v0.6.0

Stop the daemon before you upgrade and start it again after: the first open
of a cache replaces its search trigger and drops an index nothing used
(#87). Then tg db vacuum gives that index's space back. tg messages search
now reads a query the way FTS5 does: hello world finds both words
anywhere, and --phrase gives the old exact-phrase search (#84).

Added

• tg messages search filters by date and ranks by relevance. --since and
  --until take a date, a date and time, or a duration back from now (7d,
  24h); --sort relevance puts the best matches first; --count also
  returns how many messages match over all pages, as count. total is
  still the number of results on the page (#85).
• tg messages search --snippet adds a short fragment of each message around
  the matched words, with the words in **, for Latin and Cyrillic text and
  prefixes like квартир*. For tg sql, the new view message_search_text
  returns full-text matches with the message text, chat and sender, so
  WHERE message_search_text MATCH 'deploy' ORDER BY rank needs no join. The
  view stores nothing, so the cache stays the same size (#81).

Changed

• raw_json stores byte fields, such as a photo's fileReference and its
  stripped thumbnail, as base64 strings instead of objects with a key per
  byte. A made-up photo message's raw_json drops from 10,213 to 1,896
  bytes. Every cached message, chat and user is written this way; rows cached
  before keep the old form until they are fetched again.
  docs/database-schema.md shows how to read the fields with json_extract
  (#86).
• A message fetched again with nothing changed is no longer written again,
  and its search index entry is left alone. Catch-up after every daemon
  restart or reconnect fetches again the messages that arrived live, so each
  of them used to cost a row rewrite and a re-index. A message is re-indexed
  only when its text, sender or media path changes; a change only in
  raw_json, such as a channel post's views, updates the row but not the
  index, and marking a message deleted no longer re-indexes it. A side effect
  of the old re-indexing goes away: a re-fetch no longer refreshes the sender
  and chat names stored in the index, so a renamed user or chat is found by
  the new name only in messages indexed after the rename. Results still show
  the current names (#93 tracks re-indexing after a rename). The first open of
  an existing cache replaces its search trigger (#87).
• The cache no longer keeps an index on messages_cache.fetched_at: no query
  used it, and it took space for every message. The first open of an
  existing cache drops it; tg db vacuum gives the space back (#87).
• tg messages search reads a query the way FTS5 does. hello world now
  finds messages with both words anywhere in them, not only the exact phrase;
  pass --phrase for the old behaviour. Operators, phrases, column filters and
  prefixes work as --help and docs/search.md describe them: error OR timeout, "exact phrase", sender:alice, chat:team, and квартир* for
  every form of a word. A query FTS5 can't parse returns INVALID_ARGS with a
  suggestion instead of TELEGRAM_ERROR (#84).

Fixed

• tg sql can no longer change the cache with a pragma. It let
  PRAGMA user_version = 0 through, which made the next start run the
  one-time migrations again. Queries now run on a read-only connection and
  such a statement, in either form (PRAGMA writable_schema(1) too), returns
  SQL_WRITE_NOT_ALLOWED. A query with more than one statement returns
  SQL_OPERATION_BLOCKED instead of running only the first. Reading pragmas such as
  PRAGMA table_info(messages_cache) works, and no longer fails with a
  syntax error from the row limit (#88).