CuriousGeorgiy / crud

Easy assess to data stored in vshard cluster

CRUD

The CRUD module allows to perform CRUD operations on the cluster. It also provides the crud-storage and crud-router roles for Tarantool Cartridge.

Table of Contents

• Quickstart
• API
  • Package info
  • Insert
  • Insert many
  • Get
  • Update
  • Delete
  • Replace
  • Replace many
  • Upsert
  • Upsert many
  • Select
    • Select conditions
  • Pairs
  • Min and max
  • Cut extra rows
  • Cut extra objects
  • Truncate
  • Len
  • Storage info
  • Count
  • Call options for crud methods
  • Statistics
  • Read view
    • Creating a read view
    • Closing a read view
    • Read view select
      • Read view select conditions
    • Read view pairs
• Cartridge roles
  • Usage
• License

Quickstart

First, install Tarantool.

Now you have the following options for learning the crud API and using it in a project:

• Play with crud on a test dataset on a single instance:

  $ git clone https://github.com/tarantool/crud.git
  $ cd crud
  $ tt rocks make
  $ ./doc/playground.lua
  tarantool> crud.select('customers', {{'<=', 'age', 35}}, {first = 10})
  tarantool> crud.select('developers', nil, {first = 6})

• Install crud into the current directory:

  $ tt rocks install crud

  And add the initialization code to storage and router instance files.

• Add crud into dependencies of a Cartridge application and add crud roles into dependencies of your roles (see Cartridge roles section).

• Add crud into dependencies of your application (rockspec, RPM spec -- depends on your choice) and call crud initialization code from storage and router code (see API section).

API

The CRUD operations should be called from router. All storage replica sets should call crud.init_storage() (or enable the crud-storage role) first to initialize storage-side functions that are used to manipulate data across the cluster. All routers should call crud.init_router() (or enable the crud-router role) to make crud functions callable via net.box.

All operations return a table that contains rows (tuples) and metadata (space format). It can be used to convert received tuples to objects via crud.unflatten_rows function.

For example:

res, err = crud.select('customers', nil, {first = 2})
res
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 12477, 'Elizabeth', 12]
  - [2, 21401, 'David', 33]
...
crud.unflatten_rows(res.rows, res.metadata)
---
- - bucket_id: 12477
    age: 12
    name: Elizabeth
    id: 1
  - bucket_id: 21401
    age: 33
    name: David
    id: 2
...

Notes:

• A space should have a format.

Sharding key and bucket id calculation

Sharding key is a set of tuple field values used for calculation bucket ID. Sharding key definition is a set of tuple field names that describe what tuple field should be a part of sharding key. Bucket ID determines which replicaset stores certain data. Function that used for bucket ID calculation is named sharding function.

By default CRUD calculates bucket ID using primary key and a function vshard.router.bucket_id_strcrc32(key), it happen automatically and doesn't require any actions from user side. However, for operations that accepts tuple/object bucket ID can be specified as tuple/object field as well as opts.bucket_id value.

Starting from 0.10.0 users who don't want to use primary key as a sharding key may set custom sharding key definition as a part of DDL schema or insert manually to the space _ddl_sharding_key (for both cases consider a DDL module documentation). As soon as sharding key for a certain space is available in _ddl_sharding_key space CRUD will use it for bucket ID calculation automatically. Note that CRUD methods delete(), get() and update() requires that sharding key must be a part of primary key.

Starting from 0.11.0 you can specify sharding function to calculate bucket_id with sharding func definition as a part of DDL schema or insert manually to the space _ddl_sharding_func.

Automatic sharding key and function reload is supported since version 0.11.0. Version 0.11.0 contains critical bug that causes some CRUD methods to fail with "Sharding hash mismatch" error if ddl is set and bucket_id is provided explicitly (#278). Please, upgrade to 0.11.1 instead.

CRUD uses strcrc32 as sharding function by default. The reason why using of strcrc32 is undesirable is that this sharding function is not consistent for cdata numbers. In particular, it returns 3 different values for normal Lua numbers like 123, for unsigned long long cdata (like 123ULL, or ffi.cast('unsigned long long', 123)), and for signed long long cdata (like 123LL, or ffi.cast('long long', 123)).

We cannot change default sharding function strcrc32 due to backward compatibility concerns, but please consider using better alternatives for sharding function. mpcrc32 is one of them.

Table below describe what operations supports custom sharding key:

CRUD method	Sharding key support
get()	Yes
insert() / insert_object()	Yes
delete()	Yes
replace() / replace_object()	Yes
upsert() / upsert_object()	Yes
select() / pairs()	Yes
count()	Yes
update()	Yes
min() / max()	No (not required)
cut_rows() / cut_objects()	No (not required)
truncate()	No (not required)
len()	No (not required)

Current limitations for using custom sharding key:

• No support of JSON path for sharding key, see #219.
• primary_index_fieldno_map is not cached, see #243.

Package info

tarantool> require('crud')._VERSION
---
- 1.1.0
...

Use _VERSION handle to check installed module version. The handle was introduced in 1.1.0. If installed from master, _VERSION shows last tagged version.

Insert

-- Insert tuple
local result, err = crud.insert(space_name, tuple, opts)
-- Insert object
local result, err = crud.insert_object(space_name, object, opts)

where:

• space_name (string) - name of the space to insert an object
• tuple / object (table) - tuple/object to insert
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • bucket_id (?number|cdata) - bucket ID
  • fields (?table) - field names for getting only a subset of fields
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • skip_nullability_check_on_flatten (?boolean) - option for insert_object only. false by default. Set this parameter to true if you want to allow setting null values to non-nullable fields, which can be useful if non-nullable field value is generated by sequence. Warning: there is no native support for sequences in sharded systems since each replicaset has its own sequence. If sequence field is a part of the sharding key (which is true by default), choosing the bucket id is the sole responsibility of the developer
  • noreturn (?boolean) - suppress successfully processed tuple (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array contains one inserted row, error.

