The Tor Browser: toolkit/components/satchel/nsFormHistory.js@6474c204b198 (annotated)

toolkit/components/satchel/nsFormHistory.js@6474c204b198 (annotated)

toolkit/components/satchel/nsFormHistory.js

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* 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/. */
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cr = Components.results;
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 Components.utils.import("resource://gre/modules/Services.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Deprecated",
                                   "resource://gre/modules/Deprecated.jsm");
 const DB_VERSION = 4;
 const DAY_IN_MS  = 86400000; // 1 day in milliseconds
 function FormHistory() {
     Deprecated.warning(
         "nsIFormHistory2 is deprecated and will be removed in a future version",
         "https://bugzilla.mozilla.org/show_bug.cgi?id=879118");
     this.init();
 }
 FormHistory.prototype = {
     classID          : Components.ID("{0c1bb408-71a2-403f-854a-3a0659829ded}"),
     QueryInterface   : XPCOMUtils.generateQI([Ci.nsIFormHistory2,
                                               Ci.nsIObserver,
                                               Ci.nsIMessageListener,
                                               Ci.nsISupportsWeakReference,
                                               ]),
     debug          : true,
     enabled        : true,
     // The current database schema.
     dbSchema : {
         tables : {
             moz_formhistory: {
                 "id"        : "INTEGER PRIMARY KEY",
                 "fieldname" : "TEXT NOT NULL",
                 "value"     : "TEXT NOT NULL",
                 "timesUsed" : "INTEGER",
                 "firstUsed" : "INTEGER",
                 "lastUsed"  : "INTEGER",
                 "guid"      : "TEXT"
             },
             moz_deleted_formhistory: {
                 "id"          : "INTEGER PRIMARY KEY",
                 "timeDeleted" : "INTEGER",
                 "guid"        : "TEXT"
             }
         },
         indices : {
             moz_formhistory_index : {
                 table   : "moz_formhistory",
                 columns : ["fieldname"]
             },
             moz_formhistory_lastused_index : {
                 table   : "moz_formhistory",
                 columns : ["lastUsed"]
             },
             moz_formhistory_guid_index : {
                 table   : "moz_formhistory",
                 columns : ["guid"]
             },
         }
     },
     dbStmts      : null,  // Database statements for memoization
     dbFile       : null,
     _uuidService: null,
     get uuidService() {
         if (!this._uuidService)
             this._uuidService = Cc["@mozilla.org/uuid-generator;1"].
                                 getService(Ci.nsIUUIDGenerator);
         return this._uuidService;
     },
     log : function log(message) {
         if (!this.debug)
             return;
         dump("FormHistory: " + message + "\n");
         Services.console.logStringMessage("FormHistory: " + message);
     },
     init : function init() {
         this.updatePrefs();
         this.dbStmts = {};
         // Add observer
         Services.obs.addObserver(this, "profile-before-change", true);
     },
     /* ---- nsIFormHistory2 interfaces ---- */
     get hasEntries() {
         return (this.countAllEntries() > 0);
     },
     addEntry : function addEntry(name, value) {
         if (!this.enabled)
             return;
         this.log("addEntry for " + name + "=" + value);
         let now = Date.now() * 1000; // microseconds
         let [id, guid] = this.getExistingEntryID(name, value);
         let stmt;
         if (id != -1) {
             // Update existing entry.
             let query = "UPDATE moz_formhistory SET timesUsed = timesUsed + 1, lastUsed = :lastUsed WHERE id = :id";
             let params = {
                             lastUsed : now,
                             id       : id
                          };
             try {
                 stmt = this.dbCreateStatement(query, params);
                 stmt.execute();
                 this.sendStringNotification("modifyEntry", name, value, guid);
             } catch (e) {
                 this.log("addEntry (modify) failed: " + e);
                 throw e;
             } finally {
                 if (stmt) {
                     stmt.reset();
                 }
             }
         } else {
             // Add new entry.
