sqlite3_vtab_nochange
If this routine is invoked from within an xColumn method of a virtual table, then it returns true if and only if the call is during an UPDATE operation and the value of the column will not be modified by the UPDATE.
If this routine is called from any context other than within the Column method of a virtual table, then the return value is meaningless and arbitrary.
Virtual table implements might use this routine to optimize their performance by substituting a NULL result, or some other light-weight value, as a signal to the xUpdate routine that the column is unchanged.
If this routine is invoked from within an xColumn method of a virtual table, then it returns true if and only if the call is during an UPDATE operation and the value of the column will not be modified by the UPDATE.
If this routine is called from any context other than within the Column method of a virtual table, then the return value is meaningless and arbitrary.
Virtual table implements might use this routine to optimize their performance by substituting a NULL result, or some other light-weight value, as a signal to the xUpdate routine that the column is unchanged.
If this routine is invoked from within an xColumn method of a virtual table, then it returns true if and only if the call is during an UPDATE operation and the value of the column will not be modified by the UPDATE.
If this routine is called from any context other than within the Column method of a virtual table, then the return value is meaningless and arbitrary.
Virtual table implements might use this routine to optimize their performance by substituting a NULL result, or some other light-weight value, as a signal to the xUpdate routine that the column is unchanged.
If this routine is invoked from within an xColumn method of a virtual table, then it returns true if and only if the call is during an UPDATE operation and the value of the column will not be modified by the UPDATE.
If this routine is called from any context other than within the Column method of a virtual table, then the return value is meaningless and arbitrary.
Virtual table implements might use this routine to optimize their performance by substituting a NULL result, or some other light-weight value, as a signal to the xUpdate routine that the column is unchanged.
If this routine is invoked from within an xColumn method of a virtual table, then it returns true if and only if the call is during an UPDATE operation and the value of the column will not be modified by the UPDATE.
If this routine is called from any context other than within the Column method of a virtual table, then the return value is meaningless and arbitrary.
Virtual table implements might use this routine to optimize their performance by substituting a NULL result, or some other light-weight value, as a signal to the xUpdate routine that the column is unchanged.