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SQLITE3_PREUPDATE_HOOK(3)  Library Functions Manual  SQLITE3_PREUPDATE_HOOK(3)

NAME
     sqlite3_preupdate_hook, sqlite3_preupdate_old, sqlite3_preupdate_count,
     sqlite3_preupdate_depth, sqlite3_preupdate_new - The pre-update hook.

SYNOPSIS
     void *
     sqlite3_preupdate_hook(sqlite3 *db,
         void(*xPreUpdate)( void *pCtx,                   sqlite3 *db,                  int op,                       char const *zDb,              char const *zName,            sqlite3_int64 iKey1,          sqlite3_int64 iKey2           ),
         void* );

     int
     sqlite3_preupdate_old(sqlite3 *, int, sqlite3_value **);

     int
     sqlite3_preupdate_count(sqlite3 *);

     int
     sqlite3_preupdate_depth(sqlite3 *);

     int
     sqlite3_preupdate_new(sqlite3 *, int, sqlite3_value **);

DESCRIPTION
     These interfaces are only available if SQLite is compiled using the
     SQLITE_ENABLE_PREUPDATE_HOOK compile-time option.

     The sqlite3_preupdate_hook() interface registers a callback function that
     is invoked prior to each INSERT, UPDATE, and DELETE operation on a
     database table.  At most one preupdate hook may be registered at a time
     on a single database connection; each call to sqlite3_preupdate_hook()
     overrides the previous setting.  The preupdate hook is disabled by
     invoking sqlite3_preupdate_hook() with a NULL pointer as the second
     parameter.  The third parameter to sqlite3_preupdate_hook() is passed
     through as the first parameter to callbacks.

     The preupdate hook only fires for changes to real database tables; the
     preupdate hook is not invoked for changes to virtual tables or to system
     tables like sqlite_master or sqlite_stat1.

     The second parameter to the preupdate callback is a pointer to the
     database connection that registered the preupdate hook.  The third
     parameter to the preupdate callback is one of the constants
     SQLITE_INSERT, SQLITE_DELETE, or SQLITE_UPDATE to identify the kind of
     update operation that is about to occur.  The fourth parameter to the
     preupdate callback is the name of the database within the database
     connection that is being modified.  This will be "main" for the main
     database or "temp" for TEMP tables or the name given after the AS keyword
     in the ATTACH statement for attached databases.  The fifth parameter to
     the preupdate callback is the name of the table that is being modified.

     For an UPDATE or DELETE operation on a rowid table, the sixth parameter
     passed to the preupdate callback is the initial rowid of the row being
     modified or deleted.  For an INSERT operation on a rowid table, or any
     operation on a WITHOUT ROWID table, the value of the sixth parameter is
     undefined.  For an INSERT or UPDATE on a rowid table the seventh
     parameter is the final rowid value of the row being inserted or updated.
     The value of the seventh parameter passed to the callback function is not
     defined for operations on WITHOUT ROWID tables, or for INSERT operations
     on rowid tables.

     The sqlite3_preupdate_old(), sqlite3_preupdate_new(),
     sqlite3_preupdate_count(), and sqlite3_preupdate_depth() interfaces
     provide additional information about a preupdate event.  These routines
     may only be called from within a preupdate callback.  Invoking any of
     these routines from outside of a preupdate callback or with a database
     connection pointer that is different from the one supplied to the
     preupdate callback results in undefined and probably undesirable
     behavior.

     The sqlite3_preupdate_count(D) interface returns the number of columns in
     the row that is being inserted, updated, or deleted.

     The sqlite3_preupdate_old(D,N,P) interface writes into P a pointer to a
     protected sqlite3_value that contains the value of the Nth column of the
     table row before it is updated.  The N parameter must be between 0 and
     one less than the number of columns or the behavior will be undefined.
     This must only be used within SQLITE_UPDATE and SQLITE_DELETE preupdate
     callbacks; if it is used by an SQLITE_INSERT callback then the behavior
     is undefined.  The sqlite3_value that P points to will be destroyed when
     the preupdate callback returns.

     The sqlite3_preupdate_new(D,N,P) interface writes into P a pointer to a
     protected sqlite3_value that contains the value of the Nth column of the
     table row after it is updated.  The N parameter must be between 0 and one
     less than the number of columns or the behavior will be undefined.  This
     must only be used within SQLITE_INSERT and SQLITE_UPDATE preupdate
     callbacks; if it is used by an SQLITE_DELETE callback then the behavior
     is undefined.  The sqlite3_value that P points to will be destroyed when
     the preupdate callback returns.

     The sqlite3_preupdate_depth(D) interface returns 0 if the preupdate
     callback was invoked as a result of a direct insert, update, or delete
     operation; or 1 for inserts, updates, or deletes invoked by top-level
     triggers; or 2 for changes resulting from triggers called by top-level
     triggers; and so forth.

SEE ALSO
     sqlite3(3), sqlite3_value(3), sqlite3_preupdate_hook(3),
     sqlite3_update_hook(3), sqlite3_value(3), SQLITE_CREATE_INDEX(3)

NetBSD 8.0                      March 11, 2017                      NetBSD 8.0