storage/mozStorageConnection.cpp
author Bevis Tseng <btseng@mozilla.com>
Wed, 14 Jun 2017 09:27:17 +0800
changeset 364864 89963ba78c353b23feab0042ebe264049f8d4533
parent 355034 815a951139819fe85a86c994990b2be917199500
child 364866 9846de3bd9545fb2c2b803a36af85568ccf2473b
permissions -rw-r--r--
Bug 1372453 - Part 2: Name the caller of ProxyReleaseEvent. r=billm MozReview-Commit-ID: LYhSWnZkq0i

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * 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/. */

#include <stdio.h>

#include "nsError.h"
#include "nsIMutableArray.h"
#include "nsAutoPtr.h"
#include "nsIMemoryReporter.h"
#include "nsThreadUtils.h"
#include "nsIFile.h"
#include "nsIFileURL.h"
#include "mozilla/Telemetry.h"
#include "mozilla/Mutex.h"
#include "mozilla/CondVar.h"
#include "mozilla/Attributes.h"
#include "mozilla/ErrorNames.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/quota/QuotaObject.h"

#include "mozIStorageAggregateFunction.h"
#include "mozIStorageCompletionCallback.h"
#include "mozIStorageFunction.h"

#include "mozStorageAsyncStatementExecution.h"
#include "mozStorageSQLFunctions.h"
#include "mozStorageConnection.h"
#include "mozStorageService.h"
#include "mozStorageStatement.h"
#include "mozStorageAsyncStatement.h"
#include "mozStorageArgValueArray.h"
#include "mozStoragePrivateHelpers.h"
#include "mozStorageStatementData.h"
#include "StorageBaseStatementInternal.h"
#include "SQLCollations.h"
#include "FileSystemModule.h"
#include "mozStorageHelper.h"
#include "GeckoProfiler.h"

#include "mozilla/Logging.h"
#include "mozilla/Printf.h"
#include "nsProxyRelease.h"
#include <algorithm>

#define MIN_AVAILABLE_BYTES_PER_CHUNKED_GROWTH 524288000 // 500 MiB

// Maximum size of the pages cache per connection.
#define MAX_CACHE_SIZE_KIBIBYTES 2048 // 2 MiB

mozilla::LazyLogModule gStorageLog("mozStorage");

// Checks that the protected code is running on the main-thread only if the
// connection was also opened on it.
#ifdef DEBUG
#define CHECK_MAINTHREAD_ABUSE() \
  do { \
    nsCOMPtr<nsIThread> mainThread = do_GetMainThread(); \
    NS_WARNING_ASSERTION( \
      threadOpenedOn == mainThread || !NS_IsMainThread(), \
      "Using Storage synchronous API on main-thread, but the connection was " \
      "opened on another thread."); \
  } while(0)
#else
#define CHECK_MAINTHREAD_ABUSE() do { /* Nothing */ } while(0)
#endif

namespace mozilla {
namespace storage {

using mozilla::dom::quota::QuotaObject;

namespace {

int
nsresultToSQLiteResult(nsresult aXPCOMResultCode)
{
  if (NS_SUCCEEDED(aXPCOMResultCode)) {
    return SQLITE_OK;
  }

  switch (aXPCOMResultCode) {
    case NS_ERROR_FILE_CORRUPTED:
      return SQLITE_CORRUPT;
    case NS_ERROR_FILE_ACCESS_DENIED:
      return SQLITE_CANTOPEN;
    case NS_ERROR_STORAGE_BUSY:
      return SQLITE_BUSY;
    case NS_ERROR_FILE_IS_LOCKED:
      return SQLITE_LOCKED;
    case NS_ERROR_FILE_READ_ONLY:
      return SQLITE_READONLY;
    case NS_ERROR_STORAGE_IOERR:
      return SQLITE_IOERR;
    case NS_ERROR_FILE_NO_DEVICE_SPACE:
      return SQLITE_FULL;
    case NS_ERROR_OUT_OF_MEMORY:
      return SQLITE_NOMEM;
    case NS_ERROR_UNEXPECTED:
      return SQLITE_MISUSE;
    case NS_ERROR_ABORT:
      return SQLITE_ABORT;
    case NS_ERROR_STORAGE_CONSTRAINT:
      return SQLITE_CONSTRAINT;
    default:
      return SQLITE_ERROR;
  }

  MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Must return in switch above!");
}

////////////////////////////////////////////////////////////////////////////////
//// Variant Specialization Functions (variantToSQLiteT)

int
sqlite3_T_int(sqlite3_context *aCtx,
              int aValue)
{
  ::sqlite3_result_int(aCtx, aValue);
  return SQLITE_OK;
}

int
sqlite3_T_int64(sqlite3_context *aCtx,
                sqlite3_int64 aValue)
{
  ::sqlite3_result_int64(aCtx, aValue);
  return SQLITE_OK;
}

int
sqlite3_T_double(sqlite3_context *aCtx,
                 double aValue)
{
  ::sqlite3_result_double(aCtx, aValue);
  return SQLITE_OK;
}

int
sqlite3_T_text(sqlite3_context *aCtx,
               const nsCString &aValue)
{
  ::sqlite3_result_text(aCtx,
                        aValue.get(),
                        aValue.Length(),
                        SQLITE_TRANSIENT);
  return SQLITE_OK;
}

int
sqlite3_T_text16(sqlite3_context *aCtx,
                 const nsString &aValue)
{
  ::sqlite3_result_text16(aCtx,
                          aValue.get(),
                          aValue.Length() * 2, // Number of bytes.
                          SQLITE_TRANSIENT);
  return SQLITE_OK;
}

int
sqlite3_T_null(sqlite3_context *aCtx)
{
  ::sqlite3_result_null(aCtx);
  return SQLITE_OK;
}

int
sqlite3_T_blob(sqlite3_context *aCtx,
               const void *aData,
               int aSize)
{
  ::sqlite3_result_blob(aCtx, aData, aSize, free);
  return SQLITE_OK;
}

#include "variantToSQLiteT_impl.h"

////////////////////////////////////////////////////////////////////////////////
//// Modules

struct Module
{
  const char* name;
  int (*registerFunc)(sqlite3*, const char*);
};

Module gModules[] = {
  { "filesystem", RegisterFileSystemModule }
};

////////////////////////////////////////////////////////////////////////////////
//// Local Functions

int tracefunc (unsigned aReason, void *aClosure, void *aP, void *aX)
{
  switch (aReason) {
    case SQLITE_TRACE_STMT: {
      // aP is a pointer to the prepared statement.
      sqlite3_stmt* stmt = static_cast<sqlite3_stmt*>(aP);
      // aX is a pointer to a string containing the unexpanded SQL or a comment,
      // starting with "--"" in case of a trigger.
      char* expanded = static_cast<char*>(aX);
      // Simulate what sqlite_trace was doing.
      if (!::strncmp(expanded, "--", 2)) {
        MOZ_LOG(gStorageLog, LogLevel::Debug,
          ("TRACE_STMT on %p: '%s'", aClosure, expanded));
      } else {
        char* sql = ::sqlite3_expanded_sql(stmt);
        MOZ_LOG(gStorageLog, LogLevel::Debug,
          ("TRACE_STMT on %p: '%s'", aClosure, sql));
        ::sqlite3_free(sql);
      }
      break;
    }
    case SQLITE_TRACE_PROFILE: {
      // aX is pointer to a 64bit integer containing nanoseconds it took to
      // execute the last command.
      sqlite_int64 time = *(static_cast<sqlite_int64*>(aX)) / 1000000;
      if (time > 0) {
        MOZ_LOG(gStorageLog, LogLevel::Debug,
          ("TRACE_TIME on %p: %lldms", aClosure, time));
      }
      break;
    }
  }
  return 0;
}

void
basicFunctionHelper(sqlite3_context *aCtx,
                    int aArgc,
                    sqlite3_value **aArgv)
{
  void *userData = ::sqlite3_user_data(aCtx);

  mozIStorageFunction *func = static_cast<mozIStorageFunction *>(userData);

  RefPtr<ArgValueArray> arguments(new ArgValueArray(aArgc, aArgv));
  if (!arguments)
      return;

  nsCOMPtr<nsIVariant> result;
  nsresult rv = func->OnFunctionCall(arguments, getter_AddRefs(result));
  if (NS_FAILED(rv)) {
    nsAutoCString errorMessage;
    GetErrorName(rv, errorMessage);
    errorMessage.InsertLiteral("User function returned ", 0);
    errorMessage.Append('!');

