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## Session Module C Interface

## Add A Changeset To A Changegroup

>     int sqlite3changegroup_add(sqlite3_changegroup*, int nData, void *pData);

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:

Existing Change | New Change | Output Change
--- | --- | ---
INSERT | INSERT | 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.
INSERT | UPDATE | 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.
INSERT | DELETE | The existing INSERT is removed from the changegroup. The DELETE is not added.
UPDATE | INSERT | 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.
UPDATE | UPDATE | 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.
UPDATE | DELETE | The existing UPDATE is replaced by the new DELETE within the changegroup.
DELETE | INSERT | 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.
DELETE | UPDATE | 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.
DELETE | DELETE | 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.

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 state of the final contents of the changegroup is undefined.

If no error occurs, SQLITE_OK is returned.

See also lists of Objects, Constants, and Functions.