forked from mirrors/gecko-dev
760cc7e936
- Add missing include directives and forward declarations. - Remove some extra include directives. - Add missing namespace qualifications. - Move include directives out of namespace in toolkit/xre/GlobalSemaphore.h Differential Revision: https://phabricator.services.mozilla.com/D98894
326 lines
11 KiB
C++
326 lines
11 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef MOZSTORAGEHELPER_H
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#define MOZSTORAGEHELPER_H
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#include "nsCOMPtr.h"
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#include "nsString.h"
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#include "mozilla/DebugOnly.h"
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#include "mozilla/ScopeExit.h"
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#include "mozilla/storage/SQLiteMutex.h"
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#include "mozIStorageConnection.h"
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#include "mozIStorageStatement.h"
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#include "mozIStoragePendingStatement.h"
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#include "mozilla/DebugOnly.h"
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#include "nsCOMPtr.h"
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#include "nsError.h"
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/**
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* This class wraps a transaction inside a given C++ scope, guaranteeing that
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* the transaction will be completed even if you have an exception or
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* return early.
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*
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* A common use is to create an instance with aCommitOnComplete = false
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* (rollback), then call Commit() on this object manually when your function
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* completes successfully.
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*
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* @note nested transactions are not supported by Sqlite, only nested
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* savepoints, so if a transaction is already in progress, this object creates
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* a nested savepoint to the existing transaction which is considered as
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* anonymous savepoint itself. However, aType and aAsyncCommit are ignored
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* in the case of nested savepoints.
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*
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* @param aConnection
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* The connection to create the transaction on.
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* @param aCommitOnComplete
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* Controls whether the transaction is committed or rolled back when
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* this object goes out of scope.
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* @param aType [optional]
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* The transaction type, as defined in mozIStorageConnection. Uses the
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* default transaction behavior for the connection if unspecified.
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* @param aAsyncCommit [optional]
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* Whether commit should be executed asynchronously on the helper thread.
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* This is a special option introduced as an interim solution to reduce
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* main-thread fsyncs in Places. Can only be used on main-thread.
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*
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* WARNING: YOU SHOULD _NOT_ WRITE NEW MAIN-THREAD CODE USING THIS!
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*
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* Notice that async commit might cause synchronous statements to fail
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* with SQLITE_BUSY. A possible mitigation strategy is to use
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* PRAGMA busy_timeout, but notice that might cause main-thread jank.
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* Finally, if the database is using WAL journaling mode, other
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* connections won't see the changes done in async committed transactions
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* until commit is complete.
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*
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* For all of the above reasons, this should only be used as an interim
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* solution and avoided completely if possible.
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*/
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class mozStorageTransaction {
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using SQLiteMutexAutoLock = mozilla::storage::SQLiteMutexAutoLock;
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public:
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mozStorageTransaction(
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mozIStorageConnection* aConnection, bool aCommitOnComplete,
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int32_t aType = mozIStorageConnection::TRANSACTION_DEFAULT,
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bool aAsyncCommit = false)
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: mConnection(aConnection),
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mType(aType),
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mNestingLevel(0),
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mHasTransaction(false),
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mCommitOnComplete(aCommitOnComplete),
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mCompleted(false),
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mAsyncCommit(aAsyncCommit) {}
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~mozStorageTransaction() {
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if (mConnection && mHasTransaction && !mCompleted) {
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if (mCommitOnComplete) {
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mozilla::DebugOnly<nsresult> rv = Commit();
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NS_WARNING_ASSERTION(NS_SUCCEEDED(rv),
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"A transaction didn't commit correctly");
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} else {
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mozilla::DebugOnly<nsresult> rv = Rollback();
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NS_WARNING_ASSERTION(NS_SUCCEEDED(rv),
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"A transaction didn't rollback correctly");
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}
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}
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}
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/**
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* Starts the transaction.
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*/
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nsresult Start() {
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// XXX We should probably get rid of mHasTransaction and use mConnection
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// for checking if a transaction has been started. However, we need to
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// first stop supporting null mConnection and also move aConnection from
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// the constructor to Start.
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MOZ_DIAGNOSTIC_ASSERT(!mHasTransaction);
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// XXX We should probably stop supporting null mConnection.
