Use a full dbref rather than just get_connection

src/calibre/db/backend.py

@@ -337,6 +337,7 @@ class Connection(apsw.Connection):  # {{{
         set_ui_language(get_lang())
         super().__init__(path)
         plugins.load_apsw_extension(self, 'sqlite_extension')
+        self.fts_dbpath = None
 
         self.setbusytimeout(self.BUSY_TIMEOUT)
         self.execute('pragma cache_size=-5000')
@@ -492,7 +493,6 @@ class DB:
         self.initialize_prefs(default_prefs, restore_all_prefs, progress_callback)
         self.initialize_custom_columns()
         self.initialize_tables()
-        self.initialize_fts()
         self.set_user_template_functions(compile_user_template_functions(
                                  self.prefs.get('user_template_functions', [])))
         if load_user_formatter_functions:
@@ -921,17 +921,18 @@ class DB:
 
     # }}}
 
-    def initialize_fts(self):
+    def initialize_fts(self, dbref):
         self.fts = None
         if not self.prefs['fts_enabled']:
             return
         from .fts.connect import FTS
-        self.fts = FTS(self.get_connection)
+        self.fts = FTS(dbref)
 
-    def enable_fts(self, enabled=True):
+    def enable_fts(self, dbref=None):
+        enabled = dbref is not None
         if enabled != self.prefs['fts_enabled']:
             self.prefs['fts_enabled'] = enabled
-            self.initialize_fts()
+            self.initialize_fts(dbref)
             if self.fts is not None:
                 self.fts.dirty_existing()
         return self.fts

src/calibre/db/cache.py

@@ -11,6 +11,7 @@ import random
 import shutil
 import sys
 import traceback
+import weakref
 from collections import defaultdict
 from collections.abc import MutableSet, Set
 from functools import partial, wraps
@@ -168,6 +169,7 @@ class Cache:
 
         self._search_api = Search(self, 'saved_searches', self.field_metadata.get_search_terms())
         self.initialize_dynamic()
+        self.initialize_fts()
 
     @property
     def new_api(self):
@@ -421,6 +423,14 @@ class Cache:
             self.update_last_modified(self.all_book_ids())
             self.backend.prefs.set('update_all_last_mod_dates_on_start', False)
 
+    # FTS API {{{
+    def initialize_fts(self):
+        self.backend.initialize_fts(weakref.ref(self))
+
+    def enable_fts(self, enabled=True):
+        return self.backend.enable_fts(weakref.ref(self) if enabled else None)
+    # }}}
+
     # Cache Layer API {{{
 
     @write_api

src/calibre/db/fts/connect.py

@@ -11,6 +11,7 @@ from calibre.utils.date import EPOCH, utcnow
 
 from .schema_upgrade import SchemaUpgrade
 
+# TODO: check that closing of db connection works
 # TODO: db dump+restore
 # TODO: calibre export/import
 # TODO: check library and vacuuming of fts db
@@ -23,13 +24,24 @@ def print(*args, **kwargs):
 
 class FTS:
 
-    def __init__(self, get_connection):
-        self.get_connection = get_connection
-        conn = self.get_connection()
+    def __init__(self, dbref):
+        self.dbref = dbref
+
+    def initialize(self, conn):
         main_db_path = os.path.abspath(conn.db_filename('main'))
-        self.dbpath = os.path.join(os.path.dirname(main_db_path), 'full-text-search.db')
-        conn.execute(f'ATTACH DATABASE "{self.dbpath}" AS fts_db')
+        dbpath = os.path.join(os.path.dirname(main_db_path), 'full-text-search.db')
+        conn.execute(f'ATTACH DATABASE "{dbpath}" AS fts_db')
         SchemaUpgrade(conn)
+        conn.fts_dbpath = dbpath
+
+    def get_connection(self):
+        db = self.dbref()
+        if db is None:
+            raise RuntimeError('db has been garbage collected')
+        ans = db.backend.conn
+        if ans.fts_dbpath is None:
+            self.initialize(ans)
+        return ans
 
     def dirty_existing(self):
         conn = self.get_connection()

src/calibre/db/tests/fts_api.py

@@ -30,7 +30,7 @@ class FTSAPITest(BaseTest):
 
     def test_fts_triggers(self):
         cache = self.init_cache()
-        fts = cache.backend.enable_fts()
+        fts = cache.enable_fts()
         self.ae(fts.all_currently_dirty(), [(1, 'FMT1'), (1, 'FMT2'), (2, 'FMT1')])
         fts.dirty_existing()
         self.ae(fts.all_currently_dirty(), [(1, 'FMT1'), (1, 'FMT2'), (2, 'FMT1')])