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+<a href="../session/intro.html"><h2>Session Module C Interface</h2></a><h2>Rebasing changesets</h2><blockquote><pre>typedef struct sqlite3_rebaser sqlite3_rebaser;
+</pre></blockquote><p><b>Important:</b> This interface is <a href="../c3ref/experimental.html">experimental</a> and is subject to change without notice.</p><p>
+Suppose there is a site hosting a database in state S0. And that
+modifications are made that move that database to state S1 and a
+changeset recorded (the "local" changeset). Then, a changeset based
+on S0 is received from another site (the "remote" changeset) and 
+applied to the database. The database is then in state 
+(S1+"remote"), where the exact state depends on any conflict
+resolution decisions (OMIT or REPLACE) made while applying "remote".
+Rebasing a changeset is to update it to take those conflict 
+resolution decisions into account, so that the same conflicts
+do not have to be resolved elsewhere in the network. </p>
+
+<p>For example, if both the local and remote changesets contain an
+INSERT of the same key on "CREATE TABLE t1(a PRIMARY KEY, b)":</p>
+
+<p>  local:  INSERT INTO t1 VALUES(1, 'v1');
+  remote: INSERT INTO t1 VALUES(1, 'v2');</p>
+
+<p>and the conflict resolution is REPLACE, then the INSERT change is
+removed from the local changeset (it was overridden). Or, if the
+conflict resolution was "OMIT", then the local changeset is modified
+to instead contain:</p>
+
+<p>          UPDATE t1 SET b = 'v2' WHERE a=1;</p>
+
+<p>Changes within the local changeset are rebased as follows:</p>
+
+<p><dl>
+<dt>Local INSERT<dd>
+  This may only conflict with a remote INSERT. If the conflict 
+  resolution was OMIT, then add an UPDATE change to the rebased
+  changeset. Or, if the conflict resolution was REPLACE, add
+  nothing to the rebased changeset.</p>
+
+<p><dt>Local DELETE<dd>
+  This may conflict with a remote UPDATE or DELETE. In both cases the
+  only possible resolution is OMIT. If the remote operation was a
+  DELETE, then add no change to the rebased changeset. If the remote
+  operation was an UPDATE, then the old.* fields of change are updated
+  to reflect the new.* values in the UPDATE.</p>
+
+<p><dt>Local UPDATE<dd>
+  This may conflict with a remote UPDATE or DELETE. If it conflicts
+  with a DELETE, and the conflict resolution was OMIT, then the update
+  is changed into an INSERT. Any undefined values in the new.* record
+  from the update change are filled in using the old.* values from
+  the conflicting DELETE. Or, if the conflict resolution was REPLACE,
+  the UPDATE change is simply omitted from the rebased changeset.</p>
+
+<p>  If conflict is with a remote UPDATE and the resolution is OMIT, then
+  the old.* values are rebased using the new.* values in the remote
+  change. Or, if the resolution is REPLACE, then the change is copied
+  into the rebased changeset with updates to columns also updated by
+  the conflicting remote UPDATE removed. If this means no columns would 
+  be updated, the change is omitted.
+</dl></p>
+
+<p>A local change may be rebased against multiple remote changes 
+simultaneously. If a single key is modified by multiple remote 
+changesets, they are combined as follows before the local changeset
+is rebased:</p>
+
+<p><ul>
+   <li> If there has been one or more REPLACE resolutions on a
+        key, it is rebased according to a REPLACE.</p>
+
+<p>   <li> If there have been no REPLACE resolutions on a key, then
+        the local changeset is rebased according to the most recent
+        of the OMIT resolutions.
+</ul></p>
+
+<p>Note that conflict resolutions from multiple remote changesets are 
+combined on a per-field basis, not per-row. This means that in the 
+case of multiple remote UPDATE operations, some fields of a single 
+local change may be rebased for REPLACE while others are rebased for 
+OMIT.</p>
+
+<p>In order to rebase a local changeset, the remote changeset must first
+be applied to the local database using sqlite3changeset_apply_v2() and
+the buffer of rebase information captured. Then:</p>
+
+<p><ol>
+  <li> An sqlite3_rebaser object is created by calling 
+       sqlite3rebaser_create().
+  <li> The new object is configured with the rebase buffer obtained from
+       sqlite3changeset_apply_v2() by calling sqlite3rebaser_configure().
+       If the local changeset is to be rebased against multiple remote
+       changesets, then sqlite3rebaser_configure() should be called
+       multiple times, in the same order that the multiple
+       sqlite3changeset_apply_v2() calls were made.
+  <li> Each local changeset is rebased by calling sqlite3rebaser_rebase().
+  <li> The sqlite3_rebaser object is deleted by calling
+       sqlite3rebaser_delete().
+</ol>
+</p><p>See also lists of
+  <a href="../session/objlist.html">Objects</a>,
+  <a href="../session/constlist.html">Constants</a>, and
+  <a href="../session/funclist.html">Functions</a>.</p>
+