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// XXX We should probably get rid of mCompleted and allow to start the
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// transaction again if it was already committed or rolled back.
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if (!mConnection || mCompleted) {
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return NS_OK;
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}
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SQLiteMutexAutoLock lock(mConnection->GetSharedDBMutex());
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// We nee to speculatively set the nesting level to be able to decide
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// if this is a top level transaction and to be able to generate the
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// savepoint name.
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TransactionStarted(lock);
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// If there's a failure we need to revert the speculatively set nesting
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// level on the connection.
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auto autoFinishTransaction =
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mozilla::MakeScopeExit([&] { TransactionFinished(lock); });
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nsAutoCString query;
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if (TopLevelTransaction(lock)) {
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query.Assign("BEGIN");
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int32_t type = mType;
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if (type == mozIStorageConnection::TRANSACTION_DEFAULT) {
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MOZ_ALWAYS_SUCCEEDS(mConnection->GetDefaultTransactionType(&type));
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}
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switch (type) {
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case mozIStorageConnection::TRANSACTION_IMMEDIATE:
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query.AppendLiteral(" IMMEDIATE");
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break;
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case mozIStorageConnection::TRANSACTION_EXCLUSIVE:
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query.AppendLiteral(" EXCLUSIVE");
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break;
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case mozIStorageConnection::TRANSACTION_DEFERRED:
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query.AppendLiteral(" DEFERRED");
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break;
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default:
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MOZ_ASSERT(false, "Unknown transaction type");
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}
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} else {
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query.Assign("SAVEPOINT sp"_ns + IntToCString(mNestingLevel));
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}
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nsresult rv = mConnection->ExecuteSimpleSQL(query);
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NS_ENSURE_SUCCESS(rv, rv);
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autoFinishTransaction.release();
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return NS_OK;
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}
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/**
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* Commits the transaction if one is in progress. If one is not in progress,
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* this is a NOP since the actual owner of the transaction outside of our
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* scope is in charge of finally committing or rolling back the transaction.
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*/
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nsresult Commit() {
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// XXX Assert instead of returning NS_OK if the transaction hasn't been
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// started.
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if (!mConnection || mCompleted || !mHasTransaction) return NS_OK;
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SQLiteMutexAutoLock lock(mConnection->GetSharedDBMutex());
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#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
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MOZ_DIAGNOSTIC_ASSERT(CurrentTransaction(lock));
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#else
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if (!CurrentTransaction(lock)) {
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return NS_ERROR_NOT_AVAILABLE;
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}
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#endif
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mCompleted = true;
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nsresult rv;
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if (TopLevelTransaction(lock)) {
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// TODO (bug 559659): this might fail with SQLITE_BUSY, but we don't
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// handle it, thus the transaction might stay open until the next COMMIT.
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if (mAsyncCommit) {
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nsCOMPtr<mozIStoragePendingStatement> ps;
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rv = mConnection->ExecuteSimpleSQLAsync("COMMIT"_ns, nullptr,
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getter_AddRefs(ps));
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} else {
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rv = mConnection->ExecuteSimpleSQL("COMMIT"_ns);
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}
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} else {
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rv = mConnection->ExecuteSimpleSQL("RELEASE sp"_ns +
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IntToCString(mNestingLevel));
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}
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NS_ENSURE_SUCCESS(rv, rv);
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TransactionFinished(lock);
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return NS_OK;
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}
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/**
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* Rolls back the transaction if one is in progress. If one is not in
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* progress, this is a NOP since the actual owner of the transaction outside
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* of our scope is in charge of finally rolling back the transaction.
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*/
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nsresult Rollback() {
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// XXX Assert instead of returning NS_OK if the transaction hasn't been
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// started.
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if (!mConnection || mCompleted || !mHasTransaction) return NS_OK;
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SQLiteMutexAutoLock lock(mConnection->GetSharedDBMutex());
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#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
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MOZ_DIAGNOSTIC_ASSERT(CurrentTransaction(lock));
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#else
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if (!CurrentTransaction(lock)) {
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return NS_ERROR_NOT_AVAILABLE;
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}
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#endif
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mCompleted = true;
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nsresult rv;
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if (TopLevelTransaction(lock)) {
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// TODO (bug 1062823): from Sqlite 3.7.11 on, rollback won't ever return
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// a busy error, so this handling can be removed.
