2016-12-18 19:58:16 +03:00
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.Dd December 18, 2016
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2016-07-03 20:07:38 +03:00
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.Dt SQLITE3CHANGESET_INVERT 3
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.Os
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.Sh NAME
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.Nm sqlite3changeset_invert
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.Nd Invert A Changeset
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.Sh SYNOPSIS
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.Ft int
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.Fo sqlite3changeset_invert
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.Fa "int nIn"
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.Fa "const void *pIn"
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.Fa "int *pnOut"
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.Fa "void **ppOut "
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.Fc
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.Sh DESCRIPTION
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This function is used to "invert" a changeset object.
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Applying an inverted changeset to a database reverses the effects of
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applying the uninverted changeset.
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Specifically:
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.Bl -bullet
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.It
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Each DELETE change is changed to an INSERT, and
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.It
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Each INSERT change is changed to a DELETE, and
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.It
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For each UPDATE change, the old.* and new.* values are exchanged.
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.El
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.Pp
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This function does not change the order in which changes appear within
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the changeset.
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It merely reverses the sense of each individual change.
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.Pp
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If successful, a pointer to a buffer containing the inverted changeset
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is stored in *ppOut, the size of the same buffer is stored in *pnOut,
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and SQLITE_OK is returned.
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If an error occurs, both *pnOut and *ppOut are zeroed and an SQLite
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error code returned.
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.Pp
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It is the responsibility of the caller to eventually call sqlite3_free()
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on the *ppOut pointer to free the buffer allocation following a successful
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call to this function.
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.Pp
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WARNING/TODO: This function currently assumes that the input is a valid
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changeset.
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If it is not, the results are undefined.
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