Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2020 insertions, 0 deletions

diff --git a/toolkit/modules/Sqlite.sys.mjs b/toolkit/modules/Sqlite.sys.mjs
new file mode 100644
index 0000000000..2c9de0f438
--- /dev/null
+++ b/toolkit/modules/Sqlite.sys.mjs
@@ -0,0 +1,2020 @@
+/* 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/. */
+
+/**
+ * PRIVACY WARNING
+ * ===============
+ *
+ * Database file names can be exposed through telemetry and in crash reports on
+ * the https://crash-stats.mozilla.org site, to allow recognizing the affected
+ * database.
+ * if your database name may contain privacy sensitive information, e.g. an
+ * URL origin, you should use openDatabaseWithFileURL and pass an explicit
+ * TelemetryFilename to it. That name will be used both for telemetry and for
+ * thread names in crash reports.
+ * If you have different needs (e.g. using the javascript module or an async
+ * connection from the main thread) please coordinate with the mozStorage peers.
+ */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+import { setTimeout } from "resource://gre/modules/Timer.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AsyncShutdown: "resource://gre/modules/AsyncShutdown.sys.mjs",
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+  Log: "resource://gre/modules/Log.sys.mjs",
+});
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "FinalizationWitnessService",
+  "@mozilla.org/toolkit/finalizationwitness;1",
+  "nsIFinalizationWitnessService"
+);
+
+// Regular expression used by isInvalidBoundLikeQuery
+var likeSqlRegex = /\bLIKE\b\s(?![@:?])/i;
+
+// Counts the number of created connections per database basename(). This is
+// used for logging to distinguish connection instances.
+var connectionCounters = new Map();
+
+// Tracks identifiers of wrapped connections, that are Storage connections
+// opened through mozStorage and then wrapped by Sqlite.sys.mjs to use its syntactic
+// sugar API.  Since these connections have an unknown origin, we use this set
+// to differentiate their behavior.
+var wrappedConnections = new Set();
+
+/**
+ * Once `true`, reject any attempt to open or close a database.
+ */
+function isClosed() {
+  // If Barriers have not been initialized yet, just trust AppStartup.
+  if (
+    typeof Object.getOwnPropertyDescriptor(lazy, "Barriers").get == "function"
+  ) {
+    // It's still possible to open new connections at profile-before-change, so
+    // use the next phase here, as a fallback.
+    return Services.startup.isInOrBeyondShutdownPhase(
+      Ci.nsIAppStartup.SHUTDOWN_PHASE_XPCOMWILLSHUTDOWN
+    );
+  }
+  return lazy.Barriers.shutdown.client.isClosed;
+}
+
+var Debugging = {
+  // Tests should fail if a connection auto closes.  The exception is
+  // when finalization itself is tested, in which case this flag
+  // should be set to false.
+  failTestsOnAutoClose: true,
+};
+
+/**
+ * Helper function to check whether LIKE is implemented using proper bindings.
+ *
+ * @param sql
+ *        (string) The SQL query to be verified.
+ * @return boolean value telling us whether query was correct or not
+ */
+function isInvalidBoundLikeQuery(sql) {
+  return likeSqlRegex.test(sql);
+}
+
+// Displays a script error message
+function logScriptError(message) {
+  let consoleMessage = Cc["@mozilla.org/scripterror;1"].createInstance(
+    Ci.nsIScriptError
+  );
+  let stack = new Error();
+  consoleMessage.init(
+    message,
+    stack.fileName,
+    null,
+    stack.lineNumber,
+    0,
+    Ci.nsIScriptError.errorFlag,
+    "component javascript"
+  );
+  Services.console.logMessage(consoleMessage);
+
+  // This `Promise.reject` will cause tests to fail.  The debugging
+  // flag can be used to suppress this for tests that explicitly
+  // test auto closes.
+  if (Debugging.failTestsOnAutoClose) {
+    Promise.reject(new Error(message));
+  }
+}
+
+/**
+ * Gets connection identifier from its database file name.
+ *
+ * @param fileName
+ *        A database file string name.
+ * @return the connection identifier.
+ */
+function getIdentifierByFileName(fileName) {
+  let number = connectionCounters.get(fileName) || 0;
+  connectionCounters.set(fileName, number + 1);
+  return fileName + "#" + number;
+}
+
+/**
+ * Convert mozIStorageError to common NS_ERROR_*
+ * The conversion is mostly based on the one in
+ * mozStoragePrivateHelpers::ConvertResultCode, plus a few additions.
+ *
+ * @param {integer} result a mozIStorageError result code.
+ * @returns {integer} an NS_ERROR_* result code.
+ */
+function convertStorageErrorResult(result) {
+  switch (result) {
+    case Ci.mozIStorageError.PERM:
+    case Ci.mozIStorageError.AUTH:
+    case Ci.mozIStorageError.CANTOPEN:
+      return Cr.NS_ERROR_FILE_ACCESS_DENIED;
+    case Ci.mozIStorageError.LOCKED:
+      return Cr.NS_ERROR_FILE_IS_LOCKED;
+    case Ci.mozIStorageError.READONLY:
+      return Cr.NS_ERROR_FILE_READ_ONLY;
+    case Ci.mozIStorageError.ABORT:
+    case Ci.mozIStorageError.INTERRUPT:
+      return Cr.NS_ERROR_ABORT;
+    case Ci.mozIStorageError.TOOBIG:
+    case Ci.mozIStorageError.FULL:
+      return Cr.NS_ERROR_FILE_NO_DEVICE_SPACE;
+    case Ci.mozIStorageError.NOMEM:
+      return Cr.NS_ERROR_OUT_OF_MEMORY;
+    case Ci.mozIStorageError.BUSY:
+      return Cr.NS_ERROR_STORAGE_BUSY;
+    case Ci.mozIStorageError.CONSTRAINT:
+      return Cr.NS_ERROR_STORAGE_CONSTRAINT;
+    case Ci.mozIStorageError.NOLFS:
+    case Ci.mozIStorageError.IOERR:
+      return Cr.NS_ERROR_STORAGE_IOERR;
+    case Ci.mozIStorageError.SCHEMA:
+    case Ci.mozIStorageError.MISMATCH:
+    case Ci.mozIStorageError.MISUSE:
+    case Ci.mozIStorageError.RANGE:
+      return Ci.NS_ERROR_UNEXPECTED;
+    case Ci.mozIStorageError.CORRUPT:
+    case Ci.mozIStorageError.EMPTY:
+    case Ci.mozIStorageError.FORMAT:
+    case Ci.mozIStorageError.NOTADB:
+      return Cr.NS_ERROR_FILE_CORRUPTED;
+    default:
+      return Cr.NS_ERROR_FAILURE;
+  }
+}
+/**
+ * Barriers used to ensure that Sqlite.sys.mjs is shutdown after all
+ * its clients.
+ */
+ChromeUtils.defineLazyGetter(lazy, "Barriers", () => {
+  let Barriers = {
+    /**
+     * Public barrier that clients may use to add blockers to the
+     * shutdown of Sqlite.sys.mjs. Triggered by profile-before-change.
+     * Once all blockers of this barrier are lifted, we close the
+     * ability to open new connections.
+     */
+    shutdown: new lazy.AsyncShutdown.Barrier(
+      "Sqlite.sys.mjs: wait until all clients have completed their task"
+    ),
+
+    /**
+     * Private barrier blocked by connections that are still open.
+     * Triggered after Barriers.shutdown is lifted and `isClosed()` returns
+     * `true`.
+     */
+    connections: new lazy.AsyncShutdown.Barrier(
+      "Sqlite.sys.mjs: wait until all connections are closed"
+    ),
+  };
+
+  /**
+   * Observer for the event which is broadcasted when the finalization
+   * witness `_witness` of `OpenedConnection` is garbage collected.
+   *
+   * The observer is passed the connection identifier of the database
+   * connection that is being finalized.
+   */
+  let finalizationObserver = function (subject, topic, identifier) {
+    let connectionData = ConnectionData.byId.get(identifier);
+
+    if (connectionData === undefined) {
+      logScriptError(
+        "Error: Attempt to finalize unknown Sqlite connection: " +
+          identifier +
+          "\n"
+      );
+      return;
+    }
+
+    ConnectionData.byId.delete(identifier);
+    logScriptError(
+      "Warning: Sqlite connection '" +
+        identifier +
+        "' was not properly closed. Auto-close triggered by garbage collection.\n"
+    );
+    connectionData.close();
+  };
+  Services.obs.addObserver(finalizationObserver, "sqlite-finalization-witness");
+
+  /**
+   * Ensure that Sqlite.sys.mjs:
+   * - informs its clients before shutting down;
+   * - lets clients open connections during shutdown, if necessary;
+   * - waits for all connections to be closed before shutdown.
