Class: ArJdbc::PostgreSQL::ExplainSupport::ExplainPrettyPrinter

Inherits:
Object
  • Object
show all
Defined in:
lib/arjdbc/postgresql/explain_support.rb

Overview

:nodoc:

Instance Method Summary collapse

Instance Method Details

#pp(result) ⇒ Object

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)



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# File 'lib/arjdbc/postgresql/explain_support.rb', line 31

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