Add a restore-snapshot command to lbs-util.

[cumulus.git] / schema.sql

diff --git a/schema.sql b/schema.sql
index 114670c..2cca99a 100644 (file)
--- a/schema.sql
+++ b/schema.sql
@@ -3,12 +3,57 @@
 --
 -- The index is stored in an SQLite3 database.  This is its schema.
 
--- Index of all blocks which have been stored in one snapshot, by checksum.
+-- List of snapshots which have been created.
+create table snapshots (
+    snapshotid integer primary key,
+    name text not null,
+    scheme text,
+    timestamp real
+);
+
+-- List of segments which have been created.
+create table segments (
+    segmentid integer primary key,
+    segment text unique not null,
+    path text,
+    checksum text
+);
+
+-- Index of all blocks which have been stored in a snapshot, by checksum.
 create table block_index (
     blockid integer primary key,
-    segment text,
-    object text,
+    segmentid integer not null,
+    object text not null,
     checksum text,
-    size integer
+    size integer,
+    timestamp real,
+    expired integer
 );
 create index block_content_index on block_index(checksum);
+create unique index block_name_index on block_index(segmentid, object);
+
+-- Index tracking which blocks are used by which snapshots.
+create table snapshot_contents (
+    blockid integer,
+    snapshotid integer
+);
+create unique index snapshot_contents_unique
+    on snapshot_contents(blockid, snapshotid);
+
+-- Summary statistics for each segment.
+create view segment_info as select * from
+    (select segmentid, max(timestamp) as mtime,
+            sum(size) as size, count(*) as objects
+       from block_index join segments using (segmentid) group by segmentid)
+natural join
+    (select segmentid, sum(size) as used, count(*) as objects_used
+       from block_index where blockid in
+            (select blockid from snapshot_contents) group by segmentid);
+
+-- Ranking of segments to be cleaned, using a benefit function of
+-- (fraction free space)*(age of youngest object).
+create view cleaning_order as select *, (1-u)*age/(u+0.1) as benefit from
+    (select segmentid,
+            cast(used as real) / size as u, julianday('now') - mtime as age
+        from segment_info)
+where benefit > 0;