+   */
+  lazy.AsyncShutdown.profileBeforeChange.addBlocker(
+    "Sqlite.sys.mjs shutdown blocker",
+    async function () {
+      await Barriers.shutdown.wait();
+      // At this stage, all clients have had a chance to open (and close)
+      // their databases. Some previous close operations may still be pending,
+      // so we need to wait until they are complete before proceeding.
+      await Barriers.connections.wait();
+
+      // Everything closed, no finalization events to catch
+      Services.obs.removeObserver(
+        finalizationObserver,
+        "sqlite-finalization-witness"
+      );
+    },
+
+    function status() {
+      if (isClosed()) {
+        // We are waiting for the connections to close. The interesting
+        // status is therefore the list of connections still pending.
+        return {
+          description: "Waiting for connections to close",
+          state: Barriers.connections.state,
+        };
+      }
+
+      // We are still in the first stage: waiting for the barrier
+      // to be lifted. The interesting status is therefore that of
+      // the barrier.
+      return {
+        description: "Waiting for the barrier to be lifted",
+        state: Barriers.shutdown.state,
+      };
+    }
+  );
+
+  return Barriers;
+});
+
+const VACUUM_CATEGORY = "vacuum-participant";
+const VACUUM_CONTRACTID = "@sqlite.module.js/vacuum-participant;";
+var registeredVacuumParticipants = new Map();
+
+function registerVacuumParticipant(connectionData) {
+  let contractId = VACUUM_CONTRACTID + connectionData._identifier;
+  let factory = {
+    createInstance(iid) {
+      return connectionData.QueryInterface(iid);
+    },
+    QueryInterface: ChromeUtils.generateQI(["nsIFactory"]),
+  };
+  let cid = Services.uuid.generateUUID();
+  Components.manager
+    .QueryInterface(Ci.nsIComponentRegistrar)
+    .registerFactory(cid, contractId, contractId, factory);
+  Services.catMan.addCategoryEntry(
+    VACUUM_CATEGORY,
+    contractId,
+    contractId,
+    false,
+    false
+  );
+  registeredVacuumParticipants.set(contractId, { cid, factory });
+}
+
+function unregisterVacuumParticipant(connectionData) {
+  let contractId = VACUUM_CONTRACTID + connectionData._identifier;
+  let component = registeredVacuumParticipants.get(contractId);
+  if (component) {
+    Components.manager
+      .QueryInterface(Ci.nsIComponentRegistrar)
+      .unregisterFactory(component.cid, component.factory);
+    Services.catMan.deleteCategoryEntry(VACUUM_CATEGORY, contractId, false);
+  }
+}
+
+/**
+ * Connection data with methods necessary for closing the connection.
+ *
+ * To support auto-closing in the event of garbage collection, this
+ * data structure contains all the connection data of an opened
+ * connection and all of the methods needed for sucessfully closing
+ * it.
+ *
+ * By putting this information in its own separate object, it is
+ * possible to store an additional reference to it without preventing
+ * a garbage collection of a finalization witness in
+ * OpenedConnection. When the witness detects a garbage collection,
+ * this object can be used to close the connection.
+ *
+ * This object contains more methods than just `close`.  When
+ * OpenedConnection needs to use the methods in this object, it will
+ * dispatch its method calls here.
+ */
+function ConnectionData(connection, identifier, options = {}) {
+  this._log = lazy.Log.repository.getLoggerWithMessagePrefix(
+    "Sqlite.sys.mjs",
+    `Connection ${identifier}: `
+  );
+  this._log.manageLevelFromPref("toolkit.sqlitejsm.loglevel");
+  this._log.debug("Opened");
+
+  this._dbConn = connection;
+
+  // This is a unique identifier for the connection, generated through
+  // getIdentifierByFileName.  It may be used for logging or as a key in Maps.
+  this._identifier = identifier;
+
+  this._open = true;
+
+  this._cachedStatements = new Map();
+  this._anonymousStatements = new Map();
+  this._anonymousCounter = 0;
+
+  // A map from statement index to mozIStoragePendingStatement, to allow for
+  // canceling prior to finalizing the mozIStorageStatements.
+  this._pendingStatements = new Map();
+
+  // Increments for each executed statement for the life of the connection.
+  this._statementCounter = 0;
+
+  // Increments whenever we request a unique operation id.
+  this._operationsCounter = 0;
+
+  if ("defaultTransactionType" in options) {
+    this.defaultTransactionType = options.defaultTransactionType;
+  } else {
+    this.defaultTransactionType = convertStorageTransactionType(
+      this._dbConn.defaultTransactionType
+    );
+  }
+  // Tracks whether this instance initiated a transaction.
+  this._initiatedTransaction = false;
+  // Manages a chain of transactions promises, so that new transactions
+  // always happen in queue to the previous ones.  It never rejects.
+  this._transactionQueue = Promise.resolve();
+
+  this._idleShrinkMS = options.shrinkMemoryOnConnectionIdleMS;
+  if (this._idleShrinkMS) {
+    this._idleShrinkTimer = Cc["@mozilla.org/timer;1"].createInstance(
+      Ci.nsITimer
+    );
+    // We wait for the first statement execute to start the timer because
+    // shrinking now would not do anything.
+  }
+
+  // Deferred whose promise is resolved when the connection closing procedure
+  // is complete.
+  this._deferredClose = Promise.withResolvers();
+  this._closeRequested = false;
+
+  // An AsyncShutdown barrier used to make sure that we wait until clients
+  // are done before shutting down the connection.
+  this._barrier = new lazy.AsyncShutdown.Barrier(
+    `${this._identifier}: waiting for clients`
+  );
+
+  lazy.Barriers.connections.client.addBlocker(
+    this._identifier + ": waiting for shutdown",
+    this._deferredClose.promise,
+    () => ({
+      identifier: this._identifier,
+      isCloseRequested: this._closeRequested,
+      hasDbConn: !!this._dbConn,
+      initiatedTransaction: this._initiatedTransaction,
+      pendingStatements: this._pendingStatements.size,
+      statementCounter: this._statementCounter,
+    })
+  );
+
+  // We avoid creating a timer for every transaction, because in most cases they
+  // are not canceled and they are only used as a timeout.
+  // Instead the timer is reused when it's sufficiently close to the previous
+  // creation time (see `_getTimeoutPromise` for more info).
+  this._timeoutPromise = null;
+  // The last timestamp when we should consider using `this._timeoutPromise`.
+  this._timeoutPromiseExpires = 0;
+
+  this._useIncrementalVacuum = !!options.incrementalVacuum;
+  if (this._useIncrementalVacuum) {
+    this._log.debug("Set auto_vacuum INCREMENTAL");
+    this.execute("PRAGMA auto_vacuum = 2").catch(ex => {
+      this._log.error("Setting auto_vacuum to INCREMENTAL failed.");
+      console.error(ex);
+    });
+  }
+
+  this._expectedPageSize = options.pageSize ?? 0;
+  if (this._expectedPageSize) {
+    this._log.debug("Set page_size to " + this._expectedPageSize);
+    this.execute("PRAGMA page_size = " + this._expectedPageSize).catch(ex => {
+      this._log.error(`Setting page_size to ${this._expectedPageSize} failed.`);
+      console.error(ex);
+    });
+  }
+
+  this._vacuumOnIdle = options.vacuumOnIdle;
+  if (this._vacuumOnIdle) {
+    this._log.debug("Register as vacuum participant");
+    this.QueryInterface = ChromeUtils.generateQI([
+      Ci.mozIStorageVacuumParticipant,
+    ]);
+    registerVacuumParticipant(this);
+  }
+}
+
+/**
+ * Map of connection identifiers to ConnectionData objects
+ *
+ * The connection identifier is a human-readable name of the
+ * database. Used by finalization witnesses to be able to close opened
+ * connections on garbage collection.
+ *
+ * Key: _identifier of ConnectionData
+ * Value: ConnectionData object
+ */
+ConnectionData.byId = new Map();
+
+ConnectionData.prototype = Object.freeze({
+  get expectedDatabasePageSize() {
+    return this._expectedPageSize;
+  },
+
+  get useIncrementalVacuum() {
+    return this._useIncrementalVacuum;
+  },
+
+  /**
+   * This should only be used by the VacuumManager component.
+   * @see unsafeRawConnection for an official (but still unsafe) API.
