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Data model | Tarantool
 
Data model
Data model

Data model

Data model

This section describes how Tarantool stores values and what operations with data it supports.

If you tried to create a database as suggested in our “Getting started” exercises, then your test database now looks like this:

../../../_images/data_model.png

Tarantool operates data in the form of tuples.

tuple

A tuple is a group of data values in Tarantool’s memory. Think of it as a “database record” or a “row”. The data values in the tuple are called fields.

When Tarantool returns a tuple value in the console, by default it uses YAML format, for example: [3, 'Ace of Base', 1993].

Internally, Tarantool stores tuples as MsgPack arrays.

field

Fields are distinct data values, contained in a tuple. They play the same role as “row columns” or “record fields” in relational databases, with a few improvements:

  • fields can be composite structures, such as arrays or maps,
  • fields don’t need to have names.

A given tuple may have any number of fields, and the fields may be of different types.

The field’s number is the identifier of the field. Numbers are counted from base 1 in Lua and other 1-based languages, or from base 0 in languages like PHP or C/C++. So, 1 or 0 can be used in some contexts to refer to the first field of a tuple.

Tarantool stores tuples in containers called spaces. In our example there’s a space called 'tester'.

space

In Tarantool, a space is a primary container which stores data. It is analogous to tables in relational databases. Spaces contain tuples — the Tarantool name for database records. The number of tuples in a space is unlimited.

At least one space is required to store data with Tarantool. Each space has the following attributes:

  • a unique name specified by the user,
  • a unique numeric identifier which can be specified by the user, but usually is assigned automatically by Tarantool,
  • an engine: memtx (default) – in-memory engine, fast but limited in size, or vinyl – on-disk engine for huge data sets.

To be functional, a space also needs to have a primary index. It can also have secondary indexes.

Read the full information about indexes on page Indexes.

An index is a group of key values and pointers.

As with spaces, you should specify the index name, and let Tarantool come up with a unique numeric identifier (“index id”).

An index always has a type. The default index type is TREE. TREE indexes are provided by all Tarantool engines, can index unique and non-unique values, support partial key searches, comparisons and ordered results. Additionally, memtx engine supports HASH, RTREE and BITSET indexes.

An index may be multi-part, that is, you can declare that an index key value is composed of two or more fields in the tuple, in any order. For example, for an ordinary TREE index, the maximum number of parts is 255.

An index may be unique, that is, you can declare that it would be illegal to have the same key value twice.

The first index defined on a space is called the primary key index, and it must be unique. All other indexes are called secondary indexes, and they may be non-unique.

Tarantool is both a database manager and an application server. Therefore a developer often deals with two type sets: the types of the programming language (such as Lua) and the types of the Tarantool storage format (MsgPack).

Scalar / compound MsgPack   type Lua type Example value
scalar nil nil nil
scalar boolean boolean true
scalar string string 'A B C'
scalar integer number 12345
scalar float 64 (double) number 1.2345
scalar float 64 (double) cdata 1.2345
scalar binary cdata [!!binary 3t7e]
scalar ext (for Tarantool decimal) cdata 1.2
scalar ext (for Tarantool uuid) cdata 12a34b5c-de67-8f90-
123g-h4567ab8901
compound map table” (with string keys) {'a': 5, 'b': 6}
compound array table” (with integer keys) [1, 2, 3, 4, 5]
compound array tuple (“cdata”) [12345, 'A B C']

Note

MsgPack values have variable lengths. So, for example, the smallest number requires only one byte, but the largest number requires nine bytes.

nil. In Lua a nil type has only one possible value, also called nil (which Tarantool displays as null when using the default YAML format). Nils may be compared to values of any types with == (is-equal) or ~= (is-not-equal), but other comparison operations will not work. Nils may not be used in Lua tables; the workaround is to use box.NULL because nil == box.NULL is true. Example: nil.

boolean. A boolean is either true or false. Example: true.

integer. The Tarantool integer type is for integers between -9223372036854775808 and 18446744073709551615, which is about 18 quintillion. This corresponds to number in Lua and to integer in MsgPack. Example: -2^63.

unsigned. The Tarantool unsigned type is for integers between 0 and 18446744073709551615. So it is a subset of integer. Example: 123456.

