/*
* SQLite manages explicit transactions by setting a flag when a BEGIN; is
* issued, then starting an actual transaction in the btree layer when the
* first operation happens (a read txn if it's a read op, a write txn if write)
* Then each statement will be contained in a sub-transaction. Since sequences
* are implemented using a custom function, we need to emulate that
* functionality. So there are three cases here:
* - Not in an explicit transaction - start a statement, since we might do
* write operations, and thus we need a valid statement_txn.
* - In an explicit transaction, and the first statement. Start a txn and a
statement txn.
* - In an explicit transaction and not the first statemetn. Start a statement
* transaction.
*
* The SQLite vdbe will take care of closing the statement transaction for us,
* so we don't need to worry about that.
*
* Caching sequences can't be transactionally protected, so it's a no-op in
* that case (and this function should not be called).
*
* It's safe to call this method multiple times since both
* sqlite3BtreeBeginTrans and sqlite3BtreeBeginStmt are no-ops on subsequent
* calls.
*/
static int btreeSeqStartTransaction(
sqlite3_context *context, Btree *p, int is_write)
{
sqlite3 *db;
Vdbe *vdbe;
int rc;
db = sqlite3_context_db_handle(context);
/*
* TODO: This is actually a linked list of VDBEs, not necessarily
* the vdbe we want. I can't see a way to get the correct
* vdbe handle.
* It's possible that there is only one VDBE handle in DB, since
* we use a shared cache.
*/
vdbe = db->pVdbe;
if (!sqlite3BtreeIsInTrans(p) &&
(rc = btreeBeginTransInternal(p, 1)) != SQLITE_OK) {
btreeSeqError(context, SQLITE_ERROR,
"Could not begin transaction.");
return (rc);
}
/*
* TODO: Do we need logic bumping the VDBE statement count here?
* vdbe.c:OP_Transaction does, but adding it here causes an
* assert failure. It should be OK, because this code is only
* really relevant in the case where there is a single statement.
*/
rc = sqlite3BtreeBeginStmt(p, vdbe->iStatement);
return (rc);
}
/*
** Usage: btree_begin_statement ID
**
** Start a new statement transaction
*/
static int btree_begin_statement(
void *NotUsed,
Tcl_Interp *interp, /* The TCL interpreter that invoked this command */
int argc, /* Number of arguments */
const char **argv /* Text of each argument */
){
Btree *pBt;
int rc;
if( argc!=2 ){
Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
" ID\"", 0);
return TCL_ERROR;
}
pBt = sqlite3TestTextToPtr(argv[1]);
sqlite3BtreeEnter(pBt);
rc = sqlite3BtreeBeginStmt(pBt);
sqlite3BtreeLeave(pBt);
if( rc!=SQLITE_OK ){
Tcl_AppendResult(interp, errorName(rc), 0);
return TCL_ERROR;
}
return TCL_OK;
}
