This sounded fun, so I thought I'd give it a try. Here's a sample
pulling schema and data from an on-disk to an in-memory database in c.
I've omitted error handling and debug output to make it shorter.
int process_ddl_row(void * pData, int nColumns,
char **values, char **columns);
int process_dml_row(void *pData, int nColumns,
char **values, char **columns);
void test()
{
sqlite3* memorydb;
sqlite3* budb;
sqlite3_open(":memory:", &memorydb);
// Looks for backup.db in pwd. For testing, you may want to
// initialize the database to a known state.
sqlite3_open("backup.db", &budb);
// Create the in-memory schema from the backup
sqlite3_exec(budb, "BEGIN", NULL, NULL, NULL);
sqlite3_exec(budb, "SELECT sql FROM sqlite_master WHERE sql NOT
NULL",
&process_ddl_row, memorydb, NULL);
sqlite3_exec(budb, "COMMIT", NULL, NULL, NULL);
sqlite3_close(budb);
// Attach the backup to the in memory
sqlite3_exec(memorydb, "ATTACH DATABASE 'backup.db' as backup",
NULL, NULL, NULL);
// Copy the data from the backup to the in memory
sqlite3_exec(memorydb, "BEGIN", NULL, NULL, NULL);
sqlite3_exec(memorydb,
"SELECT name FROM backup.sqlite_master WHERE
type='table'",
&process_dml_row, memorydb, NULL);
sqlite3_exec(memorydb, "COMMIT", NULL, NULL, NULL);
sqlite3_exec(memorydb, "DETACH DATABASE backup", NULL, NULL,
NULL);
sqlite3_close(memorydb);
}
/**
* Exec an sql statement in values[0] against
* the database in pData.
*/
int process_ddl_row(void * pData, int nColumns,
char **values, char **columns)
{
if (nColumns != 1)
return 1; // Error
sqlite3* db = (sqlite3*)pData;
sqlite3_exec(db, values[0], NULL, NULL, NULL);
return 0;
}
/**
* Insert from a table named by backup.{values[0]}
* into main.{values[0]} in database pData.
*/
int process_dml_row(void *pData, int nColumns,
char **values, char **columns)
{
if (nColumns != 1)
return 1; // Error
sqlite3* db = (sqlite3*)pData;
char *stmt = sqlite3_mprintf("insert into main.%q "
"select * from backup.%q", values[0], values[0]);
sqlite3_exec(db, stmt, NULL, NULL, NULL);
sqlite3_free(stmt);
return 0;
}
-----Original Message-----
From: Dave Gierok [mailto:[EMAIL PROTECTED]
Sent: Monday, June 05, 2006 5:45 PM
To: sqlite-users@sqlite.org
Subject: RE: [sqlite] Memory DB: Load from file
Thank you for the help Andrew and D. Richard Hipp. But how would I do
this (page 24 & 25 of the slides) using the C/C++ interface?
{
sqlite3* pFileDB;
sqlite3* pMemoryDB;
sqlite3_open(fileName, &pFileDB);
sqlite3_open(":memory:", &pMemoryDB);
//****************************************
//WHAT DO I DO NOW?
//****************************************
}
Thanks,
Dave Gierok
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Monday, June 05, 2006 12:49 PM
To: sqlite-users@sqlite.org
Subject: Re: [sqlite] Memory DB: Load from file
Andrew Piskorski <[EMAIL PROTECTED]> wrote:
> On Mon, Jun 05, 2006 at 12:05:52PM -0700, Dave Gierok wrote:
>
> > Is there a way to load a Sqlite file based DB and then specify we
want
> > that to go into memory? Or is there a more efficient way to create
our
> > memory DB?
>
> You could use attach to copy from an on-disk SQLite database:
>
> http://www.sqlite.org/google-talk-slides/page-024.html
> http://www.sqlite.org/google-talk-slides/page-025.html
>
Andrews suggestion above is better than the sqlite3_raw_write()
routine of my previous post because Andrew's idea is portable.
Use this idea if it is fast enough for you. The raw_write()
thing will be a little bit faster, but as I said, it is subject
to break without warning.
--
D. Richard Hipp <[EMAIL PROTECTED]>
