mysql_handler/engine/
sampling_method.rs

1// Copyright (C) 2026 ren-yamanashi
2//
3// This program is free software; you can redistribute it and/or modify
4// it under the terms of the GNU General Public License, version 2.0,
5// as published by the Free Software Foundation.
6//
7// This program is designed to work with certain software (including
8// but not limited to OpenSSL) that is licensed under separate terms,
9// as designated in a particular file or component or in included license
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12// separately licensed software that they have either included with
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15// This program is distributed in the hope that it will be useful,
16// but WITHOUT ANY WARRANTY; without even the implied warranty of
17// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18// GNU General Public License for more details.
19//
20// You should have received a copy of the GNU General Public License
21// along with this program; if not, see <https://www.gnu.org/licenses/>.
22
23//! Sampling algorithm selector, mirroring MySQL's `enum_sampling_method`.
24
25/// Sampling algorithm requested for [`StorageEngine::sample_init`], mirroring
26/// MySQL's `enum_sampling_method`.
27///
28/// [`StorageEngine::sample_init`]: crate::engine::StorageEngine::sample_init
29#[derive(Debug, Clone, Copy, PartialEq, Eq)]
30#[non_exhaustive]
31pub enum SamplingMethod {
32    /// `SYSTEM` sampling: page/block-level, the only method MySQL supports today
33    System,
34    /// No sampling method selected
35    None,
36}
37
38impl SamplingMethod {
39    /// Map the raw `enum_sampling_method` integer supplied at the FFI boundary
40    /// to a variant. Any value other than `SYSTEM` (`0`) becomes
41    /// [`SamplingMethod::None`] so the engine never observes an undefined value.
42    pub(crate) fn from_raw(raw: i32) -> Self {
43        match raw {
44            0 => Self::System,
45            _ => Self::None,
46        }
47    }
48}
49
50#[cfg(test)]
51mod tests {
52    use super::*;
53
54    #[test]
55    fn system_maps_from_zero() {
56        assert_eq!(SamplingMethod::from_raw(0), SamplingMethod::System);
57    }
58
59    #[test]
60    fn non_system_codes_become_none() {
61        assert_eq!(SamplingMethod::from_raw(1), SamplingMethod::None);
62        assert_eq!(SamplingMethod::from_raw(-1), SamplingMethod::None);
63        assert_eq!(SamplingMethod::from_raw(42), SamplingMethod::None);
64    }
65}
mysql_handler/engine/sampling_method.rs

mysql_handler/engine/
sampling_method.rs
