static PyObject *
PLy_cursor_iternext(PyObject *self)
{
PLyCursorObject *cursor;
PyObject *ret;
volatile MemoryContext oldcontext;
volatile ResourceOwner oldowner;
Portal portal;
cursor = (PLyCursorObject *) self;
if (cursor->closed)
{
PLy_exception_set(PyExc_ValueError, "iterating a closed cursor");
return NULL;
}
portal = GetPortalByName(cursor->portalname);
if (!PortalIsValid(portal))
{
PLy_exception_set(PyExc_ValueError,
"iterating a cursor in an aborted subtransaction");
return NULL;
}
oldcontext = CurrentMemoryContext;
oldowner = CurrentResourceOwner;
PLy_spi_subtransaction_begin(oldcontext, oldowner);
PG_TRY();
{
SPI_cursor_fetch(portal, true, 1);
if (SPI_processed == 0)
{
PyErr_SetNone(PyExc_StopIteration);
ret = NULL;
}
else
{
if (cursor->result.is_rowtype != 1)
PLy_input_tuple_funcs(&cursor->result, SPI_tuptable->tupdesc);
ret = PLyDict_FromTuple(&cursor->result, SPI_tuptable->vals[0],
SPI_tuptable->tupdesc);
}
SPI_freetuptable(SPI_tuptable);
PLy_spi_subtransaction_commit(oldcontext, oldowner);
}
PG_CATCH();
{
PLy_spi_subtransaction_abort(oldcontext, oldowner);
return NULL;
}
PG_END_TRY();
return ret;
}
/*
* PerformPortalClose
* Close a cursor.
*/
void
PerformPortalClose(const char *name)
{
Portal portal;
/*
* Disallow empty-string cursor name (conflicts with protocol-level
* unnamed portal).
*/
if (!name || name[0] == '\0')
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_NAME),
errmsg("invalid cursor name: must not be empty")));
/*
* get the portal from the portal name
*/
portal = GetPortalByName(name);
if (!PortalIsValid(portal))
{
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_CURSOR),
errmsg("cursor \"%s\" does not exist", name)));
return; /* keep compiler happy */
}
/*
* Note: PortalCleanup is called as a side-effect
*/
PortalDrop(portal, false);
}
/*
* CreatePortal
* Returns a new portal given a name.
*
* allowDup: if true, automatically drop any pre-existing portal of the
* same name (if false, an error is raised).
*
* dupSilent: if true, don't even emit a WARNING.
*/
Portal
CreatePortal(const char *name, bool allowDup, bool dupSilent)
{
Portal portal;
AssertArg(PointerIsValid(name));
portal = GetPortalByName(name);
if (PortalIsValid(portal))
{
if (!allowDup)
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_CURSOR),
errmsg("cursor \"%s\" already exists", name)));
if (!dupSilent)
ereport(WARNING,
(errcode(ERRCODE_DUPLICATE_CURSOR),
errmsg("closing existing cursor \"%s\"",
name)));
PortalDrop(portal, false);
}
/* make new portal structure */
portal = (Portal) MemoryContextAllocZero(PortalMemory, sizeof *portal);
/* initialize portal heap context; typically it won't store much */
portal->heap = AllocSetContextCreate(PortalMemory,
"PortalHeapMemory",
ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
/* create a resource owner for the portal */
portal->resowner = ResourceOwnerCreate(CurTransactionResourceOwner,
"Portal");
/* initialize portal fields that don't start off zero */
portal->cleanup = PortalCleanup;
portal->createSubid = GetCurrentSubTransactionId();
portal->strategy = PORTAL_MULTI_QUERY;
portal->cursorOptions = CURSOR_OPT_NO_SCROLL;
portal->atStart = true;
portal->atEnd = true; /* disallow fetches until query is set */
/* put portal in table (sets portal->name) */
PortalHashTableInsert(portal, name);
return portal;
}
/*
* CreateNewPortal
* Create a new portal, assigning it a random nonconflicting name.
*/
Portal
CreateNewPortal(void)
{
static unsigned int unnamed_portal_count = 0;
char portalname[MAX_PORTALNAME_LEN];
/* Select a nonconflicting name */
for (;;)
{
unnamed_portal_count++;
sprintf(portalname, "<unnamed portal %u>", unnamed_portal_count);
if (GetPortalByName(portalname) == NULL)
break;
}
return CreatePortal(portalname, false, false);
}
/*
* PerformPortalFetch
* Execute SQL FETCH or MOVE command.
*
* stmt: parsetree node for command
* dest: where to send results
* completionTag: points to a buffer of size COMPLETION_TAG_BUFSIZE
* in which to store a command completion status string.
*
* completionTag may be NULL if caller doesn't want a status string.
*/
void
PerformPortalFetch(FetchStmt *stmt,
DestReceiver *dest,
char *completionTag)
{
Portal portal;
long nprocessed;
/*
* Disallow empty-string cursor name (conflicts with protocol-level
* unnamed portal).
