[sql] Import SQLite 3.17.0.

third_party/sqlite/src/ext/session/sqlite3session.h

Index: third_party/sqlite/src/ext/session/sqlite3session.h
diff --git a/third_party/sqlite/src/ext/session/sqlite3session.h b/third_party/sqlite/src/ext/session/sqlite3session.h
new file mode 100644
index 0000000000000000000000000000000000000000..0882cf34cf835adee16616fce6d26ec871ebd1dd
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+++ b/third_party/sqlite/src/ext/session/sqlite3session.h
@@ -0,0 +1,1288 @@
+
+#if !defined(__SQLITESESSION_H_) && defined(SQLITE_ENABLE_SESSION)
+#define __SQLITESESSION_H_ 1
+
+/*
+** Make sure we can call this stuff from C++.
+*/
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "sqlite3.h"
+
+/*
+** CAPI3REF: Session Object Handle
+*/
+typedef struct sqlite3_session sqlite3_session;
+
+/*
+** CAPI3REF: Changeset Iterator Handle
+*/
+typedef struct sqlite3_changeset_iter sqlite3_changeset_iter;
+
+/*
+** CAPI3REF: Create A New Session Object
+**
+** 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.
+**
+** It is possible to create multiple session objects attached to a single
+** database handle.
+**
+** Session objects created using this function should be deleted using the
+** [sqlite3session_delete()] function before the database handle that they
+** are attached to is itself closed. If the database handle is closed before
+** the session object is deleted, then the results of calling any session
+** module function, including [sqlite3session_delete()] on the session object
+** are undefined.
+**
+** Because the session module uses the [sqlite3_preupdate_hook()] API, it
+** is not possible for an application to register a pre-update hook on a
+** database handle that has one or more session objects attached. Nor is
+** it possible to create a session object attached to a database handle for
+** which a pre-update hook is already defined. The results of attempting 
+** either of these things are undefined.
+**
+** The session object will be used to create changesets for tables in
+** database zDb, where zDb is either "main", or "temp", or the name of an
+** attached database. It is not an error if database zDb is not attached
+** to the database when the session object is created.
+*/
+int sqlite3session_create(
+  sqlite3 *db,                    /* Database handle */
+  const char *zDb,                /* Name of db (e.g. "main") */
+  sqlite3_session **ppSession     /* OUT: New session object */
+);
+
+/*
+** CAPI3REF: Delete A Session Object
+**
+** Delete a session object previously allocated using 
+** [sqlite3session_create()]. Once a session object has been deleted, the
+** results of attempting to use pSession with any other session module
+** function are undefined.
+**
+** Session objects must be deleted before the database handle to which they
+** are attached is closed. Refer to the documentation for 
+** [sqlite3session_create()] for details.
+*/
+void sqlite3session_delete(sqlite3_session *pSession);
+
+
+/*
+** CAPI3REF: Enable Or Disable A Session Object
+**
+** 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 
+** no-op, and may be used to query the current state of the session.
+**
+** The return value indicates the final state of the session object: 0 if 
+** the session is disabled, or 1 if it is enabled.
+*/
+int sqlite3session_enable(sqlite3_session *pSession, int bEnable);
+
+/*
+** CAPI3REF: Set Or Clear the Indirect Change Flag
+**
+** Each change recorded by a session object is marked as either direct or
+** indirect. A change is marked as indirect if either:
+**
+** <ul>
+**   <li> The session object "indirect" flag is set when the change is
+**        made, or
+**   <li> The change is made by an SQL trigger or foreign key action 
+**        instead of directly as a result of a users SQL statement.
+** </ul>
+**
+** If a single row is affected by more than one operation within a session,
+** then the change is considered indirect if all operations meet the criteria
+** for an indirect change above, or direct otherwise.
+**
+** This function is used to set, clear or query the session object indirect
+** flag.  If the second argument passed to this function is zero, then the
+** indirect flag is cleared. If it is greater than zero, the indirect flag
+** is set. Passing a value less than zero does not modify the current value
+** of the indirect flag, and may be used to query the current state of the 
+** indirect flag for the specified session object.
+**
+** The return value indicates the final state of the indirect flag: 0 if 
+** it is clear, or 1 if it is set.
+*/
+int sqlite3session_indirect(sqlite3_session *pSession, int bIndirect);
+
+/*
+** CAPI3REF: Attach A Table To A Session Object
+**
+** If argument zTab is not NULL, then it is the name of a table to attach
+** to the session object passed as the first argument. All subsequent changes 
+** made to the table while the session object is enabled will be recorded. See 
+** documentation for [sqlite3session_changeset()] for further details.
+**
+** Or, if argument zTab is NULL, then changes are recorded for all tables
+** in the database. If additional tables are added to the database (by 
+** executing "CREATE TABLE" statements) after this call is made, changes for 
+** the new tables are also recorded.
+**
+** 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.
+**
+** Changes are not recorded for individual rows that have NULL values stored
+** in one or more of their PRIMARY KEY columns.
+**
+** SQLITE_OK is returned if the call completes without error. Or, if an error 
+** occurs, an SQLite error code (e.g. SQLITE_NOMEM) is returned.
+*/
+int sqlite3session_attach(
+  sqlite3_session *pSession,      /* Session object */
+  const char *zTab                /* Table name */
+);
+
+/*
+** CAPI3REF: Set a table filter on a Session Object.
+**
+** The second argument (xFilter) is the "filter callback". For changes to rows 
+** in tables that are not attached to the Session object, the filter is called
+** to determine whether changes to the table's rows should be tracked or not. 
+** If xFilter returns 0, changes is not tracked. Note that once a table is 
+** attached, xFilter will not be called again.
