In nanoarrow, an 'array stream' corresponds to the struct ArrowArrayStream
as defined in the Arrow C Stream interface. This object is used to represent
a stream of arrays with a common
schema. This is similar to an
arrow::RecordBatchReader except it can be used to represent a stream of
any type (not just record batches). Note that a stream of record batches
and a stream of non-nullable struct arrays are represented identically.
Also note that array streams are mutable objects and are passed by
reference and not by value.
Arguments
- x
An object to convert to a array_stream
- ...
Passed to S3 methods
- schema
An optional schema used to enforce conversion to a particular type. Defaults to
infer_nanoarrow_schema().
Examples
(stream <- as_nanoarrow_array_stream(data.frame(x = 1:5)))
#> <nanoarrow_array_stream struct<x: int32>>
#> $ get_schema:function ()
#> $ get_next :function (schema = x$get_schema(), validate = TRUE)
#> $ release :function ()
stream$get_schema()
#> <nanoarrow_schema struct>
#> $ format : chr "+s"
#> $ name : chr ""
#> $ metadata : list()
#> $ flags : int 0
#> $ children :List of 1
#> ..$ x:<nanoarrow_schema int32>
#> .. ..$ format : chr "i"
#> .. ..$ name : chr "x"
#> .. ..$ metadata : list()
#> .. ..$ flags : int 2
#> .. ..$ children : list()
#> .. ..$ dictionary: NULL
#> $ dictionary: NULL
stream$get_next()
#> <nanoarrow_array struct[5]>
#> $ length : int 5
#> $ null_count: int 0
#> $ offset : int 0
#> $ buffers :List of 1
#> ..$ :<nanoarrow_buffer validity<bool>[null] ``
#> $ children :List of 1
#> ..$ x:<nanoarrow_array int32[5]>
#> .. ..$ length : int 5
#> .. ..$ null_count: int 0
#> .. ..$ offset : int 0
#> .. ..$ buffers :List of 2
#> .. .. ..$ :<nanoarrow_buffer validity<bool>[null] ``
#> .. .. ..$ :<nanoarrow_buffer data<int32>[5][20 b]> `1 2 3 4 5`
#> .. ..$ dictionary: NULL
#> .. ..$ children : list()
#> $ dictionary: NULL
# The last batch is returned as NULL
stream$get_next()
#> NULL
# Release the stream
stream$release()