double. The double field type exists mainly so that there will be an equivalent to Tarantool/SQL’s DOUBLE data type. In msgpuck.h (Tarantool’s interface to MsgPack) the storage type is MP_DOUBLE and the size of the encoded value is always 9 bytes. In Lua, ‘double’ fields can only contain non-integer numeric values and cdata values with double floating-point numbers. Examples: 1.234, -44, 1.447e+44.
To avoid using the wrong kind of values inadvertently, use ffi.cast() when searching or changing ‘double’ fields. For example, instead of space_object:insert{value} say ffi = require('ffi') ... space_object:insert({ffi.cast('double',value)}). Example:

s = box.schema.space.create('s', {format = {{'d', 'double'}}})
s:create_index('ii')
s:insert({1.1})
ffi = require('ffi')
s:insert({ffi.cast('double', 1)})
s:insert({ffi.cast('double', tonumber('123'))})
s:select(1.1)
s:select({ffi.cast('double', 1)})

Arithmetic with cdata ‘double’ will not work reliably, so for Lua it is better to use the ‘number’ type. This warning does not apply for Tarantool/SQL because Tarantool/SQL does implicit casting.

number. In Lua a number is double-precision floating-point, but a Tarantool ‘number’ field may have both integer and floating-point values. Tarantool will try to store a Lua number as floating-point if the value contains a decimal point or is very large (greater than 100 trillion = 1e14), otherwise Tarantool will store it as an integer. To ensure that even very large numbers are stored as integers, use the tonumber64 function, or the LL (Long Long) suffix, or the ULL (Unsigned Long Long) suffix. Here are examples of numbers using regular notation, exponential notation, the ULL suffix and the tonumber64 function: -55, -2.7e+20, 100000000000000ULL, tonumber64('18446744073709551615').

decimal. The Tarantool decimal type is stored as a MsgPack ext (Extension). Values with the decimal type are not floating-point values although they may contain decimal points. They are exact with up to 38 digits of precision. Example: a value returned by a function in the decimal module.

string. A string is a variable-length sequence of bytes, usually represented with alphanumeric characters inside single quotes. In both Lua and MsgPack, strings are treated as binary data, with no attempts to determine a string’s character set or to perform any string conversion – unless there is an optional collation. So, usually, string sorting and comparison are done byte-by-byte, without any special collation rules applied. (Example: numbers are ordered by their point on the number line, so 2345 is greater than 500; meanwhile, strings are ordered by the encoding of the first byte, then the encoding of the second byte, and so on, so '2345' is less than '500'.) Example: 'A, B, C'.

bin. A bin (binary) value is not directly supported by Lua but there is a Tarantool type varbinary which is encoded as MsgPack binary. For an (advanced) example showing how to insert varbinary into a database, see the Cookbook Recipe for ffi_varbinary_insert. Example: "\65 \66 \67".

uuid. Since version 2.4.1. The Tarantool uuid type is stored as a MsgPack ext (Extension). Values with the uuid type are Universally unique identifiers.
Example: 64d22e4d-ac92-4a23-899a-e5934af5479.

array. An array is represented in Lua with {...} (braces). Examples: as lists of numbers representing points in a geometric figure: {10, 11}, {3, 5, 9, 10}.

table. Lua tables with string keys are stored as MsgPack maps; Lua tables with integer keys starting with 1 are stored as MsgPack arrays. Nils may not be used in Lua tables; the workaround is to use box.NULL. Example: a box.space.tester:select() request will return a Lua table.

tuple. A tuple is a light reference to a MsgPack array stored in the database. It is a special type (cdata) to avoid conversion to a Lua table on retrieval. A few functions may return tables with multiple tuples. For tuple examples, see box.tuple.

scalar. Values in a scalar field can be boolean or integer or unsigned or double or number or decimal or string or varbinary – but not array or map or tuple. Examples: true, 1, 'xxx'.

any. Values in an any field can be boolean or integer or unsigned or double or number or decimal or string or varbinary – or array or map or tuple. Examples: true, 1, 'xxx', {box.NULL, 0}.

Examples of insert requests with different field types:

tarantool> box.space.K:insert{1,nil,true,'A B C',12345,1.2345}
---
- [1, null, true, 'A B C', 12345, 1.2345]
...
tarantool> box.space.K:insert{2,{['a']=5,['b']=6}}
---
- [2, {'a': 5, 'b': 6}]
...
tarantool> box.space.K:insert{3,{1,2,3,4,5}}
---
- [3, [1, 2, 3, 4, 5]]
...

Indexes restrict values which Tarantool may store with MsgPack. This is why, for example, 'unsigned' and 'integer' are different field types although in MsgPack they are both stored as integer values – an 'unsigned' index contains only non-negative integer values while an ‘integer’ index contains any integer values.