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do {
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rv = mConnection->ExecuteSimpleSQL("ROLLBACK"_ns);
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if (rv == NS_ERROR_STORAGE_BUSY) (void)PR_Sleep(PR_INTERVAL_NO_WAIT);
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} while (rv == NS_ERROR_STORAGE_BUSY);
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} else {
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const auto nestingLevelCString = IntToCString(mNestingLevel);
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rv = mConnection->ExecuteSimpleSQL(
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"ROLLBACK TO sp"_ns + nestingLevelCString + "; RELEASE sp"_ns +
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nestingLevelCString);
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}
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NS_ENSURE_SUCCESS(rv, rv);
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TransactionFinished(lock);
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return NS_OK;
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}
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protected:
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void TransactionStarted(const SQLiteMutexAutoLock& aProofOfLock) {
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MOZ_ASSERT(mConnection);
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MOZ_ASSERT(!mHasTransaction);
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MOZ_ASSERT(mNestingLevel == 0);
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mHasTransaction = true;
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mNestingLevel = mConnection->IncreaseTransactionNestingLevel(aProofOfLock);
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}
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bool CurrentTransaction(const SQLiteMutexAutoLock& aProofOfLock) const {
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MOZ_ASSERT(mConnection);
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MOZ_ASSERT(mHasTransaction);
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MOZ_ASSERT(mNestingLevel > 0);
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return mNestingLevel ==
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mConnection->GetTransactionNestingLevel(aProofOfLock);
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}
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bool TopLevelTransaction(const SQLiteMutexAutoLock& aProofOfLock) const {
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MOZ_ASSERT(mConnection);
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MOZ_ASSERT(mHasTransaction);
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MOZ_ASSERT(mNestingLevel > 0);
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MOZ_ASSERT(CurrentTransaction(aProofOfLock));
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return mNestingLevel == 1;
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}
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void TransactionFinished(const SQLiteMutexAutoLock& aProofOfLock) {
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MOZ_ASSERT(mConnection);
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MOZ_ASSERT(mHasTransaction);
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MOZ_ASSERT(mNestingLevel > 0);
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MOZ_ASSERT(CurrentTransaction(aProofOfLock));
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mConnection->DecreaseTransactionNestingLevel(aProofOfLock);
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mNestingLevel = 0;
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mHasTransaction = false;
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}
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nsCOMPtr<mozIStorageConnection> mConnection;
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int32_t mType;
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uint32_t mNestingLevel;
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bool mHasTransaction;
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bool mCommitOnComplete;
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bool mCompleted;
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bool mAsyncCommit;
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};
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/**
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* This class wraps a statement so that it is guaraneed to be reset when
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* this object goes out of scope.
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*
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* Note that this always just resets the statement. If the statement doesn't
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* need resetting, the reset operation is inexpensive.
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*/
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class MOZ_STACK_CLASS mozStorageStatementScoper {
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public:
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explicit mozStorageStatementScoper(mozIStorageStatement* aStatement)
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: mStatement(aStatement) {}
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~mozStorageStatementScoper() {
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if (mStatement) mStatement->Reset();
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}
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mozStorageStatementScoper(mozStorageStatementScoper&&) = default;
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mozStorageStatementScoper& operator=(mozStorageStatementScoper&&) = default;
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mozStorageStatementScoper(const mozStorageStatementScoper&) = delete;
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mozStorageStatementScoper& operator=(const mozStorageStatementScoper&) =
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delete;
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/**
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* Call this to make the statement not reset. You might do this if you know
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* that the statement has been reset.
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*/
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void Abandon() { mStatement = nullptr; }
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protected:
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nsCOMPtr<mozIStorageStatement> mStatement;
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};
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// Use this to make queries uniquely identifiable in telemetry
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// statistics, especially PRAGMAs. We don't include __LINE__ so that
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// queries are stable in the face of source code changes.
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#define MOZ_STORAGE_UNIQUIFY_QUERY_STR "/* " __FILE__ " */ "
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#endif /* MOZSTORAGEHELPER_H */
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