+*/
+void sqlite3session_table_filter(
+  sqlite3_session *pSession,      /* Session object */
+  int(*xFilter)(
+    void *pCtx,                   /* Copy of third arg to _filter_table() */
+    const char *zTab              /* Table name */
+  ),
+  void *pCtx                      /* First argument passed to xFilter */
+);
+
+/*
+** CAPI3REF: Generate A Changeset From A Session Object
+**
+** Obtain a changeset containing changes to the tables attached to the 
+** session object passed as the first argument. If successful, 
+** set *ppChangeset to point to a buffer containing the changeset 
+** and *pnChangeset to the size of the changeset in bytes before returning
+** 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.
+**
+** Changes are not recorded for rows that have NULL values stored in one or 
+** more of their PRIMARY KEY columns. If such a row is inserted or deleted,
+** no corresponding change is present in the changesets returned by this
+** function. If an existing row with one or more NULL values stored in
+** PRIMARY KEY columns is updated so that all PRIMARY KEY columns are non-NULL,
+** only an INSERT is appears in the changeset. Similarly, if an existing row
+** with non-NULL PRIMARY KEY values is updated so that one or more of its
+** PRIMARY KEY columns are set to NULL, the resulting changeset contains a
+** DELETE change only.
+**
+** 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 [sqlite3changeset_apply()]
+** API.
+**
+** Within a changeset generated by this function, all changes related to a
+** single table are grouped together. In other words, when iterating through
+** a changeset or when applying a changeset to a database, all changes related
+** to a single table are processed before moving on to the next table. Tables
+** are sorted in the same order in which they were attached (or auto-attached)
+** to the sqlite3_session object. The order in which the changes related to
+** a single table are stored is undefined.
+**
+** 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()].
+**
+** <h3>Changeset Generation</h3>
+**
+** 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.
+**
+** There is one exception to the previous paragraph: when a row is inserted,
+** updated or deleted, if one or more of its primary key columns contain a
+** NULL value, no record of the change is made.
+**
+** 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 nor 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 */
+  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
+  void **ppChangeset              /* OUT: Buffer containing changeset */
+);
+
+/*
+** CAPI3REF: Load The Difference Between Tables Into A Session 
+**
+** If it is not already attached to the session object passed as the first
+** argument, this function attaches table zTbl in the same manner as the
+** [sqlite3session_attach()] function. If zTbl does not exist, or if it
+** does not have a primary key, this function is a no-op (but does not return
+** an error).
+**
+** Argument zFromDb must be the name of a database ("main", "temp" etc.)
+** attached to the same database handle as the session object that contains 
+** a table compatible with the table attached to the session by this function.
+** A table is considered compatible if it:
+**
+** <ul>
+**   <li> Has the same name,
+**   <li> Has the same set of columns declared in the same order, and
+**   <li> Has the same PRIMARY KEY definition.
+** </ul>
+**
+** If the tables are not compatible, SQLITE_SCHEMA is returned. If the tables
+** are compatible but do not have any PRIMARY KEY columns, it is not an error
+** but no changes are added to the session object. As with other session
+** APIs, tables without PRIMARY KEYs are simply ignored.
+**
+** This function adds a set of changes to the session object that could be
+** used to update the table in database zFrom (call this the "from-table") 
+** so that its content is the same as the table attached to the session 
+** object (call this the "to-table"). Specifically:
+**
+** <ul>
+**   <li> For each row (primary key) that exists in the to-table but not in 
+**     the from-table, an INSERT record is added to the session object.
+**
+**   <li> For each row (primary key) that exists in the to-table but not in 
+**     the from-table, a DELETE record is added to the session object.
+**
+**   <li> For each row (primary key) that exists in both tables, but features 
+**     different non-PK values in each, an UPDATE record is added to the
+**     session.  
+** </ul>
+**
+** To clarify, if this function is called and then a changeset constructed
+** using [sqlite3session_changeset()], then after applying that changeset to 
+** database zFrom the contents of the two compatible tables would be 
+** identical.
+**
+** It an error if database zFrom does not exist or does not contain the
+** required compatible table.
+**
+** If the operation successful, SQLITE_OK is returned. Otherwise, an SQLite
+** error code. In this case, if argument pzErrMsg is not NULL, *pzErrMsg
+** may be set to point to a buffer containing an English language error 
+** message. It is the responsibility of the caller to free this buffer using
+** sqlite3_free().
+*/
+int sqlite3session_diff(
+  sqlite3_session *pSession,
+  const char *zFromDb,
+  const char *zTbl,
+  char **pzErrMsg
+);
+
+
+/*
+** CAPI3REF: Generate A Patchset From A Session Object
+**
+** The differences between a patchset and a changeset are that:
+**
+** <ul>
+**   <li> DELETE records consist of the primary key fields only. The 
+**        original values of other fields are omitted.
+**   <li> The original values of any modified fields are omitted from 
+**        UPDATE records.
+** </ul>
+**
+** A patchset blob may be used with up to date versions of all 
+** sqlite3changeset_xxx API functions except for sqlite3changeset_invert(), 
+** which returns SQLITE_CORRUPT if it is passed a patchset. Similarly,
+** attempting to use a patchset blob with old versions of the
+** sqlite3changeset_xxx APIs also provokes an SQLITE_CORRUPT error. 
+**
+** Because the non-primary key "old.*" fields are omitted, no 
+** SQLITE_CHANGESET_DATA conflicts can be detected or reported if a patchset
+** is passed to the sqlite3changeset_apply() API. Other conflict types work
+** in the same way as for changesets.
