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SQLITE3_REBASER(3)         Library Functions Manual         SQLITE3_REBASER(3)

NAME
     sqlite3_rebaser - Rebasing changesets

SYNOPSIS
     typedef struct sqlite3_rebaser sqlite3_rebaser;

DESCRIPTION
     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.

     For example, if both the local and remote changesets contain an INSERT of
     the same key on "CREATE TABLE t1(a PRIMARY KEY, b)":

     local:  INSERT INTO t1 VALUES(1, 'v1'); remote: INSERT INTO t1 VALUES(1,

     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:

     UPDATE t1 SET b = 'v2' WHERE a=1;

     Changes within the local changeset are rebased as follows:

     Local INSERTThis 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.

     Local DELETEThis 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.

     Local UPDATEThis 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.

             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.

     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:

        If there has been one or more REPLACE resolutions on a key, it is
         rebased according to a REPLACE.

        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.

     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.

     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:

     1.   An sqlite3_rebaser object is created by calling
          sqlite3rebaser_create().

     2.   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.

     3.   Each local changeset is rebased by calling sqlite3rebaser_rebase().

     4.   The sqlite3_rebaser object is deleted by calling
          sqlite3rebaser_delete().

NetBSD 8.99.34                 December 19, 2018                NetBSD 8.99.34