** Create a new session object attached to database handle db. If successful,
** a pointer to the new object is written to *ppSession and SQLITE_OK is
** returned. If an error occurs, *ppSession is set to NULL and an SQLite
-** error code (e.g. [SQLITE_NOMEM]) is returned.
+** error code (e.g. SQLITE_NOMEM) is returned.
**
** It is possible to create multiple session objects attached to a single
** database handle.
** Enable or disable the recording of changes by a session object. When
** enabled, a session object records changes made to the database. When
** disabled - it does not. A newly created session object is enabled.
+** Refer to the documentation for [sqlite3session_changeset()] for further
+** details regarding how enabling and disabling a session object affects
+** the eventual changesets.
**
** Passing zero to this function disables the session. Passing a value
** greater than zero enables it. Passing a value less than zero is a
/*
** Attach a table to a session. All subsequent changes made to the table
-** while the session object is enabled will be recorded.
+** while the session object is enabled will be recorded. See documentation
+** for [sqlite3session_changeset()] for further details.
**
-** Only tables that have a PRIMARY KEY defined may be attached. It does
-** not matter if the PRIMARY KEY is an "INTEGER PRIMARY KEY" (rowid alias)
-** or not.
+** Changes can only be recorded for tables that have a PRIMARY KEY explicitly
+** defined as part of their CREATE TABLE statement. It does not matter if the
+** PRIMARY KEY is an "INTEGER PRIMARY KEY" (rowid alias) or not. The PRIMARY
+** KEY may consist of a single column, or may be a composite key.
+**
+** It is not an error if the named table does not exist in the database. Nor
+** is it an error if the named table does not have a PRIMARY KEY. However,
+** no changes will be recorded in either of these scenarios.
+**
+** SQLITE_OK is returned if the table is successfully attached to the session
+** object. Or, if an error occurs, an SQLite error code (e.g. SQLITE_NOMEM)
+** is returned.
*/
int sqlite3session_attach(
sqlite3_session *pSession, /* Session object */
** SQLITE_OK. If an error occurs, set both *ppChangeset and *pnChangeset to
** zero and return an SQLite error code.
**
+** A changeset consists of zero or more INSERT, UPDATE and/or DELETE changes,
+** each representing a change to a single row of an attached table. An INSERT
+** change contains the values of each field of a new database row. A DELETE
+** contains the original values of each field of a deleted database row. An
+** UPDATE change contains the original values of each field of an updated
+** database row along with the updated values for each updated non-primary-key
+** column. It is not possible for an UPDATE change to represent a change that
+** modifies the values of primary key columns. If such a change is made, it
+** is represented in a changeset as a DELETE followed by an INSERT.
+**
+** The contents of a changeset may be traversed using an iterator created
+** using the [sqlite3changeset_start()] API. A changeset may be applied to
+** a database with a compatible schema using the [sqlite3changset_apply()]
+** API.
+**
** Following a successful call to this function, it is the responsibility of
** the caller to eventually free the buffer that *ppChangeset points to using
** [sqlite3_free()].
+**
+** <h2>Changeset Generation</h2>
+**
+** Once a table has been attached to a session object, the session object
+** records the primary key values of all new rows inserted into the table.
+** It also records the original primary key and other column values of any
+** deleted or updated rows. For each unique primary key value, data is only
+** recorded once - the first time a row with said primary key is inserted,
+** updated or deleted in the lifetime of the session.
+**
+** The session object therefore accumulates two types of records - those
+** that consist of primary key values only (created when the user inserts
+** a new record) and those that consist of the primary key values and the
+** original values of other table columns (created when the users deletes
+** or updates a record).
+**
+** When this function is called, the requested changeset is created using
+** both the accumulated records and the current contents of the database
+** file. Specifically:
+**
+** <ul>
+** <li> For each record generated by an insert, the database is queried
+** for a row with a matching primary key. If one is found, an INSERT
+** change is added to the changeset. If no such row is found, no change
+** is added to the changeset.
+**
+** <li> For each record generated by an update or delete, the database is
+** queried for a row with a matching primary key. If such a row is
+** found and one or more of the non-primary key fields have been
+** modified from their original values, an UPDATE change is added to
+** the changeset. Or, if no such row is found in the table, a DELETE
+** change is added to the changeset. If there is a row with a matching
+** primary key in the database, but all fields contain their original
+** values, no change is added to the changeset.
+** </ul>
+**
+** This means, amongst other things, that if a row is inserted and then later
+** deleted while a session object is active, neither the insert or the delete
+** will be present in the changeset. Or if a row is deleted and then later a
+** row with the same primary key values inserted while a session object is
+** active, the resulting changeset will contain an UPDATE change instead of
+** a DELETE and an INSERT.
+**
+** When a session object is disabled (see the [sqlite3session_enable()] API),
+** it does not accumulate records when rows are inserted, updated or deleted.
