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Every QElectroTech on a computer shares elements_cache.sqlite. The cache set PRAGMA locking_mode = EXCLUSIVE, so a QElectroTech that had read the file once kept it locked until it closed. A second one -- a build in another folder, or a build beside a released version, which SingleApplication lets run because its key includes the program's path and version -- could not write to it: each write waited SQLite's 5 s busy timeout and failed, on the GUI thread, twice for every symbol the collection showed. The report's log is exactly that: an empty QSqlError every 5.0 s for three minutes. Use SQLite's normal locking, which holds a lock only while a statement runs, and give this connection no busy timeout: the cache only saves time, so a busy file is a cache miss, never a wait. Print the failing query's error, not the connection's, which was always empty. Measured with the real program running and a second process writing to its cache: before, the write fails "database is locked" after 5.01 s; after, it succeeds in 0.02 s. tst_elementcachelock opens two caches on one file; it fails before the fix with the report's empty QSqlError. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
50 lines
1.8 KiB
C++
50 lines
1.8 KiB
C++
// SPDX-License-Identifier: GPL-2.0-or-later
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#include <QtTest>
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#include <QElapsedTimer>
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#include <QTemporaryDir>
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#include <QUuid>
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#include "elementscollectioncache.h"
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// Every QElectroTech on a computer shares one elements_cache.sqlite. The cache
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// used PRAGMA locking_mode = EXCLUSIVE, so a QElectroTech that had once read
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// the file kept it locked until it closed, and every write from a second one
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// waited SQLite's 5 s busy timeout and failed -- on the GUI thread, twice per
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// symbol shown in the collection (#1571). Two caches on the same file in one
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// process lock each other exactly as two processes do.
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class tst_elementcachelock : public QObject
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{
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Q_OBJECT
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QTemporaryDir m_dir;
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const QUuid m_uuid = QUuid::createUuid();
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private slots:
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void secondCacheWritesWithoutWaiting()
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{
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QVERIFY(m_dir.isValid());
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const QString path = m_dir.filePath(QStringLiteral("elements_cache.sqlite"));
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ElementsCollectionCache first(path);
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QVERIFY(first.cacheName(QStringLiteral("embed://a.elmt"), m_uuid));
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QVERIFY(first.fetchNameFromCache(QStringLiteral("embed://a.elmt"), m_uuid));
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QVERIFY(!first.fetchNameFromCache(QStringLiteral("embed://missing.elmt"), m_uuid));
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ElementsCollectionCache second(path);
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QElapsedTimer timer;
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timer.start();
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QVERIFY(second.cacheName(QStringLiteral("embed://b.elmt"), m_uuid));
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QVERIFY(second.cachePixmap(QStringLiteral("embed://b.elmt"), m_uuid));
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QVERIFY2(timer.elapsed() < 1000, qPrintable(QString::number(timer.elapsed()) + " ms"));
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// and each one sees what the other wrote
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QVERIFY(second.fetchNameFromCache(QStringLiteral("embed://a.elmt"), m_uuid));
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QVERIFY(first.fetchNameFromCache(QStringLiteral("embed://b.elmt"), m_uuid));
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QVERIFY(first.cacheName(QStringLiteral("embed://c.elmt"), m_uuid));
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}
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};
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QTEST_MAIN(tst_elementcachelock)
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#include "tst_elementcachelock.moc"
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