Bizarre off-by-one post update error

I’m trying to update a set of posts in a script in rails. It seems that there is some strange off-by-one behavior where one post gets updated with the previous post’s value.

I moved all of these updates to directly do a post.raw.gsub() to “solve” this problem for the posts within the inner loop (which had previously been getting the value from the topic post), but now the topic post of topic N gets updated with the raw of the previous final post from topic N-1.

I’m extra double confused now, as the first (i.e. topic) post gets updated with tpost.raw.gsub! with the value of post.raw.gsub!(preg,"#{$2}") from the previous interation.

EDIT: Well, I never did figure out what was going wrong with the last version, but here’s a version of an update-some-posts script that creates a revision:

def fix_slack_posts
  opts = { bypass_rate_limiter: true, bypass_bump: true, skip_validations: true }
  reg=/(\*\*)(This topic was automatically generated from Slack. You can find the original thread \[here\].+?\))(\*\*\.)?\s*?([a-zA-Z, ()]* : )(.*)/m
  preg = /([a-zA-Z, ()]+? : )(.*)/m
  topic_posts = Post.where("raw like '**This topic was automatically%'")
  #topic_posts = Post.where(topic_id: [23934, 23935], post_number: 1)
  topic_posts.each do |tpost|
      puts "Fixing topic post #{} with #{tpost.raw[0..30]}"
      puts tpost.raw.gsub(reg,"1 #{$1}\n2 #{$2}\n3 #{$3}\n4 #{$4}\n 5 #{$5}")
      raw = tpost.raw.gsub(reg,"#{$5}\n\n#{$2}.")
      puts "Fixing topic post #{} with #{tpost.raw[0..30]}\n--->#{raw}"
      user = User.find(tpost.user_id)
      if raw.length > 10
        tpost.revise(user,{raw: raw,edit_reason: 'fix slack link location'}, opts)
      puts "Can't update topic post #{tpost.raw}"
    posts = Post.where(topic_id: tpost.topic_id).where("post_number > 1")
    posts.each do |post|
      if post.raw.gsub(preg,"#{$2}").length>=10
          puts "Fixing post #{} with #{post.raw[0..30]}"
          raw = post.raw.gsub(preg,"#{$2}")
          user = User.find(post.user_id)
          post.revise(user,{raw: raw,edit_reason: 'remove user name from text'}, opts)
          puts "#{}--cannot save #{post.raw}. "