+**
+** Changes within a patchset are ordered in the same way as for changesets
+** generated by the sqlite3session_changeset() function (i.e. all changes for
+** a single table are grouped together, tables appear in the order in which
+** they were attached to the session object).
+*/
+int sqlite3session_patchset(
+  sqlite3_session *pSession,      /* Session object */
+  int *pnPatchset,                /* OUT: Size of buffer at *ppChangeset */
+  void **ppPatchset               /* OUT: Buffer containing changeset */
+);
+
+/*
+** CAPI3REF: Test if a changeset has recorded any changes.
+**
+** Return non-zero if no changes to attached tables have been recorded by 
+** the session object passed as the first argument. Otherwise, if one or 
+** more changes have been recorded, return zero.
+**
+** Even if this function returns zero, it is possible that calling
+** [sqlite3session_changeset()] on the session handle may still return a
+** changeset that contains no changes. This can happen when a row in 
+** an attached table is modified and then later on the original values 
+** are restored. However, if this function returns non-zero, then it is
+** guaranteed that a call to sqlite3session_changeset() will return a 
+** changeset containing zero changes.
+*/
+int sqlite3session_isempty(sqlite3_session *pSession);
+
+/*
+** CAPI3REF: Create An Iterator To Traverse A Changeset 
+**
+** 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.
+**
+** Assuming the changeset blob was created by one of the
+** [sqlite3session_changeset()], [sqlite3changeset_concat()] or
+** [sqlite3changeset_invert()] functions, all changes within the changeset 
+** that apply to a single table are grouped together. This means that when 
+** an application iterates through a changeset using an iterator created by 
+** this function, all changes that relate to a single table are visited 
+** consecutively. There is no chance that the iterator will visit a change 
+** the applies to table X, then one for table Y, and then later on visit 
+** another change for table X.
+*/
+int sqlite3changeset_start(
+  sqlite3_changeset_iter **pp,    /* OUT: New changeset iterator handle */
+  int nChangeset,                 /* Size of changeset blob in bytes */
+  void *pChangeset                /* Pointer to blob containing changeset */
+);
+
+
+/*
+** CAPI3REF: Advance A Changeset Iterator
+**
+** 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.
+**
+** 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);
+
+/*
+** CAPI3REF: Obtain The Current Operation From A Changeset Iterator
+**
+** 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. If
+** pbIncorrect is not NULL, then *pbIndirect is set to true (1) if the change
+** is an indirect change, or false (0) otherwise. See the documentation for
+** [sqlite3session_indirect()] for a description of direct and indirect
+** changes. 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 */
+  const char **pzTab,             /* OUT: Pointer to table name */
+  int *pnCol,                     /* OUT: Number of columns in table */
+  int *pOp,                       /* OUT: SQLITE_INSERT, DELETE or UPDATE */
+  int *pbIndirect                 /* OUT: True for an 'indirect' change */
+);
+
+/*
+** CAPI3REF: Obtain The Primary Key Definition Of A Table
+**
+** For each modified table, a changeset includes the following:
+**
+** <ul>
+**   <li> The number of columns in the table, and
+**   <li> Which of those columns make up the tables PRIMARY KEY.
+** </ul>
+**
+** This function is used to find which columns comprise the PRIMARY KEY of
+** the table modified by the change that iterator pIter currently points to.
+** If successful, *pabPK is set to point to an array of nCol entries, where
+** nCol is the number of columns in the table. Elements of *pabPK are set to
+** 0x01 if the corresponding column is part of the tables primary key, or
+** 0x00 if it is not.
+**
+** If argument pnCol is not NULL, then *pnCol is set to the number of columns
+** in the table.
+**
+** If this function is called when the iterator does not point to a valid
+** entry, SQLITE_MISUSE is returned and the output variables zeroed. Otherwise,
+** SQLITE_OK is returned and the output variables populated as described
+** above.
+*/
+int sqlite3changeset_pk(
+  sqlite3_changeset_iter *pIter,  /* Iterator object */
+  unsigned char **pabPK,          /* OUT: Array of boolean - true for PK cols */
+  int *pnCol                      /* OUT: Number of entries in output array */
+);
+
+/*
+** CAPI3REF: Obtain old.* Values From A Changeset Iterator
+**
+** 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) */
+);
+
+/*
+** CAPI3REF: Obtain new.* Values From A Changeset Iterator
+**
+** 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 */
+  sqlite3_value **ppValue         /* OUT: New value (or NULL pointer) */
+);
+
+/*
+** CAPI3REF: Obtain Conflicting Row Values From A Changeset Iterator
+**
+** 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.
+**
+** 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 */
+  int iVal,                       /* Column number */
+  sqlite3_value **ppValue         /* OUT: Value from conflicting row */
+);
+
+/*
+** CAPI3REF: Determine The Number Of Foreign Key Constraint Violations
+**
+** This function may only be called with an iterator passed to an
+** SQLITE_CHANGESET_FOREIGN_KEY conflict handler callback. In this case
+** it sets the output variable to the total number of known foreign key
+** violations in the destination database and returns SQLITE_OK.
+**
+** In all other cases this function returns SQLITE_MISUSE.
+*/
+int sqlite3changeset_fk_conflicts(
+  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
+  int *pnOut                      /* OUT: Number of FK violations */
+);
+
+
+/*
+** CAPI3REF: Finalize A Changeset Iterator
+**
+** This function is used to finalize an iterator allocated with
+** [sqlite3changeset_start()].