             guid = this.generateGUID();
             let query = "INSERT INTO moz_formhistory (fieldname, value, timesUsed, firstUsed, lastUsed, guid) " +
                             "VALUES (:fieldname, :value, :timesUsed, :firstUsed, :lastUsed, :guid)";
             let params = {
                             fieldname : name,
                             value     : value,
                             timesUsed : 1,
                             firstUsed : now,
                             lastUsed  : now,
                             guid      : guid
                         };
             try {
                 stmt = this.dbCreateStatement(query, params);
                 stmt.execute();
                 this.sendStringNotification("addEntry", name, value, guid);
             } catch (e) {
                 this.log("addEntry (create) failed: " + e);
                 throw e;
             } finally {
                 if (stmt) {
                     stmt.reset();
                 }
             }
         }
     },
     removeEntry : function removeEntry(name, value) {
         this.log("removeEntry for " + name + "=" + value);
         let [id, guid] = this.getExistingEntryID(name, value);
         this.sendStringNotification("before-removeEntry", name, value, guid);
         let stmt;
         let query = "DELETE FROM moz_formhistory WHERE id = :id";
         let params = { id : id };
         let existingTransactionInProgress;
         try {
             // Don't start a transaction if one is already in progress since we can't nest them.
             existingTransactionInProgress = this.dbConnection.transactionInProgress;
             if (!existingTransactionInProgress)
                 this.dbConnection.beginTransaction();
             this.moveToDeletedTable("VALUES (:guid, :timeDeleted)", {
               guid: guid,
               timeDeleted: Date.now()
             });
             // remove from the formhistory database
             stmt = this.dbCreateStatement(query, params);
             stmt.execute();
             this.sendStringNotification("removeEntry", name, value, guid);
         } catch (e) {
             if (!existingTransactionInProgress)
                 this.dbConnection.rollbackTransaction();
             this.log("removeEntry failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
         if (!existingTransactionInProgress)
             this.dbConnection.commitTransaction();
     },
     removeEntriesForName : function removeEntriesForName(name) {
         this.log("removeEntriesForName with name=" + name);
         this.sendStringNotification("before-removeEntriesForName", name);
         let stmt;
         let query = "DELETE FROM moz_formhistory WHERE fieldname = :fieldname";
         let params = { fieldname : name };
         let existingTransactionInProgress;
         try {
             // Don't start a transaction if one is already in progress since we can't nest them.
             existingTransactionInProgress = this.dbConnection.transactionInProgress;
             if (!existingTransactionInProgress)
                 this.dbConnection.beginTransaction();
             this.moveToDeletedTable(
               "SELECT guid, :timeDeleted FROM moz_formhistory " +
               "WHERE fieldname = :fieldname", {
                 fieldname: name,
                 timeDeleted: Date.now()
             });
             stmt = this.dbCreateStatement(query, params);
             stmt.execute();
             this.sendStringNotification("removeEntriesForName", name);
         } catch (e) {
             if (!existingTransactionInProgress)
                 this.dbConnection.rollbackTransaction();
             this.log("removeEntriesForName failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
         if (!existingTransactionInProgress)
             this.dbConnection.commitTransaction();
     },
     removeAllEntries : function removeAllEntries() {
         this.log("removeAllEntries");
         this.sendNotification("before-removeAllEntries", null);
         let stmt;
         let query = "DELETE FROM moz_formhistory";
         let existingTransactionInProgress;
         try {
             // Don't start a transaction if one is already in progress since we can't nest them.
             existingTransactionInProgress = this.dbConnection.transactionInProgress;
             if (!existingTransactionInProgress)
                 this.dbConnection.beginTransaction();
             // TODO: Add these items to the deleted items table once we've sorted
             //       out the issues from bug 756701
             stmt = this.dbCreateStatement(query);
             stmt.execute();
             this.sendNotification("removeAllEntries", null);
         } catch (e) {
             if (!existingTransactionInProgress)
                 this.dbConnection.rollbackTransaction();
             this.log("removeAllEntries failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
         if (!existingTransactionInProgress)
             this.dbConnection.commitTransaction();
     },
     nameExists : function nameExists(name) {
         this.log("nameExists for name=" + name);
         let stmt;
         let query = "SELECT COUNT(1) AS numEntries FROM moz_formhistory WHERE fieldname = :fieldname";
         let params = { fieldname : name };
         try {
             stmt = this.dbCreateStatement(query, params);
             stmt.executeStep();
             return (stmt.row.numEntries > 0);
         } catch (e) {
             this.log("nameExists failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
     },
     entryExists : function entryExists(name, value) {
         this.log("entryExists for " + name + "=" + value);
         let [id, guid] = this.getExistingEntryID(name, value);
         this.log("entryExists: id=" + id);
         return (id != -1);
     },
     removeEntriesByTimeframe : function removeEntriesByTimeframe(beginTime, endTime) {
         this.log("removeEntriesByTimeframe for " + beginTime + " to " + endTime);
         this.sendIntNotification("before-removeEntriesByTimeframe", beginTime, endTime);
         let stmt;
         let query = "DELETE FROM moz_formhistory WHERE firstUsed >= :beginTime AND firstUsed <= :endTime";
         let params = {
                         beginTime : beginTime,
                         endTime   : endTime
                      };
         let existingTransactionInProgress;
         try {
             // Don't start a transaction if one is already in progress since we can't nest them.
