.Dd December 19, 2018
.Dt SQLITE3_VTAB_NOCHANGE 3
.Os
.Sh NAME
.Nm sqlite3_vtab_nochange
.Nd Determine If Virtual Table Column Access Is For UPDATE
.Sh SYNOPSIS
.Ft int 
.Fo sqlite3_vtab_nochange
.Fa "sqlite3_context*"
.Fc
.Sh DESCRIPTION
If the sqlite3_vtab_nochange(X) routine is called within the xColumn
method of a virtual table, then it returns true if and
only if the column is being fetched as part of an UPDATE operation
during which the column value will not change.
Applications might use this to substitute a return value that is less
expensive to compute and that the corresponding xUpdate method
understands as a "no-change" value.
.Pp
If the xColumn method calls sqlite3_vtab_nochange() and finds
that the column is not changed by the UPDATE statement, then the xColumn
method can optionally return without setting a result, without calling
any of the sqlite3_result_xxxxx() interfaces.
In that case, sqlite3_value_nochange(X) will
return true for the same column in the xUpdate method.
.Sh SEE ALSO
.Xr sqlite3_result_blob 3