+**
+** 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);
+
+/*
+** CAPI3REF: Invert A Changeset
+**
+** This function is used to "invert" a changeset object. Applying an inverted
+** changeset to a database reverses the effects of applying the uninverted
+** changeset. Specifically:
+**
+** <ul>
+**   <li> Each DELETE change is changed to an INSERT, and
+**   <li> Each INSERT change is changed to a DELETE, and
+**   <li> For each UPDATE change, the old.* and new.* values are exchanged.
+** </ul>
+**
+** This function does not change the order in which changes appear within
+** the changeset. It merely reverses the sense of each individual change.
+**
+** If successful, a pointer to a buffer containing the inverted changeset
+** is stored in *ppOut, the size of the same buffer is stored in *pnOut, and
+** SQLITE_OK is returned. If an error occurs, both *pnOut and *ppOut are
+** zeroed and an SQLite error code returned.
+**
+** It is the responsibility of the caller to eventually call sqlite3_free()
+** on the *ppOut pointer to free the buffer allocation following a successful 
+** call to this function.
+**
+** WARNING/TODO: This function currently assumes that the input is a valid
+** changeset. If it is not, the results are undefined.
+*/
+int sqlite3changeset_invert(
+  int nIn, const void *pIn,       /* Input changeset */
+  int *pnOut, void **ppOut        /* OUT: Inverse of input */
+);
+
+/*
+** CAPI3REF: Concatenate Two Changeset Objects
+**
+** This function is used to concatenate two changesets, A and B, into a 
+** single changeset. The result is a changeset equivalent to applying
+** changeset A followed by changeset B. 
+**
+** This function combines the two input changesets using an 
+** sqlite3_changegroup object. Calling it produces similar results as the
+** following code fragment:
+**
+**   sqlite3_changegroup *pGrp;
+**   rc = sqlite3_changegroup_new(&pGrp);
+**   if( rc==SQLITE_OK ) rc = sqlite3changegroup_add(pGrp, nA, pA);
+**   if( rc==SQLITE_OK ) rc = sqlite3changegroup_add(pGrp, nB, pB);
+**   if( rc==SQLITE_OK ){
+**     rc = sqlite3changegroup_output(pGrp, pnOut, ppOut);
+**   }else{
+**     *ppOut = 0;
+**     *pnOut = 0;
+**   }
+**
+** Refer to the sqlite3_changegroup documentation below for details.
+*/
+int sqlite3changeset_concat(
+  int nA,                         /* Number of bytes in buffer pA */
+  void *pA,                       /* Pointer to buffer containing changeset A */
+  int nB,                         /* Number of bytes in buffer pB */
+  void *pB,                       /* Pointer to buffer containing changeset B */
+  int *pnOut,                     /* OUT: Number of bytes in output changeset */
+  void **ppOut                    /* OUT: Buffer containing output changeset */
+);
+
+
+/*
+** CAPI3REF: Changegroup Handle
+*/
+typedef struct sqlite3_changegroup sqlite3_changegroup;
+
+/*
+** CAPI3REF: Create A New Changegroup Object
+**
+** An sqlite3_changegroup object is used to combine two or more changesets
+** (or patchsets) into a single changeset (or patchset). A single changegroup
+** object may combine changesets or patchsets, but not both. The output is
+** always in the same format as the input.
+**
+** If successful, this function returns SQLITE_OK and populates (*pp) with
+** a pointer to a new sqlite3_changegroup object before returning. The caller
+** should eventually free the returned object using a call to 
+** sqlite3changegroup_delete(). If an error occurs, an SQLite error code
+** (i.e. SQLITE_NOMEM) is returned and *pp is set to NULL.
+**
+** The usual usage pattern for an sqlite3_changegroup object is as follows:
+**
+** <ul>
+**   <li> It is created using a call to sqlite3changegroup_new().
+**
+**   <li> Zero or more changesets (or patchsets) are added to the object
+**        by calling sqlite3changegroup_add().
+**
+**   <li> The result of combining all input changesets together is obtained 
+**        by the application via a call to sqlite3changegroup_output().
+**
+**   <li> The object is deleted using a call to sqlite3changegroup_delete().
+** </ul>
+**
+** Any number of calls to add() and output() may be made between the calls to
+** new() and delete(), and in any order.
+**
+** As well as the regular sqlite3changegroup_add() and 
+** sqlite3changegroup_output() functions, also available are the streaming
+** versions sqlite3changegroup_add_strm() and sqlite3changegroup_output_strm().
+*/
+int sqlite3changegroup_new(sqlite3_changegroup **pp);
+
+/*
+** CAPI3REF: Add A Changeset To A Changegroup
+**
+** Add all changes within the changeset (or patchset) in buffer pData (size
+** nData bytes) to the changegroup. 
+**
+** If the buffer contains a patchset, then all prior calls to this function
+** on the same changegroup object must also have specified patchsets. Or, if
+** the buffer contains a changeset, so must have the earlier calls to this
+** function. Otherwise, SQLITE_ERROR is returned and no changes are added
+** to the changegroup.
+**
+** Rows within the changeset and changegroup are identified by the values in
+** their PRIMARY KEY columns. A change in the changeset is considered to
+** apply to the same row as a change already present in the changegroup if
+** the two rows have the same primary key.
+**
+** Changes to rows that do not already appear in the changegroup are
+** simply copied into it. Or, if both the new changeset and the changegroup
+** contain changes that apply to a single row, the final contents of the
+** changegroup depends on the type of each change, as follows:
+**
+** <table border=1 style="margin-left:8ex;margin-right:8ex">
+**   <tr><th style="white-space:pre">Existing Change  </th>
+**       <th style="white-space:pre">New Change       </th>
+**       <th>Output Change
+**   <tr><td>INSERT <td>INSERT <td>
+**       The new change is ignored. This case does not occur if the new
+**       changeset was recorded immediately after the changesets already
+**       added to the changegroup.