Example:

crud.insert('customers', {1, box.NULL, 'Elizabeth', 23})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Elizabeth', 23]
...
crud.insert_object('customers', {
    id = 2, name = 'Elizabeth', age = 24,
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [2, 401, 'Elizabeth', 24]
...

Insert many

-- Insert batch of tuples
local result, err = crud.insert_many(space_name, tuples, opts)
-- Insert batch of objects
local result, err = crud.insert_object_many(space_name, objects, opts)

where:

• space_name (string) - name of the space to insert an object
• tuples / objects (table) - array of tuples/objects to insert (at least one)
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • fields (?table) - field names for getting only a subset of fields
  • stop_on_error (?boolean) - stop on a first error and report error regarding the failed operation and error about what tuples were not performed, default is false
  • rollback_on_error (?boolean) - any failed operation will lead to rollback on a storage, where the operation is failed, report error about what tuples were rollback, default is false
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • skip_nullability_check_on_flatten (?boolean) - option for insert_object_many only. false by default. Set this parameter to true if you want to allow setting null values to non-nullable fields, which can be useful if non-nullable field value is generated by sequence. Warning: there is no native support for sequences in sharded systems since each replicaset has its own sequence. If sequence field is a part of the sharding key (which is true by default), choosing the bucket id is the sole responsibility of the developer
  • noreturn (?boolean) - suppress successfully processed tuples (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array with inserted rows, array of errors. Each error object can contain field operation_data.

operation_data field can contain:

• tuple for which the error occurred;
• object with an incorrect format;
• tuple the operation on which was performed but operation was rollback;
• tuple the operation on which was not performed because operation was stopped by error.

Right now CRUD cannot provide batch insert with full consistency. CRUD offers batch insert with partial consistency. That means that full consistency can be provided only on single replicaset using box transactions.

Example:

crud.insert_many('customers', {
  {1, box.NULL, 'Elizabeth', 23},
  {2, box.NULL, 'Anastasia', 22},
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Elizabeth', 23]
  - [2, 401, 'Anastasia', 22]
...
crud.insert_object_many('customers', {
    {id = 3, name = 'Elizabeth', age = 24},
    {id = 10, name = 'Anastasia', age = 21},
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [3, 2804, 'Elizabeth', 24]
  - [10, 569, 'Anastasia', 21]

-- Partial success
local res, errs = crud.insert_object_many('customers', {
    {id = 22, name = 'Alex', age = 34},
    {id = 3, name = 'Anastasia', age = 22},
    {id = 5, name = 'Sergey', age = 25},
})
---
res
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [5, 1172, 'Sergey', 25],
  - [22, 655, 'Alex', 34],

#errs                  -- 1
errs[1].class_name     -- BatchInsertError
errs[1].err            -- 'Duplicate key exists <...>'
errs[1].operation_data -- {3, 2804, 'Anastasia', 22}
...

-- Partial success with stop and rollback on error
-- stop_on_error = true, rollback_on_error = true
-- two error on one storage with rollback, inserts
-- stop by error on this storage inserts before
-- error are rollback
local res, errs =  crud.insert_object_many('customers', {
    {id = 6, name = 'Alex', age = 34},
    {id = 92, name = 'Artur', age = 29},
    {id = 3, name = 'Anastasia', age = 22},
    {id = 4, name = 'Sergey', age = 25},
    {id = 9, name = 'Anna', age = 30},
    {id = 71, name = 'Oksana', age = 29},
}, {
    stop_on_error = true,
    rollback_on_error  = true,
})
---
res
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [4, 1161, 'Sergey', 25],
  - [6, 1064, 'Alex', 34],
#errs                  -- 4
errs[1].class_name     -- InsertManyError
errs[1].err            -- 'Duplicate key exists <...>'
errs[1].operation_data -- {3, 2804, 'Anastasia', 22}

errs[2].class_name     -- NotPerformedError
errs[2].err            -- 'Operation with tuple was not performed'
errs[2].operation_data -- {9, 1644, "Anna", 30}

errs[3].class_name     -- NotPerformedError
errs[3].err            -- 'Operation with tuple was not performed'
errs[3].operation_data -- {71, 1802, "Oksana", 29}

errs[4].class_name     -- NotPerformedError
errs[4].err            -- 'Operation with tuple was rollback'
errs[4].operation_data -- {92, 2040, "Artur", 29}

Get

local object, err = crud.get(space_name, key, opts)

where:

• space_name (string) - name of the space
• key (any) - primary key value
• opts:
  • fields (?table) - field names for getting only a subset of fields
  • bucket_id (?number|cdata) - bucket ID
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • mode (?string, read or write) - if write is specified then get is performed on master, default value is read
  • prefer_replica (?boolean) - if true then the preferred target is one of the replicas
  • balance (?boolean) - use replica according to vshard load balancing policy
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array contains one row, error.

Example:

crud.get('customers', 1)
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Elizabeth', 23]
...

Update

local object, err = crud.update(space_name, key, operations, opts)

where:

• space_name (string) - name of the space
• key (any) - primary key value
• operations (table) - update operations
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • bucket_id (?number|cdata) - bucket ID
  • fields (?table) - field names for getting only a subset of fields
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • noreturn (?boolean) - suppress successfully processed tuple (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array contains one updated row, error.

