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Overview
Comment:More adjustments to the backup API documentation. No changes to code. (CVS 6243)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: ca650879d3168d4475a33430300a0e8ac806facf
User & Date: drh 2009-02-03 18:47:23
Context
2009-02-03
19:52
Fix buffer size in md5_cmd() in test_md5.c. Test harness change only. (CVS 6244) check-in: c1e15717 user: shane tags: trunk
18:47
More adjustments to the backup API documentation. No changes to code. (CVS 6243) check-in: ca650879 user: drh tags: trunk
18:25
Tweaks to the backup API documentation contained in comments. No changes to code. (CVS 6242) check-in: 6298bcca user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/sqlite.h.in.

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** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.424 2009/02/03 18:25:13 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
*/
int sqlite3_get_autocommit(sqlite3*);

/*
** CAPI3REF: Find The Database Handle Of A Prepared Statement {H13120} <S60600>
**
** The sqlite3_db_handle interface returns the [database connection] handle
** to which a [prepared statement] belongs.  The database handle returned by
** sqlite3_db_handle is the same database handle that was the first argument
** to the [sqlite3_prepare_v2()] call (or its variants) that was used to
** create the statement in the first place.
**
** INVARIANTS:
**
** {H13123} The [sqlite3_db_handle(S)] interface returns a pointer
**          to the [database connection] associated with the
................................................................................
** read-locked while it is actually being read, it is not locked
** continuously for the entire operation. Thus, the backup may be
** performed on a live database without preventing other users from
** writing to the database for an extended period of time.
** 
** To perform a backup operation: 
**   <ol>
**     <li>[sqlite3_backup_init()] is called once to initialize the backup, 

**     <li>[sqlite3_backup_step()] is called one or more times to transfer 
**         the data between the two databases, and finally
**     <li>[sqlite3_backup_finish()] is called to release all resources 

**         associated with the backup operation. 
**   </ol>
** There should be exactly one call to sqlite3_backup_finish() for each
** successful call to sqlite3_backup_init().
**
** <b>sqlite3_backup_init()</b>
**
** The first two arguments passed to [sqlite3_backup_init()] are the database
** handle associated with the destination database and the database name 
** used to attach the destination database to the handle. The database name
** is "main" for the main database, "temp" for the temporary database, or
** the name specified as part of the ATTACH statement if the destination is
** an attached database. The third and fourth arguments passed to 
** sqlite3_backup_init() identify the database handle and database name used

** to access the source database. The values passed for the source and 
** destination database handle parameters must not be the same.
**
** If an error occurs within sqlite3_backup_init(), then NULL is returned
** and an error code and error message written into the database handle 
** passed as the first argument. They may be retrieved using the
** sqlite3_errcode(), sqlite3_errmsg() and sqlite3_errmsg16() functions.

** Otherwise, if successful, a pointer to an [sqlite3_backup] object is
** returned. This pointer may be used with the sqlite3_backup_step() and
** sqlite3_backup_finish() functions to perform the specified backup 
** operation.
**
** <b>sqlite3_backup_step()</b>
**
** Function [sqlite3_backup_step()] is used to copy up to nPage pages between 
** the source and destination databases, where nPage is the value of the 
** second parameter passed to sqlite3_backup_step(). If nPage pages are 
** succesfully copied, but there are still more pages to copy before the 
** backup is complete, it returns SQLITE_OK. If no error occured and there 
** are no more pages to copy, then SQLITE_DONE is returned. If an error 
** occurs, then an SQLite error code is returned. As well as SQLITE_OK and
** SQLITE_DONE, a call to sqlite3_backup_step() may return SQLITE_READONLY,
** SQLITE_NOMEM, SQLITE_BUSY, SQLITE_LOCKED or an SQLITE_IOERR_XXX error code.