+   */
+  get databaseConnection() {
+    if (this._vacuumOnIdle) {
+      return this._dbConn;
+    }
+    return null;
+  },
+
+  onBeginVacuum() {
+    let granted = !this.transactionInProgress;
+    this._log.debug("Begin Vacuum - " + granted ? "granted" : "denied");
+    return granted;
+  },
+
+  onEndVacuum(succeeded) {
+    this._log.debug("End Vacuum - " + succeeded ? "success" : "failure");
+  },
+
+  /**
+   * Run a task, ensuring that its execution will not be interrupted by shutdown.
+   *
+   * As the operations of this module are asynchronous, a sequence of operations,
+   * or even an individual operation, can still be pending when the process shuts
+   * down. If any of this operations is a write, this can cause data loss, simply
+   * because the write has not been completed (or even started) by shutdown.
+   *
+   * To avoid this risk, clients are encouraged to use `executeBeforeShutdown` for
+   * any write operation, as follows:
+   *
+   * myConnection.executeBeforeShutdown("Bookmarks: Removing a bookmark",
+   *   async function(db) {
+   *     // The connection will not be closed and shutdown will not proceed
+   *     // until this task has completed.
+   *
+   *     // `db` exposes the same API as `myConnection` but provides additional
+   *     // logging support to help debug hard-to-catch shutdown timeouts.
+   *
+   *     await db.execute(...);
+   * }));
+   *
+   * @param {string} name A human-readable name for the ongoing operation, used
+   *  for logging and debugging purposes.
+   * @param {function(db)} task A function that takes as argument a Sqlite.sys.mjs
+   *  db and returns a Promise.
+   */
+  executeBeforeShutdown(parent, name, task) {
+    if (!name) {
+      throw new TypeError("Expected a human-readable name as first argument");
+    }
+    if (typeof task != "function") {
+      throw new TypeError("Expected a function as second argument");
+    }
+    if (this._closeRequested) {
+      throw new Error(
+        `${this._identifier}: cannot execute operation ${name}, the connection is already closing`
+      );
+    }
+
+    // Status, used for AsyncShutdown crash reports.
+    let status = {
+      // The latest command started by `task`, either as a
+      // sql string, or as one of "<not started>" or "<closing>".
+      command: "<not started>",
+
+      // `true` if `command` was started but not completed yet.
+      isPending: false,
+    };
+
+    // An object with the same API as `this` but with
+    // additional logging. To keep logging simple, we
+    // assume that `task` is not running several queries
+    // concurrently.
+    let loggedDb = Object.create(parent, {
+      execute: {
+        value: async (sql, ...rest) => {
+          status.isPending = true;
+          status.command = sql;
+          try {
+            return await this.execute(sql, ...rest);
+          } finally {
+            status.isPending = false;
+          }
+        },
+      },
+      close: {
+        value: async () => {
+          status.isPending = true;
+          status.command = "<close>";
+          try {
+            return await this.close();
+          } finally {
+            status.isPending = false;
+          }
+        },
+      },
+      executeCached: {
+        value: async (sql, ...rest) => {
+          status.isPending = true;
+          status.command = "cached: " + sql;
+          try {
+            return await this.executeCached(sql, ...rest);
+          } finally {
+            status.isPending = false;
+          }
+        },
+      },
+    });
+
+    let promiseResult = task(loggedDb);
+    if (
+      !promiseResult ||
+      typeof promiseResult != "object" ||
+      !("then" in promiseResult)
+    ) {
+      throw new TypeError("Expected a Promise");
+    }
+    let key = `${this._identifier}: ${name} (${this._getOperationId()})`;
+    let promiseComplete = promiseResult.catch(() => {});
+    this._barrier.client.addBlocker(key, promiseComplete, {
+      fetchState: () => status,
+    });
+
+    return (async () => {
+      try {
+        return await promiseResult;
+      } finally {
+        this._barrier.client.removeBlocker(key, promiseComplete);
+      }
+    })();
+  },
+  close() {
+    this._closeRequested = true;
+
+    if (!this._dbConn) {
+      return this._deferredClose.promise;
+    }
+
+    this._log.debug("Request to close connection.");
+    this._clearIdleShrinkTimer();
+
+    if (this._vacuumOnIdle) {
+      this._log.debug("Unregister as vacuum participant");
+      unregisterVacuumParticipant(this);
+    }
+
+    return this._barrier.wait().then(() => {
+      if (!this._dbConn) {
+        return undefined;
+      }
+      return this._finalize();
+    });
+  },
+
+  clone(readOnly = false) {
+    this.ensureOpen();
+
+    this._log.debug("Request to clone connection.");
+
+    let options = {
+      connection: this._dbConn,
+      readOnly,
+    };
+    if (this._idleShrinkMS) {
+      options.shrinkMemoryOnConnectionIdleMS = this._idleShrinkMS;
+    }
+
+    return cloneStorageConnection(options);
+  },
+  _getOperationId() {
+    return this._operationsCounter++;
+  },
+  _finalize() {
+    this._log.debug("Finalizing connection.");
+    // Cancel any pending statements.
+    for (let [, /* k */ statement] of this._pendingStatements) {
+      statement.cancel();
+    }
+    this._pendingStatements.clear();
+
+    // We no longer need to track these.
+    this._statementCounter = 0;
+
+    // Next we finalize all active statements.
+    for (let [, /* k */ statement] of this._anonymousStatements) {
+      statement.finalize();
+    }
+    this._anonymousStatements.clear();
+
+    for (let [, /* k */ statement] of this._cachedStatements) {
+      statement.finalize();
+    }
+    this._cachedStatements.clear();
+
+    // This guards against operations performed between the call to this
+    // function and asyncClose() finishing. See also bug 726990.
+    this._open = false;
+
+    // We must always close the connection at the Sqlite.sys.mjs-level, not
+    // necessarily at the mozStorage-level.
+    let markAsClosed = () => {
+      this._log.debug("Closed");
+      // Now that the connection is closed, no need to keep
+      // a blocker for Barriers.connections.
+      lazy.Barriers.connections.client.removeBlocker(
+        this._deferredClose.promise
+      );
+      this._deferredClose.resolve();
+    };
+    if (wrappedConnections.has(this._identifier)) {
+      wrappedConnections.delete(this._identifier);
+      this._dbConn = null;
+      markAsClosed();
+    } else {
+      this._log.debug("Calling asyncClose().");
+      try {
+        this._dbConn.asyncClose(markAsClosed);
+      } catch (ex) {
+        // If for any reason asyncClose fails, we must still remove the
+        // shutdown blockers and resolve _deferredClose.
+        markAsClosed();
+      } finally {
+        this._dbConn = null;
+      }
+    }
+    return this._deferredClose.promise;
+  },
+
+  executeCached(sql, params = null, onRow = null) {
+    this.ensureOpen();
+
+    if (!sql) {
+      throw new Error("sql argument is empty.");
+    }
+
+    let statement = this._cachedStatements.get(sql);
+    if (!statement) {
+      statement = this._dbConn.createAsyncStatement(sql);
+      this._cachedStatements.set(sql, statement);
+    }
+
+    this._clearIdleShrinkTimer();
+
+    return new Promise((resolve, reject) => {
+      try {
+        this._executeStatement(sql, statement, params, onRow).then(
+          result => {
+            this._startIdleShrinkTimer();
+            resolve(result);
+          },
+          error => {
+            this._startIdleShrinkTimer();
+            reject(error);
+          }
+        );
+      } catch (ex) {
+        this._startIdleShrinkTimer();
+        throw ex;
+      }
+    });
+  },
+
+  execute(sql, params = null, onRow = null) {
+    if (typeof sql != "string") {
+      throw new Error("Must define SQL to execute as a string: " + sql);
+    }
+
+    this.ensureOpen();
+
+    let statement = this._dbConn.createAsyncStatement(sql);
+    let index = this._anonymousCounter++;
+
+    this._anonymousStatements.set(index, statement);
+    this._clearIdleShrinkTimer();
+
+    let onFinished = () => {
+      this._anonymousStatements.delete(index);
+      statement.finalize();
+      this._startIdleShrinkTimer();
+    };
+
+    return new Promise((resolve, reject) => {
+      try {
+        this._executeStatement(sql, statement, params, onRow).then(
+          rows => {
+            onFinished();
+            resolve(rows);
+          },
+          error => {
+            onFinished();
+            reject(error);
+          }
+        );
+      } catch (ex) {
+        onFinished();
+        throw ex;
+      }
+    });
+  },
+
+  get transactionInProgress() {
+    return this._open && this._dbConn.transactionInProgress;
+  },
+
+  executeTransaction(func, type) {
+    // Identify the caller for debugging purposes.