Example:

crud.update('customers', 1, {{'+', 'age', 1}})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Elizabeth', 24]
...

Delete

local object, err = crud.delete(space_name, key, opts)

where:

• space_name (string) - name of the space
• key (any) - primary key value
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • bucket_id (?number|cdata) - bucket ID
  • fields (?table) - field names for getting only a subset of fields
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • noreturn (?boolean) - suppress successfully processed tuple (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array contains one deleted row (empty for vinyl), error.

Example:

crud.delete('customers', 1)
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Elizabeth', 24]

Replace

-- Replace tuple
local result, err = crud.replace(space_name, tuple, opts)
-- Replace object
local result, err = crud.replace_object(space_name, object, opts)

where:

• space_name (string) - name of the space
• tuple / object (table) - tuple/object to insert or replace exist one
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • bucket_id (?number|cdata) - bucket ID
  • fields (?table) - field names for getting only a subset of fields
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • skip_nullability_check_on_flatten (?boolean) - option for replace_object only. false by default. Set this parameter to true if you want to allow setting null values to non-nullable fields, which can be useful if non-nullable field value is generated by sequence. Warning: there is no native support for sequences in sharded systems since each replicaset has its own sequence. If sequence field is a part of the sharding key (which is true by default), choosing the bucket id is the sole responsibility of the developer
  • noreturn (?boolean) - suppress successfully processed tuple (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns inserted or replaced rows and metadata or nil with error.

Example:

crud.replace('customers', {1, box.NULL, 'Alice', 22})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Alice', 22]
...
crud.replace_object('customers', {
    id = 1, name = 'Alice', age = 22,
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Alice', 22]
...

Replace many

-- Replace batch of tuples
local result, err = crud.replace_many(space_name, tuples, opts)
-- Replace batch of objects
local result, err = crud.replace_object_many(space_name, objects, opts)

where:

• space_name (string) - name of the space to insert/replace an object
• tuples / objects (table) - array of tuples/objects to replace (at least one)
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • fields (?table) - field names for getting only a subset of fields
  • stop_on_error (?boolean) - stop on a first error and report error regarding the failed operation and error about what tuples were not performed, default is false
  • rollback_on_error (?boolean) - any failed operation will lead to rollback on a storage, where the operation is failed, report error about what tuples were rollback, default is false
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • skip_nullability_check_on_flatten (?boolean) - option for replace_object_many only. false by default. Set this parameter to true if you want to allow setting null values to non-nullable fields, which can be useful if non-nullable field value is generated by sequence. Warning: there is no native support for sequences in sharded systems since each replicaset has its own sequence. If sequence field is a part of the sharding key (which is true by default), choosing the bucket id is the sole responsibility of the developer
  • noreturn (?boolean) - suppress successfully processed tuples (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array with inserted/replaced rows, array of errors. Each error object can contain field operation_data.

operation_data field can contain:

• tuple for which the error occurred;
• object with an incorrect format;
• tuple the operation on which was performed but operation was rollback;
• tuple the operation on which was not performed because operation was stopped by error.

Right now CRUD cannot provide batch replace with full consistency. CRUD offers batch replace with partial consistency. That means that full consistency can be provided only on single replicaset using box transactions.

Example:

crud.replace_many('developers', {
  {1, box.NULL, 'Elizabeth', 'lizaaa'},
  {2, box.NULL, 'Anastasia', 'iamnewdeveloper'},
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'login', 'type': 'string'}
  rows:
  - [1, 477, 'Elizabeth', 'lizaaa']
  - [2, 401, 'Anastasia', 'iamnewdeveloper']
...
crud.replace_object_many('developers', {
    {id = 1, name = 'Inga', login = 'mylogin'},
    {id = 10, name = 'Anastasia', login = 'qwerty'},
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Inga', 'mylogin']
  - [10, 569, 'Anastasia', 'qwerty']

-- Partial success
-- Let's say login has unique secondary index
local res, errs = crud.replace_object_many('developers', {
    {id = 22, name = 'Alex', login = 'pushkinn'},
    {id = 3, name = 'Anastasia', login = 'qwerty'},
    {id = 5, name = 'Sergey', login = 's.petrenko'},
})
---
res
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [5, 1172, 'Sergey', 's.petrenko'],
  - [22, 655, 'Alex', 'pushkinn'],

#errs                  -- 1
errs[1].class_name     -- ReplaceManyError
errs[1].err            -- 'Duplicate key exists <...>'
errs[1].operation_data -- {3, 2804, 'Anastasia', 'qwerty'}

-- Partial success with stop and rollback on error
-- stop_on_error = true, rollback_on_error = true
-- two error on one storage with rollback, inserts stop by error on this storage
-- inserts before error are rollback
local res, crud.replace_object_many('developers', {
    {id = 6, name = 'Alex', login = 'alexpushkin'},
    {id = 92, name = 'Artur', login = 'AGolden'},
    {id = 11, name = 'Anastasia', login = 'qwerty'},
    {id = 4, name = 'Sergey', login = 's.smirnov'},
    {id = 9, name = 'Anna', login = 'AnnaBlack'},
    {id = 17, name = 'Oksana', login = 'OKonov'},
}, {
    stop_on_error = true,
    rollback_on_error  = true,
})
res
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [4, 1161, 'Sergey', 's.smirnov'],
  - [6, 1064, 'Alex', 'alexpushkin'],
#errs                  -- 4
errs[1].class_name     -- ReplaceManyError
errs[1].err            -- 'Duplicate key exists <...>'
errs[1].operation_data -- {11, 2652, "Anastasia", "qwerty"}

errs[2].class_name     -- NotPerformedError
errs[2].err            -- 'Operation with tuple was not performed'
errs[2].operation_data -- {9, 1644, "Anna", "AnnaBlack"}

errs[3].class_name     -- NotPerformedError
errs[3].err            -- 'Operation with tuple was not performed'
errs[3].operation_data -- {17, 2900, "Oksana", "OKonov"}

errs[4].class_name     -- NotPerformedError
errs[4].err            -- 'Operation with tuple was rollback'
errs[4].operation_data -- {92, 2040, "Artur", "AGolden"}
...