    NS_WARNING(errorMessage.get());

    ::sqlite3_result_error(aCtx, errorMessage.get(), -1);
    ::sqlite3_result_error_code(aCtx, nsresultToSQLiteResult(rv));
    return;
  }
  int retcode = variantToSQLiteT(aCtx, result);
  if (retcode == SQLITE_IGNORE) {
    ::sqlite3_result_int(aCtx, SQLITE_IGNORE);
  } else if (retcode != SQLITE_OK) {
    NS_WARNING("User function returned invalid data type!");
    ::sqlite3_result_error(aCtx,
                           "User function returned invalid data type",
                           -1);
  }
}

void
aggregateFunctionStepHelper(sqlite3_context *aCtx,
                            int aArgc,
                            sqlite3_value **aArgv)
{
  void *userData = ::sqlite3_user_data(aCtx);
  mozIStorageAggregateFunction *func =
    static_cast<mozIStorageAggregateFunction *>(userData);

  RefPtr<ArgValueArray> arguments(new ArgValueArray(aArgc, aArgv));
  if (!arguments)
    return;

  if (NS_FAILED(func->OnStep(arguments)))
    NS_WARNING("User aggregate step function returned error code!");
}

void
aggregateFunctionFinalHelper(sqlite3_context *aCtx)
{
  void *userData = ::sqlite3_user_data(aCtx);
  mozIStorageAggregateFunction *func =
    static_cast<mozIStorageAggregateFunction *>(userData);

  RefPtr<nsIVariant> result;
  if (NS_FAILED(func->OnFinal(getter_AddRefs(result)))) {
    NS_WARNING("User aggregate final function returned error code!");
    ::sqlite3_result_error(aCtx,
                           "User aggregate final function returned error code",
                           -1);
    return;
  }

  if (variantToSQLiteT(aCtx, result) != SQLITE_OK) {
    NS_WARNING("User aggregate final function returned invalid data type!");
    ::sqlite3_result_error(aCtx,
                           "User aggregate final function returned invalid data type",
                           -1);
  }
}

/**
 * This code is heavily based on the sample at:
 *   http://www.sqlite.org/unlock_notify.html
 */
class UnlockNotification
{
public:
  UnlockNotification()
  : mMutex("UnlockNotification mMutex")
  , mCondVar(mMutex, "UnlockNotification condVar")
  , mSignaled(false)
  {
  }

  void Wait()
  {
    MutexAutoLock lock(mMutex);
    while (!mSignaled) {
      (void)mCondVar.Wait();
    }
  }

  void Signal()
  {
    MutexAutoLock lock(mMutex);
    mSignaled = true;
    (void)mCondVar.Notify();
  }

private:
  Mutex mMutex;
  CondVar mCondVar;
  bool mSignaled;
};

void
UnlockNotifyCallback(void **aArgs,
                     int aArgsSize)
{
  for (int i = 0; i < aArgsSize; i++) {
    UnlockNotification *notification =
      static_cast<UnlockNotification *>(aArgs[i]);
    notification->Signal();
  }
}

int
WaitForUnlockNotify(sqlite3* aDatabase)
{
  UnlockNotification notification;
  int srv = ::sqlite3_unlock_notify(aDatabase, UnlockNotifyCallback,
                                    &notification);
  MOZ_ASSERT(srv == SQLITE_LOCKED || srv == SQLITE_OK);
  if (srv == SQLITE_OK) {
    notification.Wait();
  }

  return srv;
}

} // namespace

////////////////////////////////////////////////////////////////////////////////
//// Local Classes

namespace {

class AsyncCloseConnection final: public Runnable
{
public:
  AsyncCloseConnection(Connection *aConnection,
                       sqlite3 *aNativeConnection,
                       nsIRunnable *aCallbackEvent,
                       already_AddRefed<nsIThread> aAsyncExecutionThread)
  : mConnection(aConnection)
  , mNativeConnection(aNativeConnection)
  , mCallbackEvent(aCallbackEvent)
  , mAsyncExecutionThread(aAsyncExecutionThread)
  {
  }

  NS_IMETHOD Run() override
  {
#ifdef DEBUG
    // This code is executed on the background thread
    bool onAsyncThread = false;
    (void)mAsyncExecutionThread->IsOnCurrentThread(&onAsyncThread);
    MOZ_ASSERT(onAsyncThread);
#endif // DEBUG

    nsCOMPtr<nsIRunnable> event = NewRunnableMethod<nsCOMPtr<nsIThread>>
      (mConnection, &Connection::shutdownAsyncThread, mAsyncExecutionThread);
    (void)NS_DispatchToMainThread(event);

    // Internal close.
    (void)mConnection->internalClose(mNativeConnection);

    // Callback
    if (mCallbackEvent) {
      nsCOMPtr<nsIThread> thread;
      (void)NS_GetMainThread(getter_AddRefs(thread));
      (void)thread->Dispatch(mCallbackEvent, NS_DISPATCH_NORMAL);
    }

    return NS_OK;
  }

  ~AsyncCloseConnection() override {
    NS_ReleaseOnMainThread(
      "AsyncCloseConnection::mConnection", mConnection.forget());
    NS_ReleaseOnMainThread(
      "AsyncCloseConnection::mCallbackEvent", mCallbackEvent.forget());
  }
private:
  RefPtr<Connection> mConnection;
  sqlite3 *mNativeConnection;
  nsCOMPtr<nsIRunnable> mCallbackEvent;
  nsCOMPtr<nsIThread> mAsyncExecutionThread;
};

/**
 * An event used to initialize the clone of a connection.
 *
 * Must be executed on the clone's async execution thread.
 */
class AsyncInitializeClone final: public Runnable
{
public:
  /**
   * @param aConnection The connection being cloned.
   * @param aClone The clone.
   * @param aReadOnly If |true|, the clone is read only.
   * @param aCallback A callback to trigger once initialization
   *                  is complete. This event will be called on
   *                  aClone->threadOpenedOn.
   */
  AsyncInitializeClone(Connection* aConnection,
                       Connection* aClone,
                       const bool aReadOnly,
                       mozIStorageCompletionCallback* aCallback)
    : Runnable("storage::AsyncInitializeClone")
    , mConnection(aConnection)
    , mClone(aClone)
    , mReadOnly(aReadOnly)
    , mCallback(aCallback)
  {
    MOZ_ASSERT(NS_IsMainThread());
  }

  NS_IMETHOD Run() override {
    MOZ_ASSERT (NS_GetCurrentThread() == mConnection->getAsyncExecutionTarget());

    nsresult rv = mConnection->initializeClone(mClone, mReadOnly);
    if (NS_FAILED(rv)) {
      return Dispatch(rv, nullptr);
    }
    return Dispatch(NS_OK,
                    NS_ISUPPORTS_CAST(mozIStorageAsyncConnection*, mClone));
  }

private:
  nsresult Dispatch(nsresult aResult, nsISupports* aValue) {
    RefPtr<CallbackComplete> event = new CallbackComplete(aResult,
                                                            aValue,
                                                            mCallback.forget());
    return mClone->threadOpenedOn->Dispatch(event, NS_DISPATCH_NORMAL);
  }

  ~AsyncInitializeClone() override {
    nsCOMPtr<nsIThread> thread;
    DebugOnly<nsresult> rv = NS_GetMainThread(getter_AddRefs(thread));
    MOZ_ASSERT(NS_SUCCEEDED(rv));

    // Handle ambiguous nsISupports inheritance.
    NS_ProxyRelease(
      "AsyncInitializeClone::mConnection", thread, mConnection.forget());
    NS_ProxyRelease(
        "AsyncInitializeClone::mClone", thread, mClone.forget());

    // Generally, the callback will be released by CallbackComplete.
    // However, if for some reason Run() is not executed, we still
    // need to ensure that it is released here.
    NS_ProxyRelease(
      "AsyncInitializeClone::mCallback", thread, mCallback.forget());
  }

  RefPtr<Connection> mConnection;
  RefPtr<Connection> mClone;
  const bool mReadOnly;
  nsCOMPtr<mozIStorageCompletionCallback> mCallback;
};

} // namespace

////////////////////////////////////////////////////////////////////////////////
//// Connection