+    let caller = new Error().stack
+      .split("\n", 3)
+      .pop()
+      .match(/^([^@]*@).*\/([^\/:]+)[:0-9]*$/);
+    caller = caller[1] + caller[2];
+    this._log.debug(`Transaction (type ${type}) requested by: ${caller}`);
+
+    if (type == OpenedConnection.prototype.TRANSACTION_DEFAULT) {
+      type = this.defaultTransactionType;
+    } else if (!OpenedConnection.TRANSACTION_TYPES.includes(type)) {
+      throw new Error("Unknown transaction type: " + type);
+    }
+    this.ensureOpen();
+
+    // If a transaction yields on a never resolved promise, or is mistakenly
+    // nested, it could hang the transactions queue forever.  Thus we timeout
+    // the execution after a meaningful amount of time, to ensure in any case
+    // we'll proceed after a while.
+    let timeoutPromise = this._getTimeoutPromise();
+
+    let promise = this._transactionQueue.then(() => {
+      if (this._closeRequested) {
+        throw new Error("Transaction canceled due to a closed connection.");
+      }
+
+      let transactionPromise = (async () => {
+        // At this point we should never have an in progress transaction, since
+        // they are enqueued.
+        if (this._initiatedTransaction) {
+          this._log.error(
+            "Unexpected transaction in progress when trying to start a new one."
+          );
+        }
+        try {
+          // We catch errors in statement execution to detect nested transactions.
+          try {
+            await this.execute("BEGIN " + type + " TRANSACTION");
+            this._log.debug(`Begin transaction`);
+            this._initiatedTransaction = true;
+          } catch (ex) {
+            // Unfortunately, if we are wrapping an existing connection, a
+            // transaction could have been started by a client of the same
+            // connection that doesn't use Sqlite.sys.mjs (e.g. C++ consumer).
+            // The best we can do is proceed without a transaction and hope
+            // things won't break.
+            if (wrappedConnections.has(this._identifier)) {
+              this._log.warn(
+                "A new transaction could not be started cause the wrapped connection had one in progress",
+                ex
+              );
+            } else {
+              this._log.warn(
+                "A transaction was already in progress, likely a nested transaction",
+                ex
+              );
+              throw ex;
+            }
+          }
+
+          let result;
+          try {
+            result = await Promise.race([func(), timeoutPromise]);
+          } catch (ex) {
+            // It's possible that the exception has been caused by trying to
+            // close the connection in the middle of a transaction.
+            if (this._closeRequested) {
+              this._log.warn(
+                "Connection closed while performing a transaction",
+                ex
+              );
+            } else {
+              // Otherwise the function didn't resolve before the timeout, or
+              // generated an unexpected error. Then we rollback.
+              if (ex.becauseTimedOut) {
+                let caller_module = caller.split(":", 1)[0];
+                Services.telemetry.keyedScalarAdd(
+                  "mozstorage.sqlitejsm_transaction_timeout",
+                  caller_module,
+                  1
+                );
+                this._log.error(
+                  `The transaction requested by ${caller} timed out. Rolling back`,
+                  ex
+                );
+              } else {
+                this._log.error(
+                  `Error during transaction requested by ${caller}. Rolling back`,
+                  ex
+                );
+              }
+              // If we began a transaction, we must rollback it.
+              if (this._initiatedTransaction) {
+                try {
+                  await this.execute("ROLLBACK TRANSACTION");
+                  this._initiatedTransaction = false;
+                  this._log.debug(`Roll back transaction`);
+                } catch (inner) {
+                  this._log.error("Could not roll back transaction", inner);
+                }
+              }
+            }
+            // Rethrow the exception.
+            throw ex;
+          }
+
+          // See comment above about connection being closed during transaction.
+          if (this._closeRequested) {
+            this._log.warn(
+              "Connection closed before committing the transaction."
+            );
+            throw new Error(
+              "Connection closed before committing the transaction."
+            );
+          }
+
+          // If we began a transaction, we must commit it.
+          if (this._initiatedTransaction) {
+            try {
+              await this.execute("COMMIT TRANSACTION");
+              this._log.debug(`Commit transaction`);
+            } catch (ex) {
+              this._log.warn("Error committing transaction", ex);
+              throw ex;
+            }
+          }
+
+          return result;
+        } finally {
+          this._initiatedTransaction = false;
+        }
+      })();
+
+      return Promise.race([transactionPromise, timeoutPromise]);
+    });
+    // Atomically update the queue before anyone else has a chance to enqueue
+    // further transactions.
+    this._transactionQueue = promise.catch(ex => {
+      this._log.error(ex);
+    });
+
+    // Make sure that we do not shutdown the connection during a transaction.
+    this._barrier.client.addBlocker(
+      `Transaction (${this._getOperationId()})`,
+      this._transactionQueue
+    );
+    return promise;
+  },
+
+  shrinkMemory() {
+    this._log.debug("Shrinking memory usage.");
+    return this.execute("PRAGMA shrink_memory").finally(() => {
+      this._clearIdleShrinkTimer();
+    });
+  },
+
+  discardCachedStatements() {
+    let count = 0;
+    for (let [, /* k */ statement] of this._cachedStatements) {
+      ++count;
+      statement.finalize();
+    }
+    this._cachedStatements.clear();
+    this._log.debug("Discarded " + count + " cached statements.");
+    return count;
+  },
+
+  interrupt() {
+    this._log.debug("Trying to interrupt.");
+    this.ensureOpen();
+    this._dbConn.interrupt();
+  },
+
+  /**
+   * Helper method to bind parameters of various kinds through
+   * reflection.
+   */
+  _bindParameters(statement, params) {
+    if (!params) {
+      return;
+    }
+
+    function bindParam(obj, key, val) {
+      let isBlob =
+        val && typeof val == "object" && val.constructor.name == "Uint8Array";
+      let args = [key, val];
+      if (isBlob) {
+        args.push(val.length);
+      }
+      let methodName = `bind${isBlob ? "Blob" : ""}By${
+        typeof key == "number" ? "Index" : "Name"
+      }`;
+      obj[methodName](...args);
+    }
+
+    if (Array.isArray(params)) {
+      // It's an array of separate params.
+      if (params.length && typeof params[0] == "object" && params[0] !== null) {
+        let paramsArray = statement.newBindingParamsArray();
+        for (let p of params) {
+          let bindings = paramsArray.newBindingParams();
+          for (let [key, value] of Object.entries(p)) {
+            bindParam(bindings, key, value);
+          }
+          paramsArray.addParams(bindings);
+        }
+
+        statement.bindParameters(paramsArray);
+        return;
+      }
+
+      // Indexed params.
+      for (let i = 0; i < params.length; i++) {
+        bindParam(statement, i, params[i]);
+      }
+      return;
+    }
+
+    // Named params.
+    if (params && typeof params == "object") {
+      for (let k in params) {
+        bindParam(statement, k, params[k]);
+      }
+      return;
+    }
+
+    throw new Error(
+      "Invalid type for bound parameters. Expected Array or " +
+        "object. Got: " +
+        params
+    );
+  },
+
+  _executeStatement(sql, statement, params, onRow) {
+    if (statement.state != statement.MOZ_STORAGE_STATEMENT_READY) {
+      throw new Error("Statement is not ready for execution.");
+    }
+
+    if (onRow && typeof onRow != "function") {
+      throw new Error("onRow must be a function. Got: " + onRow);
+    }
+
+    this._bindParameters(statement, params);
+
+    let index = this._statementCounter++;
+
+    let deferred = Promise.withResolvers();
+    let userCancelled = false;
+    let errors = [];
+    let rows = [];
+    let handledRow = false;
+
+    // Don't incur overhead for serializing params unless the messages go
+    // somewhere.
+    if (this._log.level <= lazy.Log.Level.Trace) {
+      let msg = "Stmt #" + index + " " + sql;
+
+      if (params) {
+        msg += " - " + JSON.stringify(params);
+      }
+      this._log.trace(msg);
+    } else {
+      this._log.debug("Stmt #" + index + " starting");
+    }
+
+    let self = this;
+    let pending = statement.executeAsync({
+      handleResult(resultSet) {
+        // .cancel() may not be immediate and handleResult() could be called
+        // after a .cancel().