Here again are the field types described in Field Type Details, and the index types they can fit in. The default field type is 'unsigned' and the default index type is TREE. Although 'nil' is not a legal indexed field type, indexes may contain nil as a non-default option. Full information is in section Details about index field types.

Field type name string Field type
Index type
'boolean' boolean TREE or HASH
'integer' (may also be called ‘int’) integer which may include unsigned values TREE or HASH
'unsigned' (may also be called ‘uint’ or ‘num’, but ‘num’ is deprecated) unsigned TREE, BITSET or HASH
'double' double TREE or HASH
'number' number which may include integer or double values TREE or HASH
'decimal' decimal TREE or HASH
'string' (may also be called ‘str’) string TREE, BITSET or HASH
'varbinary' varbinary TREE, HASH or BITSET (since version 2.7)
'uuid' uuid TREE or HASH
'array' array RTREE
'scalar'

may include nil or boolean or integer or unsigned or number or decimal or string or varbinary values

When a scalar field contains values of different underlying types, the key order is: nils, then booleans, then numbers, then strings, then varbinaries.

TREE or HASH

By default, when Tarantool compares strings, it uses what we call a “binary” collation. The only consideration here is the numeric value of each byte in the string. Therefore, if the string is encoded with ASCII or UTF-8, then 'A' < 'B' < 'a', because the encoding of 'A' (what used to be called the “ASCII value”) is 65, the encoding of 'B' is 66, and the encoding of 'a' is 98. Binary collation is best if you prefer fast deterministic simple maintenance and searching with Tarantool indexes.

But if you want the ordering that you see in phone books and dictionaries, then you need Tarantool’s optional collations, such as unicode and unicode_ci, which allow for 'a' < 'A' < 'B' and 'a' = 'A' < 'B' respectively.

The unicode and unicode_ci optional collations use the ordering according to the Default Unicode Collation Element Table (DUCET) and the rules described in Unicode® Technical Standard #10 Unicode Collation Algorithm (UTS #10 UCA). The only difference between the two collations is about weights:

  • unicode collation observes L1 and L2 and L3 weights (strength = ‘tertiary’),
  • unicode_ci collation observes only L1 weights (strength = ‘primary’), so for example ‘a’ = ‘A’ = ‘á’ = ‘Á’.

As an example, take some Russian words:

'ЕЛЕ'
'елейный'
'ёлка'
'еловый'
'елозить'
'Ёлочка'
'ёлочный'
'ЕЛь'
'ель'

…and show the difference in ordering and selecting by index:

  • with unicode collation:

    tarantool> box.space.T:create_index('I', {parts = {{field = 1, type = 'str', collation='unicode'}}})
    ...
    tarantool> box.space.T.index.I:select()
    ---
    - - ['ЕЛЕ']
      - ['елейный']
      - ['ёлка']
      - ['еловый']
      - ['елозить']
      - ['Ёлочка']
      - ['ёлочный']
      - ['ель']
      - ['ЕЛь']
    ...
    tarantool> box.space.T.index.I:select{'ЁлКа'}
    ---
    - []
    ...
    
  • with unicode_ci collation:

    tarantool> box.space.T:create_index('I', {parts = {{field = 1, type ='str', collation='unicode_ci'}}})
    ...
    tarantool> box.space.S.index.I:select()
    ---
    - - ['ЕЛЕ']
      - ['елейный']
      - ['ёлка']
      - ['еловый']
      - ['елозить']
      - ['Ёлочка']
      - ['ёлочный']
      - ['ЕЛь']
    ...
    tarantool> box.space.S.index.I:select{'ЁлКа'}
    ---
    - - ['ёлка']
    ...
    

In all, collation involves much more than these simple examples of upper case / lower case and accented / unaccented equivalence in alphabets. We also consider variations of the same character, non-alphabetic writing systems, and special rules that apply for combinations of characters.

For English: use “unicode” and “unicode_ci”. For Russian: use “unicode” and “unicode_ci” (although a few Russians might prefer the Kyrgyz collation which says Cyrillic letters ‘Е’ and ‘Ё’ are the same with level-1 weights). For Dutch, German (dictionary), French, Indonesian, Irish, Italian, Lingala, Malay, Portuguese, Southern Soho, Xhosa, or Zulu: “unicode” and “unicode_ci” will do.