Connection::Connection(Service *aService,
                       int aFlags,
                       bool aAsyncOnly,
                       bool aIgnoreLockingMode)
: sharedAsyncExecutionMutex("Connection::sharedAsyncExecutionMutex")
, sharedDBMutex("Connection::sharedDBMutex")
, threadOpenedOn(do_GetCurrentThread())
, mDBConn(nullptr)
, mAsyncExecutionThreadShuttingDown(false)
#ifdef DEBUG
, mAsyncExecutionThreadIsAlive(false)
#endif
, mConnectionClosed(false)
, mTransactionInProgress(false)
, mProgressHandler(nullptr)
, mFlags(aFlags)
, mIgnoreLockingMode(aIgnoreLockingMode)
, mStorageService(aService)
, mAsyncOnly(aAsyncOnly)
{
  MOZ_ASSERT(!mIgnoreLockingMode || mFlags & SQLITE_OPEN_READONLY,
             "Can't ignore locking for a non-readonly connection!");
  mStorageService->registerConnection(this);
}

Connection::~Connection()
{
  (void)Close();

  MOZ_ASSERT(!mAsyncExecutionThread,
             "AsyncClose has not been invoked on this connection!");
  MOZ_ASSERT(!mAsyncExecutionThreadIsAlive,
             "The async execution thread should have been shutdown!");
}

NS_IMPL_ADDREF(Connection)

NS_INTERFACE_MAP_BEGIN(Connection)
  NS_INTERFACE_MAP_ENTRY(mozIStorageAsyncConnection)
  NS_INTERFACE_MAP_ENTRY(nsIInterfaceRequestor)
  NS_INTERFACE_MAP_ENTRY_CONDITIONAL(mozIStorageConnection, !mAsyncOnly)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, mozIStorageConnection)
NS_INTERFACE_MAP_END

// This is identical to what NS_IMPL_RELEASE provides, but with the
// extra |1 == count| case.
NS_IMETHODIMP_(MozExternalRefCountType) Connection::Release(void)
{
  NS_PRECONDITION(0 != mRefCnt, "dup release");
  nsrefcnt count = --mRefCnt;
  NS_LOG_RELEASE(this, count, "Connection");
  if (1 == count) {
    // If the refcount is 1, the single reference must be from
    // gService->mConnections (in class |Service|).  Which means we can
    // unregister it safely.
    mStorageService->unregisterConnection(this);
  } else if (0 == count) {
    mRefCnt = 1; /* stabilize */
#if 0 /* enable this to find non-threadsafe destructors: */
    NS_ASSERT_OWNINGTHREAD(Connection);
#endif
    delete (this);
    return 0;
  }
  return count;
}

int32_t
Connection::getSqliteRuntimeStatus(int32_t aStatusOption, int32_t* aMaxValue)
{
  MOZ_ASSERT(mDBConn, "A connection must exist at this point");
  int curr = 0, max = 0;
  DebugOnly<int> rc = ::sqlite3_db_status(mDBConn, aStatusOption, &curr, &max, 0);
  MOZ_ASSERT(NS_SUCCEEDED(convertResultCode(rc)));
  if (aMaxValue)
    *aMaxValue = max;
  return curr;
}

nsIEventTarget *
Connection::getAsyncExecutionTarget()
{
  MutexAutoLock lockedScope(sharedAsyncExecutionMutex);

  // If we are shutting down the asynchronous thread, don't hand out any more
  // references to the thread.
  if (mAsyncExecutionThreadShuttingDown)
    return nullptr;

  if (!mAsyncExecutionThread) {
    static nsThreadPoolNaming naming;
    nsresult rv = NS_NewNamedThread(naming.GetNextThreadName("mozStorage"),
                                    getter_AddRefs(mAsyncExecutionThread));
    if (NS_FAILED(rv)) {
      NS_WARNING("Failed to create async thread.");
      return nullptr;
    }
  }

#ifdef DEBUG
  mAsyncExecutionThreadIsAlive = true;
#endif

  return mAsyncExecutionThread;
}

nsresult
Connection::initialize()
{
  NS_ASSERTION (!mDBConn, "Initialize called on already opened database!");
  MOZ_ASSERT(!mIgnoreLockingMode, "Can't ignore locking on an in-memory db.");
  PROFILER_LABEL("mozStorageConnection", "initialize",
    js::ProfileEntry::Category::STORAGE);

  // in memory database requested, sqlite uses a magic file name
  int srv = ::sqlite3_open_v2(":memory:", &mDBConn, mFlags, nullptr);
  if (srv != SQLITE_OK) {
    mDBConn = nullptr;
    return convertResultCode(srv);
  }

  // Do not set mDatabaseFile or mFileURL here since this is a "memory"
  // database.

  nsresult rv = initializeInternal();
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

nsresult
Connection::initialize(nsIFile *aDatabaseFile)
{
  NS_ASSERTION (aDatabaseFile, "Passed null file!");
  NS_ASSERTION (!mDBConn, "Initialize called on already opened database!");
  PROFILER_LABEL("mozStorageConnection", "initialize",
    js::ProfileEntry::Category::STORAGE);

  mDatabaseFile = aDatabaseFile;

  nsAutoString path;
  nsresult rv = aDatabaseFile->GetPath(path);
  NS_ENSURE_SUCCESS(rv, rv);

#ifdef XP_WIN
  static const char* sIgnoreLockingVFS = "win32-none";
#else
  static const char* sIgnoreLockingVFS = "unix-none";
#endif
  const char* vfs = mIgnoreLockingMode ? sIgnoreLockingVFS : nullptr;

  int srv = ::sqlite3_open_v2(NS_ConvertUTF16toUTF8(path).get(), &mDBConn,
                              mFlags, vfs);
  if (srv != SQLITE_OK) {
    mDBConn = nullptr;
    return convertResultCode(srv);
  }

  // Do not set mFileURL here since this is database does not have an associated
  // URL.
  mDatabaseFile = aDatabaseFile;

  rv = initializeInternal();
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

nsresult
Connection::initialize(nsIFileURL *aFileURL)
{
  NS_ASSERTION (aFileURL, "Passed null file URL!");
  NS_ASSERTION (!mDBConn, "Initialize called on already opened database!");
  PROFILER_LABEL("mozStorageConnection", "initialize",
    js::ProfileEntry::Category::STORAGE);

  nsCOMPtr<nsIFile> databaseFile;
  nsresult rv = aFileURL->GetFile(getter_AddRefs(databaseFile));
  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoCString spec;
  rv = aFileURL->GetSpec(spec);
  NS_ENSURE_SUCCESS(rv, rv);

  int srv = ::sqlite3_open_v2(spec.get(), &mDBConn, mFlags, nullptr);
  if (srv != SQLITE_OK) {
    mDBConn = nullptr;
    return convertResultCode(srv);
  }

  // Set both mDatabaseFile and mFileURL here.
  mFileURL = aFileURL;
  mDatabaseFile = databaseFile;

  rv = initializeInternal();
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

nsresult
Connection::initializeInternal()
{
  MOZ_ASSERT(mDBConn);

  if (mFileURL) {
    const char* dbPath = ::sqlite3_db_filename(mDBConn, "main");
    MOZ_ASSERT(dbPath);

    const char* telemetryFilename =
      ::sqlite3_uri_parameter(dbPath, "telemetryFilename");
    if (telemetryFilename) {
      if (NS_WARN_IF(*telemetryFilename == '\0')) {
        return NS_ERROR_INVALID_ARG;
      }
      mTelemetryFilename = telemetryFilename;
    }
  }

  if (mTelemetryFilename.IsEmpty()) {
    mTelemetryFilename = getFilename();
    MOZ_ASSERT(!mTelemetryFilename.IsEmpty());
  }

  // Properly wrap the database handle's mutex.
  sharedDBMutex.initWithMutex(sqlite3_db_mutex(mDBConn));

  // SQLite tracing can slow down queries (especially long queries)
  // significantly. Don't trace unless the user is actively monitoring SQLite.
  if (MOZ_LOG_TEST(gStorageLog, LogLevel::Debug)) {
    ::sqlite3_trace_v2(mDBConn,
                       SQLITE_TRACE_STMT | SQLITE_TRACE_PROFILE,
                       tracefunc, this);

    MOZ_LOG(gStorageLog, LogLevel::Debug, ("Opening connection to '%s' (%p)",
                                        mTelemetryFilename.get(), this));
  }

  int64_t pageSize = Service::getDefaultPageSize();