+        for (
+          let row = resultSet.getNextRow();
+          row && !userCancelled;
+          row = resultSet.getNextRow()
+        ) {
+          if (!onRow) {
+            rows.push(row);
+            continue;
+          }
+
+          handledRow = true;
+
+          try {
+            onRow(row, () => {
+              userCancelled = true;
+              pending.cancel();
+            });
+          } catch (e) {
+            self._log.warn("Exception when calling onRow callback", e);
+          }
+        }
+      },
+
+      handleError(error) {
+        self._log.warn(
+          "Error when executing SQL (" + error.result + "): " + error.message
+        );
+        errors.push(error);
+      },
+
+      handleCompletion(reason) {
+        self._log.debug("Stmt #" + index + " finished.");
+        self._pendingStatements.delete(index);
+
+        switch (reason) {
+          case Ci.mozIStorageStatementCallback.REASON_FINISHED:
+          case Ci.mozIStorageStatementCallback.REASON_CANCELED:
+            // If there is an onRow handler, we always instead resolve to a
+            // boolean indicating whether the onRow handler was called or not.
+            let result = onRow ? handledRow : rows;
+            deferred.resolve(result);
+            break;
+
+          case Ci.mozIStorageStatementCallback.REASON_ERROR:
+            let error = new Error(
+              "Error(s) encountered during statement execution: " +
+                errors.map(e => e.message).join(", ")
+            );
+            error.errors = errors;
+
+            // Forward the error result.
+            // Corruption is the most critical one so it's handled apart.
+            if (errors.some(e => e.result == Ci.mozIStorageError.CORRUPT)) {
+              error.result = Cr.NS_ERROR_FILE_CORRUPTED;
+            } else {
+              // Just use the first error result in the other cases.
+              error.result = convertStorageErrorResult(errors[0]?.result);
+            }
+
+            deferred.reject(error);
+            break;
+
+          default:
+            deferred.reject(
+              new Error("Unknown completion reason code: " + reason)
+            );
+            break;
+        }
+      },
+    });
+
+    this._pendingStatements.set(index, pending);
+    return deferred.promise;
+  },
+
+  ensureOpen() {
+    if (!this._open) {
+      throw new Error("Connection is not open.");
+    }
+  },
+
+  _clearIdleShrinkTimer() {
+    if (!this._idleShrinkTimer) {
+      return;
+    }
+
+    this._idleShrinkTimer.cancel();
+  },
+
+  _startIdleShrinkTimer() {
+    if (!this._idleShrinkTimer) {
+      return;
+    }
+
+    this._idleShrinkTimer.initWithCallback(
+      this.shrinkMemory.bind(this),
+      this._idleShrinkMS,
+      this._idleShrinkTimer.TYPE_ONE_SHOT
+    );
+  },
+
+  /**
+   * Returns a promise that will resolve after a time comprised between 80% of
+   * `TRANSACTIONS_TIMEOUT_MS` and `TRANSACTIONS_TIMEOUT_MS`. Use
+   * this method instead of creating several individual timers that may survive
+   * longer than necessary.
+   */
+  _getTimeoutPromise() {
+    if (this._timeoutPromise && Cu.now() <= this._timeoutPromiseExpires) {
+      return this._timeoutPromise;
+    }
+    let timeoutPromise = new Promise((resolve, reject) => {
+      setTimeout(() => {
+        // Clear out this._timeoutPromise if it hasn't changed since we set it.
+        if (this._timeoutPromise == timeoutPromise) {
+          this._timeoutPromise = null;
+        }
+        let e = new Error(
+          "Transaction timeout, most likely caused by unresolved pending work."
+        );
+        e.becauseTimedOut = true;
+        reject(e);
+      }, Sqlite.TRANSACTIONS_TIMEOUT_MS);
+    });
+    this._timeoutPromise = timeoutPromise;
+    this._timeoutPromiseExpires =
+      Cu.now() + Sqlite.TRANSACTIONS_TIMEOUT_MS * 0.2;
+    return this._timeoutPromise;
+  },
+
+  /**
+   * Asynchronously makes a copy of the SQLite database while there may still be
+   * open connections on it.
+   *
+   * @param {string} destFilePath
+   *   The path on the local filesystem to write the database copy. Any existing
+   *   file at this path will be overwritten.
+   * @return Promise<undefined, nsresult>
+   */
+  async backupToFile(destFilePath) {
+    if (!this._dbConn) {
+      return Promise.reject(
+        new Error("No opened database connection to create a backup from.")
+      );
+    }
+    let destFile = await IOUtils.getFile(destFilePath);
+    return new Promise((resolve, reject) => {
+      this._dbConn.backupToFileAsync(destFile, result => {
+        if (Components.isSuccessCode(result)) {
+          resolve();
+        } else {
+          reject(result);
+        }
+      });
+    });
+  },
+});
+
+/**
+ * Opens a connection to a SQLite database.
+ *
+ * The following parameters can control the connection:
+ *
+ *   path -- (string) The filesystem path of the database file to open. If the
+ *       file does not exist, a new database will be created.
+ *
+ *   sharedMemoryCache -- (bool) Whether multiple connections to the database
+ *       share the same memory cache. Sharing the memory cache likely results
+ *       in less memory utilization. However, sharing also requires connections
+ *       to obtain a lock, possibly making database access slower. Defaults to
+ *       true.
+ *
+ *   shrinkMemoryOnConnectionIdleMS -- (integer) If defined, the connection
+ *       will attempt to minimize its memory usage after this many
+ *       milliseconds of connection idle. The connection is idle when no
+ *       statements are executing. There is no default value which means no
+ *       automatic memory minimization will occur. Please note that this is
+ *       *not* a timer on the idle service and this could fire while the
+ *       application is active.
+ *
+ *   readOnly -- (bool) Whether to open the database with SQLITE_OPEN_READONLY
+ *       set. If used, writing to the database will fail. Defaults to false.
+ *
+ *   ignoreLockingMode -- (bool) Whether to ignore locks on the database held
+ *       by other connections. If used, implies readOnly. Defaults to false.
+ *       USE WITH EXTREME CAUTION. This mode WILL produce incorrect results or
+ *       return "false positive" corruption errors if other connections write
+ *       to the DB at the same time.
+ *
+ *   vacuumOnIdle -- (bool) Whether to register this connection to be vacuumed
+ *       on idle by the VacuumManager component.
+ *       If you're vacuum-ing an incremental vacuum database, ensure to also
+ *       set incrementalVacuum to true, otherwise this will try to change it
+ *       to full vacuum mode.
+ *
+ *   incrementalVacuum -- (bool) if set to true auto_vacuum = INCREMENTAL will
+ *       be enabled for the database.
+ *       Changing auto vacuum of an already populated database requires a full
+ *       VACUUM. You can evaluate to enable vacuumOnIdle for that.
+ *
+ *   pageSize -- (integer) This allows to set a custom page size for the
+ *       database. It is usually not necessary to set it, since the default
+ *       value should be good for most consumers.
+ *       Changing the page size of an already populated database requires a full
+ *       VACUUM. You can evaluate to enable vacuumOnIdle for that.
+ *
+ *   testDelayedOpenPromise -- (promise) Used by tests to delay the open
+ *       callback handling and execute code between asyncOpen and its callback.
+ *
+ * FUTURE options to control:
+ *
+ *   special named databases
+ *   pragma TEMP STORE = MEMORY
+ *   TRUNCATE JOURNAL
+ *   SYNCHRONOUS = full
+ *
+ * @param options
+ *        (Object) Parameters to control connection and open options.
+ *
+ * @return Promise<OpenedConnection>
+ */
+function openConnection(options) {
+  let log = lazy.Log.repository.getLoggerWithMessagePrefix(
+    "Sqlite.sys.mjs",
+    `ConnectionOpener: `
+  );
+  log.manageLevelFromPref("toolkit.sqlitejsm.loglevel");
+
+  if (!options.path) {
+    throw new Error("path not specified in connection options.");
+  }
+
+  if (isClosed()) {
+    throw new Error(
+      "Sqlite.sys.mjs has been shutdown. Cannot open connection to: " +
+        options.path
+    );
+  }
+
+  // Retains absolute paths and normalizes relative as relative to profile.
+  let path = options.path;
+  let file;
+  try {
+    file = lazy.FileUtils.File(path);
+  } catch (ex) {
+    // For relative paths, we will get an exception from trying to initialize
+    // the file. We must then join this path to the profile directory.