             existingTransactionInProgress = this.dbConnection.transactionInProgress;
             if (!existingTransactionInProgress)
                 this.dbConnection.beginTransaction();
             this.moveToDeletedTable(
                   "SELECT guid, :timeDeleted FROM moz_formhistory " +
                   "WHERE firstUsed >= :beginTime AND firstUsed <= :endTime", {
               beginTime: beginTime,
               endTime: endTime
             });
             stmt = this.dbCreateStatement(query, params);
             stmt.executeStep();
             this.sendIntNotification("removeEntriesByTimeframe", beginTime, endTime);
         } catch (e) {
             if (!existingTransactionInProgress)
                 this.dbConnection.rollbackTransaction();
             this.log("removeEntriesByTimeframe failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
         if (!existingTransactionInProgress)
             this.dbConnection.commitTransaction();
     },
     moveToDeletedTable : function moveToDeletedTable(values, params) {
 #ifdef ANDROID
         this.log("Moving entries to deleted table.");
         let stmt;
         try {
             // Move the entries to the deleted items table.
             let query = "INSERT INTO moz_deleted_formhistory (guid, timeDeleted) ";
             if (values) query += values;
             stmt = this.dbCreateStatement(query, params);
             stmt.execute();
         } catch (e) {
             this.log("Moving deleted entries failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
 #endif
     },
     get dbConnection() {
         // Make sure dbConnection can't be called from now to prevent infinite loops.
         delete FormHistory.prototype.dbConnection;
         try {
             this.dbFile = Services.dirsvc.get("ProfD", Ci.nsIFile).clone();
             this.dbFile.append("formhistory.sqlite");
             this.log("Opening database at " + this.dbFile.path);
             FormHistory.prototype.dbConnection = this.dbOpen();
             this.dbInit();
         } catch (e) {
             this.log("Initialization failed: " + e);
             // If dbInit fails...
             if (e.result == Cr.NS_ERROR_FILE_CORRUPTED) {
                 this.dbCleanup();
                 FormHistory.prototype.dbConnection = this.dbOpen();
                 this.dbInit();
             } else {
                 throw "Initialization failed";
             }
         }
         return FormHistory.prototype.dbConnection;
     },
     get DBConnection() {
         return this.dbConnection;
     },
     /* ---- nsIObserver interface ---- */
     observe : function observe(subject, topic, data) {
         switch(topic) {
         case "nsPref:changed":
             this.updatePrefs();
             break;
         case "profile-before-change":
             this._dbClose(false);
             break;
         default:
             this.log("Oops! Unexpected notification: " + topic);
             break;
         }
     },
     /* ---- helpers ---- */
     generateGUID : function() {
         // string like: "{f60d9eac-9421-4abc-8491-8e8322b063d4}"
         let uuid = this.uuidService.generateUUID().toString();
         let raw = ""; // A string with the low bytes set to random values
         let bytes = 0;
         for (let i = 1; bytes < 12 ; i+= 2) {
             // Skip dashes
             if (uuid[i] == "-")
                 i++;
             let hexVal = parseInt(uuid[i] + uuid[i + 1], 16);
             raw += String.fromCharCode(hexVal);
             bytes++;
         }
         return btoa(raw);
     },
     sendStringNotification : function (changeType, str1, str2, str3) {
         function wrapit(str) {
             let wrapper = Cc["@mozilla.org/supports-string;1"].
