parse postgres core dumps

gdb.rb

require "fileutils"
require "tmpdir"

class PGCoreDump
  attr_reader :file, :term, :bt, :query, :basename, :sha256
  def initialize(file, basename)
    @basename = basename
    @file = file
  end

  def summary
    @bt.map { |l| l.match(/#\d+\s+(0x\w+ in )?(?<fn>\w+)/)[:fn] }.first(7).join(", ")
  end

  def parse
    lines = gdb("-ex bt").split("\n")
    @term = lines.find { |l| l =~ /\AProgram terminated with signal/ }
    @bt = lines.select { |l| l =~ /\A\#\d/ }.uniq
    @query = get_query
    @sha256 = `sha256sum #{file}`.split(" ").first
  end

  def get_query
    @bt.find { |f| f =~ /\A#(\d+) 0x[0-9a-f]+ in exec_simple_query/ }
    frame = $1
    gdb(%(-ex 'F #{frame}' -ex 'printf "%s", query_string')).split("\n").drop_while { |l| !l.start_with?("##{frame}") }[1..-1].join
  end

  private

  def gdb(cmd)
    `gdb #{file} --batch #{cmd} -q 2>/dev/null`
  end
end

class Extractor
  def initialize(file)
    @file = file
  end

  def call
    pg = nil
    basename = File.basename(@file)
    if @file.end_with?(".gz")
      Dir.mktmpdir do |dir|
        FileUtils.cp(@file, "#{dir}/core.gz")
        `gunzip #{dir}/core.gz`
        pg = PGCoreDump.new("#{dir}/core", basename)
        pg.parse
      end
    else
      pg = PGCoreDump.new(@file, basename)
      pg.parse
    end
    pg
  end
end

sumquery = {}
Dir.glob("/dat/tmp/core/*").each do |f|
  pg = Extractor.new(f).call
  puts "#{pg.basename} #{pg.summary}"
  old_q = sumquery[pg.summary] || pg.query + "more"
  if pg.query.size < old_q.size
    puts "new shortest query"
    puts pg.query
    sumquery[pg.summary] = pg.query
  end
end

sumquery.each do |(k, v)|
  puts
  puts k
  puts v
  puts
end