+    if (ex.result == Cr.NS_ERROR_FILE_UNRECOGNIZED_PATH) {
+      path = PathUtils.joinRelative(
+        Services.dirsvc.get("ProfD", Ci.nsIFile).path,
+        options.path
+      );
+      file = lazy.FileUtils.File(path);
+    } else {
+      throw ex;
+    }
+  }
+
+  let sharedMemoryCache =
+    "sharedMemoryCache" in options ? options.sharedMemoryCache : true;
+
+  let openedOptions = {};
+
+  if ("shrinkMemoryOnConnectionIdleMS" in options) {
+    if (!Number.isInteger(options.shrinkMemoryOnConnectionIdleMS)) {
+      throw new Error(
+        "shrinkMemoryOnConnectionIdleMS must be an integer. " +
+          "Got: " +
+          options.shrinkMemoryOnConnectionIdleMS
+      );
+    }
+
+    openedOptions.shrinkMemoryOnConnectionIdleMS =
+      options.shrinkMemoryOnConnectionIdleMS;
+  }
+
+  if ("defaultTransactionType" in options) {
+    let defaultTransactionType = options.defaultTransactionType;
+    if (!OpenedConnection.TRANSACTION_TYPES.includes(defaultTransactionType)) {
+      throw new Error(
+        "Unknown default transaction type: " + defaultTransactionType
+      );
+    }
+
+    openedOptions.defaultTransactionType = defaultTransactionType;
+  }
+
+  if ("vacuumOnIdle" in options) {
+    if (typeof options.vacuumOnIdle != "boolean") {
+      throw new Error("Invalid vacuumOnIdle: " + options.vacuumOnIdle);
+    }
+    openedOptions.vacuumOnIdle = options.vacuumOnIdle;
+  }
+
+  if ("incrementalVacuum" in options) {
+    if (typeof options.incrementalVacuum != "boolean") {
+      throw new Error(
+        "Invalid incrementalVacuum: " + options.incrementalVacuum
+      );
+    }
+    openedOptions.incrementalVacuum = options.incrementalVacuum;
+  }
+
+  if ("pageSize" in options) {
+    if (
+      ![512, 1024, 2048, 4096, 8192, 16384, 32768, 65536].includes(
+        options.pageSize
+      )
+    ) {
+      throw new Error("Invalid pageSize: " + options.pageSize);
+    }
+    openedOptions.pageSize = options.pageSize;
+  }
+
+  let identifier = getIdentifierByFileName(PathUtils.filename(path));
+
+  log.debug("Opening database: " + path + " (" + identifier + ")");
+
+  return new Promise((resolve, reject) => {
+    let dbOpenOptions = Ci.mozIStorageService.OPEN_DEFAULT;
+    if (sharedMemoryCache) {
+      dbOpenOptions |= Ci.mozIStorageService.OPEN_SHARED;
+    }
+    if (options.readOnly) {
+      dbOpenOptions |= Ci.mozIStorageService.OPEN_READONLY;
+    }
+    if (options.ignoreLockingMode) {
+      dbOpenOptions |= Ci.mozIStorageService.OPEN_IGNORE_LOCKING_MODE;
+      dbOpenOptions |= Ci.mozIStorageService.OPEN_READONLY;
+    }
+
+    let dbConnectionOptions = Ci.mozIStorageService.CONNECTION_DEFAULT;
+
+    Services.storage.openAsyncDatabase(
+      file,
+      dbOpenOptions,
+      dbConnectionOptions,
+      async (status, connection) => {
+        if (!connection) {
+          log.error(`Could not open connection to ${path}: ${status}`);
+          let error = new Components.Exception(
+            `Could not open connection to ${path}: ${status}`,
+            status
+          );
+          reject(error);
+          return;
+        }
+        log.debug("Connection opened");
+
+        if (options.testDelayedOpenPromise) {
+          await options.testDelayedOpenPromise;
+        }
+
+        if (isClosed()) {
+          connection.QueryInterface(Ci.mozIStorageAsyncConnection).asyncClose();
+          reject(
+            new Error(
+              "Sqlite.sys.mjs has been shutdown. Cannot open connection to: " +
+                options.path
+            )
+          );
+          return;
+        }
+
+        try {
+          resolve(
+            new OpenedConnection(
+              connection.QueryInterface(Ci.mozIStorageAsyncConnection),
+              identifier,
+              openedOptions
+            )
+          );
+        } catch (ex) {
+          log.error("Could not open database", ex);
+          connection.asyncClose();
+          reject(ex);
+        }
+      }
+    );
+  });
+}
+
+/**
+ * Creates a clone of an existing and open Storage connection.  The clone has
+ * the same underlying characteristics of the original connection and is
+ * returned in form of an OpenedConnection handle.
+ *
+ * The following parameters can control the cloned connection:
+ *
+ *   connection -- (mozIStorageAsyncConnection) The original Storage connection
+ *       to clone.  It's not possible to clone connections to memory databases.
+ *
+ *   readOnly -- (boolean) - If true the clone will be read-only.  If the
+ *       original connection is already read-only, the clone will be, regardless
+ *       of this option.  If the original connection is using the shared cache,
+ *       this parameter will be ignored and the clone will be as privileged as
+ *       the original connection.
+ *   shrinkMemoryOnConnectionIdleMS -- (integer) If defined, the connection
+ *       will attempt to minimize its memory usage after this many
+ *       milliseconds of connection idle. The connection is idle when no
+ *       statements are executing. There is no default value which means no
+ *       automatic memory minimization will occur. Please note that this is
+ *       *not* a timer on the idle service and this could fire while the
+ *       application is active.
+ *
+ *
+ * @param options
+ *        (Object) Parameters to control connection and clone options.
+ *
+ * @return Promise<OpenedConnection>
+ */
+function cloneStorageConnection(options) {
+  let log = lazy.Log.repository.getLoggerWithMessagePrefix(
+    "Sqlite.sys.mjs",
+    `ConnectionCloner: `
+  );
+  log.manageLevelFromPref("toolkit.sqlitejsm.loglevel");
+
+  let source = options && options.connection;
+  if (!source) {
+    throw new TypeError("connection not specified in clone options.");
+  }
+  if (!(source instanceof Ci.mozIStorageAsyncConnection)) {
+    throw new TypeError("Connection must be a valid Storage connection.");
+  }
+
+  if (isClosed()) {
+    throw new Error(
+      "Sqlite.sys.mjs has been shutdown. Cannot clone connection to: " +
+        source.databaseFile.path
+    );
+  }
+
+  let openedOptions = {};
+
+  if ("shrinkMemoryOnConnectionIdleMS" in options) {
+    if (!Number.isInteger(options.shrinkMemoryOnConnectionIdleMS)) {
+      throw new TypeError(
+        "shrinkMemoryOnConnectionIdleMS must be an integer. " +
+          "Got: " +
+          options.shrinkMemoryOnConnectionIdleMS
+      );
+    }
+    openedOptions.shrinkMemoryOnConnectionIdleMS =
+      options.shrinkMemoryOnConnectionIdleMS;
+  }
+
+  let path = source.databaseFile.path;
+  let identifier = getIdentifierByFileName(PathUtils.filename(path));
+
+  log.debug("Cloning database: " + path + " (" + identifier + ")");
+
+  return new Promise((resolve, reject) => {
+    source.asyncClone(!!options.readOnly, (status, connection) => {
+      if (!connection) {
+        log.error("Could not clone connection: " + status);
+        reject(new Error("Could not clone connection: " + status));
+        return;
+      }
+      log.debug("Connection cloned");
+
+      if (isClosed()) {
+        connection.QueryInterface(Ci.mozIStorageAsyncConnection).asyncClose();
+        reject(
+          new Error(
+            "Sqlite.sys.mjs has been shutdown. Cannot open connection to: " +
+              options.path
+          )
+        );
+        return;
+      }
+
+      try {
+        let conn = connection.QueryInterface(Ci.mozIStorageAsyncConnection);
+        resolve(new OpenedConnection(conn, identifier, openedOptions));
+      } catch (ex) {
+        log.error("Could not clone database", ex);
+        connection.asyncClose();
+        reject(ex);
+      }
+    });
+  });
+}
+
+/**
+ * Wraps an existing and open Storage connection with Sqlite.sys.mjs API.  The
+ * wrapped connection clone has the same underlying characteristics of the
+ * original connection and is returned in form of an OpenedConnection handle.
+ *
+ * Clients are responsible for closing both the Sqlite.sys.mjs wrapper and the
+ * underlying mozStorage connection.
+ *
+ * The following parameters can control the wrapped connection:
+ *
+ *   connection -- (mozIStorageAsyncConnection) The original Storage connection
+ *       to wrap.
+ *
+ * @param options
+ *        (Object) Parameters to control connection and wrap options.
