20000 Leagues Under ActiveRecord

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2. User.where(name: 'Captain Nemo').first
3. irb(main):001:0> User.where(name: 'Captain Nemo').first ! User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."name" = 'Captain Nemo' ORDER BY "users"."id" ASC LIMIT 1 ! => #<User id: 1, name: "Captain Nemo">
5. Agenda: ! - ActiveRecord::Relation - Generating SQL - Executing SQL - The B-Tree Algorithm
6. class User < ActiveRecord::Base end User ActiveRecord::Base
7. User.where(name: "Captain Nemo") User ActiveRecord::Querying def where end ActiveRecord::Relation def all end def where end
8. User ActiveRecord::Base def where end ActiveRecord::Relation def all end def where end User.all.where(name: "Captain Nemo")
9. ActiveRecord::Relation def where end ActiveRecord::Relation where: name="Captain Nemo" User.all.where(name: "Captain Nemo")
10. ActiveRecord::Relation def first end ActiveRecord::Relation where: name="Captain Nemo" order: id, ASC limit: 1 offset: 0 where: name="Captain Nemo" User.all.where(name: "Captain Nemo") .first
11. def first(limit = nil) if limit find_nth_with_limit(offset_index, limit) else find_nth(0, offset_index) end end
12. def second find_nth(1, offset_index) end def third find_nth(2, offset_index) end def fourth find_nth(3, offset_index) end def fifth find_nth(4, offset_index) end
13. def forty_two find_nth(41, offset_index) end
14. ActiveRecord::Relation def first end ActiveRecord::Relation where: name="Captain Nemo" order: id, ASC limit: 1 offset: 0 where: name="Captain Nemo" User.all.where(name: "Captain Nemo") .find_nth(0, 0)
15. ActiveRecord::Relation def first end ActiveRecord::Relation where: name="Captain Nemo" order: id, ASC limit: 1 offset: 0 where: name="Captain Nemo" User.all.where(name: "Captain Nemo") .find_nth_with_limit(0, 1)
16. ActiveRecord::Relation def first end ActiveRecord::Relation where: name="Captain Nemo" order: id, ASC limit: 1 offset: 0 where: name="Captain Nemo" User.all.where(name: "Captain Nemo") .order(arel_table[primary_key].asc) .limit(1)
17. ActiveRecord Base ActiveRecord Relation ActiveRecord Relation ActiveRecord Relation ActiveRecord Relation all where order limit User.all.where(name: "Captain Nemo") .order(arel_table[primary_key].asc) .limit(1)
18. # Converts relation objects to Array. def to_a load @records end User.all.where(name: "Captain Nemo") .order(arel_table[primary_key].asc) .limit(1).to_a PostgreSQLAdapter.select_all
20. ActiveRecord::Relation where: name="Captain Nemo" limit: 1 offset: 0 order: id, ASC
21. Arel::Nodes::Attribute ActiveRecord::Relation relation: User name: name Arel::Nodes::Equality where_values "$1"
26. SELECT * FROM users WHERE name = 'Captain Nemo' ORDER BY id ASC LIMIT 1
27. SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
28. User.where(name: 'Captain Nemo').first users = Arel::Table.new(:users)! users.project('*')! .where(users[:name].eq('Captain Nemo'))! .order(users[:id], 'ASC')! .take(1)
29. SELECT SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
30. SELECT SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
31. SELECT "users".* SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
32. SELECT "users".* FROM "users" SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
33. SELECT "users".* FROM "users"! WHERE "users"."name" = $1 SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
34. SELECT "users".* FROM "users"! WHERE "users"."name" = $1! ORDER BY "users"."id" ASC SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
35. SELECT "users".* FROM "users"! WHERE "users"."name" = $1! ORDER BY "users"."id" ASC LIMIT 1 SelectStatement Attribute JoinSource Table Top And Equality Attribute BindParam Ascending Attribute Limit Quoted SelectCore
38. - Parse - Analyze and Rewrite - Plan - Execute
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41. SELECT RESTARGET A_STAR AEXPR SORTBY A_CONST COLUMNREF users from clause fields RANGEVAR users target list where clause sort clause limit count name: "=" COLUMNREF users.id COLUMNREF users.name A_CONST val: "Captain Nemo" val: 1 lexpr rexpr node
42. QUERY RTE ALIAS jointree FROMEXPR users rtable target list sort clause limit count RANGETBLREF rtindex 1 OPEXPR users fromlist quals RELABELTYPE CONST "Captain Nemo" VAR args arg id name created_at updated_at SORTGROUPCLAUSE FUNCEXPR users CONST 1
43. PLANNEDSTMT LIMIT startup cost 21.56 total_cost: 21.57 SORT startup cost 21.56 total_cost: 21.57 SEQSCAN startup cost 0.00 total_cost: 21.55 OPEXPR users RELABELTYPE CONST "Captain Nemo" VAR args
44. == 'Captain Nemo' ? Laurianne Goodwin Candace Kris Miss Jaclyn Hansen Abby Powlowski Captain Nemo Ludwig O'Connell Jalyn Schroeder Rubye Morar etc ...
