Hi,
The sample code is below. I am trying this on windows(xp)(sqlite 3.3.13) and
have disabled almost all sqlite features.
When createUsingExec variable is true in the sample code, I am able to
reproduce the problem.
Thanks
karthik
//================================== begin
==================================
int select_while_update ();
int main ()
{
select_while_update ();
}
int select_while_update ()
{
int i = 0;
int ret;
sqlite3 *pDb = NULL;
const char *dbName = "./t.db";
const char *crTable = "CREATE TABLE A ( ID INTEGER, NAME TEXT) ;";
const char *selAll = "SELECT * from A;";
const char *insRow = "INSERT INTO A VALUES (?,?);";
const char *updRow = "UPDATE A SET NAME=? WHERE ID=?;";
sqlite3_stmt *pSelAll = NULL;
sqlite3_stmt *pInsRow = NULL;
sqlite3_stmt *pUpdRow = NULL;
int createUsingExec = 1;
char buf [64] = { 0 };
remove (dbName);
ret = sqlite3_open (dbName, &pDb);
sqlite3_busy_timeout (pDb, 3000);
if (createUsingExec) {
const char *c2 = "INSERT INTO A VALUES ( 1, 'name is 1' )
;";
const char *c3 = "INSERT INTO A VALUES ( 2, 'name is 2' )
;";
const char *c4 = "INSERT INTO A VALUES ( 3, 'name is 3') ;";
const char *c5 = "INSERT INTO A VALUES ( 4, 'name is 4' )
;";
const char *c6 = "INSERT INTO A VALUES ( 5, 'name is 5' )
;";
sqlite3_exec (pDb, crTable, 0, 0, 0);
sqlite3_exec (pDb, c2, 0, 0, 0);
sqlite3_exec (pDb, c3, 0, 0, 0);
sqlite3_exec (pDb, c4, 0, 0, 0);
sqlite3_exec (pDb, c5, 0, 0, 0);
sqlite3_exec (pDb, c6, 0, 0, 0);
} else {
ret = sqlite3_exec (pDb, crTable, NULL, NULL, NULL);
if (SQLITE_OK != ret) {
printf ("error creating table\n");
return -1;
}
ret = sqlite3_prepare_v2 (pDb, insRow, -1, &pInsRow, NULL);
for (i = 0; i < 5; i ++) {
sprintf (buf, "name is %d", i);
sqlite3_reset (pInsRow);
sqlite3_bind_int (pInsRow, 1, i);
sqlite3_bind_text (pInsRow, 2, buf, -1,
SQLITE_STATIC);
sqlite3_step (pInsRow);
}
sqlite3_finalize (pInsRow);
}
ret = sqlite3_prepare_v2 (pDb, selAll, -1, &pSelAll, NULL);
sqlite3_bind_parameter_count (pSelAll);
sqlite3_reset (pSelAll);
ret = sqlite3_step (pSelAll);
while (SQLITE_ROW == ret) {
// get id from select statemnt results
int id;
char *text;
sqlite3_data_count (pSelAll);
sqlite3_column_count (pSelAll);
sqlite3_column_type (pSelAll, 0);
sqlite3_column_bytes (pSelAll, 0);
// get id
id = sqlite3_column_int (pSelAll, 0);
sqlite3_column_type (pSelAll, 1);
sqlite3_column_bytes (pSelAll, 1);
// get text
text = sqlite3_column_text (pSelAll, 1);
sprintf (buf, "name is %d", ++i);
// prepare update statements
if (!pUpdRow) {
sqlite3_prepare_v2 (pDb, updRow, -1, &pUpdRow,
NULL);
}
sqlite3_bind_parameter_count (pUpdRow);
sqlite3_reset (pUpdRow);
// bind values to update statement
sqlite3_bind_text (pUpdRow, 1, buf, -1, SQLITE_STATIC);
sqlite3_bind_int (pUpdRow, 2, i);
sqlite3_step (pUpdRow);
// step to next result row
ret = sqlite3_step (pSelAll);
}
// need finalize other statements
return 0;
}
//================================== end ==================================
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-----Original Message-----
From: Joe Wilson [mailto:[EMAIL PROTECTED]
Sent: Sunday, August 05, 2007 12:59 AM
To: sqlite-users@sqlite.org
Subject: Re: [sqlite] Select, update on the row, and step leads to crash
It should be possible to do what you're trying to do as of 3.3.8.
See the Tcl examples at the bottom of this patch:
Allows UPDATE, INSERT, and DELETEs to occur while a SELECT is pending on
the same table.
http://www.sqlite.org/cvstrac/chngview?cn=3355
Post a complete self-contained C program demonstrating the problem if you
need further help.
--- karthikeyan <[EMAIL PROTECTED]> wrote:
> What we are doing in short is below (using Sqlite 3.3.13).
>
> Select id, data from msgTable; // ok - returns 100
> tid = sqlite3_column_int;
> data = sqlite3_column_bytes;
> // make a copy of the bytes
> // update the byte values
> update msgTable set data=new data where id=tid; //ok - returns 101
> sqlite3_step // not ok
>
> Sqlite3_step, crashes because (BtCursor *pCur)->pPage is null in
> sqlite3BtreeNext.
>
> I read somewhere that its possible to update while we are in a select.
> Is this possible?
> Or are there some other api call, which I need to call before
> sqlite3_step is called?.
>
> Both the statements are prepared using sqlite3_prepare_v2 and values
> are assigned using the bind functions.
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