  // Set page_size to the preferred default value.  This is effective only if
  // the database has just been created, otherwise, if the database does not
  // use WAL journal mode, a VACUUM operation will updated its page_size.
  nsAutoCString pageSizeQuery(MOZ_STORAGE_UNIQUIFY_QUERY_STR
                              "PRAGMA page_size = ");
  pageSizeQuery.AppendInt(pageSize);
  nsresult rv = ExecuteSimpleSQL(pageSizeQuery);
  NS_ENSURE_SUCCESS(rv, rv);

  // Setting the cache_size forces the database open, verifying if it is valid
  // or corrupt.  So this is executed regardless it being actually needed.
  // The cache_size is calculated from the actual page_size, to save memory.
  nsAutoCString cacheSizeQuery(MOZ_STORAGE_UNIQUIFY_QUERY_STR
                               "PRAGMA cache_size = ");
  cacheSizeQuery.AppendInt(-MAX_CACHE_SIZE_KIBIBYTES);
  int srv = executeSql(mDBConn, cacheSizeQuery.get());
  if (srv != SQLITE_OK) {
    ::sqlite3_close(mDBConn);
    mDBConn = nullptr;
    return convertResultCode(srv);
  }

#if defined(MOZ_MEMORY_TEMP_STORE_PRAGMA)
  (void)ExecuteSimpleSQL(NS_LITERAL_CSTRING("PRAGMA temp_store = 2;"));
#endif

  // Register our built-in SQL functions.
  srv = registerFunctions(mDBConn);
  if (srv != SQLITE_OK) {
    ::sqlite3_close(mDBConn);
    mDBConn = nullptr;
    return convertResultCode(srv);
  }

  // Register our built-in SQL collating sequences.
  srv = registerCollations(mDBConn, mStorageService);
  if (srv != SQLITE_OK) {
    ::sqlite3_close(mDBConn);
    mDBConn = nullptr;
    return convertResultCode(srv);
  }

  // Set the synchronous PRAGMA, according to the preference.
  switch (Service::getSynchronousPref()) {
    case 2:
      (void)ExecuteSimpleSQL(NS_LITERAL_CSTRING(
          "PRAGMA synchronous = FULL;"));
      break;
    case 0:
      (void)ExecuteSimpleSQL(NS_LITERAL_CSTRING(
          "PRAGMA synchronous = OFF;"));
      break;
    case 1:
    default:
      (void)ExecuteSimpleSQL(NS_LITERAL_CSTRING(
          "PRAGMA synchronous = NORMAL;"));
      break;
  }

  return NS_OK;
}

nsresult
Connection::databaseElementExists(enum DatabaseElementType aElementType,
                                  const nsACString &aElementName,
                                  bool *_exists)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  // When constructing the query, make sure to SELECT the correct db's sqlite_master
  // if the user is prefixing the element with a specific db. ex: sample.test
  nsCString query("SELECT name FROM (SELECT * FROM ");
  nsDependentCSubstring element;
  int32_t ind = aElementName.FindChar('.');
  if (ind == kNotFound) {
    element.Assign(aElementName);
  }
  else {
    nsDependentCSubstring db(Substring(aElementName, 0, ind + 1));
    element.Assign(Substring(aElementName, ind + 1, aElementName.Length()));
    query.Append(db);
  }
  query.AppendLiteral("sqlite_master UNION ALL SELECT * FROM sqlite_temp_master) WHERE type = '");

  switch (aElementType) {
    case INDEX:
      query.AppendLiteral("index");
      break;
    case TABLE:
      query.AppendLiteral("table");
      break;
  }
  query.AppendLiteral("' AND name ='");
  query.Append(element);
  query.Append('\'');

  sqlite3_stmt *stmt;
  int srv = prepareStatement(mDBConn, query, &stmt);
  if (srv != SQLITE_OK)
    return convertResultCode(srv);

  srv = stepStatement(mDBConn, stmt);
  // we just care about the return value from step
  (void)::sqlite3_finalize(stmt);

  if (srv == SQLITE_ROW) {
    *_exists = true;
    return NS_OK;
  }
  if (srv == SQLITE_DONE) {
    *_exists = false;
    return NS_OK;
  }

  return convertResultCode(srv);
}

bool
Connection::findFunctionByInstance(nsISupports *aInstance)
{
  sharedDBMutex.assertCurrentThreadOwns();

  for (auto iter = mFunctions.Iter(); !iter.Done(); iter.Next()) {
    if (iter.UserData().function == aInstance) {
      return true;
    }
  }
  return false;
}

/* static */ int
Connection::sProgressHelper(void *aArg)
{
  Connection *_this = static_cast<Connection *>(aArg);
  return _this->progressHandler();
}

int
Connection::progressHandler()
{
  sharedDBMutex.assertCurrentThreadOwns();
  if (mProgressHandler) {
    bool result;
    nsresult rv = mProgressHandler->OnProgress(this, &result);
    if (NS_FAILED(rv)) return 0; // Don't break request
    return result ? 1 : 0;
  }
  return 0;
}

nsresult
Connection::setClosedState()
{
  // Ensure that we are on the correct thread to close the database.
  bool onOpenedThread;
  nsresult rv = threadOpenedOn->IsOnCurrentThread(&onOpenedThread);
  NS_ENSURE_SUCCESS(rv, rv);
  if (!onOpenedThread) {
    NS_ERROR("Must close the database on the thread that you opened it with!");
    return NS_ERROR_UNEXPECTED;
  }

  // Flag that we are shutting down the async thread, so that
  // getAsyncExecutionTarget knows not to expose/create the async thread.
  {
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    NS_ENSURE_FALSE(mAsyncExecutionThreadShuttingDown, NS_ERROR_UNEXPECTED);
    mAsyncExecutionThreadShuttingDown = true;
  }

  // Set the property to null before closing the connection, otherwise the other
  // functions in the module may try to use the connection after it is closed.
  mDBConn = nullptr;

  return NS_OK;
}

bool
Connection::connectionReady()
{
  return mDBConn != nullptr;
}

bool
Connection::isClosing()
{
  bool shuttingDown = false;
  {
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    shuttingDown = mAsyncExecutionThreadShuttingDown;
  }
  return shuttingDown && !isClosed();
}

bool
Connection::isClosed()
{
  MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
  return mConnectionClosed;
}

void
Connection::shutdownAsyncThread(nsIThread *aThread) {
  MOZ_ASSERT(!mAsyncExecutionThread);
  MOZ_ASSERT(mAsyncExecutionThreadIsAlive);
  MOZ_ASSERT(mAsyncExecutionThreadShuttingDown);

  DebugOnly<nsresult> rv = aThread->Shutdown();
  MOZ_ASSERT(NS_SUCCEEDED(rv));
#ifdef DEBUG
  mAsyncExecutionThreadIsAlive = false;
#endif
}

nsresult
Connection::internalClose(sqlite3 *aNativeConnection)
{
  // Sanity checks to make sure we are in the proper state before calling this.
  // aNativeConnection can be null if OpenAsyncDatabase failed and is now just
  // cleaning up the async thread.
  MOZ_ASSERT(!isClosed());

#ifdef DEBUG
  { // Make sure we have marked our async thread as shutting down.
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    NS_ASSERTION(mAsyncExecutionThreadShuttingDown,
                 "Did not call setClosedState!");
  }
#endif // DEBUG

  if (MOZ_LOG_TEST(gStorageLog, LogLevel::Debug)) {
    nsAutoCString leafName(":memory");
    if (mDatabaseFile)
        (void)mDatabaseFile->GetNativeLeafName(leafName);
    MOZ_LOG(gStorageLog, LogLevel::Debug, ("Closing connection to '%s'",
                                        leafName.get()));
  }

  // At this stage, we may still have statements that need to be
  // finalized. Attempt to close the database connection. This will
  // always disconnect any virtual tables and cleanly finalize their
  // internal statements. Once this is done, closing may fail due to
  // unfinalized client statements, in which case we need to finalize
  // these statements and close again.
  {
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    mConnectionClosed = true;
  }

  // Nothing else needs to be done if we don't have a connection here.
  if (!aNativeConnection)
    return NS_OK;

  int srv = sqlite3_close(aNativeConnection);

  if (srv == SQLITE_BUSY) {
    // We still have non-finalized statements. Finalize them.