The tailored optional collations: For other languages, Tarantool supplies tailored collations for every modern language that has more than a million native speakers, and for specialized situations such as the difference between dictionary order and telephone book order. To see a complete list say box.space._collation:select(). The tailored collation names have the form unicode_[language code]_[strength] where language code is a standard 2-character or 3-character language abbreviation, and strength is s1 for “primary strength” (level-1 weights), s2 for “secondary”, s3 for “tertiary”. Tarantool uses the same language codes as the ones in the “list of tailorable locales” on man pages of Ubuntu and Fedora. Charts explaining the precise differences from DUCET order are in the Common Language Data Repository.

A sequence is a generator of ordered integer values.

As with spaces and indexes, you should specify the sequence name, and let Tarantool come up with a unique numeric identifier (“sequence id”).

As well, you can specify several options when creating a new sequence. The options determine what value will be generated whenever the sequence is used.

Options for box.schema.sequence.create()

Option name Type and meaning Default Examples
start Integer. The value to generate the first time a sequence is used 1 start=0
min Integer. Values smaller than this cannot be generated 1 min=-1000
max Integer. Values larger than this cannot be generated 9223372036854775807 max=0
cycle Boolean. Whether to start again when values cannot be generated false cycle=true
cache Integer. The number of values to store in a cache 0 cache=0
step Integer. What to add to the previous generated value, when generating a new value 1 step=-1
if_not_exists Boolean. If this is true and a sequence with this name exists already, ignore other options and use the existing values false if_not_exists=true

Once a sequence exists, it can be altered, dropped, reset, forced to generate the next value, or associated with an index.

For an initial example, we generate a sequence named ‘S’.

tarantool> box.schema.sequence.create('S',{min=5, start=5})
---
- step: 1
  id: 5
  min: 5
  cache: 0
  uid: 1
  max: 9223372036854775807
  cycle: false
  name: S
  start: 5
...

The result shows that the new sequence has all default values, except for the two that were specified, min and start.

Then we get the next value, with the next() function.

tarantool> box.sequence.S:next()
---
- 5
...

The result is the same as the start value. If we called next() again, we would get 6 (because the previous value plus the step value is 6), and so on.

Then we create a new table, and say that its primary key may be generated from the sequence.

tarantool> s=box.schema.space.create('T')
---
...
tarantool> s:create_index('I',{sequence='S'})
---
- parts:
  - type: unsigned
    is_nullable: false
    fieldno: 1
  sequence_id: 1
  id: 0
  space_id: 520
  unique: true
  type: TREE
  sequence_fieldno: 1
  name: I
...
---
...

Then we insert a tuple, without specifying a value for the primary key.

tarantool> box.space.T:insert{nil,'other stuff'}
---
- [6, 'other stuff']
...

The result is a new tuple where the first field has a value of 6. This arrangement, where the system automatically generates the values for a primary key, is sometimes called “auto-incrementing” or “identity”.

For syntax and implementation details, see the reference for box.schema.sequence.

In Tarantool, updates to the database are recorded in the so-called write ahead log (WAL) files. This ensures data persistence. When a power outage occurs or the Tarantool instance is killed incidentally, the in-memory database is lost. In this situation, WAL files are used to restore the data. Namely, Tarantool reads the WAL files and redoes the requests (this is called the “recovery process”). You can change the timing of the WAL writer, or turn it off, by setting wal_mode.

Tarantool also maintains a set of snapshot files. These files contain an on-disk copy of the entire data set for a given moment. Instead of reading every WAL file since the databases were created, the recovery process can load the latest snapshot file and then read only those WAL files that were produced after the snapshot file was made. After checkpointing, old WAL files can be removed to free up space.

To force immediate creation of a snapshot file, you can use Tarantool’s box.snapshot() request. To enable automatic creation of snapshot files, you can use Tarantool’s checkpoint daemon. The checkpoint daemon sets intervals for forced checkpoints. It makes sure that the states of both memtx and vinyl storage engines are synchronized and saved to disk, and automatically removes old WAL files.

Snapshot files can be created even if there is no WAL file.

Note

The memtx engine makes only regular checkpoints with the interval set in checkpoint daemon configuration.

The vinyl engine runs checkpointing in the background at all times.

See the Internals section for more details about the WAL writer and the recovery process.

The basic data operations supported in Tarantool are:

  • five data-manipulation operations (INSERT, UPDATE, UPSERT, DELETE, REPLACE), and
  • one data-retrieval operation (SELECT).

