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UPDATE
:ref:`space_object.update <box_space-update>` allows you to update a tuple identified by the primary key. Similarly to ``delete``, the ``update`` method accepts a full key and also an operation to execute.
-- 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}

-- Update a tuple with an existing key --
tarantool> bands:update({2}, {{'=', 2, 'Pink Floyd'}})
---
- [2, 'Pink Floyd', 1965]
...

tarantool> bands:select()
---
- - [1, 'Roxette', 1986]
- [2, 'Pink Floyd', 1965]
- [3, 'Ace of Base', 1987]
- [4, 'The Beatles', 1960]
...
:ref:`index_object.update <box_index-update>` updates a tuple identified by the specified unique index.
-- Update a tuple by the primary index --
tarantool> bands.index.primary:update({2}, {{'=', 2, 'The Rolling Stones'}})
---
- [2, 'The Rolling Stones', 1965]
...

tarantool> bands:select()
---
- - [1, 'Roxette', 1986]
- [2, 'The Rolling Stones', 1965]
- [3, 'Ace of Base', 1987]
- [4, 'The Beatles', 1960]
...

-- Update a tuple by a unique secondary index --
tarantool> bands.index.band:update({'The Rolling Stones'}, {{'=', 2, 'The Doors'}})
---
- [2, 'The Doors', 1965]
...

tarantool> bands:select()
---
- - [1, 'Roxette', 1986]
- [2, 'The Doors', 1965]
- [3, 'Ace of Base', 1987]
- [4, 'The Beatles', 1960]
...

-- Try to update a tuple by a non-unique secondary index --
tarantool> bands.index.year:update({1965}, {{'=', 2, 'Scorpions'}})
---
- error: Get() doesn't support partial keys and non-unique indexes
...
tarantool> bands:select()
---
- - [1, 'Roxette', 1986]
- [2, 'The Doors', 1965]
- [3, 'Ace of Base', 1987]
- [4, 'The Beatles', 1960]
...

-- Delete all tuples --
tarantool> bands:truncate()
---
...
UPSERT
:ref:`space_object.upsert <box_space-upsert>` updates an existing tuple or inserts a new one:
If the existing tuple is found by the primary key, Tarantool applies the update operation to this tuple and ignores the new tuple.
If no existing tuple is found, Tarantool inserts the new tuple and ignores the update operation.
tarantool> bands:insert{1, 'Scorpions', 1965}
---
- [1, 'Scorpions', 1965]
...
-- As the first argument, upsert accepts a tuple, not a key --
tarantool> bands:upsert({2}, {{'=', 2, 'Pink Floyd'}})
---
- error: Tuple field 2 (band_name) required by space format is missing
...
tarantool> bands:select()
---
- - [1, 'Scorpions', 1965]
...
tarantool> bands:delete(1)
---
- [1, 'Scorpions', 1965]
...
``upsert`` acts as ``insert`` when no existing tuple is found by the primary key.
tarantool> bands:upsert({1, 'Scorpions', 1965}, {{'=', 2, 'The Doors'}})
---
...
-- As you can see, {1, 'Scorpions', 1965} is inserted, --
-- and the update operation is not applied. --
tarantool> bands:select()
---
- - [1, 'Scorpions', 1965]
...

-- upsert with the same primary key but different values in other fields --
-- applies the update operation and ignores the new tuple. --
tarantool> bands:upsert({1, 'Scorpions', 1965}, {{'=', 2, 'The Doors'}})
---
...
tarantool> bands:select()
---
- - [1, 'The Doors', 1965]
...
``upsert`` searches for the existing tuple by the primary index, not by the secondary index. This can lead to a duplication error if the tuple violates a secondary index uniqueness.
tarantool> bands:upsert({2, 'The Doors', 1965}, {{'=', 2, 'Pink Floyd'}})
---
- error: Duplicate key exists in unique index "band" in space "bands" with old tuple
- [1, "The Doors", 1965] and new tuple - [2, "The Doors", 1965]
...
tarantool> bands:select()
---
- - [1, 'The Doors', 1965]
...

-- This works if uniqueness is preserved. --
tarantool> bands:upsert({2, 'The Beatles', 1960}, {{'=', 2, 'Pink Floyd'}})
---
...
tarantool> bands:select()
---
- - [1, 'The Doors', 1965]
- [2, 'The Beatles', 1960]
...

