snapshotid integer primary key,
name text not null,
scheme text,
- timestamp real
+ timestamp real,
+ intent real
);
-- List of segments which have been created.
path text,
checksum text,
mtime real,
- size integer
+ size integer,
+ expire_time integer -- snapshotid of latest snapshot when expired
);
-- Index of all blocks which have been stored, by checksum.
create index block_content_index on block_index(checksum);
create unique index block_name_index on block_index(segmentid, object);
+-- Checksums for the decomposition of blocks into even smaller chunks
+-- (variable-sized, but generally ~8 kB, and maximum 64 kB). Chunk boundaries
+-- are determined based on the contents using Rabin fingerprints. These
+-- checksums can be used for computing sub-file incrementals.
+--
+-- Each block stored in block_index may have an entry in the
+-- subblock_signatures table. The hash_data field is a binary blob consisting
+-- of a packed sequence of (chunk length [16-bit unsigned, big-endian],
+-- checksum [20 bytes for SHA-1]) tuples that should cover the entire block.
+create table subblock_signatures (
+ blockid integer primary key,
+ algorithm text not null,
+ signatures blob not null
+);
+
-- Summary of segment utilization for each snapshots.
create table segments_used (
snapshotid integer not null,
segmentid integer not null,
utilization real
);
+create unique index segments_used_index
+ on segments_used(snapshotid, segmentid);
-- Overall estimate of segment utilization, for all snapshots combined.
create view segment_info as
-select segmentid, mtime, size, cast(size * utilization as integer) as used,
- utilization
+select segmentid, mtime, size, expire_time,
+ cast(size * utilization as integer) as used, utilization
from segments join
(select segmentid, max(utilization) as utilization
from segments_used group by segmentid)