LEI-STORE-FORMAT(5)        public-inbox user manual        LEI-STORE-FORMAT(5)

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)

public-inbox.git                  1993-10-02               LEI-STORE-FORMAT(5)