45. == 'Captain Nemo' ? Laurianne Goodwin Candace Kris Miss Jaclyn Hansen Abby Powlowski Captain Nemo Ludwig O'Connell Jalyn Schroeder Rubye Morar etc ...
46. == 'Captain Nemo' ? Laurianne Goodwin Candace Kris Miss Jaclyn Hansen Abby Powlowski Captain Nemo Ludwig O'Connell Jalyn Schroeder Rubye Morar etc ...
47. SELECT * FROM users WHERE name = 'Captain Nemo' ORDER BY id ASC LIMIT 1
48. == 'Captain Nemo' ? Laurianne Goodwin Candace Kris Miss Jaclyn Hansen Abby Powlowski Captain Nemo Ludwig O'Connell Jalyn Schroeder Rubye Morar etc ...
50. class AddIndexOnUserName < ActiveRecord::Migration! def change! add_index :users, :name! end! end
51. Laurianne Goodwin Candace Kris Miss Jaclyn Hansen Abby Powlowski Captain Nemo Ludwig O'Connell Jalyn Schroeder Rubye Morar Abby Powlowski Candace Kris Captain Nemo Jalyn Schroeder Laurianne Goodwin Ludwig O'Connell Miss Jaclyn Hansen Rubye Morar
52. PLANNEDSTMT LIMIT startup cost 8.30 total_cost: 8.31 SORT startup cost 8.30 total_cost: 8.31 INDEXSCAN startup cost 0.28 total_cost: 8.29 OPEXPR users RELABELTYPE CONST "Captain Nemo" VAR args
53. < 'Captain Nemo' ? Amina Doyle Arlie Walsh Boyd Pagac Candace Kris Captain Nemo Catherine Wisoky PhD Cheyenne Jenkins Conor Collier Conseil Della Christiansen Desmond Wintheiser Era Beier Fanny Reinger Giovanni Rau Godfrey Fadel Ines Halvorson V Jaleel O'Hara Jalyn Schroeder Jermaine Schuppe Keara Schumm Kendall Ledner MD Keon Fisher Laurianne Goodwin Ludwig O'Connell Merlin Davis Miss Deja Kris Miss Jaclyn Hansen Mr. Hadley Bode Mr. Kenneth Wiza Ms. Kaylie Morar Ned Land Professor Aronnax Rae Dare Rubye Morar Samson Auer MD Santino Sipes Sibyl Ebert V Torrance Schmitt Tyrese Walsh Zora Emmerich 50%
54. < 'Captain Nemo' ? Amina Doyle Arlie Walsh Boyd Pagac Candace Kris Captain Nemo Catherine Wisoky PhD Cheyenne Jenkins Conor Collier Conseil Della Christiansen Desmond Wintheiser Era Beier Fanny Reinger Giovanni Rau Godfrey Fadel Ines Halvorson V Jaleel O'Hara Jalyn Schroeder Jermaine Schuppe Keara Schumm Kendall Ledner MD Keon Fisher Laurianne Goodwin Ludwig O'Connell Merlin Davis Miss Deja Kris Miss Jaclyn Hansen Mr. Hadley Bode Mr. Kenneth Wiza Ms. Kaylie Morar Ned Land Professor Aronnax Rae Dare Rubye Morar Samson Auer MD Santino Sipes Sibyl Ebert V Torrance Schmitt Tyrese Walsh Zora Emmerich 25%
55. < 'Captain Nemo' ? Amina Doyle Arlie Walsh Boyd Pagac Candace Kris Captain Nemo Catherine Wisoky PhD Cheyenne Jenkins Conor Collier Conseil Della Christiansen Desmond Wintheiser Era Beier Fanny Reinger Giovanni Rau Godfrey Fadel Ines Halvorson V Jaleel O'Hara Jalyn Schroeder Jermaine Schuppe Keara Schumm Kendall Ledner MD Keon Fisher Laurianne Goodwin Ludwig O'Connell Merlin Davis Miss Deja Kris Miss Jaclyn Hansen Mr. Hadley Bode Mr. Kenneth Wiza Ms. Kaylie Morar Ned Land Professor Aronnax Rae Dare Rubye Morar Samson Auer MD Santino Sipes Sibyl Ebert V Torrance Schmitt Tyrese Walsh Zora Emmerich 12.5%
56. Insert: “Captain Nemo” ? Amina Doyle Arlie Walsh Boyd Pagac 200 more names ... Torrance Schmitt Tyrese Walsh Zora Emmerich
57. available space… NULL Monte Nicolas Amina Doyle Arlie Walsh Boyd Pagac Monte Nicolas Ned Land Professor Aronnax available space… Captain Nemo
58. available space… Amina Doyle Arlie Walsh Boyd Pagac Monte Nicolas Ned Land Professor Aronnax available space… Captain Nemo available space… Amina Doyle Arlie Walsh Boyd Pagac Captain Nemo NULL Julius Powlowski Monte Nicolas
64. available space… Amina Doyle Arlie Walsh Boyd Pagac Monte Nicolas Ned Land Professor Aronnax available space… Captain Nemo available space… Amina Doyle Arlie Walsh Boyd Pagac Captain Nemo NULL Julius Powlowski Monte Nicolas
65. What have we learned?