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SQLite - Save As?

开发者 https://www.devze.com 2023-02-12 18:06 出处:网络
How do you do a \"Save As\" for SQLite. Meaning, There\'s an open file database and I want to do a \"Save As\",

How do you do a "Save As" for SQLite.

Meaning,

There's an open file database and I want to do a "Save As", make a copy of an on-line S开发者_开发知识库QL database.

Similar to File|Save As in Word, App. would prompt for new filename and then start using new filename instead.

Is there a way to do it without closing the database?


Taken from sqlite.org:

/*
** Perform an online backup of database pDb to the database file named
** by zFilename. This function copies 5 database pages from pDb to
** zFilename, then unlocks pDb and sleeps for 250 ms, then repeats the
** process until the entire database is backed up.
** 
** The third argument passed to this function must be a pointer to a progress
** function. After each set of 5 pages is backed up, the progress function
** is invoked with two integer parameters: the number of pages left to
** copy, and the total number of pages in the source file. This information
** may be used, for example, to update a GUI progress bar.
**
** While this function is running, another thread may use the database pDb, or
** another process may access the underlying database file via a separate 
** connection.
**
** If the backup process is successfully completed, SQLITE_OK is returned.
** Otherwise, if an error occurs, an SQLite error code is returned.
*/
int backupDb(
  sqlite3 *pDb,               /* Database to back up */
  const char *zFilename,      /* Name of file to back up to */
  void(*xProgress)(int, int)  /* Progress function to invoke */     
){
  int rc;                     /* Function return code */
  sqlite3 *pFile;             /* Database connection opened on zFilename */
  sqlite3_backup *pBackup;    /* Backup handle used to copy data */

  /* Open the database file identified by zFilename. */
  rc = sqlite3_open(zFilename, &pFile);
  if( rc==SQLITE_OK ){

    /* Open the sqlite3_backup object used to accomplish the transfer */
    pBackup = sqlite3_backup_init(pFile, "main", pDb, "main");
    if( pBackup ){

      /* Each iteration of this loop copies 5 database pages from database
      ** pDb to the backup database. If the return value of backup_step()
      ** indicates that there are still further pages to copy, sleep for
      ** 250 ms before repeating. */
      do {
        rc = sqlite3_backup_step(pBackup, 5);
        xProgress(
            sqlite3_backup_remaining(pBackup),
            sqlite3_backup_pagecount(pBackup)
        );
        if( rc==SQLITE_OK || rc==SQLITE_BUSY || rc==SQLITE_LOCKED ){
          sqlite3_sleep(250);
        }
      } while( rc==SQLITE_OK || rc==SQLITE_BUSY || rc==SQLITE_LOCKED );

      /* Release resources allocated by backup_init(). */
      (void)sqlite3_backup_finish(pBackup);
    }
    rc = sqlite3_errcode(pFile);
  }

  /* Close the database connection opened on database file zFilename
  ** and return the result of this function. */
  (void)sqlite3_close(pFile);
  return rc;
}

HTH Cheers

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