+**   <tr><td>INSERT <td>UPDATE <td>
+**       The INSERT change remains in the changegroup. The values in the 
+**       INSERT change are modified as if the row was inserted by the
+**       existing change and then updated according to the new change.
+**   <tr><td>INSERT <td>DELETE <td>
+**       The existing INSERT is removed from the changegroup. The DELETE is
+**       not added.
+**   <tr><td>UPDATE <td>INSERT <td>
+**       The new change is ignored. This case does not occur if the new
+**       changeset was recorded immediately after the changesets already
+**       added to the changegroup.
+**   <tr><td>UPDATE <td>UPDATE <td>
+**       The existing UPDATE remains within the changegroup. It is amended 
+**       so that the accompanying values are as if the row was updated once 
+**       by the existing change and then again by the new change.
+**   <tr><td>UPDATE <td>DELETE <td>
+**       The existing UPDATE is replaced by the new DELETE within the
+**       changegroup.
+**   <tr><td>DELETE <td>INSERT <td>
+**       If one or more of the column values in the row inserted by the
+**       new change differ from those in the row deleted by the existing 
+**       change, the existing DELETE is replaced by an UPDATE within the
+**       changegroup. Otherwise, if the inserted row is exactly the same 
+**       as the deleted row, the existing DELETE is simply discarded.
+**   <tr><td>DELETE <td>UPDATE <td>
+**       The new change is ignored. This case does not occur if the new
+**       changeset was recorded immediately after the changesets already
+**       added to the changegroup.
+**   <tr><td>DELETE <td>DELETE <td>
+**       The new change is ignored. This case does not occur if the new
+**       changeset was recorded immediately after the changesets already
+**       added to the changegroup.
+** </table>
+**
+** If the new changeset contains changes to a table that is already present
+** in the changegroup, then the number of columns and the position of the
+** primary key columns for the table must be consistent. If this is not the
+** case, this function fails with SQLITE_SCHEMA. If the input changeset
+** appears to be corrupt and the corruption is detected, SQLITE_CORRUPT is
+** returned. Or, if an out-of-memory condition occurs during processing, this
+** function returns SQLITE_NOMEM. In all cases, if an error occurs the
+** final contents of the changegroup is undefined.
+**
+** If no error occurs, SQLITE_OK is returned.
+*/
+int sqlite3changegroup_add(sqlite3_changegroup*, int nData, void *pData);
+
+/*
+** CAPI3REF: Obtain A Composite Changeset From A Changegroup
+**
+** Obtain a buffer containing a changeset (or patchset) representing the
+** current contents of the changegroup. If the inputs to the changegroup
+** were themselves changesets, the output is a changeset. Or, if the
+** inputs were patchsets, the output is also a patchset.
+**
+** As with the output of the sqlite3session_changeset() and
+** sqlite3session_patchset() functions, all changes related to a single
+** table are grouped together in the output of this function. Tables appear
+** in the same order as for the very first changeset added to the changegroup.
+** If the second or subsequent changesets added to the changegroup contain
+** changes for tables that do not appear in the first changeset, they are
+** appended onto the end of the output changeset, again in the order in
+** which they are first encountered.
+**
+** If an error occurs, an SQLite error code is returned and the output
+** variables (*pnData) and (*ppData) are set to 0. Otherwise, SQLITE_OK
+** is returned and the output variables are set to the size of and a 
+** pointer to the output buffer, respectively. In this case it is the
+** responsibility of the caller to eventually free the buffer using a
+** call to sqlite3_free().
+*/
+int sqlite3changegroup_output(
+  sqlite3_changegroup*,
+  int *pnData,                    /* OUT: Size of output buffer in bytes */
+  void **ppData                   /* OUT: Pointer to output buffer */
+);
+
+/*
+** CAPI3REF: Delete A Changegroup Object
+*/
+void sqlite3changegroup_delete(sqlite3_changegroup*);
+
+/*
+** CAPI3REF: Apply A Changeset To A Database
+**
+** Apply a changeset to a database. This function attempts to update the
+** "main" database attached to handle db with the changes found in the
+** changeset passed via the second and third arguments.
+**
+** The fourth argument (xFilter) passed to this function is the "filter
+** callback". If it is not NULL, then for each table affected by at least one
+** change in the changeset, the filter callback is invoked with
+** the table name as the second argument, and a copy of the context pointer
+** passed as the sixth argument to this function as the first. If the "filter
+** callback" returns zero, then no attempt is made to apply any changes to 
+** the table. Otherwise, if the return value is non-zero or the xFilter
+** argument to this function is NULL, all changes related to the table are
+** attempted.
+**
+** For each table that is not excluded by the filter callback, this function 
+** tests that the target database contains a compatible table. A table is 
+** considered compatible if all of the following are true:
+**
+** <ul>
+**   <li> The table has the same name as the name recorded in the 
+**        changeset, and
+**   <li> The table has at least as many columns as recorded in the 
+**        changeset, and
+**   <li> The table has primary key columns in the same position as 
+**        recorded in the changeset.
+** </ul>
+**
+** If there is no compatible table, it is not an error, but none of the
+** changes associated with the table are applied. A warning message is issued
+** via the sqlite3_log() mechanism with the error code SQLITE_SCHEMA. At most
+** one such warning is issued for each table in the changeset.
+**
+** For each change for which there is a compatible table, an attempt is made 
+** to modify the table contents according to the UPDATE, INSERT or DELETE 
+** change. If a change cannot be applied cleanly, the conflict handler 
+** function passed as the fifth argument to sqlite3changeset_apply() may be 
+** invoked. A description of exactly when the conflict handler is invoked for 
+** each type of change is below.
