From 6bf0a5cb5034a7e684dcc3500e841785237ce2dd Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 19:32:43 +0200 Subject: Adding upstream version 1:115.7.0. Signed-off-by: Daniel Baumann --- storage/mozStorageHelper.h | 326 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 326 insertions(+) create mode 100644 storage/mozStorageHelper.h (limited to 'storage/mozStorageHelper.h') diff --git a/storage/mozStorageHelper.h b/storage/mozStorageHelper.h new file mode 100644 index 0000000000..35ee54faa3 --- /dev/null +++ b/storage/mozStorageHelper.h @@ -0,0 +1,326 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef MOZSTORAGEHELPER_H +#define MOZSTORAGEHELPER_H + +#include "nsCOMPtr.h" +#include "nsString.h" +#include "mozilla/DebugOnly.h" +#include "mozilla/ScopeExit.h" + +#include "mozilla/storage/SQLiteMutex.h" +#include "mozIStorageConnection.h" +#include "mozIStorageStatement.h" +#include "mozIStoragePendingStatement.h" +#include "mozilla/DebugOnly.h" +#include "nsCOMPtr.h" +#include "nsError.h" + +/** + * This class wraps a transaction inside a given C++ scope, guaranteeing that + * the transaction will be completed even if you have an exception or + * return early. + * + * A common use is to create an instance with aCommitOnComplete = false + * (rollback), then call Commit() on this object manually when your function + * completes successfully. + * + * @note nested transactions are not supported by Sqlite, only nested + * savepoints, so if a transaction is already in progress, this object creates + * a nested savepoint to the existing transaction which is considered as + * anonymous savepoint itself. However, aType and aAsyncCommit are ignored + * in the case of nested savepoints. + * + * @param aConnection + * The connection to create the transaction on. + * @param aCommitOnComplete + * Controls whether the transaction is committed or rolled back when + * this object goes out of scope. + * @param aType [optional] + * The transaction type, as defined in mozIStorageConnection. Uses the + * default transaction behavior for the connection if unspecified. + * @param aAsyncCommit [optional] + * Whether commit should be executed asynchronously on the helper thread. + * This is a special option introduced as an interim solution to reduce + * main-thread fsyncs in Places. Can only be used on main-thread. + * + * WARNING: YOU SHOULD _NOT_ WRITE NEW MAIN-THREAD CODE USING THIS! + * + * Notice that async commit might cause synchronous statements to fail + * with SQLITE_BUSY. A possible mitigation strategy is to use + * PRAGMA busy_timeout, but notice that might cause main-thread jank. + * Finally, if the database is using WAL journaling mode, other + * connections won't see the changes done in async committed transactions + * until commit is complete. + * + * For all of the above reasons, this should only be used as an interim + * solution and avoided completely if possible. + */ +class mozStorageTransaction { + using SQLiteMutexAutoLock = mozilla::storage::SQLiteMutexAutoLock; + + public: + mozStorageTransaction( + mozIStorageConnection* aConnection, bool aCommitOnComplete, + int32_t aType = mozIStorageConnection::TRANSACTION_DEFAULT, + bool aAsyncCommit = false) + : mConnection(aConnection), + mType(aType), + mNestingLevel(0), + mHasTransaction(false), + mCommitOnComplete(aCommitOnComplete), + mCompleted(false), + mAsyncCommit(aAsyncCommit) {} + + ~mozStorageTransaction() { + if (mConnection && mHasTransaction && !mCompleted) { + if (mCommitOnComplete) { + mozilla::DebugOnly rv = Commit(); + NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), + "A transaction didn't commit correctly"); + } else { + mozilla::DebugOnly rv = Rollback(); + NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), + "A transaction didn't rollback correctly"); + } + } + } + + /** + * Starts the transaction. + */ + nsresult Start() { + // XXX We should probably get rid of mHasTransaction and use mConnection + // for checking if a transaction has been started. However, we need to + // first stop supporting null mConnection and also move aConnection from + // the constructor to Start. + MOZ_DIAGNOSTIC_ASSERT(!mHasTransaction); + + // XXX We should probably stop supporting null mConnection. + + // XXX We should probably get rid of mCompleted and allow to start the + // transaction again if it was already committed or rolled back. + if (!mConnection || mCompleted) { + return NS_OK; + } + + SQLiteMutexAutoLock lock(mConnection->GetSharedDBMutex()); + + // We nee to speculatively set the nesting level to be able to decide + // if this is a top level transaction and to be able to generate the + // savepoint name. + TransactionStarted(lock); + + // If there's a failure we need to revert the speculatively set nesting + // level on the connection. + auto autoFinishTransaction = + mozilla::MakeScopeExit([&] { TransactionFinished(lock); }); + + nsAutoCString query; + + if (TopLevelTransaction(lock)) { + query.Assign("BEGIN"); + int32_t type = mType; + if (type == mozIStorageConnection::TRANSACTION_DEFAULT) { + MOZ_ALWAYS_SUCCEEDS(mConnection->GetDefaultTransactionType(&type)); + } + switch (type) { + case mozIStorageConnection::TRANSACTION_IMMEDIATE: + query.AppendLiteral(" IMMEDIATE"); + break; + case mozIStorageConnection::TRANSACTION_EXCLUSIVE: + query.AppendLiteral(" EXCLUSIVE"); + break; + case mozIStorageConnection::TRANSACTION_DEFERRED: + query.AppendLiteral(" DEFERRED"); + break; + default: + MOZ_ASSERT(false, "Unknown transaction type"); + } + } else { + query.Assign("SAVEPOINT sp"_ns + IntToCString(mNestingLevel)); + } + + nsresult rv = mConnection->ExecuteSimpleSQL(query); + NS_ENSURE_SUCCESS(rv, rv); + + autoFinishTransaction.release(); + + return NS_OK; + } + + /** + * Commits the transaction if one is in progress. If one is not in progress, + * this is a NOP since the actual owner of the transaction outside of our + * scope is in charge of finally committing or rolling back the transaction. + */ + nsresult Commit() { + // XXX Assert instead of returning NS_OK if the transaction hasn't been + // started. + if (!mConnection || mCompleted || !mHasTransaction) return NS_OK; + + SQLiteMutexAutoLock lock(mConnection->GetSharedDBMutex()); + +#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED + MOZ_DIAGNOSTIC_ASSERT(CurrentTransaction(lock)); +#else + if (!CurrentTransaction(lock)) { + return NS_ERROR_NOT_AVAILABLE; + } +#endif + + mCompleted = true; + + nsresult rv; + + if (TopLevelTransaction(lock)) { + // TODO (bug 559659): this might fail with SQLITE_BUSY, but we don't + // handle it, thus the transaction might stay open until the next COMMIT. + if (mAsyncCommit) { + nsCOMPtr ps; + rv = mConnection->ExecuteSimpleSQLAsync("COMMIT"_ns, nullptr, + getter_AddRefs(ps)); + } else { + rv = mConnection->ExecuteSimpleSQL("COMMIT"_ns); + } + } else { + rv = mConnection->ExecuteSimpleSQL("RELEASE sp"_ns + + IntToCString(mNestingLevel)); + } + + NS_ENSURE_SUCCESS(rv, rv); + + TransactionFinished(lock); + + return NS_OK; + } + + /** + * Rolls back the transaction if one is in progress. If one is not in + * progress, this is a NOP since the actual owner of the transaction outside + * of our scope is in charge of finally rolling back the transaction. + */ + nsresult Rollback() { + // XXX Assert instead of