tuple_object[field-path]
tuple_object
tuple_object[field-path]
If t is a tuple instance, t['path'] will return the field or subset
of fields that are in path. path must be a well formed JSON
specification. path may contain field names if the tuple has been
retrieved from a space that has an associated
format.
To prevent ambiguity, Tarantool first tries to interpret the request as
/reference/reference_lua/box_tuple/field_number or
/reference/reference_lua/box_tuple/field_name. If and only if that fails, Tarantool tries to interpret the
request as tuple_object[field-path].
The path must be a well formed JSON specification, but it may be preceded by '.'. The '.' is a signal that the path acts as a suffix for the tuple.
The advantage of specifying a path is that Tarantool will use it to search through a tuple body and get only the tuple part, or parts, that are actually necessary.
In the following example, a tuple named t is returned from replace
and then only the relevant part (in this case, matching a name) of a
relevant field is returned. Namely: the second field, its third item,
the value following 'key='.
tarantool> format = {}---...tarantool> format[1] = {name = 'field1', type = 'unsigned'}---...tarantool> format[2] = {name = 'field2', type = 'array'}---...tarantool> s = box.schema.space.create('test', {format = format})---...tarantool> pk = s:create_index('pk')---...tarantool> field2_value = {1, "ABC", {key="Hello", value="world"}}---...tarantool> t = s:replace{1, field2_value}---...tarantool> t["[2][3]['key']"]---- Hello...