risingwave_connector_codec/decoder/
mod.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15pub mod avro;
16pub mod json;
17pub mod protobuf;
18pub mod utils;
19
20use risingwave_common::error::NotImplemented;
21use risingwave_common::types::{DataType, Datum, DatumCow, ToOwnedDatum};
22use thiserror::Error;
23use thiserror_ext::Macro;
24
25#[derive(Error, Debug, Macro)]
26#[thiserror_ext(macro(mangle, path = "crate::decoder"))]
27pub enum AccessError {
28    #[error("Undefined field `{name}` at `{path}`")]
29    Undefined { name: String, path: String },
30    #[error("Cannot parse value `{value}` with type `{got}` into expected type `{expected}`")]
31    TypeError {
32        expected: String,
33        got: String,
34        value: String,
35    },
36    #[error("Unsupported data type `{ty}`")]
37    UnsupportedType { ty: String },
38
39    #[error("Unsupported additional column `{name}`")]
40    UnsupportedAdditionalColumn { name: String },
41
42    #[error("Fail to convert protobuf Any into jsonb: {0}")]
43    ProtobufAnyToJson(#[source] serde_json::Error),
44
45    /// Errors that are not categorized into variants above.
46    #[error("{message}")]
47    Uncategorized { message: String },
48
49    #[error(transparent)]
50    NotImplemented(#[from] NotImplemented),
51    // NOTE: We intentionally don't embed `anyhow::Error` in `AccessError` since it happens
52    // in record-level and it might be too heavy to capture the backtrace
53    // when creating a new `anyhow::Error`.
54}
55
56pub type AccessResult<T = Datum> = std::result::Result<T, AccessError>;
57
58/// Access to a field in the data structure. Created by `AccessBuilder`.
59///
60/// It's the `ENCODE ...` part in `FORMAT ... ENCODE ...`
61pub trait Access {
62    /// Accesses `path` in the data structure (*parsed* Avro/JSON/Protobuf data),
63    /// and then converts it to RisingWave `Datum`.
64    ///
65    /// `type_expected` might or might not be used during the conversion depending on the implementation.
66    ///
67    /// # Path
68    ///
69    /// We usually expect the data (`Access` instance) is a record (struct), and `path` represents field path.
70    /// The data (or part of the data) represents the whole row (`Vec<Datum>`),
71    /// and we use different `path` to access one column at a time.
72    ///
73    /// TODO: the meaning of `path` is a little confusing and maybe over-abstracted.
74    /// `access` does not need to serve arbitrarily deep `path` access, but just "top-level" access.
75    /// The API creates an illusion that arbitrary access is supported, but it's not.
76    /// Perhaps we should separate out another trait like `ToDatum`,
77    /// which only does type mapping, without caring about the path. And `path` itself is only an `enum` instead of `&[&str]`.
78    ///
79    /// What `path` to access is decided by the CDC layer, i.e., the `FORMAT ...` part (`ChangeEvent`).
80    /// e.g.,
81    /// - `DebeziumChangeEvent` accesses `["before", "col_name"]` for value,
82    ///   `["source", "db"]`, `["source", "table"]` etc. for additional columns' values,
83    ///   `["op"]` for op type.
84    /// - `MaxwellChangeEvent` accesses `["data", "col_name"]` for value, `["type"]` for op type.
85    /// - In the simplest case, for `FORMAT PLAIN/UPSERT` (`KvEvent`), they just access `["col_name"]` for value, and op type is derived.
86    ///
87    /// # Returns
88    ///
89    /// The implementation should prefer to return a borrowed [`DatumRef`](risingwave_common::types::DatumRef)
90    /// through [`DatumCow::Borrowed`] to avoid unnecessary allocation if possible, especially for fields
91    /// with string or bytes data. If that's not the case, it may return an owned [`Datum`] through
92    /// [`DatumCow::Owned`].
93    fn access<'a>(&'a self, path: &[&str], type_expected: &DataType) -> AccessResult<DatumCow<'a>>;
94}
95
96// Note: made an extension trait to disallow implementing or overriding `access_owned`.
97#[easy_ext::ext(AccessExt)]
98impl<A: Access> A {
99    /// Similar to `access`, but always returns an owned [`Datum`]. See [`Access::access`] for more details.
100    ///
101    /// Always prefer calling `access` directly if possible to avoid unnecessary allocation.
102    pub fn access_owned(&self, path: &[&str], type_expected: &DataType) -> AccessResult<Datum> {
103        self.access(path, type_expected)
104            .map(ToOwnedDatum::to_owned_datum)
105    }
106}
risingwave_connector_codec/decoder/mod.rs

risingwave_connector_codec/decoder/
mod.rs
