "CREATE EXTENSION IF NOT EXISTS test_fileops;" >/dev/null 2>&1
F=$($PSQL -c "SELECT test_fileops_create_tempfile('ctr_lat.dat');")

median() { sort -n | awk '{a[NR]=$1} END{ if(NR==0){print "NA"} else if(NR%2){print a[(NR+1)/2]} else {printf "%.3f\n",(a[NR/2]+a[NR/2+1])/2} }'; }

# ROLLBACK latency (ms) for one trial at chain length N and threshold THR.
# Everything in one psql session; the LAST "Time:" line is the ROLLBACK.
one_trial() {
  local n=$1 thr=$2
  $PSQL 2>/dev/null <<SQL | grep -oE 'Time: [0-9.]+ ms' | tail -1 | grep -oE '[0-9.]+'
SET undo_instant_abort_threshold = $thr;
BEGIN;
SELECT count(test_fileops_chmod('$F', (0400 + (g%2)*0200))) FROM generate_series(1,$n) g;
\timing on
ROLLBACK;
SQL
}

echo -e "threshold\tN\trollback_ms_median\ttrials" | tee "$OUT"
for THR in $THRS; do
  for n in $NS; do
    vals=""
    for r in $(seq 1 $REPEATS); do
      t=$(one_trial "$n" "$THR")
      [ -n "$t" ] && vals="${vals}${t}"$'\n'
    done
    med=$(printf '%s' "$vals" | median)
    echo -e "$THR\t$n\t$med\t$REPEATS" | tee -a "$OUT"
  done
done
echo "=== DONE ctr_rollback_latency ==="