From 1e0d34306c3ecffe65abd30d2e82cf671c055345 Mon Sep 17 00:00:00 2001 From: Michael Hierweck Date: Sat, 4 May 2019 10:24:29 +0200 Subject: [PATCH] Transaction as foreign key. Example usage. --- sql/history-demo.sql | 93 +++++++++++++++++++++++++++----------------- 1 file changed, 58 insertions(+), 35 deletions(-) diff --git a/sql/history-demo.sql b/sql/history-demo.sql index df21171d..df6493a7 100644 --- a/sql/history-demo.sql +++ b/sql/history-demo.sql @@ -1,17 +1,33 @@ +-- +-- Historization +-- + +CREATE TABLE history ( + history_id serial PRIMARY KEY, + history_transaction bigint NOT NULL UNIQUE, + history_timestamp timestamp NOT NULL +); + CREATE FUNCTION historicize() RETURNS trigger AS $$ BEGIN IF (TG_OP = 'INSERT') OR (TG_OP = 'UPDATE') THEN - EXECUTE format('INSERT INTO %I_history VALUES (DEFAULT, now(), txid_current(), False, $1.*)', TG_TABLE_NAME) USING NEW; + EXECUTE 'INSERT INTO history VALUES (DEFAULT, txid_current(), now()) ON CONFLICT DO NOTHING'; + EXECUTE format('INSERT INTO %I_history VALUES (DEFAULT, txid_current(), False, $1.*)', TG_TABLE_NAME) USING NEW; RETURN NEW; ELSE - EXECUTE format('INSERT INTO %I_history VALUES (DEFAULT, now(), txid_current(), True, $1.*)', TG_TABLE_NAME) USING OLD; + EXECUTE 'INSERT INTO history VALUES (DEFAULT, txid_current(), now()) ON CONFLICT DO NOTHING'; + EXECUTE format('INSERT INTO %I_history VALUES (DEFAULT, txid_current(), True, $1.*)', TG_TABLE_NAME) USING OLD; RETURN OLD; END IF; END; $$ LANGUAGE plpgsql; +-- +-- Entity with History +-- + CREATE TABLE person ( id serial PRIMARY KEY, name character varying(50) NOT NULL UNIQUE, @@ -20,8 +36,7 @@ CREATE TABLE person ( CREATE TABLE person_history ( history_id serial PRIMARY KEY, - history_timestamp timestamp NOT NULL, - history_transaction bigint NOT NULL, + history_transaction bigint NOT NULL REFERENCES history(history_transaction), history_tombstone boolean NOT NULL, id integer NOT NULL, name character varying(50) NOT NULL, @@ -30,37 +45,9 @@ CREATE TABLE person_history ( CREATE TRIGGER person_historicize AFTER INSERT OR DELETE OR UPDATE ON person FOR EACH ROW EXECUTE PROCEDURE historicize(); -CREATE OR REPLACE FUNCTION person_history(transaction bigint, VARIADIC groupby text[]) RETURNS TABLE ( - history_id integer, - history_timestamp timestamp, - history_transaction bigint, - history_tombstone boolean, - id integer, - name character varying(50), - email character varying(50) -) -AS $$ -BEGIN - RETURN QUERY EXECUTE format('SELECT * FROM person_history WHERE history_id IN (SELECT max(history_id) AS history_id FROM person_history WHERE history_transaction <= $1 GROUP BY %s)', array_to_string(groupby, ', ')) USING transaction; -END; -$$ -LANGUAGE plpgsql; - -CREATE OR REPLACE FUNCTION person_history(VARIADIC groupby text[]) RETURNS TABLE ( - history_id integer, - history_timestamp timestamp, - history_transaction bigint, - history_tombstone boolean, - id integer, - name character varying(50), - email character varying(50) -) -AS $$ -BEGIN - RETURN QUERY EXECUTE format('SELECT * FROM person_history WHERE history_id IN (SELECT max(history_id) AS history_id FROM person_history GROUP BY %s)', array_to_string(groupby, ', ')); -END; -$$ -LANGUAGE plpgsql; +-- +-- Sample data +-- INSERT INTO person (name, email) VALUES ('michael', 'michael@hierweck.de'); INSERT INTO person (name, email) VALUES ('annika', 'annika@hierweck.de'); @@ -80,3 +67,39 @@ INSERT INTO person (name, email) VALUES ('ax', 'ax@hierweck.de'); UPDATE person SET email='mxx@hierweck.de' WHERE name='mx'; UPDATE person SET email='axx@hierweck.de' WHERE name='ax'; COMMIT; + +-- +-- Approach 1: Function +-- +-- +-- Usage: +-- +-- SELECT * FROM person_history(12345, 'name'); +-- + +CREATE OR REPLACE FUNCTION person_history(transaction bigint, VARIADIC groupby text[]) RETURNS TABLE ( + history_id integer, + history_transaction bigint, + history_tombstone boolean, + id integer, + name character varying(50), + email character varying(50) +) +AS $$ +BEGIN + RETURN QUERY EXECUTE format('SELECT * FROM person_history WHERE history_id IN (SELECT max(history_id) AS history_id FROM person_history WHERE history_transaction <= $1 GROUP BY %s)', array_to_string(groupby, ', ')) USING transaction; +END; +$$ +LANGUAGE plpgsql; + +-- +-- Approach 2: View +-- +-- Usage: +-- +-- SET history_transaction = 12345; +-- SELECT * FROM person_history_view; +-- + +CREATE VIEW person_history_view +AS (SELECT * FROM person_history WHERE history_id IN (SELECT max(history_id) AS history_id FROM person_history WHERE history_transaction <= current_setting('history.transaction')::bigint GROUP BY name));