+ *
+ * @return Promise<OpenedConnection>
+ */
+function wrapStorageConnection(options) {
+  let log = lazy.Log.repository.getLoggerWithMessagePrefix(
+    "Sqlite.sys.mjs",
+    `ConnectionCloner: `
+  );
+  log.manageLevelFromPref("toolkit.sqlitejsm.loglevel");
+
+  let connection = options && options.connection;
+  if (!connection || !(connection instanceof Ci.mozIStorageAsyncConnection)) {
+    throw new TypeError("connection not specified or invalid.");
+  }
+
+  if (isClosed()) {
+    throw new Error(
+      "Sqlite.sys.mjs has been shutdown. Cannot wrap connection to: " +
+        connection.databaseFile.path
+    );
+  }
+
+  let identifier = getIdentifierByFileName(connection.databaseFile.leafName);
+
+  log.debug("Wrapping database: " + identifier);
+  return new Promise(resolve => {
+    try {
+      let conn = connection.QueryInterface(Ci.mozIStorageAsyncConnection);
+      let wrapper = new OpenedConnection(conn, identifier);
+      // We must not handle shutdown of a wrapped connection, since that is
+      // already handled by the opener.
+      wrappedConnections.add(identifier);
+      resolve(wrapper);
+    } catch (ex) {
+      log.error("Could not wrap database", ex);
+      throw ex;
+    }
+  });
+}
+
+/**
+ * Handle on an opened SQLite database.
+ *
+ * This is essentially a glorified wrapper around mozIStorageConnection.
+ * However, it offers some compelling advantages.
+ *
+ * The main functions on this type are `execute` and `executeCached`. These are
+ * ultimately how all SQL statements are executed. It's worth explaining their
+ * differences.
+ *
+ * `execute` is used to execute one-shot SQL statements. These are SQL
+ * statements that are executed one time and then thrown away. They are useful
+ * for dynamically generated SQL statements and clients who don't care about
+ * performance (either their own or wasting resources in the overall
+ * application). Because of the performance considerations, it is recommended
+ * to avoid `execute` unless the statement you are executing will only be
+ * executed once or seldomly.
+ *
+ * `executeCached` is used to execute a statement that will presumably be
+ * executed multiple times. The statement is parsed once and stuffed away
+ * inside the connection instance. Subsequent calls to `executeCached` will not
+ * incur the overhead of creating a new statement object. This should be used
+ * in preference to `execute` when a specific SQL statement will be executed
+ * multiple times.
+ *
+ * Instances of this type are not meant to be created outside of this file.
+ * Instead, first open an instance of `UnopenedSqliteConnection` and obtain
+ * an instance of this type by calling `open`.
+ *
+ * FUTURE IMPROVEMENTS
+ *
+ *   Ability to enqueue operations. Currently there can be race conditions,
+ *   especially as far as transactions are concerned. It would be nice to have
+ *   an enqueueOperation(func) API that serially executes passed functions.
+ *
+ *   Support for SAVEPOINT (named/nested transactions) might be useful.
+ *
+ * @param connection
+ *        (mozIStorageConnection) Underlying SQLite connection.
+ * @param identifier
+ *        (string) The unique identifier of this database. It may be used for
+ *        logging or as a key in Maps.
+ * @param options [optional]
+ *        (object) Options to control behavior of connection. See
+ *        `openConnection`.
+ */
+function OpenedConnection(connection, identifier, options = {}) {
+  // Store all connection data in a field distinct from the
+  // witness. This enables us to store an additional reference to this
+  // field without preventing garbage collection of
+  // OpenedConnection. On garbage collection, we will still be able to
+  // close the database using this extra reference.
+  this._connectionData = new ConnectionData(connection, identifier, options);
+
+  // Store the extra reference in a map with connection identifier as
+  // key.
+  ConnectionData.byId.set(
+    this._connectionData._identifier,
+    this._connectionData
+  );
+
+  // Make a finalization witness. If this object is garbage collected
+  // before its `forget` method has been called, an event with topic
+  // "sqlite-finalization-witness" is broadcasted along with the
+  // connection identifier string of the database.
+  this._witness = lazy.FinalizationWitnessService.make(
+    "sqlite-finalization-witness",
+    this._connectionData._identifier
+  );
+}
+
+OpenedConnection.TRANSACTION_TYPES = ["DEFERRED", "IMMEDIATE", "EXCLUSIVE"];
+
+// Converts a `mozIStorageAsyncConnection::TRANSACTION_*` constant into the
+// corresponding `OpenedConnection.TRANSACTION_TYPES` constant.
+function convertStorageTransactionType(type) {
+  if (!(type in OpenedConnection.TRANSACTION_TYPES)) {
+    throw new Error("Unknown storage transaction type: " + type);
+  }
+  return OpenedConnection.TRANSACTION_TYPES[type];
+}
+
+OpenedConnection.prototype = Object.freeze({
+  TRANSACTION_DEFAULT: "DEFAULT",
+  TRANSACTION_DEFERRED: "DEFERRED",
+  TRANSACTION_IMMEDIATE: "IMMEDIATE",
+  TRANSACTION_EXCLUSIVE: "EXCLUSIVE",
+
+  /**
+   * Returns a handle to the underlying `mozIStorageAsyncConnection`. This is
+   * ⚠️ **extremely unsafe** ⚠️ because `Sqlite.sys.mjs` continues to manage the
+   * connection's lifecycle, including transactions and shutdown blockers.
+   * Misusing the raw connection can easily lead to data loss, memory leaks,
+   * and errors.
+   *
+   * Consumers of the raw connection **must not** close or re-wrap it,
+   * and should not run statements concurrently with `Sqlite.sys.mjs`.
+   *
+   * It's _much_ safer to open a `mozIStorage{Async}Connection` yourself,
+   * and access it from JavaScript via `Sqlite.wrapStorageConnection`.
+   * `unsafeRawConnection` is an escape hatch for cases where you can't
+   * do that.
+   *
+   * Please do _not_ add new uses of `unsafeRawConnection` without review
+   * from a storage peer.
+   */
+  get unsafeRawConnection() {
+    return this._connectionData._dbConn;
+  },
+
+  /**
+   * Returns the maximum number of bound parameters for statements executed
+   * on this connection.
+   *
+   * @type {number}
+   */
+  get variableLimit() {
+    return this.unsafeRawConnection.variableLimit;
+  },
+
+  /**
+   * The integer schema version of the database.
+   *
+   * This is 0 if not schema version has been set.
+   *
+   * @return Promise<int>
+   */
+  getSchemaVersion(schemaName = "main") {
+    return this.execute(`PRAGMA ${schemaName}.user_version`).then(result =>
+      result[0].getInt32(0)
+    );
+  },
+
+  setSchemaVersion(value, schemaName = "main") {
+    if (!Number.isInteger(value)) {
+      // Guarding against accidental SQLi
+      throw new TypeError("Schema version must be an integer. Got " + value);
+    }
+    this._connectionData.ensureOpen();
+    return this.execute(`PRAGMA ${schemaName}.user_version = ${value}`);
+  },
+
+  /**
+   * Close the database connection.
+   *
+   * This must be performed when you are finished with the database.
+   *
+   * Closing the database connection has the side effect of forcefully
+   * cancelling all active statements. Therefore, callers should ensure that
+   * all active statements have completed before closing the connection, if
+   * possible.
+   *
+   * The returned promise will be resolved once the connection is closed.
+   * Successive calls to close() return the same promise.
+   *
+   * IMPROVEMENT: Resolve the promise to a closed connection which can be
+   * reopened.
+   *
+   * @return Promise<>
+   */
+  close() {
+    // Unless cleanup has already been done by a previous call to
+    // `close`, delete the database entry from map and tell the
+    // finalization witness to forget.
+    if (ConnectionData.byId.has(this._connectionData._identifier)) {
+      ConnectionData.byId.delete(this._connectionData._identifier);
+      this._witness.forget();
+    }
+    return this._connectionData.close();
+  },
+
+  /**
+   * Clones this connection to a new Sqlite one.
+   *
+   * The following parameters can control the cloned connection:
+   *
+   * @param readOnly
+   *        (boolean) - If true the clone will be read-only.  If the original
+   *        connection is already read-only, the clone will be, regardless of
+   *        this option.  If the original connection is using the shared cache,
+   *        this parameter will be ignored and the clone will be as privileged as
+   *        the original connection.
+   *
+   * @return Promise<OpenedConnection>
+   */
+  clone(readOnly = false) {
+    return this._connectionData.clone(readOnly);
+  },
+
+  executeBeforeShutdown(name, task) {
+    return this._connectionData.executeBeforeShutdown(this, name, task);
+  },
+
+  /**
+   * Execute a SQL statement and cache the underlying statement object.
+   *
+   * This function executes a SQL statement and also caches the underlying
+   * derived statement object so subsequent executions are faster and use
+   * less resources.
+   *
+   * This function optionally binds parameters to the statement as well as
+   * optionally invokes a callback for every row retrieved.
+   *
+   * By default, no parameters are bound and no callback will be invoked for
+   * every row.
