(aka "Historical records")
Temporal tables maintain historical versions of data. Modifying operations (UPDATE, DELETE) on these tables don't cause permanent changes to entries, but create new versions of them. Hence this might be used to:
- log changes (security/auditing)
- undo functionalities
- track interactions (customer support)
Under the hood a history table with the same structure, but without constraints is created (unless option addAssociation is set to true).
The normal singular/plural naming scheme in Sequelize is used:
- model name:
modelName + History - table name:
modelName + Histories
npm install sequelize-temporal
var Sequelize = require('sequelize');
var Temporal = require('sequelize-temporal');
Create a sequelize instance and your models, e.g.
var sequelize = new Sequelize('', '', '', {
dialect: 'sqlite',
storage: __dirname + '/.test.sqlite'
});
var User = Temporal(sequelize.define('User'), sequelize);
The output of temporal is its input model, so assigning it's output to your
Model is not necessary, hence it's just the lazy version of:
var User = sequelize.define('User', {.types.}, {.options.}); // Sequelize Docu
Temporal(User, sequelize);
The default syntax for Temporal is:
Temporal(model, sequelizeInstance, options)
whereas the options are listed here (with default value).
{
/* runs the insert within the sequelize hook chain, disable
for increased performance without warranties */
blocking: true,
/* By default sequelize-temporal persist only changes, and saves the previous state in the history table.
The "full" option saves all transactions into the temporal database
(i.e. this includes the latest state.)
This allows to only query the history table to get the full history of an entity.
*/
full: false,
/*
By default sequelize-temporal will add 'History' to the history Model name and 'Histories' to the history table.
By updating the modelSuffix value, you can decide what the naming will be.
The value will be appended to the history Model name and its plural will be appended to the history tablename.
examples for table User:
modelSuffix: '_Hist' --> History Model Name: User_Hist --> History Table Name: User_Hists
modelSuffix: 'Memory' --> History Model Name: UserMemory --> History Table Name: UserMemories
modelSuffix: 'Pass' --> History Model Name: UserPass --> History Table Name: UserPasses
*/
modelSuffix: 'History',
/*
By default sequelize-temporal will create the history table without associations.
However, setting this flag to true, you can keep association between the history table and the table with the latest value (origin).
NOTE: THIS DOES NOT WORK IF YOU ARE USING A SEPARATE DB FOR THE HISTORICAL TABLES. IN THAT CASE, KEEP THE VALUE TO FALSE OR YOU WILL GET AN ERROR.
example for table User:
model: 'User'
history model: 'UserHistories'
--> This would add function User.getUserHistories() to return all history entries for that user entry.
--> This would add function UserHistories.getUser() to get the original user from an history.
If a model has associations, those would be mirrored to the history table.
Origin model can only get its own histories.
Even if a history table is associated to another origin table thought a foreign key field, the history table is not accessible from that origin table
Basically, what you can access in the origin table can be accessed from the history table.
example:
model: User
history model: UserHistories
model: Creation
history model: CreationHistories
User <-> Creation: 1 to many
User.getCreations() exists (1 to many)
Creation.getUser() exists (1 to 1)
User <-> UserHistories: 1 to many
User.getUserHistories() exists (1 to many)
UserHistories.getUser() exists (1 to 1)
Creation <-> CreationHistories: 1 to many
Creation.getCreationHistories() exists (1 to many)
CreationHistories.getCreation() exists (1 to 1)
CreationHistories -> User: many to 1
CreationHistories.getUser() exists (1 to 1) (same as Creation.getUser())
User.GetCreationHistories DOES NOT EXIST. THE ORIGIN TABLE IS NOT MODIFIED.
UserHistories -> Creation: many to many
UserHistories.getCreations() exists (1 to many) (same as User.getCreations())
CreationHistories.getUser() DOES NOT EXIST. THE ORIGIN TABLE IS NOT MODIFIED.
*/
addAssociations: false,
/*
By default, transactions are allowed but can be disabled with that flag for the historical tables (transactions on original tables should stay the same). It is useful in case you are using a separate DB than the one use by the original DB.
NOTE: IF YOU USE A SEPARATE DB FOR HISTORICAL TABLE, SET THE VALUE TO FALSE OR YOU WILL GET AN ERROR.
*/
allowTransactions: true@See: https://wiki.postgresql.org/wiki/SQL2011Temporal
History table stores historical versions of rows, which are inserted by triggers on every modifying operation executed on current table. It has the same structure and indexes as current table, but it doesn’t have any constraints. History tables are insert only and creator should prevent other users from executing updates or deletes by correct user rights settings. Otherwise the history can be violated.
Triggers for storing old versions of rows to history table are inspired by referential integrity triggers. They are fired for each row before UPDATE and DELETE (within the same transaction)
If you only use Postgres, you might want to have a look at the Temporal Table extension.
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Copyright (c) 2015 BonaVal
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