    sqlite3_stmt *stmt = nullptr;
    while ((stmt = ::sqlite3_next_stmt(aNativeConnection, stmt))) {
      MOZ_LOG(gStorageLog, LogLevel::Debug,
             ("Auto-finalizing SQL statement '%s' (%p)",
              ::sqlite3_sql(stmt),
              stmt));

#ifdef DEBUG
      {
        SmprintfPointer msg = ::mozilla::Smprintf("SQL statement '%s' (%p) should have been finalized before closing the connection",
                                           ::sqlite3_sql(stmt),
                                           stmt);
        NS_WARNING(msg.get());
      }
#endif // DEBUG

      srv = ::sqlite3_finalize(stmt);

#ifdef DEBUG
      if (srv != SQLITE_OK) {
        SmprintfPointer msg = ::mozilla::Smprintf("Could not finalize SQL statement '%s' (%p)",
                                           ::sqlite3_sql(stmt),
                                           stmt);
        NS_WARNING(msg.get());
      }
#endif // DEBUG

      // Ensure that the loop continues properly, whether closing has succeeded
      // or not.
      if (srv == SQLITE_OK) {
        stmt = nullptr;
      }
    }

    // Now that all statements have been finalized, we
    // should be able to close.
    srv = ::sqlite3_close(aNativeConnection);

  }

  if (srv != SQLITE_OK) {
    MOZ_ASSERT(srv == SQLITE_OK,
               "sqlite3_close failed. There are probably outstanding statements that are listed above!");
  }

  return convertResultCode(srv);
}

nsCString
Connection::getFilename()
{
  nsCString leafname(":memory:");
  if (mDatabaseFile) {
    (void)mDatabaseFile->GetNativeLeafName(leafname);
  }
  return leafname;
}

int
Connection::stepStatement(sqlite3 *aNativeConnection, sqlite3_stmt *aStatement)
{
  MOZ_ASSERT(aStatement);
  bool checkedMainThread = false;
  TimeStamp startTime = TimeStamp::Now();

  // The connection may have been closed if the executing statement has been
  // created and cached after a call to asyncClose() but before the actual
  // sqlite3_close().  This usually happens when other tasks using cached
  // statements are asynchronously scheduled for execution and any of them ends
  // up after asyncClose. See bug 728653 for details.
  if (isClosed())
    return SQLITE_MISUSE;

  (void)::sqlite3_extended_result_codes(aNativeConnection, 1);

  int srv;
  while ((srv = ::sqlite3_step(aStatement)) == SQLITE_LOCKED_SHAREDCACHE) {
    if (!checkedMainThread) {
      checkedMainThread = true;
      if (::NS_IsMainThread()) {
        NS_WARNING("We won't allow blocking on the main thread!");
        break;
      }
    }

    srv = WaitForUnlockNotify(aNativeConnection);
    if (srv != SQLITE_OK) {
      break;
    }

    ::sqlite3_reset(aStatement);
  }

  // Report very slow SQL statements to Telemetry
  TimeDuration duration = TimeStamp::Now() - startTime;
  const uint32_t threshold =
    NS_IsMainThread() ? Telemetry::kSlowSQLThresholdForMainThread
                      : Telemetry::kSlowSQLThresholdForHelperThreads;
  if (duration.ToMilliseconds() >= threshold) {
    nsDependentCString statementString(::sqlite3_sql(aStatement));
    Telemetry::RecordSlowSQLStatement(statementString, mTelemetryFilename,
                                      duration.ToMilliseconds());
  }

  (void)::sqlite3_extended_result_codes(aNativeConnection, 0);
  // Drop off the extended result bits of the result code.
  return srv & 0xFF;
}

int
Connection::prepareStatement(sqlite3 *aNativeConnection, const nsCString &aSQL,
                             sqlite3_stmt **_stmt)
{
  // We should not even try to prepare statements after the connection has
  // been closed.
  if (isClosed())
    return SQLITE_MISUSE;

  bool checkedMainThread = false;

  (void)::sqlite3_extended_result_codes(aNativeConnection, 1);

  int srv;
  while((srv = ::sqlite3_prepare_v2(aNativeConnection,
                                    aSQL.get(),
                                    -1,
                                    _stmt,
                                    nullptr)) == SQLITE_LOCKED_SHAREDCACHE) {
    if (!checkedMainThread) {
      checkedMainThread = true;
      if (::NS_IsMainThread()) {
        NS_WARNING("We won't allow blocking on the main thread!");
        break;
      }
    }

    srv = WaitForUnlockNotify(aNativeConnection);
    if (srv != SQLITE_OK) {
      break;
    }
  }

  if (srv != SQLITE_OK) {
    nsCString warnMsg;
    warnMsg.AppendLiteral("The SQL statement '");
    warnMsg.Append(aSQL);
    warnMsg.AppendLiteral("' could not be compiled due to an error: ");
    warnMsg.Append(::sqlite3_errmsg(aNativeConnection));

#ifdef DEBUG
    NS_WARNING(warnMsg.get());
#endif
    MOZ_LOG(gStorageLog, LogLevel::Error, ("%s", warnMsg.get()));
  }

  (void)::sqlite3_extended_result_codes(aNativeConnection, 0);
  // Drop off the extended result bits of the result code.
  int rc = srv & 0xFF;
  // sqlite will return OK on a comment only string and set _stmt to nullptr.
  // The callers of this function are used to only checking the return value,
  // so it is safer to return an error code.
  if (rc == SQLITE_OK && *_stmt == nullptr) {
    return SQLITE_MISUSE;
  }

  return rc;
}


int
Connection::executeSql(sqlite3 *aNativeConnection, const char *aSqlString)
{
  if (isClosed())
    return SQLITE_MISUSE;

  TimeStamp startTime = TimeStamp::Now();
  int srv = ::sqlite3_exec(aNativeConnection, aSqlString, nullptr, nullptr,
                           nullptr);

  // Report very slow SQL statements to Telemetry
  TimeDuration duration = TimeStamp::Now() - startTime;
  const uint32_t threshold =
    NS_IsMainThread() ? Telemetry::kSlowSQLThresholdForMainThread
                      : Telemetry::kSlowSQLThresholdForHelperThreads;
  if (duration.ToMilliseconds() >= threshold) {
    nsDependentCString statementString(aSqlString);
    Telemetry::RecordSlowSQLStatement(statementString, mTelemetryFilename,
                                      duration.ToMilliseconds());
  }

  return srv;
}

////////////////////////////////////////////////////////////////////////////////
//// nsIInterfaceRequestor

NS_IMETHODIMP
Connection::GetInterface(const nsIID &aIID,
                         void **_result)
{
  if (aIID.Equals(NS_GET_IID(nsIEventTarget))) {
    nsIEventTarget *background = getAsyncExecutionTarget();
    NS_IF_ADDREF(background);
    *_result = background;
    return NS_OK;
  }
  return NS_ERROR_NO_INTERFACE;
}

////////////////////////////////////////////////////////////////////////////////
//// mozIStorageConnection

NS_IMETHODIMP
Connection::Close()
{
  if (!mDBConn)
    return NS_ERROR_NOT_INITIALIZED;

  { // Make sure we have not executed any asynchronous statements.
    // If this fails, the mDBConn will be left open, resulting in a leak.
    // Ideally we'd schedule some code to destroy the mDBConn once all its
    // async statements have finished executing;  see bug 704030.
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    bool asyncCloseWasCalled = !mAsyncExecutionThread;
    NS_ENSURE_TRUE(asyncCloseWasCalled, NS_ERROR_UNEXPECTED);
  }