Upsert

-- Upsert tuple
local result, err = crud.upsert(space_name, tuple, operations, opts)
-- Upsert object
local result, err = crud.upsert_object(space_name, tuple, operations, opts)

where:

• space_name (string) - name of the space
• tuple / object (table) - tuple/object to insert if there is no existing tuple which matches the key fields
• operations (table) - update operations if there is an existing tuple which matches the key fields of tuple
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • bucket_id (?number|cdata) - bucket ID
  • fields (?table) - field names for getting only a subset of fields
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • noreturn (?boolean) - suppress successfully processed tuple (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and empty array of rows or nil, error.

Example:

crud.upsert('customers',
    {1, box.NULL, 'Alice', 22},
    {{'+', 'age', 1}})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows: []
...
crud.upsert_object('customers',
    {id = 1, name = 'Alice', age = 22},
    {{'+', 'age', 1}})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows: []
...

Upsert many

-- Upsert batch of tuples
local result, err = crud.upsert_many(space_name, tuples_operation_data, opts)
-- Upsert batch of objects
local result, err = crud.upsert_object_many(space_name, objects_operation_data, opts)

where:

• space_name (string) - name of the space to insert an object
• tuples_operation_data / objects_operation_data (table) - array of tuples/objects to insert and update operations in format {{tuple_1, operation_1}, ..., {tuple_n, operation_n}} (at least one), if there is tuple with duplicate key then existing tuple will be updated with update operations
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • fields (?table) - field names for getting only a subset of fields
  • stop_on_error (?boolean) - stop on a first error and report error regarding the failed operation and error about what tuples were not performed, default is false
  • rollback_on_error (?boolean) - any failed operation will lead to rollback on a storage, where the operation is failed, report error about what tuples were rollback, default is false
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • noreturn (?boolean) - suppress successfully processed tuples (first return value is nil). false by default
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array of errors. Each error object can contain field operation_data.

operation_data field can contain:

• tuple for which the error occurred;
• object with an incorrect format;
• tuple the operation on which was performed but operation was rollback;
• tuple the operation on which was not performed because operation was stopped by error.

Right now CRUD cannot provide batch upsert with full consistency. CRUD offers batch upsert with partial consistency. That means that full consistency can be provided only on single replicaset using box transactions.

Example:

crud.upsert_many('customers', {
    {{1, box.NULL, 'Elizabeth', 23}, {{'+', 'age', 1}}},
    {{2, box.NULL, 'Anastasia', 22}, {{'+', 'age', 2}, {'=', 'name', 'Oleg'}}}
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}

...
crud.upsert_object_many('customers', {
    {{id = 3, name = 'Elizabeth', age = 24}, {{'+', 'age', 1}}},
    {{id = 10, name = 'Anastasia', age = 21}, {{'+', 'age', 2}}}
})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}

-- Partial success
local res, errs = crud.upsert_object_many('customers', {
    {{id = 22, name = 'Alex', age = 34}, {{'+', 'age', 12}}},
    {{id = 3, name = 'Anastasia', age = 22}, {{'=', 'age', 'invalid type'}}},
    {{id = 5, name = 'Sergey', age = 25}, {{'+', 'age', 10}}}
})
---
res
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}

#errs                  -- 1
errs[1].class_name     -- BatchUpsertError
errs[1].err            -- 'Tuple field 4 (age) type does not match one required by operation <...>'
errs[1].operation_data -- {3, 2804, 'Anastasia', 22}
...
-- Partial success success with stop and rollback on error
-- stop_on_error = true, rollback_on_error = true
-- two error on one storage with rollback,
-- inserts stop by error on this storage
-- inserts before error are rollback
local res, errs = crud.upsert_object_many('customers', {
    {{id = 6, name = 'Alex', age = 34}, {{'+', 'age', 1}}},
    {{id = 92, name = 'Artur', age = 29}, {{'+', 'age', 2}}},
    {{id = 3, name = 'Anastasia', age = 22}, {{'+', 'age', '3'}}},
    {{id = 4, name = 'Sergey', age = 25}, {{'+', 'age', 4}}},
    {{id = 9, name = 'Anna', age = 30}, {{'+', 'age', 5}}},
    {{id = 71, name = 'Oksana', age = 29}, {{'+', 'age', '6'}}},
}, {
    stop_on_error = true,
    rollback_on_error  = true,
})
res
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
#errs                  -- 4
errs[1].class_name     -- UpsertManyError
errs[1].err            -- 'Duplicate key exists <...>'
errs[1].operation_data -- {3, 2804, 'Anastasia', 22}

errs[2].class_name     -- NotPerformedError
errs[2].err            -- 'Operation with tuple was not performed'
errs[2].operation_data -- {9, 1644, "Anna", 30}

errs[3].class_name     -- NotPerformedError
errs[3].err            -- 'Operation with tuple was not performed'
errs[3].operation_data -- {71, 1802, "Oksana", 29}

errs[4].class_name     -- NotPerformedError
errs[4].err            -- 'Operation with tuple was rollback'
errs[4].operation_data -- {92, 2040, "Artur", 29}

