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Gay Marriage! From a database engineering perspective @lizTheDeveloper Adapted from an essay by Sam Hughes @ qntm.org/gay Friday, March 15, 13

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Friday, March 15, 13

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What is Marriage? Friday, March 15, 13

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Love? Friday, March 15, 13

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Childbearing? Friday, March 15, 13

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Sociological construct designed to make agricultural societies run smoother? Friday, March 15, 13

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A Relationship Friday, March 15, 13

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A Relationship... • Recognized by the state Friday, March 15, 13

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A Relationship... • Recognized by the state • That affords certain legal rights Friday, March 15, 13

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A Relationship... • Recognized by the state • That affords certain legal rights • Defines common property Friday, March 15, 13

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A Relationship... • Recognized by the state • That affords certain legal rights • Defines common property • Automagically determines parentage of children created while in the relationship. Friday, March 15, 13

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That’s all we track. Friday, March 15, 13

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That’s all we track. From a database engineering perspective. Friday, March 15, 13

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Everything else.... Friday, March 15, 13

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Everything else.... is beyond the scope of this talk. Friday, March 15, 13

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How to store a relationship? Friday, March 15, 13

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Quick Vocabulary • Entities • Relationship • Metadata • Key Friday, March 15, 13

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Foreign Keys • Every entity has an ID • Other entities reference that ID Friday, March 15, 13

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“Good Enough for Government Work” `males` - `id` - `forename` - `surname` - `birthdate` - `wife_id` (foreign key references column `females`.`id`, may be NULL if male is unmarried) `females` - `id` - `forename` - `surname` - `birthdate` - `husband_id` (foreign key references column `males`.`id`, may be NULL if female is unmarried) Friday, March 15, 13

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Problem? • Bad Referential Integrity • Relationships can be one-way • Duplicates data • No metadata about relationship • Lots of other things Friday, March 15, 13

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Sexist Database Design `males` - `id` - `forename` - `surname` - `birthdate` - `wife_id` (unique foreign key references column `females`.`id`, may be NULL if male is unmarried) `females` - `id` - `forename` - `surname` - `birthdate` Friday, March 15, 13

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Friday, March 15, 13

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Serious problems • Mind-bogglingly sexist • But slightly better, from an engineering perspective (shockingly.) • Still have a lack of metadata Friday, March 15, 13

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Sexism with Metadata `males` - `id` - `forename` - `surname` - `birthdate` - `wife_id` (foreign key references column `females`.`id`, may be NULL if male is unmarried) - `marriage_date` (may be NULL if male is unmarried) - `divorce_date` (may be NULL if male is unmarried or married but not yet divorced) `females` - `id` - `forename` - `surname` - `birthdate` Friday, March 15, 13

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Problem? • Still sexist! • Also, men can only be married/divorced once. • “Flat” data presents these problems. Friday, March 15, 13

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So... what do we do? Friday, March 15, 13

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Relationship Tables `males` - `id` - `forename` - `surname` - `birthdate` `females` - `id` - `forename` - `surname` - `birthdate` `marriages` - `id` - `husband_id` (foreign key references column `males`.`id`) - `wife_id` (foreign key references column `females`.`id`) - `marriage_date` - `divorce_date` (NULL if marriage not ended) Friday, March 15, 13

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Storing a relationship makes sense. Friday, March 15, 13

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But we still have problems • Still sexist • Separating genders doesn’t make sense. Friday, March 15, 13

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If two entities are equal (like men and women) then there is no reason to stratify them. Friday, March 15, 13

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We are all humans. `humans` - `id` - `forename` - `surname` - `birthdate` - `sex` ("male" or "female") `marriages` - `id` - `partner_1_id` (foreign key references column `humans`.`id`) - `partner_2_id` (foreign key references column `humans`.`id`) - `marriage_date` - `divorce_date` (NULL if marriage not ended) Friday, March 15, 13

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Problems? • Unary marriages are now possible - you can marry yourself. • The “sex” column is more limiting than it seems. Friday, March 15, 13

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“There’s gonna be a lot more guys with makeup this millennium” - Eddie Izzard `humans` - `id` - `forename` - `surname` - `birthdate` - `sex_id` (foreign key references column `sexes`) `marriages` - `id` - `partner_1_id` (foreign key references column `humans`.`id`) - `partner_2_id` (foreign key references column `humans`.`id`) - `marriage_date` - `divorce_date` (NULL if marriage not ended) `sexes` - `id` - `string` Friday, March 15, 13

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What is Sex/Gender? Friday, March 15, 13

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`humans` - `id` - `forename` - `surname` - `birthdate` - `sex_id` (foreign key references column `sexes`) - `gender_id` (foreign key references column `genders`) `marriages` - `id` - `partner_1_id` (foreign key references column `humans`.`id`) - `partner_2_id` (foreign key references column `humans`.`id`) - `marriage_date` - `divorce_date` (NULL if marriage not ended) `sexes` - `id` - `string` `genders` - `id` - `string` Gender is a Spectrum Friday, March 15, 13

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Existential Crisis mode! Friday, March 15, 13

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Let’s just forget about it. `humans` - `id` - `forename` - `surname` - `birthdate` `marriages` - `id` - `partner_1_id` (foreign key references column `humans`.`id`) - `partner_2_id` (foreign key references column `humans`.`id`) - `marriage_date` - `divorce_date` (NULL if marriage not ended) Friday, March 15, 13

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We’re done, right? Please oh please let us be done. Friday, March 15, 13

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Friday, March 15, 13

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Relationships are discrete entities, but so are marriage partners. Friday, March 15, 13

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Let’s take it slowly. `humans` - `id` - `forename` - `surname` - `birthdate` `marriages` - `id` - `marriage_date` - `divorce_date` (NULL if marriage not ended) `marriage_partners` - `id` - `human_id` (foreign key references column `humans`.`id`) - `marriage_id` (foreign key references column `marriages`.`id`) Friday, March 15, 13

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Problems? • What if a human joins the marriage after it begins? From a database engineering perspective. Friday, March 15, 13

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It’s all about metadata `humans` - `id` - `forename` - `surname` - `birthdate` `marriages` - `id` `marriage_partners` - `id` - `human_id` (foreign key references column `humans`.`id`) - `marriage_id` (foreign key references column `marriages`.`id`) - `marriage_date` - `divorce_date` (NULL if still in marriage) Friday, March 15, 13

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Marriage == Graph Theory Friday, March 15, 13

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Intransitive Marriage Friday, March 15, 13

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Non-communicative Marriage Friday, March 15, 13

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Architecture Astronauts never get married Friday, March 15, 13