--- HYPERCACHE ---

Definitions :
1. persistent representation of STAR Offline db on disk;
2. "database on demand" feature;

Each STAR Offline DB request is :

1.   fetched from original db server by timestamp (or run number);
2.   stored on disk in some format for later use;
3.   subsequent requests check disk cache first, try db next, eventually building local db cache accessible by db name/table + timestamp;

3. data on disk is to be partitioned by :
 a) "db path" AND ("validity time" OR "run number");

POSSIBLE IMPLEMENTATIONS:
a) local sqlite3 database + data blobs as separate files, SINGLE index file like "/tmp/STAR/offline.sqlite3.cache" for ALL requests;
b) local sqlite3 database + data blobs as separate files, MULTIPLE index files, one per request path. Say, request is "bemc/mapping/2003/emcPed", therefore, we will have "/tmp/STAR/sha1(request_path).sqlite3.cache" file for all data entries;
c) local embedded MySQL server (possibly, standalone app) + data blobs as separate files;
d) other in-house developed solution;

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SQLITE 3 database table format : [char sha1( path_within_subsystem ) ] [timestamp: beginTime] [timestamp: endTime] [seconds: expire] [char: flavor]

SQLITE 3 table file : /tmp/STAR_OFFLINE_DB/ sha1 ( [POOL] / [DOMAIN] / [SUBSYSTEM] ) / index.cache

SQLITE 3 blob is located at : /tmp/STAR_OFFLINE_DB/ sha1 ( [POOL] / [DOMAIN] / [SUBSYSTEM] ) / [SEGMENT] / sha1( [path_within_subsystem][beginTime][endTime] ).blob.cache

[SEGMENT] = int [0]...[N], for faster filesystem access