  // setClosedState nullifies our connection pointer, so we take a raw pointer
  // off it, to pass it through the close procedure.
  sqlite3 *nativeConn = mDBConn;
  nsresult rv = setClosedState();
  NS_ENSURE_SUCCESS(rv, rv);

  return internalClose(nativeConn);
}

NS_IMETHODIMP
Connection::AsyncClose(mozIStorageCompletionCallback *aCallback)
{
  if (!NS_IsMainThread()) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  // The two relevant factors at this point are whether we have a database
  // connection and whether we have an async execution thread.  Here's what the
  // states mean and how we handle them:
  //
  // - (mDBConn && asyncThread): The expected case where we are either an
  //   async connection or a sync connection that has been used asynchronously.
  //   Either way the caller must call us and not Close().  Nothing surprising
  //   about this.  We'll dispatch AsyncCloseConnection to the already-existing
  //   async thread.
  //
  // - (mDBConn && !asyncThread): A somewhat unusual case where the caller
  //   opened the connection synchronously and was planning to use it
  //   asynchronously, but never got around to using it asynchronously before
  //   needing to shutdown.  This has been observed to happen for the cookie
  //   service in a case where Firefox shuts itself down almost immediately
  //   after startup (for unknown reasons).  In the Firefox shutdown case,
  //   we may also fail to create a new async execution thread if one does not
  //   already exist.  (nsThreadManager will refuse to create new threads when
  //   it has already been told to shutdown.)  As such, we need to handle a
  //   failure to create the async execution thread by falling back to
  //   synchronous Close() and also dispatching the completion callback because
  //   at least Places likes to spin a nested event loop that depends on the
  //   callback being invoked.
  //
  //   Note that we have considered not trying to spin up the async execution
  //   thread in this case if it does not already exist, but the overhead of
  //   thread startup (if successful) is significantly less expensive than the
  //   worst-case potential I/O hit of synchronously closing a database when we
  //   could close it asynchronously.
  //
  // - (!mDBConn && asyncThread): This happens in some but not all cases where
  //   OpenAsyncDatabase encountered a problem opening the database.  If it
  //   happened in all cases AsyncInitDatabase would just shut down the thread
  //   directly and we would avoid this case.  But it doesn't, so for simplicity
  //   and consistency AsyncCloseConnection knows how to handle this and we
  //   act like this was the (mDBConn && asyncThread) case in this method.
  //
  // - (!mDBConn && !asyncThread): The database was never successfully opened or
  //   Close() or AsyncClose() has already been called (at least) once.  This is
  //   undeniably a misuse case by the caller.  We could optimize for this
  //   case by adding an additional check of mAsyncExecutionThread without using
  //   getAsyncExecutionTarget() to avoid wastefully creating a thread just to
  //   shut it down.  But this complicates the method for broken caller code
  //   whereas we're still correct and safe without the special-case.
  nsIEventTarget *asyncThread = getAsyncExecutionTarget();

  // Create our callback event if we were given a callback.  This will
  // eventually be dispatched in all cases, even if we fall back to Close() and
  // the database wasn't open and we return an error.  The rationale is that
  // no existing consumer checks our return value and several of them like to
  // spin nested event loops until the callback fires.  Given that, it seems
  // preferable for us to dispatch the callback in all cases.  (Except the
  // wrong thread misuse case we bailed on up above.  But that's okay because
  // that is statically wrong whereas these edge cases are dynamic.)
  nsCOMPtr<nsIRunnable> completeEvent;
  if (aCallback) {
    completeEvent = newCompletionEvent(aCallback);
  }

  if (!asyncThread) {
    // We were unable to create an async thread, so we need to fall back to
    // using normal Close().  Since there is no async thread, Close() will
    // not complain about that.  (Close() may, however, complain if the
    // connection is closed, but that's okay.)
    if (completeEvent) {
      // Closing the database is more important than returning an error code
      // about a failure to dispatch, especially because all existing native
      // callers ignore our return value.
      Unused << NS_DispatchToMainThread(completeEvent.forget());
    }
    return Close();
  }

  // setClosedState nullifies our connection pointer, so we take a raw pointer
  // off it, to pass it through the close procedure.
  sqlite3 *nativeConn = mDBConn;
  nsresult rv = setClosedState();
  NS_ENSURE_SUCCESS(rv, rv);

  // Create and dispatch our close event to the background thread.
  nsCOMPtr<nsIRunnable> closeEvent;
  {
    // We need to lock because we're modifying mAsyncExecutionThread
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    closeEvent = new AsyncCloseConnection(this,
                                          nativeConn,
                                          completeEvent,
                                          mAsyncExecutionThread.forget());
  }

  rv = asyncThread->Dispatch(closeEvent, NS_DISPATCH_NORMAL);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

NS_IMETHODIMP
Connection::AsyncClone(bool aReadOnly,
                       mozIStorageCompletionCallback *aCallback)
{
  PROFILER_LABEL("mozStorageConnection", "AsyncClone",
    js::ProfileEntry::Category::STORAGE);

  if (!NS_IsMainThread()) {
    return NS_ERROR_NOT_SAME_THREAD;
  }
  if (!mDBConn)
    return NS_ERROR_NOT_INITIALIZED;
  if (!mDatabaseFile)
    return NS_ERROR_UNEXPECTED;

  int flags = mFlags;
  if (aReadOnly) {
    // Turn off SQLITE_OPEN_READWRITE, and set SQLITE_OPEN_READONLY.
    flags = (~SQLITE_OPEN_READWRITE & flags) | SQLITE_OPEN_READONLY;
    // Turn off SQLITE_OPEN_CREATE.
    flags = (~SQLITE_OPEN_CREATE & flags);
  }

  RefPtr<Connection> clone = new Connection(mStorageService, flags,
                                              mAsyncOnly);

  RefPtr<AsyncInitializeClone> initEvent =
    new AsyncInitializeClone(this, clone, aReadOnly, aCallback);
  // Dispatch to our async thread, since the originating connection must remain
  // valid and open for the whole cloning process.  This also ensures we are
  // properly serialized with a `close` operation, rather than race with it.
  nsCOMPtr<nsIEventTarget> target = getAsyncExecutionTarget();
  if (!target) {
    return NS_ERROR_UNEXPECTED;
  }
  return target->Dispatch(initEvent, NS_DISPATCH_NORMAL);
}

nsresult
Connection::initializeClone(Connection* aClone, bool aReadOnly)
{
  nsresult rv = mFileURL ? aClone->initialize(mFileURL)
                         : aClone->initialize(mDatabaseFile);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Re-attach on-disk databases that were attached to the original connection.
  {
    nsCOMPtr<mozIStorageStatement> stmt;
    rv = CreateStatement(NS_LITERAL_CSTRING("PRAGMA database_list"),
                         getter_AddRefs(stmt));
    MOZ_ASSERT(NS_SUCCEEDED(rv));
    bool hasResult = false;
    while (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      nsAutoCString name;
      rv = stmt->GetUTF8String(1, name);
      if (NS_SUCCEEDED(rv) && !name.Equals(NS_LITERAL_CSTRING("main")) &&
                              !name.Equals(NS_LITERAL_CSTRING("temp"))) {
        nsCString path;
        rv = stmt->GetUTF8String(2, path);
        if (NS_SUCCEEDED(rv) && !path.IsEmpty()) {
          rv = aClone->ExecuteSimpleSQL(NS_LITERAL_CSTRING("ATTACH DATABASE '") +
            path + NS_LITERAL_CSTRING("' AS ") + name);
          MOZ_ASSERT(NS_SUCCEEDED(rv), "couldn't re-attach database to cloned connection");
        }
      }
    }
  }

  // Copy over pragmas from the original connection.
  static const char * pragmas[] = {
    "cache_size",
    "temp_store",
    "foreign_keys",
    "journal_size_limit",
    "synchronous",
    "wal_autocheckpoint",
    "busy_timeout"
  };
  for (auto& pragma : pragmas) {
    // Read-only connections just need cache_size and temp_store pragmas.
    if (aReadOnly && ::strcmp(pragma, "cache_size") != 0 &&
                     ::strcmp(pragma, "temp_store") != 0) {
      continue;
    }

    nsAutoCString pragmaQuery("PRAGMA ");
    pragmaQuery.Append(pragma);
    nsCOMPtr<mozIStorageStatement> stmt;
    rv = CreateStatement(pragmaQuery, getter_AddRefs(stmt));
    MOZ_ASSERT(NS_SUCCEEDED(rv));
    bool hasResult = false;
    if (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      pragmaQuery.AppendLiteral(" = ");
      pragmaQuery.AppendInt(stmt->AsInt32(0));
      rv = aClone->ExecuteSimpleSQL(pragmaQuery);
      MOZ_ASSERT(NS_SUCCEEDED(rv));
    }
  }

  // Copy any functions that have been added to this connection.
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  for (auto iter = mFunctions.Iter(); !iter.Done(); iter.Next()) {
    const nsACString &key = iter.Key();
    Connection::FunctionInfo data = iter.UserData();

    MOZ_ASSERT(data.type == Connection::FunctionInfo::SIMPLE ||
               data.type == Connection::FunctionInfo::AGGREGATE,
               "Invalid function type!");

    if (data.type == Connection::FunctionInfo::SIMPLE) {
      mozIStorageFunction *function =
        static_cast<mozIStorageFunction *>(data.function.get());
      rv = aClone->CreateFunction(key, data.numArgs, function);
      if (NS_FAILED(rv)) {
        NS_WARNING("Failed to copy function to cloned connection");
      }

