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diff --git a/locale/pt/LC_MESSAGES/_articles/2021-04-29-a-relational-model-of-data-for-large-shared-data-banks-article-review.po b/locale/pt/LC_MESSAGES/_articles/2021-04-29-a-relational-model-of-data-for-large-shared-data-banks-article-review.po deleted file mode 100644 index 6a98ab5..0000000 --- a/locale/pt/LC_MESSAGES/_articles/2021-04-29-a-relational-model-of-data-for-large-shared-data-banks-article-review.po +++ /dev/null @@ -1,211 +0,0 @@ -# -msgid "" -msgstr "" - -msgid "" -"title: A Relational Model of Data for Large Shared Data Banks - article-" -"review" -msgstr "" - -msgid "date: 2021-04-29" -msgstr "" - -msgid "layout: post" -msgstr "" - -msgid "lang: en" -msgstr "" - -msgid "" -"ref: a-relational-model-of-data-for-large-shared-data-banks-article-review" -msgstr "" - -msgid "" -"This is a review of the article \"[A Relational Model of Data for Large " -"Shared Data Banks](https://www.seas.upenn.edu/~zives/03f/cis550/codd.pdf)\"," -" by E. F. Codd." -msgstr "" - -msgid "Data Independence" -msgstr "" - -msgid "" -"Codd brings the idea of *data independence* as a better approach to use on " -"databases. This is contrast with the existing approaches, namely " -"hierarquical (tree-based) and network-based." -msgstr "" - -msgid "" -"His main argument is that queries in applications shouldn't depende and be " -"coupled with how the data is represented internally by the database system. " -"This key idea is very powerful, and something that we strive for in many " -"other places: decoupling the interface from the implementation." -msgstr "" - -msgid "" -"If the database system has this separation, it can kep the querying " -"interface stable, while having the freedom to change its internal " -"representation at will, for better performance, less storage, etc." -msgstr "" - -msgid "" -"This is true for most modern database systems. They can change from B-Trees " -"with leafs containing pointers to data, to B-Trees with leafs containing the" -" raw data , to hash tables. All that without changing the query interface, " -"only its performance." -msgstr "" - -msgid "" -"Codd mentions that, from an information representation standpoint, any index" -" is a duplication, but useful for perfomance." -msgstr "" - -msgid "" -"This data independence also impacts ordering (a *relation* doesn't rely on " -"the insertion order)." -msgstr "" - -msgid "Duplicates" -msgstr "" - -msgid "" -"His definition of relational data is a bit differente from most modern " -"database systems, namely **no duplicate rows**." -msgstr "" - -msgid "" -"I couldn't find a reason behind this restriction, though. For practical " -"purposes, I find it useful to have it." -msgstr "" - -msgid "Relational Data" -msgstr "" - -msgid "" -"In the article, Codd doesn't try to define a language, and today's most " -"popular one is SQL." -msgstr "" - -msgid "" -"However, there is no restriction that says that \"SQL database\" and " -"\"relational database\" are synonyms. One could have a relational database " -"without using SQL at all, and it would still be a relational one." -msgstr "" - -msgid "" -"The main one that I have in mind, and the reason that led me to reading this" -" paper in the first place, is Datomic." -msgstr "" - -msgid "" -"Is uses an [edn]-based representation for datalog queries[^edn-queries], and" -" a particular schema used to represent data." -msgstr "" - -msgid "" -"Even though it looks very weird when coming from SQL, I'd argue that it " -"ticks all the boxes (except for \"no duplicates\") that defines a relational" -" database, since building relations and applying operations on them is " -"possible." -msgstr "" - -msgid "" -"Compare and contrast a contrived example of possible representations of SQL " -"and datalog of the same data:" -msgstr "" - -msgid "" -"-- create schema\n" -"CREATE TABLE people (\n" -" id UUID PRIMARY KEY,\n" -" name TEXT NOT NULL,\n" -" manager_id UUID,\n" -" FOREIGN KEY (manager_id) REFERENCES people (id)\n" -");\n" -"\n" -"-- insert data\n" -"INSERT INTO people (id, name, manager_id) VALUES\n" -" (\"d3f29960-ccf0-44e4-be66-1a1544677441\", \"Foo\", \"076356f4-1a0e-451c-b9c6-a6f56feec941\"),\n" -" (\"076356f4-1a0e-451c-b9c6-a6f56feec941\", \"Bar\");\n" -"\n" -"-- query data, make a relation\n" -"\n" -"SELECT employees.name AS 'employee-name',\n" -" managers.name AS 'manager-name'\n" -"FROM people employees\n" -"INNER JOIN people managers ON employees.manager_id = managers.id;\n" -msgstr "" - -msgid "{% raw %}" -msgstr "" - -msgid "" -";; create schema\n" -"#{ {:db/ident :person/id\n" -" :db/valueType :db.type/uuid\n" -" :db/cardinality :db.cardinality/one\n" -" :db/unique :db.unique/value}\n" -" {:db/ident :person/name\n" -" :db/valueType :db.type/string\n" -" :db/cardinality :db.cardinality/one}\n" -" {:db/ident :person/manager\n" -" :db/valueType :db.type/ref\n" -" :db/cardinality :db.cardinality/one}}\n" -"\n" -";; insert data\n" -"#{ {:person/id #uuid \"d3f29960-ccf0-44e4-be66-1a1544677441\"\n" -" :person/name \"Foo\"\n" -" :person/manager [:person/id #uuid \"076356f4-1a0e-451c-b9c6-a6f56feec941\"]}\n" -" {:person/id #uuid \"076356f4-1a0e-451c-b9c6-a6f56feec941\"\n" -" :person/name \"Bar\"}}\n" -"\n" -";; query data, make a relation\n" -"{:find [?employee-name ?manager-name]\n" -" :where [[?person :person/name ?employee-name]\n" -" [?person :person/manager ?manager]\n" -" [?manager :person/name ?manager-name]]}\n" -msgstr "" - -msgid "{% endraw %}" -msgstr "" - -msgid "" -"(forgive any errors on the above SQL and datalog code, I didn't run them to " -"check. Patches welcome!)" -msgstr "" - -msgid "" -"This employee example comes from the paper, and both SQL and datalog " -"representations match the paper definition of \"relational\"." -msgstr "" - -msgid "" -"Both \"Foo\" and \"Bar\" are employees, and the data is normalized. SQL " -"represents data as tables, and Datomic as datoms, but relations could be " -"derived from both, which we could view as:" -msgstr "" - -msgid "" -"employee_name | manager_name\n" -"----------------------------\n" -"\"Foo\" | \"Bar\"\n" -msgstr "" - -msgid "" -"[^edn-queries]: You can think of it as JSON, but with a Clojure taste. " -"[edn]: https://github.com/edn-format/edn" -msgstr "" - -msgid "Conclusion" -msgstr "" - -msgid "" -"The article also talks about operators, consistency and normalization, which" -" are now so widespread and well-known that it feels a bit weird seeing " -"someone advocating for it." -msgstr "" - -msgid "" -"I also stablish that `relational != SQL`, and other databases such as " -"Datomic are also relational, following Codd's original definition." -msgstr "" |