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Do not perform XID alignment because looks like it has no noticeable impact on performance but can cause problrems with restoring running xacts from CLOG

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This commit is contained in:
Konstantin Knizhnik
2024-07-05 18:01:33 +03:00
parent c9fd8d7693
commit ed8aea612f
1 changed files with 2 additions and 15 deletions
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17
libs/postgres_ffi/src/xlog_utils.rs
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@@ -48,15 +48,6 @@ pub const XLOG_SIZE_OF_XLOG_RECORD: usize = std::mem::size_of::<XLogRecord>();
#[allow(clippy::identity_op)]
pub const SIZE_OF_XLOG_RECORD_DATA_HEADER_SHORT: usize = 1 * 2;
/// Interval of checkpointing metadata file. We should store metadata file to enforce
/// predicate that checkpoint.nextXid is larger than any XID in WAL.
/// But flushing checkpoint file for each transaction seems to be too expensive,
/// so XID_CHECKPOINT_INTERVAL is used to forward align nextXid and so perform
/// metadata checkpoint only once per XID_CHECKPOINT_INTERVAL transactions.
/// XID_CHECKPOINT_INTERVAL should not be larger than BLCKSZ*CLOG_XACTS_PER_BYTE
/// in order to let CLOG_TRUNCATE mechanism correctly extend CLOG.
const XID_CHECKPOINT_INTERVAL: u32 = 1024;
pub fn XLogSegmentsPerXLogId(wal_segsz_bytes: usize) -> XLogSegNo {
(0x100000000u64 / wal_segsz_bytes as u64) as XLogSegNo
}
@@ -331,14 +322,10 @@ impl CheckPoint {
/// Returns 'true' if the XID was updated.
pub fn update_next_xid(&mut self, xid: u32) -> bool {
// nextXid should be greater than any XID in WAL, so increment provided XID and check for wraparround.
let mut new_xid = std::cmp::max(
let new_xid = std::cmp::max(
xid.wrapping_add(1),
pg_constants::FIRST_NORMAL_TRANSACTION_ID,
);
// To reduce number of metadata checkpoints, we forward align XID on XID_CHECKPOINT_INTERVAL.
// XID_CHECKPOINT_INTERVAL should not be larger than BLCKSZ*CLOG_XACTS_PER_BYTE
new_xid =
new_xid.wrapping_add(XID_CHECKPOINT_INTERVAL - 1) & !(XID_CHECKPOINT_INTERVAL - 1);
let full_xid = self.nextXid.value;
let old_xid = full_xid as u32;
if new_xid.wrapping_sub(old_xid) as i32 > 0 {
@@ -360,7 +347,7 @@ impl CheckPoint {
/// Advance next multi-XID/offset to those given in arguments.
///
/// It's important that this handles wraparound correctly. This should match the
/// MultiXactAdvanceNextMXact() logic in PostgreSQL's xlog_redo() function.
/// MultiXactAdvceNextMXact() logic in PostgreSQL's xlog_redo() function.
///
/// Returns 'true' if the Checkpoint was updated.
pub fn update_next_multixid(&mut self, multi_xid: u32, multi_offset: u32) -> bool {