+** This may appear to have some counter-intuitive effects if a single row
+** is written to more than once during a session. For example, if a row
+** is inserted while a session object is enabled, then later deleted while
+** the same session object is disabled, no INSERT record will appear in the
+** changeset, even though the delete took place while the session was disabled.
+** Or, if one field of a row is updated while a session is disabled, and
+** another field of the same row is updated while the session is enabled, the
+** resulting changeset will contain an UPDATE change that updates both fields.
*/
int sqlite3session_changeset(
sqlite3_session *pSession, /* Session object */
/*
** Create an iterator used to iterate through the contents of a changeset.
+** If successful, *pp is set to point to the iterator handle and SQLITE_OK
+** is returned. Otherwise, if an error occurs, *pp is set to zero and an
+** SQLite error code is returned.
+**
+** The following functions can be used to advance and query a changeset
+** iterator created by this function:
+**
+** <ul>
+** <li> [sqlite3changeset_next()]
+** <li> [sqlite3changeset_op()]
+** <li> [sqlite3changeset_new()]
+** <li> [sqlite3changeset_old()]
+** </ul>
+**
+** It is the responsibility of the caller to eventually destroy the iterator
+** by passing it to [sqlite3changeset_finalize()]. The buffer containing the
+** changeset (pChangeset) must remain valid until after the iterator is
+** destroyed.
*/
int sqlite3changeset_start(
- sqlite3_changeset_iter **ppIter,
- int nChangeset,
- void *pChangeset
+ sqlite3_changeset_iter **pp, /* OUT: New changeset iterator handle */
+ int nChangeset, /* Size of changeset blob in bytes */
+ void *pChangeset /* Pointer to blob containing changeset */
);
/*
-** Advance an iterator created by sqlite3changeset_start() to the next
-** change in the changeset. This function may return SQLITE_ROW, SQLITE_DONE
-** or SQLITE_CORRUPT.
+** This function may only be used with iterators created by function
+** [sqlite3changeset_start()]. If it is called on an iterator passed to
+** a conflict-handler callback by [sqlite3changeset_apply()], SQLITE_MISUSE
+** is returned and the call has no effect.
**
-** This function may not be called on iterators passed to a conflict handler
-** callback by changeset_apply().
+** Immediately after an iterator is created by sqlite3changeset_start(), it
+** does not point to any change in the changeset. Assuming the changeset
+** is not empty, the first call to this function advances the iterator to
+** point to the first change in the changeset. Each subsequent call advances
+** the iterator to point to the next change in the changeset (if any). If
+** no error occurs and the iterator points to a valid change after a call
+** to sqlite3changeset_next() has advanced it, SQLITE_ROW is returned.
+** Otherwise, if all changes in the changeset have already been visited,
+** SQLITE_DONE is returned.
+**
+** If an error occurs, an SQLite error code is returned. Possible error
+** codes include SQLITE_CORRUPT (if the changeset buffer is corrupt) or
+** SQLITE_NOMEM.
*/
int sqlite3changeset_next(sqlite3_changeset_iter *pIter);
/*
-** The following three functions extract information on the current change
-** from a changeset iterator. They may only be called after changeset_next()
-** has returned SQLITE_ROW.
+** The pIter argument passed to this function may either be an iterator
+** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator
+** created by [sqlite3changeset_start()]. In the latter case, the most recent
+** call to [sqlite3changeset_next()] must have returned SQLITE_ROW. If this
+** is not the case, this function returns SQLITE_MISUSE.
+**
+** If argument pzTab is not NULL, then *pzTab is set to point to a
+** nul-terminated utf-8 encoded string containing the name of the table
+** affected by the current change. The buffer remains valid until either
+** sqlite3changeset_next() is called on the iterator or until the
+** conflict-handler function returns. If pnCol is not NULL, then *pnCol is
+** set to the number of columns in the table affected by the change. Finally,
+** if pOp is not NULL, then *pOp is set to one of SQLITE_INSERT, SQLITE_DELETE
+** or SQLITE_UPDATE, depending on the type of change that the iterator
+** currently points to.
+**
+** If no error occurs, SQLITE_OK is returned. If an error does occur, an
+** SQLite error code is returned. The values of the output variables may not
+** be trusted in this case.
*/
int sqlite3changeset_op(
sqlite3_changeset_iter *pIter, /* Iterator object */
int *pnCol, /* OUT: Number of columns in table */
int *pOp /* OUT: SQLITE_INSERT, DELETE or UPDATE */
);
+
+/*
+** The pIter argument passed to this function may either be an iterator
+** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator
+** created by [sqlite3changeset_start()]. In the latter case, the most recent
+** call to [sqlite3changeset_next()] must have returned SQLITE_ROW.
+** Furthermore, it may only be called if the type of change that the iterator
+** currently points to is either SQLITE_DELETE or SQLITE_UPDATE. Otherwise,
+** this function returns SQLITE_MISUSE and sets *ppValue to NULL.
