path: root/storage/mozIStorageAsyncConnection.idl

/* -*- Mode: idl; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

interface mozIStorageCompletionCallback;
interface mozIStorageFunction;
interface mozIStorageProgressHandler;
interface mozIStorageBaseStatement;
interface mozIStorageStatement;
interface mozIStorageAsyncStatement;
interface mozIStorageStatementCallback;
interface mozIStoragePendingStatement;
interface nsIFile;

/**
 * mozIStorageAsyncConnection represents an asynchronous database
 * connection attached to a specific file or to an in-memory data
 * storage.  It is the primary interface for interacting with a
 * database from the main thread, including creating prepared
 * statements, executing SQL, and examining database errors.
 */
[scriptable, uuid(8bfd34d5-4ddf-4e4b-89dd-9b14f33534c6)]
interface mozIStorageAsyncConnection : nsISupports {
  /**
   * Transaction behavior constants.
   */
  const int32_t TRANSACTION_DEFAULT = -1;
  const int32_t TRANSACTION_DEFERRED = 0;
  const int32_t TRANSACTION_IMMEDIATE = 1;
  const int32_t TRANSACTION_EXCLUSIVE = 2;

  /**
   * The default behavior for all transactions run on this connection. Defaults
   * to `TRANSACTION_DEFERRED`, and can be overridden for individual
   * transactions.
   */
  attribute int32_t defaultTransactionType;

  /**
   * The maximum number of bound parameters for statements executed on this
   * connection. If your statement has more params than this limit, you'll
   * need to chunk them into multiple statements. See `PlacesUtils.chunkArray`
   * and its callers in Places for examples of how to do this, or read on for
   * an overview.
   *
   * Keep in mind that the variable limit is for the _total_ number of
   * parameters, including ones bound by name (using the `:VVV`, `@VVV`, or
   * `?VVV` syntax) and index (`?` and `?NNN`).
   *
   * This means, when chunking:
   *
   * - If you're binding 1 param per 1 value per chunk (for example, if you
   *   have a list of GUIDs and a clause like `WHERE guid IN (?, ?, ?, ...)`,
   *   your chunk length is just `variableLimit`.
   * - If you're binding 1 param per 1 value per chunk, but using that
   *   param in multiple positions in the query (for example, `WHERE url_hash
   *   IN (hash(?1), hash(?2), ...) AND url IN (?1, ?2, ...)`), you can use the
   *   `?NNN` syntax with a chunk length of `variableLimit`.
   * - If you're binding N params per 1 value per chunk (for example, if you
   *   have a list of items with GUIDs and parent GUIDs, and you want to bind
   *   both), your chunk length is `variableLimit / N`, since you're binding
   *   two params for each element.
   * - If you're binding K params per L values per chunk, plus M fixed ones
   *   (for example, `WHERE parentGuid = :parentGuid AND guid IN (?, ?, ...)`),
   *   your chunk length is `variableLimit - M`, to ensure there's space for the
   *   fixed variables.
   *
   * If you bind more params than this limit, `create{Async}Statement` will
   * fail with a "too many SQL variables" error.
   */
  readonly attribute int32_t variableLimit;

  /**
   * Returns true if a transaction is active on this connection.
   *
   * Note that this is true if a transaction is active on the connection,
   * regardless of how it was opened. There are several ways to open one:
   *
   * 1. Explicitly calling `beginTransaction` on a `mozIStorageConnection`.
   * 2. Calling `executeSimpleSQL("BEGIN")` or
   *    `createStatement("BEGIN").execute()` on a `mozIStorageConnection`.
   * 3. Executing an async statement, like
   *    `createAsyncStatement("BEGIN").executeAsync(...)`. This is what
   *    `Sqlite.jsm` does under the hood.
   *
   * Because of this, it's important *not* to use this attribute to decide
   * whether to *commit* the active transaction, because the caller that opened
   * it may not expect that. This is why both `mozStorageTransaction` and
   * `Sqlite.jsm` use an internal variable (`mHasTransaction` for the former;
   * `_hasInProgressTransaction` for the latter) to check if their transaction
   * is already in progress, instead of just checking this attribute before
   * committing. Otherwise, mozStorage might accidentally commit (or roll back!)
   * a transaction started by `Sqlite.jsm`, and vice versa.
   */
  readonly attribute boolean transactionInProgress;

  /**
   * Close this database connection, allowing all pending statements
   * to complete first.
   *
   * @param aCallback [optional]
   *        A callback that will be notified when the close is completed,
   *        with the following arguments:
   *        - status: the status of the call
   *        - value: |null|
   *
   * @throws NS_ERROR_NOT_SAME_THREAD
   *         If called on a thread other than the one that opened it.  The
   *         callback will not be dispatched.
   * @throws NS_ERROR_NOT_INITIALIZED
   *         If called on a connection that has already been closed or was
   *         never properly opened.  The callback will still be dispatched
   *         to the main thread despite the returned error.
   * @note If this call should fail, the callback won't be invoked.
   */
  void asyncClose([optional] in mozIStorageCompletionCallback aCallback);

  /**
   * Forcibly closes a database connection synchronously.
   * This should only be used when it's required to close and replace the
   * database synchronously to return control to the consumer, for example in
   * case of a detected corruption on database opening.
   * Since this spins the events loop, it should be used only in very particular
   * and rare situations, or it may cause unexpected consequences (crashes).
   *
   * @throws NS_ERROR_NOT_SAME_THREAD
   *         If called on a thread other than the one that opened it.
   */
  [noscript] void spinningSynchronousClose();

