How to add new fields to an existing index?

Question

I already have a space with some indexes.

box.schema.sequence.create('user_seq')
box.schema.space.create('user', {
    if_not_exists = true,
    format = {
        { name = 'id', type = 'unsigned'},
        { name = 'user_id', type = 'string'}
    }
})
box.space.user:create_index('id', {
     sequence = 'user_seq',
     parts = {'id'}
})
box.space.user:create_index('user_id', {
     parts = {'user_id'},
     if_not_exists = true,
     unique = false
})

Want to add new fields into user_id index. What I should do?

Oleg Babin · Answer 1 · 2020-09-22T08:52:22.723

Consider usage of index.alter function (https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_index/#box-index-alter)

E.g. you want to add "id" field to your "user_id" index.

box.space.user.index.user_id:alter({
    parts = {
        {field = 'user_id', type = 'string'},
        {field = 'id', type = 'unsigned'}},   -- Add "id" field to your index
})

or e.g. you want to add new field to your schema and then to schema (e.g. "name"). Firstly, you should update your format:

box.space.user:format({
    { name = 'id', type = 'unsigned'},
    { name = 'user_id', type = 'string'},  -- Preserve to existing fields
    -- Add a new one
    -- It's important to define them as nullable because
    -- you don't have them physically
    -- If you want to define them as non-nullable
    -- You should append "name" to each tuple before
    -- It's possible because format checks only defined fields
    -- But basically tuple is a list of values and
    -- it can have arbitrary length.
    -- For simplification I say it as nullable.
    { name = 'name', type = 'string', is_nullable = true},
})

-- Then you can to alter your index
box.space.user.index.user_id:alter({
    parts = {
        {field = 'user_id', type = 'string'},
        {field = 'name', type = 'string', is_nullable = true},
    },
})

Also I see you use parts = {'id'} and parts = {'user_id'}. It's a correct way to define indexes - provide an array of fields that should be indexed. But it makes your schema less expressive and allows you to make a mistake. Instead of it I suggest you to use strict schema definition. - specify parts explicitly {field = <field_name/field_number>, type = <type>, collation = <collation>, is_nullable = <true/false>}. You can omit type specification if format is already defined. As shows the second example it's important. You can't specify parts={'user_id', 'name'} with is_nullable=true flag.

How to add new fields to an existing index?

1 Answers1