All of them are implemented as functions in box.space submodule.

Examples:

  • INSERT: Add a new tuple to space ‘tester’.

    The first field, field[1], will be 999 (MsgPack type is integer).

    The second field, field[2], will be ‘Taranto’ (MsgPack type is string).

    tarantool> box.space.tester:insert{999, 'Taranto'}
    
  • UPDATE: Update the tuple, changing field field[2].

    The clause “{999}”, which has the value to look up in the index of the tuple’s primary-key field, is mandatory, because update() requests must always have a clause that specifies a unique key, which in this case is field[1].

    The clause “{{‘=’, 2, ‘Tarantino’}}” specifies that assignment will happen to field[2] with the new value.

    tarantool> box.space.tester:update({999}, {{'=', 2, 'Tarantino'}})
    
  • UPSERT: Upsert the tuple, changing field field[2] again.

    The syntax of upsert() is similar to the syntax of update(). However, the execution logic of these two requests is different. UPSERT is either UPDATE or INSERT, depending on the database’s state. Also, UPSERT execution is postponed until after transaction commit, so, unlike update(), upsert() doesn’t return data back.

    tarantool> box.space.tester:upsert({999, 'Taranted'}, {{'=', 2, 'Tarantism'}})
    
  • REPLACE: Replace the tuple, adding a new field.

    This is also possible with the update() request, but the update() request is usually more complicated.

    tarantool> box.space.tester:replace{999, 'Tarantella', 'Tarantula'}
    
  • SELECT: Retrieve the tuple.

    The clause “{999}” is still mandatory, although it does not have to mention the primary key.

    tarantool> box.space.tester:select{999}
    
  • DELETE: Delete the tuple.

    In this example, we identify the primary-key field.

    tarantool> box.space.tester:delete{999}
    

Summarizing the examples:

  • Functions insert and replace accept a tuple (where a primary key comes as part of the tuple).
  • Function upsert accepts a tuple (where a primary key comes as part of the tuple), and also the update operations to execute.
  • Function delete accepts a full key of any unique index (primary or secondary).
  • Function update accepts a full key of any unique index (primary or secondary), and also the operations to execute.
  • Function select accepts any key: primary/secondary, unique/non-unique, full/partial.

See reference on box.space for more details on using data operations.

Note

Besides Lua, you can use Perl, PHP, Python or other programming language connectors. The client server protocol is open and documented. See this annotated BNF.

In reference for box.space and Submodule box.index submodules, there are notes about which complexity factors might affect the resource usage of each function.

Complexity factor Effect
Index size The number of index keys is the same as the number of tuples in the data set. For a TREE index, if there are more keys, then the lookup time will be greater, although of course the effect is not linear. For a HASH index, if there are more keys, then there is more RAM used, but the number of low-level steps tends to remain constant.
Index type Typically, a HASH index is faster than a TREE index if the number of tuples in the space is greater than one.
Number of indexes accessed

Ordinarily, only one index is accessed to retrieve one tuple. But to update the tuple, there must be N accesses if the space has N different indexes.

Note re storage engine: Vinyl optimizes away such accesses if secondary index fields are unchanged by the update. So, this complexity factor applies only to memtx, since it always makes a full-tuple copy on every update.

Number of tuples accessed A few requests, for example SELECT, can retrieve multiple tuples. This factor is usually less important than the others.
WAL settings The important setting for the write-ahead log is wal_mode. If the setting causes no writing or delayed writing, this factor is unimportant. If the setting causes every data-change request to wait for writing to finish on a slow device, this factor is more important than all the others.

In Tarantool, the use of a data schema is optional.

When creating a space, you do not have to define a data schema. In this case, the tuples store random data. This rule does not apply to indexed fields. Such fields must contain data of the same type.

You can define a data schema when creating a space. Read more in the description of the box.schema.space.create() function. If you have already created a space without specifying a data schema, you can do it later using space_object:format().

After the data schema is defined, all the data is validated by type. Before any insert or update, you will get an error if the data types do not match.

We recommend using a data schema because it helps avoid mistakes.

In Tarantool, you can define a data schema in two different ways.

The code file is usually called init.lua and contains the following schema description:

box.cfg()

users = box.schema.create_space('users', { if_not_exists = true })
users:format({{ name = 'user_id', type = 'number'}, { name = 'fullname', type = 'string'}})

users:create_index('pk', { parts = { { field = 'user_id', type = 'number'}}})

This is quite simple: when you run tarantool, it executes this code and creates a data schema. To run this file, use:

tarantool init.lua

However, if you do not plan to dive deep into the Lua language and its syntax, it may seem complicated.

