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Add the sqlite3_vtab_nochange() method which virtual table implementations

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can use to optimize UPDATEs.

FossilOrigin-Name: d444b1ff39f0a1673a977b8047e1e14a49d461c9934be080d27c2392a830c1c0
This commit is contained in:
drh
2018-01-11 17:04:26 +00:00
parent e4185bda9a
commit 6f390beb7f
7 changed files with 58 additions and 16 deletions
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19
src/vdbeapi.c
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@@ -745,6 +745,25 @@ sqlite3 *sqlite3_context_db_handle(sqlite3_context *p){
return p->pOut->db;
}
/*
** If this routine is invoked from within an xColumn method of a virtual
** table, then it returns true if and only if the 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
** xColumn 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.
*/
int sqlite3_vtab_nochange(sqlite3_context *p){
assert( p );
return p->bVtabNoChng;
}
/*
** Return the current time for a statement. If the current time
** is requested more than once within the same run of a single prepared