+**
+** Unlike the xFilter argument, xConflict may not be passed NULL. The results
+** of passing anything other than a valid function pointer as the xConflict
+** argument are undefined.
+**
+** Each time the conflict handler function is invoked, it must return one
+** of [SQLITE_CHANGESET_OMIT], [SQLITE_CHANGESET_ABORT] or 
+** [SQLITE_CHANGESET_REPLACE]. SQLITE_CHANGESET_REPLACE may only be returned
+** if the second argument passed to the conflict handler is either
+** SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT. If the conflict-handler
+** returns an illegal value, any changes already made are rolled back and
+** the call to sqlite3changeset_apply() returns SQLITE_MISUSE. Different 
+** actions are taken by sqlite3changeset_apply() depending on the value
+** returned by each invocation of the conflict-handler function. Refer to
+** the documentation for the three 
+** [SQLITE_CHANGESET_OMIT|available return values] for details.
+**
+** <dl>
+** <dt>DELETE Changes<dd>
+**   For each DELETE change, this function checks if the target database 
+**   contains a row with the same primary key value (or values) as the 
+**   original row values stored in the changeset. If it does, and the values 
+**   stored in all non-primary key columns also match the values stored in 
+**   the changeset the row is deleted from the target database.
+**
+**   If a row with matching primary key values is found, but one or more of
+**   the non-primary key fields contains a value different from the original
+**   row value stored in the changeset, the conflict-handler function is
+**   invoked with [SQLITE_CHANGESET_DATA] as the second argument. If the
+**   database table has more columns than are recorded in the changeset,
+**   only the values of those non-primary key fields are compared against
+**   the current database contents - any trailing database table columns
+**   are ignored.
+**
+**   If no row with matching primary key values is found in the database,
+**   the conflict-handler function is invoked with [SQLITE_CHANGESET_NOTFOUND]
+**   passed as the second argument.
+**
+**   If the DELETE operation is attempted, but SQLite returns SQLITE_CONSTRAINT
+**   (which can only happen if a foreign key constraint is violated), the
+**   conflict-handler function is invoked with [SQLITE_CHANGESET_CONSTRAINT]
+**   passed as the second argument. This includes the case where the DELETE
+**   operation is attempted because an earlier call to the conflict handler
+**   function returned [SQLITE_CHANGESET_REPLACE].
+**
+** <dt>INSERT Changes<dd>
+**   For each INSERT change, an attempt is made to insert the new row into
+**   the database. If the changeset row contains fewer fields than the
+**   database table, the trailing fields are populated with their default
+**   values.
+**
+**   If the attempt to insert the row fails because the database already 
+**   contains a row with the same primary key values, the conflict handler
+**   function is invoked with the second argument set to 
+**   [SQLITE_CHANGESET_CONFLICT].
+**
+**   If the attempt to insert the row fails because of some other constraint
+**   violation (e.g. NOT NULL or UNIQUE), the conflict handler function is 
+**   invoked with the second argument set to [SQLITE_CHANGESET_CONSTRAINT].
+**   This includes the case where the INSERT operation is re-attempted because 
+**   an earlier call to the conflict handler function returned 
+**   [SQLITE_CHANGESET_REPLACE].
+**
+** <dt>UPDATE Changes<dd>
+**   For each UPDATE change, this function checks if the target database 
+**   contains a row with the same primary key value (or values) as the 
+**   original row values stored in the changeset. If it does, and the values 
+**   stored in all modified non-primary key columns also match the values
+**   stored in the changeset the row is updated within the target database.
+**
+**   If a row with matching primary key values is found, but one or more of
+**   the modified non-primary key fields contains a value different from an
+**   original row value stored in the changeset, the conflict-handler function
+**   is invoked with [SQLITE_CHANGESET_DATA] as the second argument. Since
+**   UPDATE changes only contain values for non-primary key fields that are
+**   to be modified, only those fields need to match the original values to
+**   avoid the SQLITE_CHANGESET_DATA conflict-handler callback.
+**
+**   If no row with matching primary key values is found in the database,
+**   the conflict-handler function is invoked with [SQLITE_CHANGESET_NOTFOUND]
+**   passed as the second argument.
+**
+**   If the UPDATE operation is attempted, but SQLite returns 
+**   SQLITE_CONSTRAINT, the conflict-handler function is invoked with 
+**   [SQLITE_CHANGESET_CONSTRAINT] passed as the second argument.
+**   This includes the case where the UPDATE operation is attempted after 
+**   an earlier call to the conflict handler function returned
+**   [SQLITE_CHANGESET_REPLACE].  
+** </dl>
+**
+** It is safe to execute SQL statements, including those that write to the
+** table that the callback related to, from within the xConflict callback.
+** This can be used to further customize the applications conflict
+** resolution strategy.
+**
+** All changes made by this function are enclosed in a savepoint transaction.
+** If any other error (aside from a constraint failure when attempting to
+** write to the target database) occurs, then the savepoint transaction is
+** rolled back, restoring the target database to its original state, and an 
+** SQLite error code returned.
+*/
+int sqlite3changeset_apply(
+  sqlite3 *db,                    /* Apply change to "main" db of this handle */
+  int nChangeset,                 /* Size of changeset in bytes */
+  void *pChangeset,               /* Changeset blob */
+  int(*xFilter)(
+    void *pCtx,                   /* Copy of sixth arg to _apply() */
+    const char *zTab              /* Table name */
+  ),
+  int(*xConflict)(
+    void *pCtx,                   /* Copy of sixth arg to _apply() */
+    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
+    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
+  ),
+  void *pCtx                      /* First argument passed to xConflict */
+);
+
+/* 
+** CAPI3REF: Constants Passed To The Conflict Handler
+**
+** Values that may be passed as the second argument to a conflict-handler.
