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Minor fixes

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This commit is contained in:
Heikki Linnakangas
2021-09-09 22:46:58 +03:00
committed by lubennikovaav
parent 3dea06b825
commit 59e7ca585d
2 changed files with 13 additions and 6 deletions
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8
docs/glossary.md
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@@ -127,12 +127,16 @@ How much history do we need to keep around for PITR and read-only nodes?
NOTE: This is an overloaded term.
A physical file which stores data for a given relation. File segments are limited in size by a configuration value (typically 1 gigabyte), so if a relation exceeds that size, it is split into multiple segments.
A physical file that stores data for a given relation. File segments are
limited in size by a compile-time setting (1 gigabyte by default), so if a
relation exceeds that size, it is split into multiple segments.
### Segment (Layered Repository)
NOTE: This is an overloaded term.
Segment is a RELISH_SEG_SIZE slice of relish (defined by a SegmentTag).
Segment is a RELISH_SEG_SIZE slice of relish (identified by a SegmentTag).
### SLRU
SLRUs include pg_clog, pg_multixact/members, and

11
pageserver/src/layered_repository/README.md
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@@ -5,15 +5,17 @@ receives a stream of incoming WAL, parses the WAL records to determine
which pages they apply to, and accumulates the incoming changes in
memory. Every now and then, the accumulated changes are written out to
new immutable files. This process is called checkpointing. Old versions
of on-disk files not needed by any timeline are removed by GC process.
of on-disk files that are not needed by any timeline are removed by GC
process.
# Terms used in layered repository
- Relish - one PostgreSQL relation or similarly threated file.
- Relish - one PostgreSQL relation or similarly treated file.
- Segment - one slice of a Relish that is stored in a LayeredTimeline.
- Layer - specific version of a relish Segment in a range of LSNs.
Layers can be InMemory or OnDisk:
- InMemory layer is not durably stored and should be rebuild from WAL on pageserver start.
- InMemory layer is not durably stored and needs to rebuild from WAL on pageserver start.
- OnDisk layer is durably stored.
OnDisk layers can be Image or Delta:
@@ -51,7 +53,8 @@ For example, timeline.list_rels(lsn) will return all segments that are visible i
including ones that were not modified in this timeline and thus don't have a layer in the timeline's LayerMap.
TODO:
Describe GC and chekpoint interval settings.
Describe GC and checkpoint interval settings.
# Layer files (On-disk layers)
The files are called "layer files". Each layer file corresponds