class ArJdbc::PostgreSQL::ExplainSupport::ExplainPrettyPrinter

@private

Public Instance Methods

pp(result) click to toggle source

Pretty prints the result of a EXPLAIN in a way that resembles the output of the PostgreSQL shell:

QUERY PLAN


Nested Loop Left Join (cost=0.00..37.24 rows=8 width=0) Join Filter: (posts.user_id = users.id) -> Index Scan using users_pkey on users (cost=0.00..8.27 rows=1 width=4) Index Cond: (id = 1) -> Seq Scan on posts (cost=0.00..28.88 rows=8 width=4) Filter: (posts.user_id = 1) (6 rows)

# File lib/arjdbc/postgresql/explain_support.rb, line 29
def pp(result)
  header = result.columns.first
  lines = result.rows.map(&:first)

  # We add 2 because there's one char of padding at both sides, note
  # the extra hyphens in the example above.
  width = [header, *lines].map(&:length).max + 2

  pp = []

  pp << header.center(width).rstrip
  pp << '-' * width

  pp += lines.map {|line| " #{line}"}

  nrows = result.rows.length
  rows_label = nrows == 1 ? 'row' : 'rows'
  pp << "(#{nrows} #{rows_label})"

  pp.join("\n") + "\n"
end