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Add calculate_walrecord_end_lsn function

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Konstantin Knizhnik
2024-10-11 10:33:39 +03:00
parent fa3dc91fb5
commit cfcb197d85
5 changed files with 40 additions and 27 deletions
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1
libs/postgres_ffi/src/lib.rs
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@@ -247,6 +247,7 @@ pub const WAL_SEGMENT_SIZE: usize = 16 * 1024 * 1024;
pub const MAX_SEND_SIZE: usize = XLOG_BLCKSZ * 16;
// Export some version independent functions that are used outside of this mod
pub use v14::xlog_utils::calculate_walrecord_end_lsn;
pub use v14::xlog_utils::encode_logical_message;
pub use v14::xlog_utils::get_current_timestamp;
pub use v14::xlog_utils::to_pg_timestamp;

21
libs/postgres_ffi/src/xlog_utils.rs
View File

@@ -499,6 +499,27 @@ pub fn encode_logical_message(prefix: &str, message: &str) -> Bytes {
.encode(Lsn(0))
}
/// Given the start LSN of a WAL record and its length, calculate its end LSN.
///
/// In the simple cases, the end LSN is just `start_lsn + len`, but it's more complicated if
/// the record crosses a page boundary.
///
/// `len` is the length not including any WAL page headers. It should match the `xl_tot_len`
/// field on the WAL record.
pub fn calculate_walrecord_end_lsn(start_lsn: Lsn, len: usize) -> Lsn {
let aligned_len = ((len + 7) & !7) as u64;
let page_header_size = if (XLOG_BLCKSZ as u64) - start_lsn.0 % (XLOG_BLCKSZ as u64) < aligned_len {
if (start_lsn.0 & ((WAL_SEGMENT_SIZE - 1) as u64)) < (XLOG_BLCKSZ as u64) {
XLOG_SIZE_OF_XLOG_LONG_PHD
} else {
XLOG_SIZE_OF_XLOG_SHORT_PHD
}
} else {
0
} as u64;
start_lsn + aligned_len + page_header_size
}
#[cfg(test)]
mod tests {
use super::*;