returning NS_OK if the transaction hasn't been + // started. + if (!mConnection || mCompleted || !mHasTransaction) return NS_OK; + + SQLiteMutexAutoLock lock(mConnection->GetSharedDBMutex()); + +#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED + MOZ_DIAGNOSTIC_ASSERT(CurrentTransaction(lock)); +#else + if (!CurrentTransaction(lock)) { + return NS_ERROR_NOT_AVAILABLE; + } +#endif + + mCompleted = true; + + nsresult rv; + + if (TopLevelTransaction(lock)) { + // TODO (bug 1062823): from Sqlite 3.7.11 on, rollback won't ever return + // a busy error, so this handling can be removed. + do { + rv = mConnection->ExecuteSimpleSQL("ROLLBACK"_ns); + if (rv == NS_ERROR_STORAGE_BUSY) (void)PR_Sleep(PR_INTERVAL_NO_WAIT); + } while (rv == NS_ERROR_STORAGE_BUSY); + } else { + const auto nestingLevelCString = IntToCString(mNestingLevel); + rv = mConnection->ExecuteSimpleSQL( + "ROLLBACK TO sp"_ns + nestingLevelCString + "; RELEASE sp"_ns + + nestingLevelCString); + } + + NS_ENSURE_SUCCESS(rv, rv); + + TransactionFinished(lock); + + return NS_OK; + } + + protected: + void TransactionStarted(const SQLiteMutexAutoLock& aProofOfLock) { + MOZ_ASSERT(mConnection); + MOZ_ASSERT(!mHasTransaction); + MOZ_ASSERT(mNestingLevel == 0); + mHasTransaction = true; + mNestingLevel = mConnection->IncreaseTransactionNestingLevel(aProofOfLock); + } + + bool CurrentTransaction(const SQLiteMutexAutoLock& aProofOfLock) const { + MOZ_ASSERT(mConnection); + MOZ_ASSERT(mHasTransaction); + MOZ_ASSERT(mNestingLevel > 0); + return mNestingLevel == + mConnection->GetTransactionNestingLevel(aProofOfLock); + } + + bool TopLevelTransaction(const SQLiteMutexAutoLock& aProofOfLock) const { + MOZ_ASSERT(mConnection); + MOZ_ASSERT(mHasTransaction); + MOZ_ASSERT(mNestingLevel > 0); + MOZ_ASSERT(CurrentTransaction(aProofOfLock)); + return mNestingLevel == 1; + } + + void TransactionFinished(const SQLiteMutexAutoLock& aProofOfLock) { + MOZ_ASSERT(mConnection); + MOZ_ASSERT(mHasTransaction); + MOZ_ASSERT(mNestingLevel > 0); + MOZ_ASSERT(CurrentTransaction(aProofOfLock)); + mConnection->DecreaseTransactionNestingLevel(aProofOfLock); + mNestingLevel = 0; + mHasTransaction = false; + } + + nsCOMPtr mConnection; + int32_t mType; + uint32_t mNestingLevel; + bool mHasTransaction; + bool mCommitOnComplete; + bool mCompleted; + bool mAsyncCommit; +}; + +/** + * This class wraps a statement so that it is guaraneed to be reset when + * this object goes out of scope. + * + * Note that this always just resets the statement. If the statement doesn't + * need resetting, the reset operation is inexpensive. + */ +class MOZ_STACK_CLASS mozStorageStatementScoper { + public: + explicit mozStorageStatementScoper(mozIStorageStatement* aStatement) + : mStatement(aStatement) {} + ~mozStorageStatementScoper() { + if (mStatement) mStatement->Reset(); + } + + mozStorageStatementScoper(mozStorageStatementScoper&&) = default; + mozStorageStatementScoper& operator=(mozStorageStatementScoper&&) = default; + mozStorageStatementScoper(const mozStorageStatementScoper&) = delete; + mozStorageStatementScoper& operator=(const mozStorageStatementScoper&) = + delete; + + /** + * Call this to make the statement not reset. You might do this if you know + * that the statement has been reset. + */ + void Abandon() { mStatement = nullptr; } + + protected: + nsCOMPtr mStatement; +}; + +// Use this to make queries uniquely identifiable in telemetry +// statistics, especially PRAGMAs. We don't include __LINE__ so that +// queries are stable in the face of source code changes. +#define MOZ_STORAGE_UNIQUIFY_QUERY_STR "/* " __FILE__ " */ " + +#endif /* MOZSTORAGEHELPER_H */ -- cgit v1.2.3