+**
+** <dl>
+** <dt>SQLITE_CHANGESET_DATA<dd>
+**   The conflict handler is invoked with CHANGESET_DATA as the second argument
+**   when processing a DELETE or UPDATE change if a row with the required
+**   PRIMARY KEY fields is present in the database, but one or more other 
+**   (non primary-key) fields modified by the update do not contain the 
+**   expected "before" values.
+** 
+**   The conflicting row, in this case, is the database row with the matching
+**   primary key.
+** 
+** <dt>SQLITE_CHANGESET_NOTFOUND<dd>
+**   The conflict handler is invoked with CHANGESET_NOTFOUND as the second
+**   argument when processing a DELETE or UPDATE change if a row with the
+**   required PRIMARY KEY fields is not present in the database.
+** 
+**   There is no conflicting row in this case. The results of invoking the
+**   sqlite3changeset_conflict() API are undefined.
+** 
+** <dt>SQLITE_CHANGESET_CONFLICT<dd>
+**   CHANGESET_CONFLICT is passed as the second argument to the conflict
+**   handler while processing an INSERT change if the operation would result 
+**   in duplicate primary key values.
+** 
+**   The conflicting row in this case is the database row with the matching
+**   primary key.
+**
+** <dt>SQLITE_CHANGESET_FOREIGN_KEY<dd>
+**   If foreign key handling is enabled, and applying a changeset leaves the
+**   database in a state containing foreign key violations, the conflict 
+**   handler is invoked with CHANGESET_FOREIGN_KEY as the second argument
+**   exactly once before the changeset is committed. If the conflict handler
+**   returns CHANGESET_OMIT, the changes, including those that caused the
+**   foreign key constraint violation, are committed. Or, if it returns
+**   CHANGESET_ABORT, the changeset is rolled back.
+**
+**   No current or conflicting row information is provided. The only function
+**   it is possible to call on the supplied sqlite3_changeset_iter handle
+**   is sqlite3changeset_fk_conflicts().
+** 
+** <dt>SQLITE_CHANGESET_CONSTRAINT<dd>
+**   If any other constraint violation occurs while applying a change (i.e. 
+**   a UNIQUE, CHECK or NOT NULL constraint), the conflict handler is 
+**   invoked with CHANGESET_CONSTRAINT as the second argument.
+** 
+**   There is no conflicting row in this case. The results of invoking the
+**   sqlite3changeset_conflict() API are undefined.
+**
+** </dl>
+*/
+#define SQLITE_CHANGESET_DATA        1
+#define SQLITE_CHANGESET_NOTFOUND    2
+#define SQLITE_CHANGESET_CONFLICT    3
+#define SQLITE_CHANGESET_CONSTRAINT  4
+#define SQLITE_CHANGESET_FOREIGN_KEY 5
+
+/* 
+** CAPI3REF: Constants Returned By The Conflict Handler
+**
+** A conflict handler callback must return one of the following three values.
+**
+** <dl>
+** <dt>SQLITE_CHANGESET_OMIT<dd>
+**   If a conflict handler returns this value no special action is taken. The
+**   change that caused the conflict is not applied. The session module 
+**   continues to the next change in the changeset.
+**
+** <dt>SQLITE_CHANGESET_REPLACE<dd>
+**   This value may only be returned if the second argument to the conflict
+**   handler was SQLITE_CHANGESET_DATA or SQLITE_CHANGESET_CONFLICT. If this
+**   is not the case, any changes applied so far are rolled back and the 
+**   call to sqlite3changeset_apply() returns SQLITE_MISUSE.
+**
+**   If CHANGESET_REPLACE is returned by an SQLITE_CHANGESET_DATA conflict
+**   handler, then the conflicting row is either updated or deleted, depending
+**   on the type of change.
+**
+**   If CHANGESET_REPLACE is returned by an SQLITE_CHANGESET_CONFLICT conflict
+**   handler, then the conflicting row is removed from the database and a
+**   second attempt to apply the change is made. If this second attempt fails,
+**   the original row is restored to the database before continuing.
+**
+** <dt>SQLITE_CHANGESET_ABORT<dd>
+**   If this value is returned, any changes applied so far are rolled back 
+**   and the call to sqlite3changeset_apply() returns SQLITE_ABORT.
+** </dl>
+*/
+#define SQLITE_CHANGESET_OMIT       0
+#define SQLITE_CHANGESET_REPLACE    1
+#define SQLITE_CHANGESET_ABORT      2
+
+/*
+** CAPI3REF: Streaming Versions of API functions.
+**
+** The six streaming API xxx_strm() functions serve similar purposes to the 
+** corresponding non-streaming API functions:
+**
+** <table border=1 style="margin-left:8ex;margin-right:8ex">
+**   <tr><th>Streaming function<th>Non-streaming equivalent</th>
+**   <tr><td>sqlite3changeset_apply_str<td>[sqlite3changeset_apply] 
+**   <tr><td>sqlite3changeset_concat_str<td>[sqlite3changeset_concat] 
+**   <tr><td>sqlite3changeset_invert_str<td>[sqlite3changeset_invert] 
+**   <tr><td>sqlite3changeset_start_str<td>[sqlite3changeset_start] 
+**   <tr><td>sqlite3session_changeset_str<td>[sqlite3session_changeset] 
+**   <tr><td>sqlite3session_patchset_str<td>[sqlite3session_patchset] 
+** </table>
+**
+** Non-streaming functions that accept changesets (or patchsets) as input
+** require that the entire changeset be stored in a single buffer in memory. 