+   *
+   * Bound parameters can be defined as an Array of positional arguments or
+   * an object mapping named parameters to their values. If there are no bound
+   * parameters, the caller can pass nothing or null for this argument.
+   *
+   * Callers are encouraged to pass objects rather than Arrays for bound
+   * parameters because they prevent foot guns. With positional arguments, it
+   * is simple to modify the parameter count or positions without fixing all
+   * users of the statement. Objects/named parameters are a little safer
+   * because changes in order alone won't result in bad things happening.
+   *
+   * When `onRow` is not specified, all returned rows are buffered before the
+   * returned promise is resolved. For INSERT or UPDATE statements, this has
+   * no effect because no rows are returned from these. However, it has
+   * implications for SELECT statements.
+   *
+   * If your SELECT statement could return many rows or rows with large amounts
+   * of data, for performance reasons it is recommended to pass an `onRow`
+   * handler. Otherwise, the buffering may consume unacceptable amounts of
+   * resources.
+   *
+   * If the second parameter of an `onRow` handler is called during execution
+   * of the `onRow` handler, the execution of the statement is immediately
+   * cancelled. Subsequent rows will not be processed and no more `onRow`
+   * invocations will be made. The promise is resolved immediately.
+   *
+   * If an exception is thrown by the `onRow` handler, the exception is logged
+   * and processing of subsequent rows occurs as if nothing happened. The
+   * promise is still resolved (not rejected).
+   *
+   * The return value is a promise that will be resolved when the statement
+   * has completed fully.
+   *
+   * The promise will be rejected with an `Error` instance if the statement
+   * did not finish execution fully. The `Error` may have an `errors` property.
+   * If defined, it will be an Array of objects describing individual errors.
+   * Each object has the properties `result` and `message`. `result` is a
+   * numeric error code and `message` is a string description of the problem.
+   *
+   * @param name
+   *        (string) The name of the registered statement to execute.
+   * @param params optional
+   *        (Array or object) Parameters to bind.
+   * @param onRow optional
+   *        (function) Callback to receive each row from result.
+   */
+  executeCached(sql, params = null, onRow = null) {
+    if (isInvalidBoundLikeQuery(sql)) {
+      throw new Error("Please enter a LIKE clause with bindings");
+    }
+    return this._connectionData.executeCached(sql, params, onRow);
+  },
+
+  /**
+   * Execute a one-shot SQL statement.
+   *
+   * If you find yourself feeding the same SQL string in this function, you
+   * should *not* use this function and instead use `executeCached`.
+   *
+   * See `executeCached` for the meaning of the arguments and extended usage info.
+   *
+   * @param sql
+   *        (string) SQL to execute.
+   * @param params optional
+   *        (Array or Object) Parameters to bind to the statement.
+   * @param onRow optional
+   *        (function) Callback to receive result of a single row.
+   */
+  execute(sql, params = null, onRow = null) {
+    if (isInvalidBoundLikeQuery(sql)) {
+      throw new Error("Please enter a LIKE clause with bindings");
+    }
+    return this._connectionData.execute(sql, params, onRow);
+  },
+
+  /**
+   * The default behavior for transactions run on this connection.
+   */
+  get defaultTransactionType() {
+    return this._connectionData.defaultTransactionType;
+  },
+
+  /**
+   * Whether a transaction is currently in progress.
+   *
+   * Note that this is true if a transaction is active on the connection,
+   * regardless of whether it was started by `Sqlite.sys.mjs` or another consumer.
+   * See the explanation above `mozIStorageConnection.transactionInProgress` for
+   * why this distinction matters.
+   */
+  get transactionInProgress() {
+    return this._connectionData.transactionInProgress;
+  },
+
+  /**
+   * Perform a transaction.
+   *
+   * *****************************************************************************
+   * YOU SHOULD _NEVER_ NEST executeTransaction CALLS FOR ANY REASON, NOR
+   * DIRECTLY, NOR THROUGH OTHER PROMISES.
+   * FOR EXAMPLE, NEVER DO SOMETHING LIKE:
+   *   await executeTransaction(async function () {
+   *     ...some_code...
+   *     await executeTransaction(async function () { // WRONG!
+   *       ...some_code...
+   *     })
+   *     await someCodeThatExecuteTransaction(); // WRONG!
+   *     await neverResolvedPromise; // WRONG!
+   *   });
+   * NESTING CALLS WILL BLOCK ANY FUTURE TRANSACTION UNTIL A TIMEOUT KICKS IN.
+   * *****************************************************************************
+   *
+   * A transaction is specified by a user-supplied function that is an
+   * async function. The function receives this connection instance as its argument.
+   *
+   * The supplied function is expected to return promises. These are often
+   * promises created by calling `execute` and `executeCached`. If the
+   * generator is exhausted without any errors being thrown, the
+   * transaction is committed. If an error occurs, the transaction is
+   * rolled back.
+   *
+   * The returned value from this function is a promise that will be resolved
+   * once the transaction has been committed or rolled back. The promise will
+   * be resolved to whatever value the supplied function resolves to. If
+   * the transaction is rolled back, the promise is rejected.
+   *
+   * @param func
+   *        (function) What to perform as part of the transaction.
+   * @param type optional
+   *        One of the TRANSACTION_* constants attached to this type.
+   */
+  executeTransaction(func, type = this.TRANSACTION_DEFAULT) {
+    return this._connectionData.executeTransaction(() => func(this), type);
+  },
+
+  /**
+   * Whether a table exists in the database (both persistent and temporary tables).
+   *
+   * @param name
+   *        (string) Name of the table.
+   *
+   * @return Promise<bool>
+   */
+  tableExists(name) {
+    return this.execute(
+      "SELECT name FROM (SELECT * FROM sqlite_master UNION ALL " +
+        "SELECT * FROM sqlite_temp_master) " +
+        "WHERE type = 'table' AND name=?",
+      [name]
+    ).then(function onResult(rows) {
+      return Promise.resolve(!!rows.length);
+    });
+  },
+
+  /**
+   * Whether a named index exists (both persistent and temporary tables).
+   *
+   * @param name
+   *        (string) Name of the index.
+   *
+   * @return Promise<bool>
+   */
+  indexExists(name) {
+    return this.execute(
+      "SELECT name FROM (SELECT * FROM sqlite_master UNION ALL " +
+        "SELECT * FROM sqlite_temp_master) " +
+        "WHERE type = 'index' AND name=?",
+      [name]
+    ).then(function onResult(rows) {
+      return Promise.resolve(!!rows.length);
+    });
+  },
+
+  /**
+   * Free up as much memory from the underlying database connection as possible.
+   *
+   * @return Promise<>
+   */
+  shrinkMemory() {
+    return this._connectionData.shrinkMemory();
+  },
+
+  /**
+   * Discard all cached statements.
+   *
+   * Note that this relies on us being non-interruptible between
+   * the insertion or retrieval of a statement in the cache and its
+   * execution: we finalize all statements, which is only safe if
+   * they will not be executed again.
+   *
+   * @return (integer) the number of statements discarded.
+   */
+  discardCachedStatements() {
+    return this._connectionData.discardCachedStatements();
+  },
+
+  /**
+   * Interrupts pending database operations returning at the first opportunity.
+   * Statement execution will throw an NS_ERROR_ABORT failure.
+   * Can only be used on read-only connections.
+   */
+  interrupt() {
+    this._connectionData.interrupt();
+  },
+
+  /**
+   * Asynchronously makes a copy of the SQLite database while there may still be
+   * open connections on it.
+   *
+   * @param {string} destFilePath
+   *   The path on the local filesystem to write the database copy. Any existing
+   *   file at this path will be overwritten.
+   * @return Promise<undefined, nsresult>
+   */
+  backup(destFilePath) {
+    return this._connectionData.backupToFile(destFilePath);
+  },
+});
+
+export var Sqlite = {
+  // The maximum time to wait before considering a transaction stuck and
+  // issuing a ROLLBACK, see `executeTransaction`. Could be modified by tests.
+  TRANSACTIONS_TIMEOUT_MS: 300000, // 5 minutes
+
+  openConnection,
+  cloneStorageConnection,
+  wrapStorageConnection,
+  /**
+   * Shutdown barrier client. May be used by clients to perform last-minute
+   * cleanup prior to the shutdown of this module.
+   *
+   * See the documentation of AsyncShutdown.Barrier.prototype.client.
+   */
+  get shutdown() {
+    return lazy.Barriers.shutdown.client;
+  },
+  failTestsOnAutoClose(enabled) {
+    Debugging.failTestsOnAutoClose = enabled;
+  },
+};