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Avoid the possibility when curs_get_last_result would block

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It was trying to get all pending results from the connection and if
the client sent many and anyone except the first one would not be
immediately available the loop in curs_get_last_result would call
PQgetResult blockingly.
Avoid that by calling PQisBusy every time and telling the client to
wait for more data if it returns 1.
This commit is contained in:
Jan Urbański 2010-03-31 01:55:44 +02:00 committed by Federico Di Gregorio
parent 25a609c9a7
commit 58eb868db6
2 changed files with 32 additions and 8 deletions
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2
psycopg/cursor.h
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@ -86,7 +86,7 @@ typedef struct {
/* C-callable functions in cursor_int.c and cursor_ext.c */ /* C-callable functions in cursor_int.c and cursor_ext.c */
HIDDEN void curs_reset(cursorObject *self); HIDDEN void curs_reset(cursorObject *self);
HIDDEN void curs_get_last_result(cursorObject *self); HIDDEN int curs_get_last_result(cursorObject *self);
HIDDEN PyObject *curs_poll_send(cursorObject *self); HIDDEN PyObject *curs_poll_send(cursorObject *self);
HIDDEN PyObject *curs_poll_fetch(cursorObject *self); HIDDEN PyObject *curs_poll_fetch(cursorObject *self);

38
psycopg/cursor_int.c
View File

@ -59,18 +59,30 @@ curs_reset(cursorObject *self)
* curs_get_last_result * curs_get_last_result
* *
* read all results from the connection, save the last one * read all results from the connection, save the last one
* returns 0 if all results were read, 1 if there are remaining results, but
* their retrieval would block, -1 if there was an error
*/ */
void int
curs_get_last_result(cursorObject *self) { curs_get_last_result(cursorObject *self) {
PGresult *pgres; PGresult *pgres;
IFCLEARPGRES(self->pgres); IFCLEARPGRES(self->pgres);
Py_BEGIN_ALLOW_THREADS; Py_BEGIN_ALLOW_THREADS;
pthread_mutex_lock(&(self->conn->lock)); pthread_mutex_lock(&(self->conn->lock));
/* read all results: there can be multiple if the client sent multiple /* read one result, there can be multiple if the client sent multiple
statements */ statements */
while ((pgres = PQgetResult(self->conn->pgconn)) != NULL) { while ((pgres = PQgetResult(self->conn->pgconn)) != NULL) {
if (PQisBusy(self->conn->pgconn) == 1) {
/* there is another result waiting, need to tell the client to
wait more */
Dprintf("curs_get_last_result: gut result, but more are pending");
self->pgres = pgres;
pthread_mutex_unlock(&(self->conn->lock));
Py_BLOCK_THREADS;
return 1;
}
Dprintf("curs_get_last_result: got result %p", pgres);
IFCLEARPGRES(self->pgres); IFCLEARPGRES(self->pgres);
self->pgres = pgres; self->pgres = pgres;
} }
@ -79,6 +91,7 @@ curs_get_last_result(cursorObject *self) {
pthread_mutex_unlock(&(self->conn->lock)); pthread_mutex_unlock(&(self->conn->lock));
Py_END_ALLOW_THREADS; Py_END_ALLOW_THREADS;
self->needsfetch = 1; self->needsfetch = 1;
return 0;
} }
/* curs_poll_send - handle cursor polling when flushing output */ /* curs_poll_send - handle cursor polling when flushing output */
@ -114,6 +127,7 @@ PyObject *
curs_poll_fetch(cursorObject *self) curs_poll_fetch(cursorObject *self)
{ {
int is_busy; int is_busy;
int last_result;
/* consume the input */ /* consume the input */
is_busy = pq_is_busy(self->conn); is_busy = pq_is_busy(self->conn);
@ -127,9 +141,19 @@ curs_poll_fetch(cursorObject *self)
return PyInt_FromLong(PSYCO_POLL_READ); return PyInt_FromLong(PSYCO_POLL_READ);
} }
/* all data has arrived */ /* data has arrived, try to fetch all of it or, if it failed, tell the
curs_get_last_result(self); user to wait more */
last_result = curs_get_last_result(self);
Dprintf("cur_poll_fetch: returning %d", PSYCO_POLL_OK); if (last_result == 0) {
return PyInt_FromLong(PSYCO_POLL_OK); Dprintf("cur_poll_fetch: returning %d", PSYCO_POLL_OK);
return PyInt_FromLong(PSYCO_POLL_OK);
}
else if (last_result == 1) {
Dprintf("cur_poll_fetch: got result, but data remaining, "
"returning %d", PSYCO_POLL_READ);
return PyInt_FromLong(PSYCO_POLL_READ);
}
else {
return NULL;
}
} }