**
** As well as the case where the destination database file was opened for
** read-only access, sqlite3_backup_step() may return SQLITE_READONLY if
** the destination is an in-memory database with a different page size
** from the source database.
**
** If sqlite3_backup_step() cannot obtain a required file-system lock, then

** the busy-handler function is invoked (if one is specified). If the 
** busy-handler returns non-zero before the lock is available, then 
** SQLITE_BUSY is returned to the caller. In this case the call to
** sqlite3_backup_step() can be retried later. If the source database handle

** is being used to write to the source database when sqlite3_backup_step()
** is called, then SQLITE_LOCKED is returned immediately. Again, in this
** case the call to sqlite3_backup_step() can be retried later on. If
** SQLITE_IOERR_XXX, SQLITE_NOMEM or SQLITE_READONLY is returned, then 


** there is no point in retrying the call to sqlite3_backup_step(). These 
** errors are considered fatal. At this point the application must accept 
** that the backup operation has failed and pass the backup operation handle 
** to the sqlite3_backup_finish() to release associated resources.
**
** Following the first call to sqlite3_backup_step(), an exclusive lock is
** obtained on the destination file. It is not released until either 
** sqlite3_backup_finish() is called or the backup operation is complete 
** and sqlite3_backup_step() returns SQLITE_DONE. Additionally, each time 
** a call to sqlite3_backup_step() is made a shared lock is obtained on
** the source database file. This lock is released before the
** sqlite3_backup_step() call returns. Because the source database is not
** locked between calls to sqlite3_backup_step(), it may be modified mid-way
** through the backup procedure. If the source database is modified by an
** external process or via a database connection other than the one being
** used by the backup operation, then the backup will be transparently
** restarted by the next call to sqlite3_backup_step(). If the source 
** database is modified by the using the same database connection as is used
** by the backup operation, then the backup database is transparently 
** updated at the same time.
**
** <b>sqlite3_backup_finish()</b>
**
** Once sqlite3_backup_step() has returned SQLITE_DONE, or when the 
** application wishes to abandon the backup operation, the [sqlite3_backup]
** object should be passed to sqlite3_backup_finish(). This releases all
** resources associated with the backup operation. If sqlite3_backup_step()
** has not yet returned SQLITE_DONE, then any active write-transaction on the
** destination database is rolled back. The [sqlite3_backup] object is invalid
** and may not be used following a call to sqlite3_backup_finish().
**
** The value returned by sqlite3_backup_finish is SQLITE_OK if no error
** occured, regardless or whether or not sqlite3_backup_step() was called
** a sufficient number of times to complete the backup operation. Or, if
** an out-of-memory condition or IO error occured during a call to
** sqlite3_backup_step() then SQLITE_NOMEM or an SQLITE_IOERR_XXX error code

** is returned. In this case the error code and an error message are
** written to the destination database handle.
**
** A return of SQLITE_BUSY or SQLITE_LOCKED from sqlite3_backup_step() is

** not considered an error and does not affect the return value of
** sqlite3_backup_finish().
**
** <b>sqlite3_backup_remaining(), sqlite3_backup_pagecount()</b>
**
** Each call to sqlite3_backup_step() sets two values stored internally
** by an [sqlite3_backup] object. The number of pages still to be backed
** up, which may be queried by sqlite3_backup_remaining(), and the total
................................................................................
** sqlite3_backup_step(). If the source database is modified during a backup
** operation, then the values are not updated to account for any extra
** pages that need to be updated or the size of the source database file
** changing.
**
** <b>Concurrent Usage of Database Handles</b>
**
** The source database handle may be used by the application for other
** purposes while a backup operation is underway or being initialized.
** If SQLite is compiled and configured to support threadsafe database
** connections, then the source database connection may be used concurrently
** from within other threads.
**
** However, the application must guarantee that the destination database
** connection handle is not passed to any other API (by any thread) after 
** sqlite3_backup_init() is called and before the corresponding call to
** sqlite3_backup_finish(). Unfortunately SQLite does not currently check
** for this, if the application does use the destination database handle
** for some other purpose during a backup operation, things may appear to
** work correctly but in fact be subtly malfunctioning.
**
** Furthermore, if running in shared cache mode, the application must
** guarantee that the shared cache used by the destination database
** is not accessed while the backup is running. In practice this means
** that the application must guarantee that the file-system file being 
** backed up to is not accessed by any connection within the process,
** not just the specific connection that was passed to sqlite3_backup_init().
**
** The [sqlite3_backup] object itself is partially threadsafe. Multiple 