  /**
   * Clone a database and make the clone read only if needed.
   * SQL Functions and attached on-disk databases are applied to the new clone.
   *
   * @param aReadOnly
   *        If true, the returned database should be put into read-only mode.
   *
   * @param aCallback
   *        A callback that will be notified when the operation is complete,
   *        with the following arguments:
   *        - status: the status of the operation
   *        - value: in case of success, an intance of
   *             mozIStorageAsyncConnection cloned from this one.
   *
   * @throws NS_ERROR_NOT_SAME_THREAD
   *         If is called on a thread other than the one that opened it.
   * @throws NS_ERROR_UNEXPECTED
   *         If this connection is a memory database.
   *
   * @note If your connection is already read-only, you will get a read-only
   *       clone.
   * @note The resulting connection will implement `mozIStorageConnection`, but
   *       all synchronous methods will throw if called from the main thread.
   * @note Due to a bug in SQLite, if you use the shared cache
   *       (see mozIStorageService), you end up with the same privileges as the
   *       first connection opened regardless of what is specified in aReadOnly.
   * @note The following pragmas are copied over to a read-only clone:
   *        - cache_size
   *        - temp_store
   *       The following pragmas are copied over to a writeable clone:
   *        - cache_size
   *        - temp_store
   *        - foreign_keys
   *        - journal_size_limit
   *        - synchronous
   *        - wal_autocheckpoint
   *       All SQL functions are copied over to read-only and writeable clones.
   *       Additionally, all temporary tables, triggers, and views, as well as
   *       any indexes on temporary tables, are copied over to writeable clones.
   *       For temporary tables, only the schemas are copied, not their
   *       contents.
   */
  void asyncClone(in boolean aReadOnly,
                  in mozIStorageCompletionCallback aCallback);

  /**
   * The current database nsIFile.  Null if the database
   * connection refers to an in-memory database.
   */
  readonly attribute nsIFile databaseFile;

  /**
   * Causes any pending database operation to abort and return at the first
   * opportunity.
   * This can only be used on read-only connections that don't implement
   * the mozIStorageConnection interface.
   * @note operations that are nearly complete may still be able to complete.
   * @throws if used on an unsupported connection type, or a closed connection.
   */
  void interrupt();

  //////////////////////////////////////////////////////////////////////////////
  //// Statement creation

  /**
   * Create an asynchronous statement for the given SQL. An
   * asynchronous statement can only be used to dispatch asynchronous
   * requests to the asynchronous execution thread and cannot be used
   * to take any synchronous actions on the database.
   *
   * The expression may use ? to indicate sequential numbered arguments,
   * ?1, ?2 etc. to indicate specific numbered arguments or :name and
   * $var to indicate named arguments.
   *
   * @param aSQLStatement
   *        The SQL statement to execute.
   * @return a new mozIStorageAsyncStatement
   * @note The statement is created lazily on first execution.
   */
  mozIStorageAsyncStatement createAsyncStatement(in AUTF8String aSQLStatement);

  /**
   * Execute an array of statements created with this connection using
   * any currently bound parameters. When the array contains multiple
   * statements, the execution is wrapped in a single
   * transaction. These statements can be reused immediately, and
   * reset does not need to be called.
   *
   * @param aStatements
   *        The array of statements to execute asynchronously, in the order they
   *        are given in the array.
   * @param aCallback [optional]
   *        The callback object that will be notified of progress, errors, and
   *        completion.
   * @return an object that can be used to cancel the statements execution.
   *
   * @note If you have any custom defined functions, they must be
   *        re-entrant since they can be called on multiple threads.
   */
  mozIStoragePendingStatement executeAsync(
    in Array<mozIStorageBaseStatement> aStatements,
    [optional] in mozIStorageStatementCallback aCallback
  );

  /**
   * Execute asynchronously an SQL expression, expecting no arguments.
   *
   * @param aSQLStatement
   *        The SQL statement to execute
   * @param aCallback [optional]
   *        The callback object that will be notified of progress, errors, and
   *        completion.
   * @return an object that can be used to cancel the statement execution.
   */
  mozIStoragePendingStatement executeSimpleSQLAsync(
    in AUTF8String aSQLStatement,
    [optional] in mozIStorageStatementCallback aCallback);

  //////////////////////////////////////////////////////////////////////////////
  //// Functions

  /**
   * Create a new SQL function.  If you use your connection on multiple threads,
   * your function needs to be threadsafe, or it should only be called on one
   * thread.
   *
   * @param aFunctionName
   *        The name of function to create, as seen in SQL.
   * @param aNumArguments
   *        The number of arguments the function takes. Pass -1 for
   *        variable-argument functions.
   * @param aFunction
   *        The instance of mozIStorageFunction, which implements the function
   *        in question.
   */
  void createFunction(in AUTF8String aFunctionName,
                      in long aNumArguments,
                      in mozIStorageFunction aFunction);

  /**
   * Delete custom SQL function.
   *
   * @param aFunctionName
   *        The name of function to remove.
   */
  void removeFunction(in AUTF8String aFunctionName);

  /**
   * Sets a progress handler. Only one handler can be registered at a time.
   * If you need more than one, you need to chain them yourself.  This progress
   * handler should be threadsafe if you use this connection object on more than
   * one thread.
   *
   * @param aGranularity
   *        The number of SQL virtual machine steps between progress handler
   *        callbacks.
   * @param aHandler
   *        The instance of mozIStorageProgressHandler.
   * @return previous registered handler.
   */
  mozIStorageProgressHandler setProgressHandler(in int32_t aGranularity,
                                                in mozIStorageProgressHandler aHandler);

  /**
   * Remove a progress handler.
   *
   * @return previous registered handler.
   */
  mozIStorageProgressHandler removeProgressHandler();
};