discourse/lib/db_helper.rb

# frozen_string_literal: true

require_dependency "migration/base_dropper"

class DbHelper

  REMAP_SQL ||= <<~SQL
    SELECT table_name, column_name, character_maximum_length
      FROM information_schema.columns
     WHERE table_schema = 'public'
       AND is_updatable = 'YES'
       AND (data_type LIKE 'char%' OR data_type LIKE 'text%')
  ORDER BY table_name, column_name
  SQL

  TRIGGERS_SQL ||= <<~SQL
    SELECT trigger_name
      FROM information_schema.triggers
     WHERE trigger_name LIKE '%_readonly'
  SQL

  TRUNCATABLE_COLUMNS ||= [
    'topic_links.url'
  ]

  def self.remap(from, to, anchor_left: false, anchor_right: false, excluded_tables: [], verbose: false)
    like = "#{anchor_left ? '' : "%"}#{from}#{anchor_right ? '' : "%"}"
    text_columns = find_text_columns(excluded_tables)

    text_columns.each do |table, columns|
      set = columns.map do |column|
        replace = "REPLACE(\"#{column[:name]}\", :from, :to)"
        replace = truncate(replace, table, column)
        "\"#{column[:name]}\" = #{replace}"
      end.join(", ")

      where = columns.map do |column|
        "\"#{column[:name]}\" IS NOT NULL AND \"#{column[:name]}\" LIKE :like"
      end.join(" OR ")

      rows = DB.exec(<<~SQL, from: from, to: to, like: like)
        UPDATE \"#{table}\"
           SET #{set}
         WHERE #{where}
      SQL

      puts "#{table}=#{rows}" if verbose && rows > 0
    end

    finish!
  end

  def self.regexp_replace(pattern, replacement, flags: "gi", match: "~*", excluded_tables: [], verbose: false)
    text_columns = find_text_columns(excluded_tables)

    text_columns.each do |table, columns|
      set = columns.map do |column|
        replace = "REGEXP_REPLACE(\"#{column[:name]}\", :pattern, :replacement, :flags)"
        replace = truncate(replace, table, column)
        "\"#{column[:name]}\" = #{replace}"
      end.join(", ")

      where = columns.map do |column|
        "\"#{column[:name]}\" IS NOT NULL AND \"#{column[:name]}\" #{match} :pattern"
      end.join(" OR ")

      rows = DB.exec(<<~SQL, pattern: pattern, replacement: replacement, flags: flags, match: match)
        UPDATE \"#{table}\"
           SET #{set}
         WHERE #{where}
      SQL

      puts "#{table}=#{rows}" if verbose && rows > 0
    end

    finish!
  end

  def self.find(needle, anchor_left: false, anchor_right: false, excluded_tables: [])
    found = {}
    like = "#{anchor_left ? '' : "%"}#{needle}#{anchor_right ? '' : "%"}"

    DB.query(REMAP_SQL).each do |r|
      next if excluded_tables.include?(r.table_name)

      rows = DB.query(<<~SQL, like: like)
        SELECT \"#{r.column_name}\"
          FROM \"#{r.table_name}\"
         WHERE \""#{r.column_name}"\" LIKE :like
      SQL

      if rows.size > 0
        found["#{r.table_name}.#{r.column_name}"] = rows.map do |row|
          row.public_send(r.column_name)
        end
      end
    end

    found
  end

  private

  def self.finish!
    SiteSetting.refresh!
    Theme.expire_site_cache!
    SiteIconManager.ensure_optimized!
    ApplicationController.banner_json_cache.clear
  end

  def self.find_text_columns(excluded_tables)
    triggers = DB.query(TRIGGERS_SQL).map(&:trigger_name).to_set
    text_columns = Hash.new { |h, k| h[k] = [] }

    DB.query(REMAP_SQL).each do |r|
      next if excluded_tables.include?(r.table_name) ||
        triggers.include?(Migration::BaseDropper.readonly_trigger_name(r.table_name, r.column_name))

      text_columns[r.table_name] << {
        name: r.column_name,
        max_length: r.character_maximum_length
      }
    end

    text_columns
  end

  def self.truncate(sql, table, column)
    if column[:max_length] && TRUNCATABLE_COLUMNS.include?("#{table}.#{column[:name]}")
      "LEFT(#{sql}, #{column[:max_length]})"
    else
      sql
    end
  end
end