    } else {
      mozIStorageAggregateFunction *function =
        static_cast<mozIStorageAggregateFunction *>(data.function.get());
      rv = aClone->CreateAggregateFunction(key, data.numArgs, function);
      if (NS_FAILED(rv)) {
        NS_WARNING("Failed to copy aggregate function to cloned connection");
      }
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
Connection::Clone(bool aReadOnly,
                  mozIStorageConnection **_connection)
{
  MOZ_ASSERT(threadOpenedOn == NS_GetCurrentThread());

  PROFILER_LABEL("mozStorageConnection", "Clone",
    js::ProfileEntry::Category::STORAGE);

  if (!mDBConn)
    return NS_ERROR_NOT_INITIALIZED;
  if (!mDatabaseFile)
    return NS_ERROR_UNEXPECTED;

  int flags = mFlags;
  if (aReadOnly) {
    // Turn off SQLITE_OPEN_READWRITE, and set SQLITE_OPEN_READONLY.
    flags = (~SQLITE_OPEN_READWRITE & flags) | SQLITE_OPEN_READONLY;
    // Turn off SQLITE_OPEN_CREATE.
    flags = (~SQLITE_OPEN_CREATE & flags);
  }

  RefPtr<Connection> clone = new Connection(mStorageService, flags,
                                              mAsyncOnly);

  nsresult rv = initializeClone(clone, aReadOnly);
  if (NS_FAILED(rv)) {
    return rv;
  }

  NS_IF_ADDREF(*_connection = clone);
  return NS_OK;
}

NS_IMETHODIMP
Connection::GetDefaultPageSize(int32_t *_defaultPageSize)
{
  *_defaultPageSize = Service::getDefaultPageSize();
  return NS_OK;
}

NS_IMETHODIMP
Connection::GetConnectionReady(bool *_ready)
{
  *_ready = connectionReady();
  return NS_OK;
}

NS_IMETHODIMP
Connection::GetDatabaseFile(nsIFile **_dbFile)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  NS_IF_ADDREF(*_dbFile = mDatabaseFile);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetLastInsertRowID(int64_t *_id)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  sqlite_int64 id = ::sqlite3_last_insert_rowid(mDBConn);
  *_id = id;

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetAffectedRows(int32_t *_rows)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  *_rows = ::sqlite3_changes(mDBConn);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetLastError(int32_t *_error)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  *_error = ::sqlite3_errcode(mDBConn);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetLastErrorString(nsACString &_errorString)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  const char *serr = ::sqlite3_errmsg(mDBConn);
  _errorString.Assign(serr);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetSchemaVersion(int32_t *_version)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  nsCOMPtr<mozIStorageStatement> stmt;
  (void)CreateStatement(NS_LITERAL_CSTRING("PRAGMA user_version"),
                        getter_AddRefs(stmt));
  NS_ENSURE_TRUE(stmt, NS_ERROR_OUT_OF_MEMORY);

  *_version = 0;
  bool hasResult;
  if (NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult)
    *_version = stmt->AsInt32(0);

  return NS_OK;
}

NS_IMETHODIMP
Connection::SetSchemaVersion(int32_t aVersion)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  nsAutoCString stmt(NS_LITERAL_CSTRING("PRAGMA user_version = "));
  stmt.AppendInt(aVersion);

  return ExecuteSimpleSQL(stmt);
}

NS_IMETHODIMP
Connection::CreateStatement(const nsACString &aSQLStatement,
                            mozIStorageStatement **_stmt)
{
  NS_ENSURE_ARG_POINTER(_stmt);
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  RefPtr<Statement> statement(new Statement());
  NS_ENSURE_TRUE(statement, NS_ERROR_OUT_OF_MEMORY);

  nsresult rv = statement->initialize(this, mDBConn, aSQLStatement);
  NS_ENSURE_SUCCESS(rv, rv);

  Statement *rawPtr;
  statement.forget(&rawPtr);
  *_stmt = rawPtr;
  return NS_OK;
}

NS_IMETHODIMP
Connection::CreateAsyncStatement(const nsACString &aSQLStatement,
                                 mozIStorageAsyncStatement **_stmt)
{
  NS_ENSURE_ARG_POINTER(_stmt);
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  RefPtr<AsyncStatement> statement(new AsyncStatement());
  NS_ENSURE_TRUE(statement, NS_ERROR_OUT_OF_MEMORY);

  nsresult rv = statement->initialize(this, mDBConn, aSQLStatement);
  NS_ENSURE_SUCCESS(rv, rv);

  AsyncStatement *rawPtr;
  statement.forget(&rawPtr);
  *_stmt = rawPtr;
  return NS_OK;
}

NS_IMETHODIMP
Connection::ExecuteSimpleSQL(const nsACString &aSQLStatement)
{
  CHECK_MAINTHREAD_ABUSE();
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  int srv = executeSql(mDBConn, PromiseFlatCString(aSQLStatement).get());
  return convertResultCode(srv);
}

NS_IMETHODIMP
Connection::ExecuteAsync(mozIStorageBaseStatement **aStatements,
                         uint32_t aNumStatements,
                         mozIStorageStatementCallback *aCallback,
                         mozIStoragePendingStatement **_handle)
{
  nsTArray<StatementData> stmts(aNumStatements);
  for (uint32_t i = 0; i < aNumStatements; i++) {
    nsCOMPtr<StorageBaseStatementInternal> stmt =
      do_QueryInterface(aStatements[i]);

    // Obtain our StatementData.
    StatementData data;
    nsresult rv = stmt->getAsynchronousStatementData(data);
    NS_ENSURE_SUCCESS(rv, rv);

    NS_ASSERTION(stmt->getOwner() == this,
                 "Statement must be from this database connection!");

    // Now append it to our array.
    NS_ENSURE_TRUE(stmts.AppendElement(data), NS_ERROR_OUT_OF_MEMORY);
  }

  // Dispatch to the background
  return AsyncExecuteStatements::execute(stmts, this, mDBConn, aCallback,
                                         _handle);
}

NS_IMETHODIMP
Connection::ExecuteSimpleSQLAsync(const nsACString &aSQLStatement,
                                  mozIStorageStatementCallback *aCallback,
                                  mozIStoragePendingStatement **_handle)
{
  if (!NS_IsMainThread()) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  nsCOMPtr<mozIStorageAsyncStatement> stmt;
  nsresult rv = CreateAsyncStatement(aSQLStatement, getter_AddRefs(stmt));
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsCOMPtr<mozIStoragePendingStatement> pendingStatement;
  rv = stmt->ExecuteAsync(aCallback, getter_AddRefs(pendingStatement));
  if (NS_FAILED(rv)) {
    return rv;
  }

  pendingStatement.forget(_handle);
  return rv;
}

NS_IMETHODIMP
Connection::TableExists(const nsACString &aTableName,
                        bool *_exists)
{
    return databaseElementExists(TABLE, aTableName, _exists);
}

NS_IMETHODIMP
Connection::IndexExists(const nsACString &aIndexName,
                        bool* _exists)
{
    return databaseElementExists(INDEX, aIndexName, _exists);
}

NS_IMETHODIMP
Connection::GetTransactionInProgress(bool *_inProgress)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  *_inProgress = mTransactionInProgress;
  return NS_OK;
}

NS_IMETHODIMP
Connection::BeginTransaction()
{
  return BeginTransactionAs(mozIStorageConnection::TRANSACTION_DEFERRED);
}

NS_IMETHODIMP
Connection::BeginTransactionAs(int32_t aTransactionType)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  return beginTransactionInternal(mDBConn, aTransactionType);
}

nsresult
Connection::beginTransactionInternal(sqlite3 *aNativeConnection,
                                     int32_t aTransactionType)
{
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  if (mTransactionInProgress)
    return NS_ERROR_FAILURE;
  nsresult rv;
  switch(aTransactionType) {
    case TRANSACTION_DEFERRED:
      rv = convertResultCode(executeSql(aNativeConnection, "BEGIN DEFERRED"));
      break;
    case TRANSACTION_IMMEDIATE:
      rv = convertResultCode(executeSql(aNativeConnection, "BEGIN IMMEDIATE"));
      break;
    case TRANSACTION_EXCLUSIVE:
      rv = convertResultCode(executeSql(aNativeConnection, "BEGIN EXCLUSIVE"));
      break;
    default:
      return NS_ERROR_ILLEGAL_VALUE;
  }
  if (NS_SUCCEEDED(rv))
    mTransactionInProgress = true;
  return rv;
}