Select

CRUD supports multi-conditional selects, treating a cluster as a single space. The conditions may include field names, as well as index names. (Refer to #352 for field number.) The recommended first condition is a TREE index; this helps reducing the number of tuples to scan. Otherwise a full scan is performed.

local objects, err = crud.select(space_name, conditions, opts)

where:

• space_name (string) - name of the space
• conditions (?table) - array of select conditions
• opts:
  • first (?number) - the maximum count of the objects to return. If negative value is specified, the objects behind after are returned (after option is required in this case). See pagination examples.
  • after (?table) - tuple after which objects should be selected
  • batch_size (?number) - number of tuples to process per one request to storage
  • bucket_id (?number|cdata) - bucket ID
  • force_map_call (?boolean) - if true then the map call is performed without any optimizations even if full primary key equal condition is specified
  • timeout (?number) - vshard.call timeout (in seconds)
  • fields (?table) - field names for getting only a subset of fields
  • fullscan (?boolean) - if true then a critical log entry will be skipped on potentially long select, see avoiding full scan.
  • mode (?string, read or write) - if write is specified then select is performed on master, default value is read
  • prefer_replica (?boolean) - if true then the preferred target is one of the replicas
  • balance (?boolean) - use replica according to vshard load balancing policy
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • yield_every (?number) - number of tuples processed on storage to yield after, yield_every should be > 0, default value is 1000
  • fetch_latest_metadata (?boolean) - guarantees the up-to-date metadata (space format) in first return value, otherwise it may not take into account the latest migration of the data format. Performance overhead is up to 15%. false by default

Returns metadata and array of rows, error.

Select conditions

Select conditions are very similar to Tarantool update operations.

Each condition is a table {operator, field-identifier, value}:

• Supported operators are: = (or ==), >, >=, <, <=.
• Field identifier can be field name or index name. (Refer to #352 for field number.)

Example:

crud.select('customers', {{'<=', 'age', 35}}, {first = 10})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [5, 1172, 'Jack', 35]
  - [3, 2804, 'David', 33]
  - [6, 1064, 'William', 25]
  - [7, 693, 'Elizabeth', 18]
  - [1, 477, 'Elizabeth', 12]
...

Note: tuples are sorted by age because space has index age. Otherwise, tuples are sorted by primary key.

See more examples of select queries here.

Pairs

You can iterate across a distributed space using the crud.pairs function. Its arguments are the same as crud.select arguments except fullscan (it does not exist because crud.pairs does not generate a critical log entry on potentially long requests) and negative first values aren't allowed. User could pass use_tomap flag (false by default) to iterate over flat tuples or objects.

Example:

local tuples = {}
for _, tuple in crud.pairs('customers', {{'<=', 'age', 35}}, {use_tomap = false}) do
    -- {5, 1172, 'Jack', 35}
    table.insert(tuples, tuple)
end

local objects = {}
for _, object in crud.pairs('customers', {{'<=', 'age', 35}}, {use_tomap = true}) do
    -- {id = 5, name = 'Jack', bucket_id = 1172, age = 35}
    table.insert(objects, object)
end

See more examples of pairs queries here.

Min and max

-- Find the minimum value in the specified index
local result, err = crud.min(space_name, 'age', opts)
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [1, 477, 'Elizabeth', 12]

-- Find the maximum value in the specified index
local result, err = crud.max(space_name, 'age', opts)
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [5, 1172, 'Jack', 35]

Cut extra rows

You could use crud.cut_rows function to cut off scan key and primary key values that were merged to the select/pairs partial result (select/pairs with fields option).

local res, err = crud.cut_rows(rows, metadata, fields)

where:

• rows (table) - array of tuples for cutting
• metadata (?table) - metadata about rows fields
• fields (table) - field names of fields that should be contained in the result

Returns metadata and array of rows, error.

See more examples of crud.cut_rows usage here and here.

Cut extra objects

If you use pairs with use_tomap flag and you need to cut off scan key and primary key values that were merged to the pairs partial result (pairs with fields option) you should use crud.cut_objects.

local new_objects = crud.cut_objects(objects, fields)

where:

• objects (table) - array of objects for cutting
• fields (table) - field names of fields that should be contained in the result

Returns array of objects.

See more examples of crud.cut_objects usage here.

Truncate

-- Truncate space
local result, err = crud.truncate(space_name, opts)

where:

• space_name (string) - name of the space
• opts:
  • timeout (?number) - vshard.call timeout (in seconds)
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster

Returns true or nil with error.

Example:

#crud.select('customers', {{'<=', 'age', 35}}, {first = 10})
---
- 1
...
crud.truncate('customers', {timeout = 2})
---
- true
...
#crud.select('customers', {{'<=', 'age', 35}}, {first = 10})
---
- 0
...

Len

-- Calculates the number of tuples in the space for memtx engine
-- Calculates the maximum approximate number of tuples in the space for vinyl engine
local result, err = crud.len(space_name, opts)

where:

• space_name (string) - name of the space
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster

Returns number or nil with error.

Using space id instead of space name is also possible, but deprecated and will be removed in future releases.

Using space id in crud.len and custom vshard_router is not supported by statistics: space labels may be inconsistent.

Example:

Using memtx:

#crud.select('customers', nil, {fullscan = true})
---
- 5
...
crud.len('customers', {timeout = 2})
---
- 5
...

Using vinyl:

crud.len('customers')
---
- 0
...
crud.delete('customers', 1)
---
...
crud.len('customers')
---
- 1
...