Possible difficulty: The snippet above has a function call with a colon: users:format. It is used to pass the format variable as the first argument of the format function. This is similar to self in object-based languages.

So it might be more convenient for you to describe the data schema with YAML.

The DDL module allows you to describe a data schema in the YAML format in a declarative way.

The schema would look something like this:

spaces:
    users:
      engine: memtx
      is_local: false
      temporary: false
      format:
      - {name: user_id, type: uuid, is_nullable: false}
      - {name: fullname, type: string,  is_nullable: false}
      indexes:
      - name: user_id
        unique: true
        parts: [{path: user_id, type: uuid, is_nullable: false}]
        type: HASH

This alternative is simpler to use, and you do not have to dive deep into Lua.

DDL is a built-in Cartridge module. Cartridge is a cluster solution for Tarantool. In its WebUI, there is a separate tab called “Schema”. On this tab, you can define the schema, check its correctness, and apply it to the whole cluster.

If you do not use Cartridge, you can still use the DDL module: put the following Lua code into the file that you use to run Tarantool. This file is usually called init.lua.

local yaml = require('yaml')
local ddl = require('ddl')

box.cfg{}

local fh = io.open('ddl.yml', 'r')
local schema = yaml.decode(fh:read('*all'))
fh:close()
local ok, err = ddl.check_schema(schema)
if not ok then
    print(err)
end
local ok, err = ddl.set_schema(schema)
if not ok then
    print(err)
end

Warning

It is forbidden to modify the data schema in DDL after it has been applied. For migration, there are different scenarios described below.

Migration refers to any change in a data schema: adding/removing a field, creating/dropping an index, changing a field format, etc.

In Tarantool, there are two types of schema migration that do not require data migration:

  • adding a field to the end of a space
  • creating an index

You can add a field as follows:

local users = box.space.users
local fmt = users:format()

table.insert(fmt, { name = 'age', type = 'number', is_nullable = true })
users:format(fmt)

Note that the field must have the is_nullable parameter. Otherwise, an error will occur.

After creating a new field, you probably want to fill it with data. The tarantool/moonwalker module is useful for this task. The README file describes how to work with this module.

Index creation is described in the space_object:create_index() method.

Other types of migrations are also allowed but it would be more difficult to maintain data consistency.

Migrations are possible in two cases:

  • When Tarantool starts, and no client uses the database yet
  • During request processing, when active clients are already using the database

For the first case, it is enough to write and test the migration code. The most difficult task is to migrate data when there are active clients. You should keep it in mind when you initially design the data schema.

We identify the following problems if there are active clients:

  • Associated data can change atomically.
  • The system should be able to transfer data using both the new schema and the old one.
  • When data is being transferred to a new space, data access should take into account that the data might be in one space or another.
  • Write requests must not interfere with the migration. A common approach is to write according to the new data schema.

These issues may or may not be relevant depending on your application and its availability requirements.

Tarantool has a transaction mechanism. It is useful when writing a migration, because it allows you to work with the data atomically. But before using the transaction mechanism, you should explore its limitations.

For details, see the section about transactions.

The migration code is executed on a running Tarantool instance. Important: no method guarantees you transactional application of migrations on the whole cluster.

Method 1: include migrations in the application code

This is quite simple: when you reload the code, the data is migrated at the right moment, and the database schema is updated. However, this method may not work for everyone. You may not be able to restart Tarantool or to update the code using the hot-reload mechanism.

Method 2: tarantool/migrations (only for a Tarantool Cartridge cluster)

This method is described in the README file of the tarantool/migrations module.

Note

There are also two methods that we do not recommend but you may find them useful for one reason or another.

Method 3: the tarantoolctl utility

The tarantoolctl utility ships with Tarantool. Connect to the necessary instance using tarantoolctl connect.

$ tarantoolctl connect admin:password@localhost:3301
  • If your migration is written in a Lua file, you can execute it using dofile(). Call this function and specify the path to the migration file as the first argument. It looks like this:

    tarantool> dofile('0001-delete-space.lua')
    ---
    ...
    
  • (or) Copy the migration script code, paste it into the console, and run it.

Method 4: applying migration with Ansible

If you use an Ansible role to deploy a Tarantool cluster, you can use eval. You can find more information about eval here.