autoIncrement

Summary

Auto-migration settings in Sails.js define how database fields are physically created. One such setting is autoIncrement, which ensures that a field (typically id) automatically increments its value with each new record. When a record is created without specifying a value for an autoIncrement attribute, Sails assigns it the next available integer. Some databases allow only one autoIncrement field per table. This is especially useful for sequential numeric IDs.

Transcript

In this chapter, we're looking at auto-migration settings, which tell Sails how to create physical fields in databases like PostgreSQL, MySQL, or MongoDB. Unlike validation rules, which check attribute values, auto-migration settings define the database structure itself.

One such setting is autoIncrement. If we look at our model, we see:

id: {
  type: 'number',
  autoIncrement: true
}

This tells Sails that when creating a new record without specifying an ID, the database should assign the next available number by incrementing the last created record’s ID. This is useful for sequential integer IDs (1, 2, 3, etc.).

However, some databases restrict the number of autoIncrement fields per table to just one. In most cases, autoIncrement is used for the id field, making it the primary key.

This setting ensures that records have a unique and sequentially increasing identifier without needing manual input.