Use a fast/slow indexing control since fast indexing is only appropriate when scanning a backlog

src/calibre/db/cache.py

@@ -17,9 +17,9 @@ from collections import defaultdict
 from collections.abc import MutableSet, Set
 from functools import partial, wraps
 from io import DEFAULT_BUFFER_SIZE, BytesIO
-from threading import Lock
-from time import time
 from queue import Queue
+from threading import Lock
+from time import sleep, time
 
 from calibre import as_unicode, isbytestring
 from calibre.constants import iswindows, preferred_encoding
@@ -138,6 +138,7 @@ class Cache:
     was necessary for maximum performance and flexibility.
     '''
     EventType = EventType
+    fts_indexing_sleep_time = 4  # seconds
 
     def __init__(self, backend):
         self.shutting_down = False
@@ -512,6 +513,7 @@ class Cache:
                     if self.backend.fts_enabled:
                         import traceback
                         traceback.print_exc()
+                sleep(self.fts_indexing_sleep_time)
 
         while not getattr(dbref(), 'shutting_down', True):
             x = queue.get()

src/calibre/db/fts/pool.py

@@ -13,7 +13,6 @@ from threading import Event, Thread
 from time import monotonic
 
 from calibre import detect_ncpus, human_readable
-from calibre.utils.config import dynamic
 from calibre.utils.ipc.simple_worker import start_pipe_worker
 
 check_for_work = object()
@@ -117,13 +116,8 @@ class Worker(Thread):
 
 class Pool:
 
-    MAX_WORKERS_PREF_NAME = 'fts_pool_max_workers'
-
     def __init__(self, dbref):
-        try:
-            self.max_workers = min(max(1, int(dynamic.get(self.MAX_WORKERS_PREF_NAME, 1))), detect_ncpus())
-        except Exception:
-            self.max_workers = 1
+        self.max_workers = 1
         self.jobs_queue = Queue()
         self.supervise_queue = Queue()
         self.workers = []
@@ -170,7 +164,6 @@ class Pool:
         num = min(max(1, num), detect_ncpus())
         if num != self.max_workers:
             self.max_workers = num
-            dynamic.set(self.MAX_WORKERS_PREF_NAME, num)
             if num > len(self.workers):
                 self.expand_workers()
             elif num < len(self.workers):

src/calibre/db/tests/fts_api.py

@@ -26,9 +26,9 @@ class FTSAPITest(BaseTest):
     def setUp(self):
         super().setUp()
         from calibre_extensions.sqlite_extension import set_ui_language
-        from calibre.db.fts.pool import Pool
-        self.orig_pw_pref_name = Pool.MAX_WORKERS_PREF_NAME
-        Pool.MAX_WORKERS_PREF_NAME = 'test_fts_max_workers'
+        from calibre.db.cache import Cache
+        self.orig_sleep_time = Cache.fts_indexing_sleep_time
+        Cache.fts_indexing_sleep_time = 0
         set_ui_language('en')
         self.libraries_to_close = []
 
@@ -36,8 +36,8 @@ class FTSAPITest(BaseTest):
         [c.close() for c in self.libraries_to_close]
         super().tearDown()
         from calibre_extensions.sqlite_extension import set_ui_language
-        from calibre.db.fts.pool import Pool
-        Pool.MAX_WORKERS_PREF_NAME = self.orig_pw_pref_name
+        from calibre.db.cache import Cache
+        Cache.fts_indexing_sleep_time = self.orig_sleep_time
         set_ui_language('en')
 
     def new_library(self):

src/calibre/gui2/fts/scan.py

@@ -4,14 +4,14 @@
 
 import os
 from qt.core import (
-    QCheckBox, QDialog, QHBoxLayout, QLabel, QSpinBox, QTimer, QVBoxLayout, QWidget
+    QCheckBox, QDialog, QHBoxLayout, QLabel, QRadioButton, QTimer, QVBoxLayout,
+    QWidget
 )
 
 from calibre import detect_ncpus
-from calibre.db.fts.pool import Pool
+from calibre.db.cache import Cache
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.fts.utils import get_db
-from calibre.utils.config import dynamic
 
 
 class IndexingProgress:
@@ -35,29 +35,28 @@ class ScanProgress(QWidget):
         l.addWidget(la)
         self.h = h = QHBoxLayout()
         l.addLayout(h)
-        self.niwl = la = QLabel(_('Number of workers used for indexing:'))
-        h.addWidget(la)
-        self.num_of_workers = n = QSpinBox(self)
-        n.setMinimum(1)
-        n.setMaximum(detect_ncpus())
-        self.debounce_timer = t = QTimer(self)
-        t.setInterval(750)
-        t.timeout.connect(self.change_num_of_workers)
-        t.setSingleShot(True)
-        n.valueChanged.connect(self.schedule_change_num_of_workers)
-        try:
-            c = min(max(1, int(dynamic.get(Pool.MAX_WORKERS_PREF_NAME, 1))), n.maximum())
-        except Exception:
-            c = 1
-        n.setValue(c)
-        h.addWidget(n), h.addStretch(10)
         self.wl = la = QLabel(_(
-            'Increasing the number of workers used for indexing will'
-            ' speed up indexing at the cost of using more of the computer\'s resources.'
-            ' Changes will take a few seconds to take effect.'
+            'Normally, calibre indexes books slowly in the background,'
+            ' to avoid overloading your computer. You can instead ask'
+            ' calibre to speed up indexing, if you intend to leave your'
+            ' computer running overnight or similar to quickly finish the indexing.'
+            ' Doing so will likely make both calibre and your computer less responsive,'
+            ' while the fast indexing is running.'
         ))
         la.setWordWrap(True)
         l.addWidget(la)
+        self.h = h = QHBoxLayout()
+        l.addLayout(h)
+        h.addWidget(QLabel(_('Indexing speed:')))
+        self.slow_button = sb = QRadioButton(_('&Slow'), self)
+        sb.setChecked(True)
+        h.addWidget(sb)
+        self.fast_button = fb = QRadioButton(_('&Fast'), self)
+        h.addWidget(fb)
+        fb.toggled.connect(self.change_speed)
+        h.addStretch(10)
+
+        l.addStretch(10)
         self.warn_label = la = QLabel('<p><span style="color: red">{}</span>: {}'.format(
             _('WARNING'), _(
                 'Not all the books in this library have been indexed yet.'
@@ -65,12 +64,14 @@ class ScanProgress(QWidget):
         la.setWordWrap(True)
         l.addWidget(la)
 
-    def schedule_change_num_of_workers(self):
-        self.debounce_timer.stop()
-        self.debounce_timer.start()
-
-    def change_num_of_workers(self):
-        get_db().set_fts_num_of_workers(self.num_of_workers.value())
+    def change_speed(self):
+        db = get_db()
+        if self.fast_button.isChecked():
+            db.fts_indexing_sleep_time = 0.1
+            db.set_fts_num_of_workers(max(1, detect_ncpus()))
+        else:
+            db.fts_indexing_sleep_time = Cache.fts_indexing_sleep_time
+            db.set_fts_num_of_workers(1)
 
     def update(self, indexing_progress):
         if indexing_progress.complete:
@@ -141,6 +142,7 @@ class ScanStatus(QWidget):
 
     def shutdown(self):
         self.indexing_status_timer.stop()
+        self.scan_progress.slow_button.setChecked(True)
 
 
 if __name__ == '__main__':