space_object:select()

object space_object¶

space_object:select([key[, options]])¶

Search for a tuple or a set of tuples in the given space by the primary key. To search by the specific index, use the index_object:select() method.

Примечание

Note that this method doesn’t yield. For details, see Cooperative multitasking.

Параметры:

Параметры:	space_object (`space_object`) – an object reference. key (`scalar/table`) – a value to be matched against the index key, which may be multi-part. options (`table/nil`) – none, any, or all of the same options that index_object:select() allows: `options.iterator` – the iterator type. The default iterator type is „EQ“. `options.limit` – the maximum number of tuples. `options.offset` – the number of tuples to skip. `options.after` – a tuple or the position of a tuple (tuple_pos) after which `select` starts the search. You can pass an empty string or box.NULL to this option to start the search from the first tuple. `options.fetch_pos` – if true, the `select` method returns the position of the last selected tuple as the second value. Примечание The `after` and `fetch_pos` options are supported for the `TREE` index only.
возвращает:	This function might return one or two values: The tuples whose primary-key fields are equal to the fields of the passed key. If the number of passed fields is less than the number of fields in the primary key, then only the passed fields are compared, so `select{1,2}` matches a tuple whose primary key is `{1,2,3}`. (Optionally) If `options.fetch_pos` is set to true, returns a base64-encoded string representing the position of the last selected tuple as the second value. If no tuples are fetched, returns `nil`.
тип возвращаемого значения:
	массив кортежей (Optionally) string

space_object (space_object) – an object reference.
key (scalar/table) – a value to be matched against the index key, which may be multi-part.
options (table/nil) –
none, any, or all of the same options that index_object:select() allows:
- options.iterator – the iterator type. The default iterator type is „EQ“.
- options.limit – the maximum number of tuples.
- options.offset – the number of tuples to skip.
- options.after – a tuple or the position of a tuple (tuple_pos) after which select starts the search. You can pass an empty string or box.NULL to this option to start the search from the first tuple.
- options.fetch_pos – if true, the select method returns the position of the last selected tuple as the second value.
  
  Примечание
  
  The after and fetch_pos options are supported for the TREE index only.

возвращает:

This function might return one or two values:

The tuples whose primary-key fields are equal to the fields of the passed key. If the number of passed fields is less than the number of fields in the primary key, then only the passed fields are compared, so select{1,2} matches a tuple whose primary key is {1,2,3}.
(Optionally) If options.fetch_pos is set to true, returns a base64-encoded string representing the position of the last selected tuple as the second value. If no tuples are fetched, returns nil.

тип возвращаемого значения:

массив кортежей
(Optionally) string

Возможные ошибки:

no such space
wrong type
ER_TRANSACTION_CONFLICT if a transaction conflict is detected in the MVCC transaction mode
iterator position is invalid

Факторы сложности: Размер индекса, тип индекса

Examples:

Below are few examples of using select with different parameters. To try out these examples, you need to bootstrap a Tarantool instance as described in Using data operations.

-- Insert test data --
tarantool> bands:insert{1, 'Roxette', 1986}
           bands:insert{2, 'Scorpions', 1965}
           bands:insert{3, 'Ace of Base', 1987}
           bands:insert{4, 'The Beatles', 1960}
           bands:insert{5, 'Pink Floyd', 1965}
           bands:insert{6, 'The Rolling Stones', 1962}
           bands:insert{7, 'The Doors', 1965}
           bands:insert{8, 'Nirvana', 1987}
           bands:insert{9, 'Led Zeppelin', 1968}
           bands:insert{10, 'Queen', 1970}
---
...

-- Select a tuple by the specified primary key --
tarantool> bands:select(4)
---
- - [4, 'The Beatles', 1960]
...

-- Select maximum 3 tuples with the primary key value greater than 3 --
tarantool> bands:select({3}, {iterator='GT', limit = 3})
---
- - [4, 'The Beatles', 1960]
  - [5, 'Pink Floyd', 1965]
  - [6, 'The Rolling Stones', 1962]
...

-- Select maximum 3 tuples after the specified tuple --
tarantool> bands:select({}, {after = {4, 'The Beatles', 1960}, limit = 3})
---
- - [5, 'Pink Floyd', 1965]
  - [6, 'The Rolling Stones', 1962]
  - [7, 'The Doors', 1965]
...

-- Select first 3 tuples and fetch a last tuple's position --
tarantool> result, position = bands:select({}, {limit = 3, fetch_pos = true})
---
...
-- Then, pass this position as the 'after' parameter --
tarantool> bands:select({}, {limit = 3, after = position})
---
- - [4, 'The Beatles', 1960]
  - [5, 'Pink Floyd', 1965]
  - [6, 'The Rolling Stones', 1962]
...

Примечание

You can get a field from a tuple both by the field number and field name. See example: using field names instead of field numbers.

Версия:

space_object:select()