Storage info

-- Get storages status
local result, err = crud.storage_info(opts)

where:

• opts:
  • timeout (?number) - maximum time (in seconds, default: 2) to wait for response from cluster instances.
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance.

Returns storages status table by instance UUID or nil with error. Status table fields:

• status contains a string representing the status:
  • "running" - storage is initialized and running.
  • "uninitialized" - storage is not initialized or disabled.
  • "error" - error getting the status from a storage. Connection error, for example.
• is_master is true if an instance is a master, false - otherwise.
• message is nil unless a problem occurs with getting storage status.

Example:

crud.storage_info()

---
- fe1b5bd9-42d4-4955-816c-3aa015e0eb81:
    status: running
    is_master: true
  a1eefe51-9869-4c4c-9676-76431b08c97a:
    status: running
    is_master: true
  777415f4-d656-440e-8834-7124b7267b6d:
    status: uninitialized
    is_master: false
  e1b2e202-b0f7-49cd-b0a2-6b3a584f995e:
    status: error
    message: 'connect, called on fd 36, aka 127.0.0.1:49762: Connection refused'
    is_master: false
...

Count

CRUD supports multi-conditional count, treating a cluster as a single space. The same as with select() the conditions may include field names or numbers, as well as index names. The recommended first condition is a TREE index; this helps to reduce the number of tuples to scan. Otherwise a full scan is performed. If compared with len(), count() method scans the entire space to count the tuples according user conditions. This method does yield that's why result may be approximate. Number of tuples before next yield() is under control with option yield_every.

local result, err = crud.count(space_name, conditions, opts)

where:

• space_name (string) - name of the space
• conditions (?table) - array of conditions
• opts:
  • yield_every (?number) - number of tuples processed to yield after, yield_every should be > 0, default value is 1000
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • bucket_id (?number|cdata) - bucket ID
  • force_map_call (?boolean) - if true then the map call is performed without any optimizations even, default value is false
  • fullscan (?boolean) - if true then a critical log entry will be skipped on potentially long count, see avoiding full scan.
  • mode (?string, read or write) - if write is specified then count is performed on master, default value is read
  • prefer_replica (?boolean) - if true then the preferred target is one of the replicas, default value is false
  • balance (?boolean) - use replica according to vshard load balancing policy, default value is false
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster

crud.count('customers', {{'==', 'age', 35}})
---
- 1
...

Call options for crud methods

Combinations of mode, prefer_replica and balance options lead to:

• mode == write - method performed on master with vshard call callrw
• mode == read
  • not prefer_replica, not balance - vshard call callro
  • not prefer_replica, balance - vshard call callbro
  • prefer_replica, not balance - vshard call callre
  • prefer_replica, balance - vshard call callbre

Statistics

crud routers can provide statistics on called operations.

-- Enable statistics collect.
crud.cfg{ stats = true }

-- Returns table with statistics information.
crud.stats()

-- Returns table with statistics information for specific space.
crud.stats('my_space')

-- Disables statistics collect and destroys all collectors.
crud.cfg{ stats = false }

-- Destroys all statistics collectors and creates them again.
crud.reset_stats()

If metrics 0.10.0 or greater found, metrics collectors will be used by default to store statistics instead of local collectors. Quantiles in metrics summary collections are disabled by default. You can manually choose driver and enable quantiles.

-- Use simple local collectors (default if no required metrics version found).
crud.cfg{ stats = true, stats_driver = 'local' }

-- Use metrics collectors (default if metrics rock found).
crud.cfg{ stats = true, stats_driver = 'metrics' }

-- Use metrics collectors with 0.99 quantiles.
crud.cfg{ stats = true, stats_driver = 'metrics', stats_quantiles = true }

You can use crud.cfg to check current stats state.

crud.cfg
---
- stats_quantiles: true
  stats: true
  stats_driver: metrics
...

Performance overhead is 3-10% in case of local driver and 5-15% in case of metrics driver, up to 20% for metrics with quantiles.

Beware that iterating through crud.cfg with pairs is not supported yet, refer to tarantool/crud#265.

Format is as follows.

crud.stats()
---
- spaces:
    my_space:
      insert:
        ok:
          latency: 0.0015
          latency_average: 0.002
          latency_quantile_recent: 0.0015
          count: 19800
          time: 39.6
        error:
          latency: 0.0000008
          latency_average: 0.000001
          latency_quantile_recent: 0.0000008
          count: 4
          time: 0.000004
...
crud.stats('my_space')
---
- insert:
    ok:
      latency: 0.0015
      latency_average: 0.002
      latency_quantile_recent: 0.0015
      count: 19800
      time: 39.6
    error:
      latency: 0.0000008
      latency_average: 0.000001
      latency_quantile_recent: 0.0000008
      count: 4
      time: 0.000004
...

spaces section contains statistics for each observed space. If operation has never been called for a space, the corresponding field will be empty. If no requests has been called for a space, it will not be represented. Space data is based on client requests rather than storages schema, so requests for non-existing spaces are also collected.

Possible statistics operation labels are insert (for insert and insert_object calls), get, replace (for replace and replace_object calls), update, upsert (for upsert and upsert_object calls), delete, select (for select and pairs calls), truncate, len, count and borders (for min and max calls).

Each operation section consists of different collectors for success calls and error (both error throw and nil, err) returns. count is the total requests count since instance start or stats restart. time is the total time of requests execution. latency_average is time / count. latency_quantile_recent is the 0.99 quantile of request execution time for a recent period (see metrics summary API). It is computed only if metrics driver is used and quantiles are enabled. latency_quantile_recent value may be -nan if there wasn't any observations for several ages, see tarantool/metrics#303. latency is a latency_quantile_recent if metrics driver is used and quantiles are enabled, otherwise it's latency_average.

