implement the /compare/pkg1/pkg2 page differently

The original version had two major drawbacks:
 1) The SQL query used would cause a btree sort, so the time waiting
    for the first output was rather long.
 2) For packages with many equal files, the output would grow with
    O(n^2).

Thanks to the suggestions by Christine Grohne and Klaus Aehlig. The
approach now groups files in package1 by their main hash value (sha512).
It also does some work SQL was designed to solve manually now. To speed
up page generation a new caching table was added identifying which files
have corresponding shared files.

1 files changed, 1 insertions, 0 deletions

diff --git a/schema.sql b/schema.sql
index a67c807..e942c7b 100644
--- a/schema.sql
+++ b/schema.sql
@@ -9,3 +9,4 @@ CREATE INDEX hash_hash_index ON hash (hash);
 CREATE TABLE sharing (package1 TEXT, package2 TEXT, func1 TEXT, func2 TEXT, files INTEGER, size INTEGER, FOREIGN KEY (package1) REFERENCES package(package) ON DELETE CASCADE, FOREIGN KEY (package2) REFERENCES package(package) ON DELETE CASCADE);
 CREATE INDEX sharing_insert_index ON sharing (package1, package2, func1, func2);
 CREATE INDEX sharing_package_index ON sharing (package1);
+CREATE TABLE duplicate (cid INTEGER PRIMARY KEY, FOREIGN KEY (cid) REFERENCES content(id) ON DELETE CASCADE);