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Do not cache dropped relation metadata

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This commit is contained in:
Konstantin Knizhnik
2021-06-11 09:20:21 +03:00
committed by Stas Kelvich
parent 9b7b311815
commit 9af04b3b8d
1 changed files with 16 additions and 7 deletions
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23
pageserver/src/object_repository.rs
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@@ -159,9 +159,18 @@ impl Repository for ObjectRepository {
}
}
///
/// Relation metadata (currently only size) is stored in separate record
/// in object store and is update by each put operation: we need to check if
/// new block size is greater or equal than existed relation size and if so: update
/// the relation metadata. So it requires extra object storage lookup at each
/// put operation. To avoid this lookup we maintain in-memory cache of relation metadata.
/// To prevent memory overflow metadata only of the most recent version of relation is cached.
/// If page server needs to access some older version, then object storage has to be accessed.
///
struct RelMetadata {
size: Option<u32>,
last_updated: Lsn,
size: u32, // size of relation
last_updated: Lsn, // lsn of last metadata update (used to determine when cache value can be used)
}
///
@@ -259,7 +268,7 @@ impl Timeline for ObjectTimeline {
let rel_meta = self.rel_meta.read().unwrap();
if let Some(meta) = rel_meta.get(&rel) {
if meta.last_updated <= lsn {
return Ok(meta.size.is_some());
return Ok(true);
}
}
}
@@ -352,7 +361,7 @@ impl Timeline for ObjectTimeline {
rel_meta.insert(
tag.rel,
RelMetadata {
size: Some(new_nblocks),
size: new_nblocks,
last_updated: lsn,
},
);
@@ -400,7 +409,7 @@ impl Timeline for ObjectTimeline {
rel_meta.insert(
tag.rel,
RelMetadata {
size: Some(new_nblocks),
size: new_nblocks,
last_updated: lsn,
},
);
@@ -425,7 +434,7 @@ impl Timeline for ObjectTimeline {
rel_meta.insert(
rel,
RelMetadata {
size: Some(nblocks),
size: nblocks,
last_updated: lsn,
},
);
@@ -580,7 +589,7 @@ impl ObjectTimeline {
let rel_meta = self.rel_meta.read().unwrap();
if let Some(meta) = rel_meta.get(&rel) {
if meta.last_updated <= lsn {
return Ok(meta.size);
return Ok(Some(meta.size));
}
}
}