1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
|
// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
include "Schema.fbs";
include "SparseTensor.fbs";
include "Tensor.fbs";
namespace org.apache.arrow.flatbuf;
/// ----------------------------------------------------------------------
/// Data structures for describing a table row batch (a collection of
/// equal-length Arrow arrays)
/// Metadata about a field at some level of a nested type tree (but not
/// its children).
///
/// For example, a List<Int16> with values `[[1, 2, 3], null, [4], [5, 6], null]`
/// would have {length: 5, null_count: 2} for its List node, and {length: 6,
/// null_count: 0} for its Int16 node, as separate FieldNode structs
struct FieldNode {
/// The number of value slots in the Arrow array at this level of a nested
/// tree
length: long;
/// The number of observed nulls. Fields with null_count == 0 may choose not
/// to write their physical validity bitmap out as a materialized buffer,
/// instead setting the length of the bitmap buffer to 0.
null_count: long;
}
enum CompressionType:byte {
// LZ4 frame format, for portability, as provided by lz4frame.h or wrappers
// thereof. Not to be confused with "raw" (also called "block") format
// provided by lz4.h
LZ4_FRAME,
// Zstandard
ZSTD
}
/// Provided for forward compatibility in case we need to support different
/// strategies for compressing the IPC message body (like whole-body
/// compression rather than buffer-level) in the future
enum BodyCompressionMethod:byte {
/// Each constituent buffer is first compressed with the indicated
/// compressor, and then written with the uncompressed length in the first 8
/// bytes as a 64-bit little-endian signed integer followed by the compressed
/// buffer bytes (and then padding as required by the protocol). The
/// uncompressed length may be set to -1 to indicate that the data that
/// follows is not compressed, which can be useful for cases where
/// compression does not yield appreciable savings.
BUFFER
}
/// Optional compression for the memory buffers constituting IPC message
/// bodies. Intended for use with RecordBatch but could be used for other
/// message types
table BodyCompression {
/// Compressor library
codec: CompressionType = LZ4_FRAME;
/// Indicates the way the record batch body was compressed
method: BodyCompressionMethod = BUFFER;
}
/// A data header describing the shared memory layout of a "record" or "row"
/// batch. Some systems call this a "row batch" internally and others a "record
/// batch".
table RecordBatch {
/// number of records / rows. The arrays in the batch should all have this
/// length
length: long;
/// Nodes correspond to the pre-ordered flattened logical schema
nodes: [FieldNode];
/// Buffers correspond to the pre-ordered flattened buffer tree
///
/// The number of buffers appended to this list depends on the schema. For
/// example, most primitive arrays will have 2 buffers, 1 for the validity
/// bitmap and 1 for the values. For struct arrays, there will only be a
/// single buffer for the validity (nulls) bitmap
buffers: [Buffer];
/// Optional compression of the message body
compression: BodyCompression;
}
/// For sending dictionary encoding information. Any Field can be
/// dictionary-encoded, but in this case none of its children may be
/// dictionary-encoded.
/// There is one vector / column per dictionary, but that vector / column
/// may be spread across multiple dictionary batches by using the isDelta
/// flag
table DictionaryBatch {
id: long;
data: RecordBatch;
/// If isDelta is true the values in the dictionary are to be appended to a
/// dictionary with the indicated id. If isDelta is false this dictionary
/// should replace the existing dictionary.
isDelta: bool = false;
}
/// ----------------------------------------------------------------------
/// The root Message type
/// This union enables us to easily send different message types without
/// redundant storage, and in the future we can easily add new message types.
///
/// Arrow implementations do not need to implement all of the message types,
/// which may include experimental metadata types. For maximum compatibility,
/// it is best to send data using RecordBatch
union MessageHeader {
Schema, DictionaryBatch, RecordBatch, Tensor, SparseTensor
}
table Message {
version: org.apache.arrow.flatbuf.MetadataVersion;
header: MessageHeader;
bodyLength: long;
custom_metadata: [ KeyValue ];
}
root_type Message;
|