+**
+** Argument iVal must be greater than or equal to 0, and less than the number
+** of columns in the table affected by the current change. Otherwise,
+** SQLITE_RANGE is returned and *ppValue is set to NULL.
+**
+** If successful, this function sets *ppValue to point to a protected
+** sqlite3_value object containing the iVal'th value from the vector of
+** original row values stored as part of the UPDATE or DELETE change and
+** returns SQLITE_OK. The name of the function comes from the fact that this
+** is similar to the "old.*" columns available to update or delete triggers.
+**
+** If some other error occurs (e.g. an OOM condition), an SQLite error code
+** is returned and *ppValue is set to NULL.
+*/
int sqlite3changeset_old(
sqlite3_changeset_iter *pIter, /* Changeset iterator */
int iVal, /* Column number */
sqlite3_value **ppValue /* OUT: Old value (or NULL pointer) */
);
+
+/*
+** The pIter argument passed to this function may either be an iterator
+** passed to a conflict-handler by [sqlite3changeset_apply()], or an iterator
+** created by [sqlite3changeset_start()]. In the latter case, the most recent
+** call to [sqlite3changeset_next()] must have returned SQLITE_ROW.
+** Furthermore, it may only be called if the type of change that the iterator
+** currently points to is either SQLITE_UPDATE or SQLITE_INSERT. Otherwise,
+** this function returns SQLITE_MISUSE and sets *ppValue to NULL.
+**
+** Argument iVal must be greater than or equal to 0, and less than the number
+** of columns in the table affected by the current change. Otherwise,
+** SQLITE_RANGE is returned and *ppValue is set to NULL.
+**
+** If successful, this function sets *ppValue to point to a protected
+** sqlite3_value object containing the iVal'th value from the vector of
+** new row values stored as part of the UPDATE or INSERT change and
+** returns SQLITE_OK. If the change is an UPDATE and does not include
+** a new value for the requested column, *ppValue is set to NULL and
+** SQLITE_OK returned. The name of the function comes from the fact that
+** this is similar to the "new.*" columns available to update or delete
+** triggers.
+**
+** If some other error occurs (e.g. an OOM condition), an SQLite error code
+** is returned and *ppValue is set to NULL.
+*/
int sqlite3changeset_new(
sqlite3_changeset_iter *pIter, /* Changeset iterator */
int iVal, /* Column number */
);
/*
-** This function is only usable with sqlite3_changeset_iter objects passed
-** to the xConflict callback by sqlite3changeset_apply(). It cannot be used
-** with iterators created using sqlite3changeset_start().
+** This function should only be used with iterator objects passed to a
+** conflict-handler callback by [sqlite3changeset_apply()] with either
+** SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT. If this function
+** is called on any other iterator, SQLITE_MISUSE is returned and *ppValue
+** is set to NULL.
**
-** It is used to access the "conflicting row" information available to the
-** conflict handler if the second argument is either SQLITE_CHANGESET_DATA
-** or SQLITE_CHANGESET_CONFLICT.
+** Argument iVal must be greater than or equal to 0, and less than the number
+** of columns in the table affected by the current change. Otherwise,
+** SQLITE_RANGE is returned and *ppValue is set to NULL.
+**
+** If successful, this function sets *ppValue to point to a protected
+** sqlite3_value object containing the iVal'th value from the
+** "conflicting row" associated with the current conflict-handler callback
+** and returns SQLITE_OK.
+**
+** If some other error occurs (e.g. an OOM condition), an SQLite error code
+** is returned and *ppValue is set to NULL.
*/
int sqlite3changeset_conflict(
sqlite3_changeset_iter *pIter, /* Changeset iterator */
/*
** Finalize an iterator allocated with sqlite3changeset_start().
**
-** This function may not be called on iterators passed to a conflict handler
-** callback by changeset_apply().
+** This function should only be called on iterators created using the
+** [sqlite3changeset_start()] function. If an application calls this
+** function with an iterator passed to a conflict-handler by
+** [sqlite3changeset_apply()], SQLITE_MISUSE is immediately returned and the
+** call has no effect.
+**
+** If an error was encountered within a call to an sqlite3changeset_xxx()
+** function (for example an SQLITE_CORRUPT in sqlite3changeset_next() or an
+** SQLITE_NOMEM in sqlite3changeset_new()) then an error code corresponding
+** to that error is returned by this function. Otherwise, SQLITE_OK is
+** returned. This is to allow the following pattern (pseudo-code):
+**
+** sqlite3changeset_start();
+** while( SQLITE_ROW==sqlite3changeset_next() ){
+** // Do something with change.
+** }
+** rc = sqlite3changeset_finalize();
+** if( rc!=SQLITE_OK ){
+** // An error has occurred
+** }
*/
int sqlite3changeset_finalize(sqlite3_changeset_iter *pIter);
projects / thirdparty / sqlite.git / commitdiff