                           createInstance(Ci.nsISupportsString);
             wrapper.data = str;
             return wrapper;
         }
         let strData;
         if (arguments.length == 2) {
             // Just 1 string, no need to put it in an array
             strData = wrapit(str1);
         } else {
             // 3 strings, put them in an array.
             strData = Cc["@mozilla.org/array;1"].
                       createInstance(Ci.nsIMutableArray);
             strData.appendElement(wrapit(str1), false);
             strData.appendElement(wrapit(str2), false);
             strData.appendElement(wrapit(str3), false);
         }
         this.sendNotification(changeType, strData);
     },
     sendIntNotification : function (changeType, int1, int2) {
         function wrapit(int) {
             let wrapper = Cc["@mozilla.org/supports-PRInt64;1"].
                           createInstance(Ci.nsISupportsPRInt64);
             wrapper.data = int;
             return wrapper;
         }
         let intData;
         if (arguments.length == 2) {
             // Just 1 int, no need for an array
             intData = wrapit(int1);
         } else {
             // 2 ints, put them in an array.
             intData = Cc["@mozilla.org/array;1"].
                       createInstance(Ci.nsIMutableArray);
             intData.appendElement(wrapit(int1), false);
             intData.appendElement(wrapit(int2), false);
         }
         this.sendNotification(changeType, intData);
     },
     sendNotification : function (changeType, data) {
         Services.obs.notifyObservers(data, "satchel-storage-changed", changeType);
     },
     getExistingEntryID : function (name, value) {
         let id = -1, guid = null;
         let stmt;
         let query = "SELECT id, guid FROM moz_formhistory WHERE fieldname = :fieldname AND value = :value";
         let params = {
                         fieldname : name,
                         value     : value
                      };
         try {
             stmt = this.dbCreateStatement(query, params);
             if (stmt.executeStep()) {
                 id   = stmt.row.id;
                 guid = stmt.row.guid;
             }
         } catch (e) {
             this.log("getExistingEntryID failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
         return [id, guid];
     },
     countAllEntries : function () {
         let query = "SELECT COUNT(1) AS numEntries FROM moz_formhistory";
         let stmt, numEntries;
         try {
             stmt = this.dbCreateStatement(query, null);
             stmt.executeStep();
             numEntries = stmt.row.numEntries;
         } catch (e) {
             this.log("countAllEntries failed: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
         this.log("countAllEntries: counted entries: " + numEntries);
         return numEntries;
     },
     updatePrefs : function () {
         this.debug          = Services.prefs.getBoolPref("browser.formfill.debug");
         this.enabled        = Services.prefs.getBoolPref("browser.formfill.enable");
     },
 //**************************************************************************//
     // Database Creation & Access
     /*
      * dbCreateStatement
      *
      * Creates a statement, wraps it, and then does parameter replacement
      * Will use memoization so that statements can be reused.
      */
     dbCreateStatement : function (query, params) {
         let stmt = this.dbStmts[query];
         // Memoize the statements
         if (!stmt) {
             this.log("Creating new statement for query: " + query);
             stmt = this.dbConnection.createStatement(query);
             this.dbStmts[query] = stmt;
         }
         // Replace parameters, must be done 1 at a time
         if (params)
             for (let i in params)
                 stmt.params[i] = params[i];
         return stmt;
     },
     /*
      * dbOpen
      *
      * Open a connection with the database and returns it.
      *
      * @returns a db connection object.
      */
     dbOpen : function () {
         this.log("Open Database");
         let storage = Cc["@mozilla.org/storage/service;1"].
                       getService(Ci.mozIStorageService);
         return storage.openDatabase(this.dbFile);
     },
     /*
      * dbInit
      *
      * Attempts to initialize the database. This creates the file if it doesn't
      * exist, performs any migrations, etc.
      */
     dbInit : function () {
         this.log("Initializing Database");
         let version = this.dbConnection.schemaVersion;
         // Note: Firefox 3 didn't set a schema value, so it started from 0.
