mirror of
https://github.com/scylladb/scylladb.git
synced 2026-04-20 00:20:47 +00:00
43c76aaf2b
Split the `log_record` to `log_record_header` type that has the record
metadata fields and the mutation as a separate field which is the actual
record data:
struct log_record {
log_record_header header;
canonical_mutation mut;
};
Both the header and mutation have variable serialized size. When a
record is serialized in a write_buffer, we first put a small
`record_header` that has the header size and data size, then the
serialized header and data follow. The `log_location` of a record points
to the beginning of the `record_header`, and the size includes the
`record_header`.
This allows us to read a record header without reading the data when
it's not needed and avoid deserializing it:
* on recovery, when scanning all segments, we read only the record
headers.
* on compaction, we read the record header first to determine if the
record is alive, if yes then we read the data.
Closes scylladb/scylladb#29457