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** on how SQLite interfaces are suppose to operate.
**
** The name of this file under configuration management is "sqlite.h.in".
** The makefile makes some minor changes to this file (such as inserting
** the version number) and changes its name to "sqlite3.h" as
** part of the build process.
**
** @(#) $Id: sqlite.h.in,v 1.425 2009/02/03 18:47:23 drh Exp $
*/
#ifndef _SQLITE3_H_
#define _SQLITE3_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** Make sure we can call this stuff from C++.
................................................................................
*/
int sqlite3_get_autocommit(sqlite3*);

/*
** CAPI3REF: Find The Database Handle Of A Prepared Statement {H13120} <S60600>
**
** The sqlite3_db_handle interface returns the [database connection] handle
** to which a [prepared statement] belongs.  The [database connection]
** returned by sqlite3_db_handle is the same [database connection] that was the first argument
** to the [sqlite3_prepare_v2()] call (or its variants) that was used to
** create the statement in the first place.
**
** INVARIANTS:
**
** {H13123} The [sqlite3_db_handle(S)] interface returns a pointer
**          to the [database connection] associated with the
................................................................................
** read-locked while it is actually being read, it is not locked
** continuously for the entire operation. Thus, the backup may be
** performed on a live database without preventing other users from
** writing to the database for an extended period of time.
** 
** To perform a backup operation: 
**   <ol>
**     <li><b>sqlite3_backup_init()</b> is called once to initialize the
**         backup, 
**     <li><b>sqlite3_backup_step()</b> is called one or more times to transfer 
**         the data between the two databases, and finally

**     <li><b>sqlite3_backup_finish()</b> is called to release all resources 
**         associated with the backup operation. 
**   </ol>
** There should be exactly one call to sqlite3_backup_finish() for each
** successful call to sqlite3_backup_init().
**
** <b>sqlite3_backup_init()</b>
**
** The first two arguments passed to [sqlite3_backup_init()] are the database
** handle associated with the destination database and the database name 
** used to attach the destination database to the handle. The database name
** is "main" for the main database, "temp" for the temporary database, or
** the name specified as part of the [ATTACH] statement if the destination is
** an attached database. The third and fourth arguments passed to 
** sqlite3_backup_init() identify the [database connection]
** and database name used
** to access the source database. The values passed for the source and 
** destination [database connection] parameters must not be the same.
**
** If an error occurs within sqlite3_backup_init(), then NULL is returned
** and an error code and error message written into the [database connection] 
** passed as the first argument. They may be retrieved using the

** [sqlite3_errcode()], [sqlite3_errmsg()], and [sqlite3_errmsg16()] functions.
** Otherwise, if successful, a pointer to an [sqlite3_backup] object is
** returned. This pointer may be used with the sqlite3_backup_step() and
** sqlite3_backup_finish() functions to perform the specified backup 
** operation.
**
** <b>sqlite3_backup_step()</b>
**
** Function [sqlite3_backup_step()] is used to copy up to nPage pages between 
** the source and destination databases, where nPage is the value of the 
** second parameter passed to sqlite3_backup_step(). If nPage pages are 
** succesfully copied, but there are still more pages to copy before the 
** backup is complete, it returns [SQLITE_OK]. If no error occured and there 
** are no more pages to copy, then [SQLITE_DONE] is returned. If an error 
** occurs, then an SQLite error code is returned. As well as [SQLITE_OK] and
** [SQLITE_DONE], a call to sqlite3_backup_step() may return [SQLITE_READONLY],
** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
**
** As well as the case where the destination database file was opened for
** read-only access, sqlite3_backup_step() may return [SQLITE_READONLY] if
** the destination is an in-memory database with a different page size
** from the source database.
**
** If sqlite3_backup_step() cannot obtain a required file-system lock, then
** the [sqlite3_busy_handler | busy-handler function]
** is invoked (if one is specified). If the 
** busy-handler returns non-zero before the lock is available, then 
** [SQLITE_BUSY] is returned to the caller. In this case the call to
** sqlite3_backup_step() can be retried later. If the source
** [database connection]
** is being used to write to the source database when sqlite3_backup_step()
** is called, then [SQLITE_LOCKED] is returned immediately. Again, in this
** case the call to sqlite3_backup_step() can be retried later on. If

** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX], [SQLITE_NOMEM], or
** [SQLITE_READONLY] is returned, then 
** there is no point in retrying the call to sqlite3_backup_step(). These 
** errors are considered fatal. At this point the application must accept 
** that the backup operation has failed and pass the backup operation handle 
** to the sqlite3_backup_finish() to release associated resources.
**
** Following the first call to sqlite3_backup_step(), an exclusive lock is
** obtained on the destination file. It is not released until either 
** sqlite3_backup_finish() is called or the backup operation is complete 
** and sqlite3_backup_step() returns [SQLITE_DONE]. Additionally, each time 
** a call to sqlite3_backup_step() is made a [shared lock] is obtained on
** the source database file. This lock is released before the
** sqlite3_backup_step() call returns. Because the source database is not
** locked between calls to sqlite3_backup_step(), it may be modified mid-way
** through the backup procedure. If the source database is modified by an
** external process or via a database connection other than the one being
** used by the backup operation, then the backup will be transparently
** restarted by the next call to sqlite3_backup_step(). If the source 
** database is modified by the using the same database connection as is used
** by the backup operation, then the backup database is transparently 
** updated at the same time.
**
** <b>sqlite3_backup_finish()</b>
**
** Once sqlite3_backup_step() has returned [SQLITE_DONE], or when the 
** application wishes to abandon the backup operation, the [sqlite3_backup]
** object should be passed to sqlite3_backup_finish(). This releases all
** resources associated with the backup operation. If sqlite3_backup_step()
** has not yet returned [SQLITE_DONE], then any active write-transaction on the
** destination database is rolled back. The [sqlite3_backup] object is invalid
** and may not be used following a call to sqlite3_backup_finish().
**
** The value returned by sqlite3_backup_finish is [SQLITE_OK] if no error
** occurred, regardless or whether or not sqlite3_backup_step() was called
** a sufficient number of times to complete the backup operation. Or, if
** an out-of-memory condition or IO error occured during a call to
** sqlite3_backup_step() then [SQLITE_NOMEM] or an
** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] error code
** is returned. In this case the error code and an error message are
** written to the destination [database connection].
**

** A return of [SQLITE_BUSY] or [SQLITE_LOCKED] from sqlite3_backup_step() is
** not a permanent error and does not affect the return value of
** sqlite3_backup_finish().
**
** <b>sqlite3_backup_remaining(), sqlite3_backup_pagecount()</b>
**
** Each call to sqlite3_backup_step() sets two values stored internally
** by an [sqlite3_backup] object. The number of pages still to be backed
** up, which may be queried by sqlite3_backup_remaining(), and the total
................................................................................
** sqlite3_backup_step(). If the source database is modified during a backup
** operation, then the values are not updated to account for any extra
** pages that need to be updated or the size of the source database file
** changing.
**
** <b>Concurrent Usage of Database Handles</b>
**
** The source [database connection] may be used by the application for other
** purposes while a backup operation is underway or being initialized.
** If SQLite is compiled and configured to support threadsafe database
** connections, then the source database connection may be used concurrently
** from within other threads.
**
** However, the application must guarantee that the destination database
** connection handle is not passed to any other API (by any thread) after 
** sqlite3_backup_init() is called and before the corresponding call to
** sqlite3_backup_finish(). Unfortunately SQLite does not currently check
** for this, if the application does use the destination [database connection]
** for some other purpose during a backup operation, things may appear to
** work correctly but in fact be subtly malfunctioning.
**
** Furthermore, if running in [shared cache mode], the application must
** guarantee that the shared cache used by the destination database
** is not accessed while the backup is running. In practice this means
** that the application must guarantee that the file-system file being 
** backed up to is not accessed by any connection within the process,
** not just the specific connection that was passed to sqlite3_backup_init().
**
** The [sqlite3_backup] object itself is partially threadsafe. Multiple