         // So we can't depend on a simple version == 0 check
         if (version == 0 && !this.dbConnection.tableExists("moz_formhistory"))
             this.dbCreate();
         else if (version != DB_VERSION)
             this.dbMigrate(version);
     },
     dbCreate: function () {
         this.log("Creating DB -- tables");
         for (let name in this.dbSchema.tables) {
             let table = this.dbSchema.tables[name];
             this.dbCreateTable(name, table);
         }
         this.log("Creating DB -- indices");
         for (let name in this.dbSchema.indices) {
             let index = this.dbSchema.indices[name];
             let statement = "CREATE INDEX IF NOT EXISTS " + name + " ON " + index.table +
                             "(" + index.columns.join(", ") + ")";
             this.dbConnection.executeSimpleSQL(statement);
         }
         this.dbConnection.schemaVersion = DB_VERSION;
     },
     dbCreateTable: function(name, table) {
         let tSQL = [[col, table[col]].join(" ") for (col in table)].join(", ");
         this.log("Creating table " + name + " with " + tSQL);
         this.dbConnection.createTable(name, tSQL);
     },
     dbMigrate : function (oldVersion) {
         this.log("Attempting to migrate from version " + oldVersion);
         if (oldVersion > DB_VERSION) {
             this.log("Downgrading to version " + DB_VERSION);
             // User's DB is newer. Sanity check that our expected columns are
             // present, and if so mark the lower version and merrily continue
             // on. If the columns are borked, something is wrong so blow away
             // the DB and start from scratch. [Future incompatible upgrades
             // should swtich to a different table or file.]
             if (!this.dbAreExpectedColumnsPresent())
                 throw Components.Exception("DB is missing expected columns",
                                            Cr.NS_ERROR_FILE_CORRUPTED);
             // Change the stored version to the current version. If the user
             // runs the newer code again, it will see the lower version number
             // and re-upgrade (to fixup any entries the old code added).
             this.dbConnection.schemaVersion = DB_VERSION;
             return;
         }
         // Upgrade to newer version...
         this.dbConnection.beginTransaction();
         try {
             for (let v = oldVersion + 1; v <= DB_VERSION; v++) {
                 this.log("Upgrading to version " + v + "...");
                 let migrateFunction = "dbMigrateToVersion" + v;
                 this[migrateFunction]();
             }
         } catch (e) {
             this.log("Migration failed: "  + e);
             this.dbConnection.rollbackTransaction();
             throw e;
         }
         this.dbConnection.schemaVersion = DB_VERSION;
         this.dbConnection.commitTransaction();
         this.log("DB migration completed.");
     },
     /*
      * dbMigrateToVersion1
      *
      * Updates the DB schema to v1 (bug 463154).
      * Adds firstUsed, lastUsed, timesUsed columns.
      */
     dbMigrateToVersion1 : function () {
         // Check to see if the new columns already exist (could be a v1 DB that
         // was downgraded to v0). If they exist, we don't need to add them.
         let query;
         ["timesUsed", "firstUsed", "lastUsed"].forEach(function(column) {
             if (!this.dbColumnExists(column)) {
                 query = "ALTER TABLE moz_formhistory ADD COLUMN " + column + " INTEGER";
                 this.dbConnection.executeSimpleSQL(query);
             }
         }, this);
         // Set the default values for the new columns.
         //
         // Note that we set the timestamps to 24 hours in the past. We want a
         // timestamp that's recent (so that "keep form history for 90 days"
         // doesn't expire things surprisingly soon), but not so recent that
         // "forget the last hour of stuff" deletes all freshly migrated data.
         let stmt;
         query = "UPDATE moz_formhistory " +
                 "SET timesUsed = 1, firstUsed = :time, lastUsed = :time " +
                 "WHERE timesUsed isnull OR firstUsed isnull or lastUsed isnull";
         let params = { time: (Date.now() - DAY_IN_MS) * 1000 }
         try {
             stmt = this.dbCreateStatement(query, params);
             stmt.execute();
         } catch (e) {
             this.log("Failed setting timestamps: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
     },
     /*
      * dbMigrateToVersion2
      *
      * Updates the DB schema to v2 (bug 243136).
      * Adds lastUsed index, removes moz_dummy_table
      */
     dbMigrateToVersion2 : function () {
         let query = "DROP TABLE IF EXISTS moz_dummy_table";
         this.dbConnection.executeSimpleSQL(query);
         query = "CREATE INDEX IF NOT EXISTS moz_formhistory_lastused_index ON moz_formhistory (lastUsed)";
         this.dbConnection.executeSimpleSQL(query);
     },
     /*
      * dbMigrateToVersion3
      *
      * Updates the DB schema to v3 (bug 506402).
      * Adds guid column and index.