-- Delete all tuples --
tarantool> bands:truncate()
---
...
REPLACE
:ref:`space_object.replace <box_space-replace>` accepts a well-formatted tuple and searches for the existing tuple by the primary key of the new tuple:
If the existing tuple is found, Tarantool deletes it and inserts the new tuple.
If no existing tuple is found, Tarantool inserts the new tuple.
tarantool> bands:replace{1, 'Scorpions', 1965}
---
- [1, 'Scorpions', 1965]
...
tarantool> bands:select()
---
- - [1, 'Scorpions', 1965]
...
tarantool> bands:replace{1, 'The Beatles', 1960}
---
- [1, 'The Beatles', 1960]
...
tarantool> bands:select()
---
- - [1, 'The Beatles', 1960]
...
tarantool> bands:truncate()
---
...
``replace`` can violate unique constraints, like ``upsert`` does.
tarantool> bands:insert{1, 'Scorpions', 1965}
- [1, 'Scorpions', 1965]
...
tarantool> bands:insert{2, 'The Beatles', 1960}
---
- [2, 'The Beatles', 1960]
...
tarantool> bands:replace{2, 'Scorpions', 1965}
---
- error: Duplicate key exists in unique index "band" in space "bands" with old tuple
- [1, "Scorpions", 1965] and new tuple - [2, "Scorpions", 1965]
...
tarantool> bands:truncate()
---
...
SELECT
The :ref:`space_object.select <box_space-select>` request searches for a tuple or a set of tuples in the given space by the primary key. To search by the specified index, use :ref:`index_object.select <box_index-select>`. These methods work with any keys, including unique and non-unique, full and partial. If a key is partial, ``select`` searches by all keys where the prefix matches the specified key part.
tarantool> bands:insert{1, 'Roxette', 1986}
bands:insert{2, 'Scorpions', 1965}
bands:insert{3, 'The Doors', 1965}
bands:insert{4, 'The Beatles', 1960}

tarantool> bands:select(1)
---
- - [1, 'Roxette', 1986]
...

tarantool> bands:select()
---
- - [1, 'Roxette', 1986]
- [2, 'Scorpions', 1965]
- [3, 'The Doors', 1965]
- [4, 'The Beatles', 1960]
...

tarantool> bands.index.primary:select(2)
---
- - [2, 'Scorpions', 1965]
...

tarantool> bands.index.band:select('The Doors')
---
- - [3, 'The Doors', 1965]
...

tarantool> bands.index.year:select(1965)
---
- - [2, 'Scorpions', 1965]
- [3, 'The Doors', 1965]
...
Using box.space functions to read _space tuples
This example illustrates how to look at all the spaces, and for each display: approximately how many tuples it contains, and the first field of its first tuple. The function uses the Tarantool's ``box.space`` functions ``len()`` and ``pairs()``. The iteration through the spaces is coded as a scan of the ``_space`` system space, which contains metadata. The third field in ``_space`` contains the space name, so the key instruction ``space_name = v[3]`` means ``space_name`` is the ``space_name`` field in the tuple of ``_space`` that we've just fetched with ``pairs()``. The function returns a table:
function example()
local tuple_count, space_name, line
local ta = {}
for k, v in box.space._space:pairs() do
space_name = v[3]
if box.space[space_name].index[0] ~= nil then
tuple_count = '1 or more'
else
tuple_count = '0'
end
line = space_name .. ' tuple_count =' .. tuple_count
if tuple_count == '1 or more' then
for k1, v1 in box.space[space_name]:pairs() do
line = line .. '. first field in first tuple = ' .. v1[1]
break
end
end
table.insert(ta, line)
end
return ta
end
The output below shows what happens if you invoke this function:
tarantool> example()
---
- - _schema tuple_count =1 or more. first field in first tuple = cluster
- _space tuple_count =1 or more. first field in first tuple = 272
- _vspace tuple_count =1 or more. first field in first tuple = 272
- _index tuple_count =1 or more. first field in first tuple = 272
- _vindex tuple_count =1 or more. first field in first tuple = 272
- _func tuple_count =1 or more. first field in first tuple = 1
- _vfunc tuple_count =1 or more. first field in first tuple = 1
- _user tuple_count =1 or more. first field in first tuple = 0
- _vuser tuple_count =1 or more. first field in first tuple = 0
- _priv tuple_count =1 or more. first field in first tuple = 1
- _vpriv tuple_count =1 or more. first field in first tuple = 1
- _cluster tuple_count =1 or more. first field in first tuple = 1
...
Using box.space functions to organize a _space tuple
This examples shows how to display field names and field types of a system space -- using metadata to find metadata.

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testing_project / Documentation: how-to/db/crud — English

:ref:`space_object.replace <box_space-replace>` accepts a well-formatted tuple and searches for the existing tuple by the primary key of the new tuple:
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