From 351e39c27a882ccd1269265b757b960b0dcab3c3 Mon Sep 17 00:00:00 2001
From: Ryuta Kamizono <kamipo@gmail.com>
Date: Mon, 1 Feb 2016 11:12:56 +0900
Subject: Extract `ExplainPrettyPrinter` to appropriate files

---
 .../postgresql/explain_pretty_printer.rb           | 42 ++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb

(limited to 'activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb')

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
new file mode 100644
index 0000000000..789b88912c
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
@@ -0,0 +1,42 @@
+module ActiveRecord
+  module ConnectionAdapters
+    module PostgreSQL
+      class ExplainPrettyPrinter # :nodoc:
+        # Pretty prints the result of an 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)
+        #
+        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
+      end
+    end
+  end
+end
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