In metrics registry statistics are stored as tnt_crud_stats metrics with operation, status and name labels.

metrics:collect()
---
- - label_pairs:
      status: ok
      operation: insert
      name: customers
    value: 221411
    metric_name: tnt_crud_stats_count
  - label_pairs:
      status: ok
      operation: insert
      name: customers
    value: 10.49834896344692
    metric_name: tnt_crud_stats_sum
  - label_pairs:
      status: ok
      operation: insert
      name: customers
      quantile: 0.99
    value: 0.00023606420935973
    metric_name: tnt_crud_stats
...

If you see -Inf value in quantile metrics, try to decrease the tolerated error:

crud.cfg{stats_quantile_tolerated_error = 1e-4}

See tarantool/metrics#189 for details about the issue. You can also configure quantile age_bucket_count (default: 2) and max_age_time (in seconds, default: 60):

crud.cfg{
    stats_quantile_age_bucket_count = 3,
    stats_quantile_max_age_time = 30,
}

See metrics summary API for details. These parameters can be used to smooth time window move or reduce the amount on -nan gaps for low request frequency applications.

select section additionally contains details collectors.

crud.stats('my_space').select.details
---
- map_reduces: 4
  tuples_fetched: 10500
  tuples_lookup: 238000
...

map_reduces is the count of planned map reduces (including those not executed successfully). tuples_fetched is the count of tuples fetched from storages during execution, tuples_lookup is the count of tuples looked up on storages while collecting responses for calls (including scrolls for multibatch requests). Details data is updated as part of the request process, so you may get new details before select/pairs call is finished and observed with count, latency and time collectors. In metrics registry they are stored as tnt_crud_map_reduces, tnt_crud_tuples_fetched and tnt_crud_tuples_lookup metrics with { operation = 'select', name = space_name } labels.

Since pairs request behavior differs from any other crud request, its statistics collection also has specific behavior. Statistics (select section) are updated after pairs cycle is finished: you either have iterated through all records or an error was thrown. If your pairs cycle was interrupted with break, statistics will be collected when pairs objects are cleaned up with Lua garbage collector.

Statistics are preserved between package reloads. Statistics are preserved between Tarantool Cartridge role reloads if you use CRUD Cartridge roles. Beware that metrics 0.12.0 and below do not support preserving stats between role reload (see tarantool/metrics#334), thus this feature will be unsupported for metrics driver.

Read view

A read view is an in-memory snapshot of data on instance that isn’t affected by future data modifications. Read views allow you to retrieve data using the read_view_object:select() and read_view_object:pairs() operations.

Read views can be used to make complex analytical queries. This reduces the load on the main database and improves RPS for a single Tarantool instance.

Read views have the following limitations:

• Only the memtx engine is supported.
• Read view can be used starting from Tarantool Enterprise v2.11.0.
• There is no clusterwide readview support. For a sharded cluster, we open a readview on each storage. Due to a cluster's distributed nature, it is not guaranteed that they will open simultaneously.

Creating a read view

To create a read view, call the crud.readview() function.

local rv = crud.readview(opts)

where:

• opts:
  • name (?string) - name of the read view
  • timeout (?number) - vshard.call timeout (in seconds)

Example:

local rv = crud.readview({name = 'foo', timeout = 3})

Closing a read view

When a read view is no longer needed, close it using the read_view_object:close() method because a read view may consume a substantial amount of memory.

local rv = crud.readview()
rv:close(opts)

where:

• opts:
  • timeout (?number) - vshard.call timeout (in seconds)

A read view is also closed implicitly when the read view object is collected by the Lua garbage collector.

Example:

local rv = crud.readview()
rv:close({timeout = 3})

Read view select

read_view_object:select() supports multi-conditional selects, treating a cluster as a single space, same as crud.select.

local rv = crud.readview()
local objects, err = rv:select(space_name, conditions, opts)
rv:close()

Opts are the same as select opts, except balance, prefer_replica and mode are not supported.

Returns metadata and array of rows, error.

Example:

local rv = crud.readview()
rv:select('customers', nil, {batch_size=1, fullscan=true})
---
- metadata: [{'name': 'id', 'type': 'unsigned'}, {'name': 'bucket_id', 'type': 'unsigned'},
    {'name': 'name', 'type': 'string'}, {'name': 'age', 'type': 'number'}]
  rows:
  - [1, 477, 'Elizabeth', 12]
  - [2, 401, 'Mary', 46]
  - [3, 2804, 'David', 33]
  - [4, 1161, 'William', 81]
  - [5, 1172, 'Jack', 35]
  - [6, 1064, 'William', 25]
  - [7, 693, 'Elizabeth', 18]
- null
...
crud.insert('customers', {8, box.NULL, 'Elizabeth', 23})
---
- rows:
  - [8, 185, 'Elizabeth', 23]
  metadata: [{'name': 'id', 'type': 'unsigned'}, {'name': 'bucket_id', 'type': 'unsigned'},
    {'name': 'name', 'type': 'string'}, {'name': 'age', 'type': 'number'}]
- null
...
rv:select('customers', nil, {batch_size=1, fullscan=true})
---
- metadata: [{'name': 'id', 'type': 'unsigned'}, {'name': 'bucket_id', 'type': 'unsigned'},
    {'name': 'name', 'type': 'string'}, {'name': 'age', 'type': 'number'}]
  rows:
  - [1, 477, 'Elizabeth', 12]
  - [2, 401, 'Mary', 46]
  - [3, 2804, 'David', 33]
  - [4, 1161, 'William', 81]
  - [5, 1172, 'Jack', 35]
  - [6, 1064, 'William', 25]
  - [7, 693, 'Elizabeth', 18]
- null
...
rv:close()

Read view select conditions

Select conditions for read_view_object:select() are the same as select conditions for crud.select.

