NAME

       lei-store-format - lei/store format description

DESCRIPTION

       "lei/store" is a hybrid store based on public-inbox-extindex-format(5) ("extindex")
       combined with public-inbox-v2-format(5) ("v2") for blob storage.  While v2 is ideal for
       archiving a single public mailing list; it was never intended for personal mail nor
       storing multiple blobs of the "same" message.

       As with extindex, it can index disparate "List-Id" headers belonging to the "same" message
       with different git blob OIDs.  Unlike v2 and extindex, "Message-ID" headers are NOT
       required; allowing unsent draft messages to be stored and indexed.

DIRECTORY LAYOUT

       Blob storage exists in the form of v2-style epochs.  These epochs are under the "local/"
       directory (instead of "git/") to prevent them from being accidentally treated as a v2
       inbox.

   INDEX OVERVIEW AND DEFINITIONS
         $EPOCH - Integer starting with 0 based on time
         $SCHEMA_VERSION - DB schema version (for Xapian)
         $SHARD - Integer starting with 0 based on parallelism

         ~/.local/share/lei/store
         - local/$EPOCH.git                # normal bare git repositories
         - mail_sync.sqlite3               # sync state IMAP, Maildir, NNTP

       Additionally, the following share the same roles they do in extindex:

         - ei.lock                         # lock file to protect global state
         - ALL.git                         # empty, alternates for local/*.git
         - ei$SCHEMA_VERSION/$SHARD        # per-shard Xapian DB
         - ei$SCHEMA_VERSION/over.sqlite3  # overview DB for WWW, IMAP
         - ei$SCHEMA_VERSION/misc          # misc Xapian DB

   XREF3 DEDUPLICATION
       Index deduplication follows extindex, see "XREF3 DEDUPLICATION" in
       public-inbox-extindex-format(5) for more information.

   BLOB DEDUPLICATION
       The contents of "local/*.git" repos is deduplicated by git blob object IDs (currently
       SHA-1).  This allows multiple copies of cross-posted and personally Cc-ed messages to be
       stored with different "Received:", "X-Spam-Status:" and similar headers to allow
       troubleshooting.

   VOLATILE METADATA
       Keywords and label information (as described in RFC 8621 for JMAP) is stored in existing
       Xapian shards ("ei$SCHEMA_VERSION/$SHARD").  It is possible to search for messages
       matching labels and keywords using "L:" and "kw:", respectively.  As with all data stored
       in Xapian indices, volatile metadata is associated with the Xapian document, thus it is
       shared across different blobs of the "same" message.

   mail_sync.sqlite3
       This SQLite database maintained for bidirectional mapping of git blobs to IMAP UIDs,
       Maildir file names, and NNTP article numbers.

       It is also used for retrieving messages from Maildirs indexed by lei-index(1).

IPC

       lei-daemon(8) communicates with the "lei/store" process using unix(7) "SOCK_SEQPACKET"
       sockets.

CAVEATS

       Reindexing and synchronization is not yet supported.

THANKS

       Thanks to the Linux Foundation for sponsoring the development and testing.

COPYRIGHT

       Copyright 2021 all contributors <mailto:meta@public-inbox.org>

       License: AGPL-3.0+ <http://www.gnu.org/licenses/agpl-3.0.txt>

SEE ALSO

       public-inbox-v2-format(5), public-inbox-extindex(5)