      */
     dbMigrateToVersion3 : function () {
         // Check to see if GUID column already exists, add if needed
         let query;
         if (!this.dbColumnExists("guid")) {
             query = "ALTER TABLE moz_formhistory ADD COLUMN guid TEXT";
             this.dbConnection.executeSimpleSQL(query);
             query = "CREATE INDEX IF NOT EXISTS moz_formhistory_guid_index ON moz_formhistory (guid)";
             this.dbConnection.executeSimpleSQL(query);
         }
         // Get a list of IDs for existing logins
         let ids = [];
         query = "SELECT id FROM moz_formhistory WHERE guid isnull";
         let stmt;
         try {
             stmt = this.dbCreateStatement(query);
             while (stmt.executeStep())
                 ids.push(stmt.row.id);
         } catch (e) {
             this.log("Failed getting IDs: " + e);
             throw e;
         } finally {
             if (stmt) {
                 stmt.reset();
             }
         }
         // Generate a GUID for each login and update the DB.
         query = "UPDATE moz_formhistory SET guid = :guid WHERE id = :id";
         for each (let id in ids) {
             let params = {
                 id   : id,
                 guid : this.generateGUID()
             };
             try {
                 stmt = this.dbCreateStatement(query, params);
                 stmt.execute();
             } catch (e) {
                 this.log("Failed setting GUID: " + e);
                 throw e;
             } finally {
                 if (stmt) {
                     stmt.reset();
                 }
             }
         }
     },
     dbMigrateToVersion4 : function () {
         if (!this.dbConnection.tableExists("moz_deleted_formhistory")) {
             this.dbCreateTable("moz_deleted_formhistory", this.dbSchema.tables.moz_deleted_formhistory);
         }
     },
     /*
      * dbAreExpectedColumnsPresent
      *
      * Sanity check to ensure that the columns this version of the code expects
      * are present in the DB we're using.
      */
     dbAreExpectedColumnsPresent : function () {
         for (let name in this.dbSchema.tables) {
             let table = this.dbSchema.tables[name];
             let query = "SELECT " +
                         [col for (col in table)].join(", ") +
                         " FROM " + name;
             try {
                 let stmt = this.dbConnection.createStatement(query);
                 // (no need to execute statement, if it compiled we're good)
                 stmt.finalize();
             } catch (e) {
                 return false;
             }
         }
         this.log("verified that expected columns are present in DB.");
         return true;
     },
     /*
      * dbColumnExists
      *
      * Checks to see if the named column already exists.
      */
     dbColumnExists : function (columnName) {
         let query = "SELECT " + columnName + " FROM moz_formhistory";
         try {
             let stmt = this.dbConnection.createStatement(query);
             // (no need to execute statement, if it compiled we're good)
             stmt.finalize();
             return true;
         } catch (e) {
             return false;
         }
     },
     /**
      * _dbClose
      *
      * Finalize all statements and close the connection.
      *
       * @param aBlocking - Should we spin the loop waiting for the db to be
       *                    closed.
      */
     _dbClose : function FH__dbClose(aBlocking) {
         for each (let stmt in this.dbStmts) {
             stmt.finalize();
         }
         this.dbStmts = {};
         let connectionDescriptor = Object.getOwnPropertyDescriptor(FormHistory.prototype, "dbConnection");
         // Return if the database hasn't been opened.
         if (!connectionDescriptor || connectionDescriptor.value === undefined)
             return;
         let completed = false;
         try {
             this.dbConnection.asyncClose(function () { completed = true; });
         } catch (e) {
             completed = true;
             Components.utils.reportError(e);
         }
         let thread = Services.tm.currentThread;
         while (aBlocking && !completed) {
             thread.processNextEvent(true);
         }
     },
     /*
      * dbCleanup
      *
      * Called when database creation fails. Finalizes database statements,
      * closes the database connection, deletes the database file.
      */
     dbCleanup : function () {
         this.log("Cleaning up DB file - close & remove & backup")
         // Create backup file
         let storage = Cc["@mozilla.org/storage/service;1"].
                       getService(Ci.mozIStorageService);
         let backupFile = this.dbFile.leafName + ".corrupt";
         storage.backupDatabaseFile(this.dbFile, backupFile);
         this._dbClose(true);
         this.dbFile.remove(false);
     }
 };
 let component = [FormHistory];
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory(component);