+** Similarly, those that return a changeset or patchset do so by returning 
+** a pointer to a single large buffer allocated using sqlite3_malloc(). 
+** Normally this is convenient. However, if an application running in a 
+** low-memory environment is required to handle very large changesets, the
+** large contiguous memory allocations required can become onerous.
+**
+** In order to avoid this problem, instead of a single large buffer, input
+** is passed to a streaming API functions by way of a callback function that
+** the sessions module invokes to incrementally request input data as it is
+** required. In all cases, a pair of API function parameters such as
+**
+**  <pre>
+**  &nbsp;     int nChangeset,
+**  &nbsp;     void *pChangeset,
+**  </pre>
+**
+** Is replaced by:
+**
+**  <pre>
+**  &nbsp;     int (*xInput)(void *pIn, void *pData, int *pnData),
+**  &nbsp;     void *pIn,
+**  </pre>
+**
+** Each time the xInput callback is invoked by the sessions module, the first
+** argument passed is a copy of the supplied pIn context pointer. The second 
+** argument, pData, points to a buffer (*pnData) bytes in size. Assuming no 
+** error occurs the xInput method should copy up to (*pnData) bytes of data 
+** into the buffer and set (*pnData) to the actual number of bytes copied 
+** before returning SQLITE_OK. If the input is completely exhausted, (*pnData) 
+** should be set to zero to indicate this. Or, if an error occurs, an SQLite 
+** error code should be returned. In all cases, if an xInput callback returns
+** an error, all processing is abandoned and the streaming API function
+** returns a copy of the error code to the caller.
+**
+** In the case of sqlite3changeset_start_strm(), the xInput callback may be
+** invoked by the sessions module at any point during the lifetime of the
+** iterator. If such an xInput callback returns an error, the iterator enters
+** an error state, whereby all subsequent calls to iterator functions 
+** immediately fail with the same error code as returned by xInput.
+**
+** Similarly, streaming API functions that return changesets (or patchsets)
+** return them in chunks by way of a callback function instead of via a
+** pointer to a single large buffer. In this case, a pair of parameters such
+** as:
+**
+**  <pre>
+**  &nbsp;     int *pnChangeset,
+**  &nbsp;     void **ppChangeset,
+**  </pre>
+**
+** Is replaced by:
+**
+**  <pre>
+**  &nbsp;     int (*xOutput)(void *pOut, const void *pData, int nData),
+**  &nbsp;     void *pOut
+**  </pre>
+**
+** The xOutput callback is invoked zero or more times to return data to
+** the application. The first parameter passed to each call is a copy of the
+** pOut pointer supplied by the application. The second parameter, pData,
+** points to a buffer nData bytes in size containing the chunk of output
+** data being returned. If the xOutput callback successfully processes the
+** supplied data, it should return SQLITE_OK to indicate success. Otherwise,
+** it should return some other SQLite error code. In this case processing
+** is immediately abandoned and the streaming API function returns a copy
+** of the xOutput error code to the application.
+**
+** The sessions module never invokes an xOutput callback with the third 
+** parameter set to a value less than or equal to zero. Other than this,
+** no guarantees are made as to the size of the chunks of data returned.
+*/
+int sqlite3changeset_apply_strm(
+  sqlite3 *db,                    /* Apply change to "main" db of this handle */
+  int (*xInput)(void *pIn, void *pData, int *pnData), /* Input function */
+  void *pIn,                                          /* First arg for xInput */
+  int(*xFilter)(
+    void *pCtx,                   /* Copy of sixth arg to _apply() */
+    const char *zTab              /* Table name */
+  ),
+  int(*xConflict)(
+    void *pCtx,                   /* Copy of sixth arg to _apply() */
+    int eConflict,                /* DATA, MISSING, CONFLICT, CONSTRAINT */
+    sqlite3_changeset_iter *p     /* Handle describing change and conflict */
+  ),
+  void *pCtx                      /* First argument passed to xConflict */
+);
+int sqlite3changeset_concat_strm(
+  int (*xInputA)(void *pIn, void *pData, int *pnData),
+  void *pInA,
+  int (*xInputB)(void *pIn, void *pData, int *pnData),
+  void *pInB,
+  int (*xOutput)(void *pOut, const void *pData, int nData),
+  void *pOut
+);
+int sqlite3changeset_invert_strm(
+  int (*xInput)(void *pIn, void *pData, int *pnData),
+  void *pIn,
+  int (*xOutput)(void *pOut, const void *pData, int nData),
+  void *pOut
+);
+int sqlite3changeset_start_strm(
+  sqlite3_changeset_iter **pp,
+  int (*xInput)(void *pIn, void *pData, int *pnData),
+  void *pIn
+);
+int sqlite3session_changeset_strm(
+  sqlite3_session *pSession,
+  int (*xOutput)(void *pOut, const void *pData, int nData),
+  void *pOut
+);
+int sqlite3session_patchset_strm(
+  sqlite3_session *pSession,
+  int (*xOutput)(void *pOut, const void *pData, int nData),
+  void *pOut
+);
+int sqlite3changegroup_add_strm(sqlite3_changegroup*, 
+    int (*xInput)(void *pIn, void *pData, int *pnData),
+    void *pIn
+);
+int sqlite3changegroup_output_strm(sqlite3_changegroup*,
+    int (*xOutput)(void *pOut, const void *pData, int nData), 
+    void *pOut
+);
+
+
+/*
+** Make sure we can call this stuff from C++.
+*/
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* !defined(__SQLITESESSION_H_) && defined(SQLITE_ENABLE_SESSION) */