NS_IMETHODIMP
Connection::CommitTransaction()
{
  if (!mDBConn)
    return NS_ERROR_NOT_INITIALIZED;

  return commitTransactionInternal(mDBConn);
}

nsresult
Connection::commitTransactionInternal(sqlite3 *aNativeConnection)
{
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  if (!mTransactionInProgress)
    return NS_ERROR_UNEXPECTED;
  nsresult rv =
    convertResultCode(executeSql(aNativeConnection, "COMMIT TRANSACTION"));
  if (NS_SUCCEEDED(rv))
    mTransactionInProgress = false;
  return rv;
}

NS_IMETHODIMP
Connection::RollbackTransaction()
{
  if (!mDBConn)
    return NS_ERROR_NOT_INITIALIZED;

  return rollbackTransactionInternal(mDBConn);
}

nsresult
Connection::rollbackTransactionInternal(sqlite3 *aNativeConnection)
{
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  if (!mTransactionInProgress)
    return NS_ERROR_UNEXPECTED;

  nsresult rv =
    convertResultCode(executeSql(aNativeConnection, "ROLLBACK TRANSACTION"));
  if (NS_SUCCEEDED(rv))
    mTransactionInProgress = false;
  return rv;
}

NS_IMETHODIMP
Connection::CreateTable(const char *aTableName,
                        const char *aTableSchema)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  SmprintfPointer buf = ::mozilla::Smprintf("CREATE TABLE %s (%s)", aTableName, aTableSchema);
  if (!buf)
    return NS_ERROR_OUT_OF_MEMORY;

  int srv = executeSql(mDBConn, buf.get());

  return convertResultCode(srv);
}

NS_IMETHODIMP
Connection::CreateFunction(const nsACString &aFunctionName,
                           int32_t aNumArguments,
                           mozIStorageFunction *aFunction)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  // Check to see if this function is already defined.  We only check the name
  // because a function can be defined with the same body but different names.
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_ENSURE_FALSE(mFunctions.Get(aFunctionName, nullptr), NS_ERROR_FAILURE);

  int srv = ::sqlite3_create_function(mDBConn,
                                      nsPromiseFlatCString(aFunctionName).get(),
                                      aNumArguments,
                                      SQLITE_ANY,
                                      aFunction,
                                      basicFunctionHelper,
                                      nullptr,
                                      nullptr);
  if (srv != SQLITE_OK)
    return convertResultCode(srv);

  FunctionInfo info = { aFunction,
                        Connection::FunctionInfo::SIMPLE,
                        aNumArguments };
  mFunctions.Put(aFunctionName, info);

  return NS_OK;
}

NS_IMETHODIMP
Connection::CreateAggregateFunction(const nsACString &aFunctionName,
                                    int32_t aNumArguments,
                                    mozIStorageAggregateFunction *aFunction)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  // Check to see if this function name is already defined.
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_ENSURE_FALSE(mFunctions.Get(aFunctionName, nullptr), NS_ERROR_FAILURE);

  // Because aggregate functions depend on state across calls, you cannot have
  // the same instance use the same name.  We want to enumerate all functions
  // and make sure this instance is not already registered.
  NS_ENSURE_FALSE(findFunctionByInstance(aFunction), NS_ERROR_FAILURE);

  int srv = ::sqlite3_create_function(mDBConn,
                                      nsPromiseFlatCString(aFunctionName).get(),
                                      aNumArguments,
                                      SQLITE_ANY,
                                      aFunction,
                                      nullptr,
                                      aggregateFunctionStepHelper,
                                      aggregateFunctionFinalHelper);
  if (srv != SQLITE_OK)
    return convertResultCode(srv);

  FunctionInfo info = { aFunction,
                        Connection::FunctionInfo::AGGREGATE,
                        aNumArguments };
  mFunctions.Put(aFunctionName, info);

  return NS_OK;
}

NS_IMETHODIMP
Connection::RemoveFunction(const nsACString &aFunctionName)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_ENSURE_TRUE(mFunctions.Get(aFunctionName, nullptr), NS_ERROR_FAILURE);

  int srv = ::sqlite3_create_function(mDBConn,
                                      nsPromiseFlatCString(aFunctionName).get(),
                                      0,
                                      SQLITE_ANY,
                                      nullptr,
                                      nullptr,
                                      nullptr,
                                      nullptr);
  if (srv != SQLITE_OK)
    return convertResultCode(srv);

  mFunctions.Remove(aFunctionName);

  return NS_OK;
}

NS_IMETHODIMP
Connection::SetProgressHandler(int32_t aGranularity,
                               mozIStorageProgressHandler *aHandler,
                               mozIStorageProgressHandler **_oldHandler)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  // Return previous one
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_IF_ADDREF(*_oldHandler = mProgressHandler);

  if (!aHandler || aGranularity <= 0) {
    aHandler = nullptr;
    aGranularity = 0;
  }
  mProgressHandler = aHandler;
  ::sqlite3_progress_handler(mDBConn, aGranularity, sProgressHelper, this);

  return NS_OK;
}

NS_IMETHODIMP
Connection::RemoveProgressHandler(mozIStorageProgressHandler **_oldHandler)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  // Return previous one
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_IF_ADDREF(*_oldHandler = mProgressHandler);

  mProgressHandler = nullptr;
  ::sqlite3_progress_handler(mDBConn, 0, nullptr, nullptr);

  return NS_OK;
}

NS_IMETHODIMP
Connection::SetGrowthIncrement(int32_t aChunkSize, const nsACString &aDatabaseName)
{
  // Bug 597215: Disk space is extremely limited on Android
  // so don't preallocate space. This is also not effective
  // on log structured file systems used by Android devices
#if !defined(ANDROID) && !defined(MOZ_PLATFORM_MAEMO)
  // Don't preallocate if less than 500MiB is available.
  int64_t bytesAvailable;
  nsresult rv = mDatabaseFile->GetDiskSpaceAvailable(&bytesAvailable);
  NS_ENSURE_SUCCESS(rv, rv);
  if (bytesAvailable < MIN_AVAILABLE_BYTES_PER_CHUNKED_GROWTH) {
    return NS_ERROR_FILE_TOO_BIG;
  }

  (void)::sqlite3_file_control(mDBConn,
                               aDatabaseName.Length() ? nsPromiseFlatCString(aDatabaseName).get()
                                                      : nullptr,
                               SQLITE_FCNTL_CHUNK_SIZE,
                               &aChunkSize);
#endif
  return NS_OK;
}

NS_IMETHODIMP
Connection::EnableModule(const nsACString& aModuleName)
{
  if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;

  for (auto& gModule : gModules) {
    struct Module* m = &gModule;
    if (aModuleName.Equals(m->name)) {
      int srv = m->registerFunc(mDBConn, m->name);
      if (srv != SQLITE_OK)
        return convertResultCode(srv);

      return NS_OK;
    }
  }

  return NS_ERROR_FAILURE;
}

// Implemented in TelemetryVFS.cpp
already_AddRefed<QuotaObject>
GetQuotaObjectForFile(sqlite3_file *pFile);

NS_IMETHODIMP
Connection::GetQuotaObjects(QuotaObject** aDatabaseQuotaObject,
                            QuotaObject** aJournalQuotaObject)
{
  MOZ_ASSERT(aDatabaseQuotaObject);
  MOZ_ASSERT(aJournalQuotaObject);

  if (!mDBConn) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  sqlite3_file* file;
  int srv = ::sqlite3_file_control(mDBConn,
                                   nullptr,
                                   SQLITE_FCNTL_FILE_POINTER,
                                   &file);
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  RefPtr<QuotaObject> databaseQuotaObject = GetQuotaObjectForFile(file);

  srv = ::sqlite3_file_control(mDBConn,
                               nullptr,
                               SQLITE_FCNTL_JOURNAL_POINTER,
                               &file);
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  RefPtr<QuotaObject> journalQuotaObject = GetQuotaObjectForFile(file);

  databaseQuotaObject.forget(aDatabaseQuotaObject);
  journalQuotaObject.forget(aJournalQuotaObject);
  return NS_OK;
}

} // namespace storage
} // namespace mozilla