Example:

rv = crud.readview()
rv:select('customers', {{'<=', 'age', 35}}, {first = 10})
---
- metadata:
  - {'name': 'id', 'type': 'unsigned'}
  - {'name': 'bucket_id', 'type': 'unsigned'}
  - {'name': 'name', 'type': 'string'}
  - {'name': 'age', 'type': 'number'}
  rows:
  - [5, 1172, 'Jack', 35]
  - [3, 2804, 'David', 33]
  - [6, 1064, 'William', 25]
  - [7, 693, 'Elizabeth', 18]
  - [1, 477, 'Elizabeth', 12]
...
rv.close()

Read view pairs

You can iterate across a distributed space using the read_view_object:pairs() method. Its arguments are the same as crud.readview.select arguments except fullscan (it does not exist because crud.pairs does not generate a critical log entry on potentially long requests) and negative first values aren't allowed. User could pass use_tomap flag (false by default) to iterate over flat tuples or objects.

Example:

rv = crud.readview()
local tuples = {}
for _, tuple in rv:pairs('customers', {{'<=', 'age', 35}}, {use_tomap = false}) do
    -- {5, 1172, 'Jack', 35}
    table.insert(tuples, tuple)
end

local objects = {}
for _, object in rv:pairs('customers', {{'<=', 'age', 35}}, {use_tomap = true}) do
    -- {id = 5, name = 'Jack', bucket_id = 1172, age = 35}
    table.insert(objects, object)
end
rv:close()

Schema

crud routers provide API to introspect spaces schema.

local schema, err = crud.update(space_name, opts)

where:

• space_name (?string) - name of the space (if nil, provides info for all spaces)
• opts:
  • timeout (?number) - vshard.call timeout and vshard master discovery timeout (in seconds), default value is 2
  • vshard_router (?string|table) - Cartridge vshard group name or vshard router instance. Set this parameter if your space is not a part of the default vshard cluster
  • cached (?boolean) - if false, reloads storages schema on call; if true, return last known schema; default value is false

Returns space schema (or spaces schema map), error.

Beware that schema info is not exactly the same as underlying storage spaces schema. The reason is that crud generates bucket_id, if it isn't provided, so this field is actually nullable for a crud user. We also do not expose bucket_id index info since it's a vshard utility and do not related to application logic.

Example:

crud.schema('customers')
---
- format:
    - name: id
      type: unsigned
    - name: bucket_id
      type: unsigned
      is_nullable: true
    - name: name
      type: string
    - name: age
      type: number
  indexes:
    0:
      unique: true
      parts:
      - fieldno: 1
        type: unsigned
        exclude_null: false
        is_nullable: false
      id: 0
      type: TREE
      name: primary_index
    2:
      unique: false
      parts:
      - fieldno: 4
        type: number
        exclude_null: false
        is_nullable: false
      id: 2
      type: TREE
      name: age
...

crud.schema()
---
- customers:
    format: ...
    indexes: ...
  shops:
    format: ...
    indexes: ...

Cartridge roles

cartridge.roles.crud-storage is a Tarantool Cartridge role that depends on the vshard-storage role, but also initializes functions that are used on the storage side to perform CRUD operations.

cartridge.roles.crud-router is a role that depends on the vshard-router role, but also exposes public crud functions in the global scope, so that you can call them via net.box.

Usage

1. Add crud to dependencies in the project rockspec.

Note: it's better to use tagged version than scm-1. Check the latest available release tag and use it.

-- <project-name>-scm-1.rockspec
dependencies = {
    ...
    'crud == <the-latest-tag>-1',
    ...
}

2. Create the role that stores your data and depends on crud-storage.

-- app.roles.customers-storage.lua
local cartridge = require('cartridge')

return {
        role_name = 'customers-storage',
        init = function()
            local customers_space = box.schema.space.create('customers', {
                format = {
                    {name = 'id', type = 'unsigned'},
                    {name = 'bucket_id', type = 'unsigned'},
                    {name = 'name', type = 'string'},
                    {name = 'age', type = 'number'},
                },
                if_not_exists = true,
            })
            customers_space:create_index('id', {
                parts = { {field ='id', is_nullable = false} },
                if_not_exists = true,
            })
            customers_space:create_index('bucket_id', {
                parts = { {field ='bucket_id', is_nullable = false} },
                if_not_exists = true,
            })
            customers_space:create_index('age', {
                parts = { {field ='age'} },
                unique = false,
                if_not_exists = true,
            })
        end,
        dependencies = {'cartridge.roles.crud-storage'},
    }

-- app.roles.customers-router.lua
local cartridge = require('cartridge')
return {
        role_name = 'customers-router',
        dependencies = {'cartridge.roles.crud-router'},
    }

3. Start the application and create customers-storage and customers-router replica sets.

4. Don't forget to bootstrap vshard.

5. Configure the statistics with clusterwide configuration (see crud.cfg options in statistics section):

crud:
  stats: true
  stats_driver: metrics
  stats_quantiles: false
  stats_quantile_tolerated_error: 0.001
  stats_quantile_age_buckets_count: 5
  stats_quantile_max_age_time: 180

Now your cluster contains storages that are configured to be used for CRUD-operations. You can simply call CRUD functions on the router to insert, select, and update data across the cluster.

License

BSD-2-Clause. See the LICENSE file.