*/
if (!stmt->portalname || stmt->portalname[0] == '\0')
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_NAME),
errmsg("invalid cursor name: must not be empty")));
/* get the portal from the portal name */
portal = GetPortalByName(stmt->portalname);
if (!PortalIsValid(portal))
{
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_CURSOR),
errmsg("cursor \"%s\" does not exist", stmt->portalname)));
return; /* keep compiler happy */
}
/* Adjust dest if needed. MOVE wants destination DestNone */
if (stmt->ismove)
dest = None_Receiver;
/* Do it */
nprocessed = PortalRunFetch(portal,
stmt->direction,
stmt->howMany,
dest);
/* Return command status if wanted */
if (completionTag)
snprintf(completionTag, COMPLETION_TAG_BUFSIZE, "%s %ld",
stmt->ismove ? "MOVE" : "FETCH",
nprocessed);
}
static PyObject *
PLy_cursor_close(PyObject *self, PyObject *unused)
{
PLyCursorObject *cursor = (PLyCursorObject *) self;
if (!cursor->closed)
{
Portal portal = GetPortalByName(cursor->portalname);
if (!PortalIsValid(portal))
{
PLy_exception_set(PyExc_ValueError,
"closing a cursor in an aborted subtransaction");
return NULL;
}
SPI_cursor_close(portal);
cursor->closed = true;
}
Py_INCREF(Py_None);
return Py_None;
}
static void
PLy_cursor_dealloc(PyObject *arg)
{
PLyCursorObject *cursor;
Portal portal;
cursor = (PLyCursorObject *) arg;
if (!cursor->closed)
{
portal = GetPortalByName(cursor->portalname);
if (PortalIsValid(portal))
SPI_cursor_close(portal);
cursor->closed = true;
}
if (cursor->mcxt)
{
MemoryContextDelete(cursor->mcxt);
cursor->mcxt = NULL;
}
arg->ob_type->tp_free(arg);
}
/*
* SPI_cursor_find()
*
* Find the portal of an existing open cursor
*/
Portal
SPI_cursor_find(const char *name)
{
return GetPortalByName(name);
}
/*
* execCurrentOf
*
* Given a CURRENT OF expression and the OID of a table, determine which row
* of the table is currently being scanned by the cursor named by CURRENT OF,
* and return the row's TID into *current_tid.
*
* Returns true if a row was identified. Returns false if the cursor is valid
* for the table but is not currently scanning a row of the table (this is a
* legal situation in inheritance cases). Raises error if cursor is not a
* valid updatable scan of the specified table.
*/
bool
execCurrentOf(CurrentOfExpr *cexpr,
ExprContext *econtext,
Oid table_oid,
ItemPointer current_tid)
{
char *cursor_name;
char *table_name;
Portal portal;
QueryDesc *queryDesc;
/* Get the cursor name --- may have to look up a parameter reference */
if (cexpr->cursor_name)
cursor_name = cexpr->cursor_name;
else
cursor_name = fetch_cursor_param_value(econtext, cexpr->cursor_param);
/* Fetch table name for possible use in error messages */
table_name = get_rel_name(table_oid);
if (table_name == NULL)
elog(ERROR, "cache lookup failed for relation %u", table_oid);
/* Find the cursor's portal */
portal = GetPortalByName(cursor_name);
if (!PortalIsValid(portal))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_CURSOR),
errmsg("cursor \"%s\" does not exist", cursor_name)));
/*
* We have to watch out for non-SELECT queries as well as held cursors,
* both of which may have null queryDesc.
*/
if (portal->strategy != PORTAL_ONE_SELECT)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" is not a SELECT query",
cursor_name)));
queryDesc = portal->queryDesc;
if (queryDesc == NULL || queryDesc->estate == NULL)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" is held from a previous transaction",
cursor_name)));
/*
* We have two different strategies depending on whether the cursor uses
* FOR UPDATE/SHARE or not. The reason for supporting both is that the
* FOR UPDATE code is able to identify a target table in many cases where
* the other code can't, while the non-FOR-UPDATE case allows use of WHERE
* CURRENT OF with an insensitive cursor.
*/
if (queryDesc->estate->es_rowmarks)
{
ExecRowMark *erm;
Index i;
/*
* Here, the query must have exactly one FOR UPDATE/SHARE reference to
* the target table, and we dig the ctid info out of that.
*/
erm = NULL;
for (i = 0; i < queryDesc->estate->es_range_table_size; i++)
{
ExecRowMark *thiserm = queryDesc->estate->es_rowmarks[i];
if (thiserm == NULL ||
!RowMarkRequiresRowShareLock(thiserm->markType))
continue; /* ignore non-FOR UPDATE/SHARE items */
if (thiserm->relid == table_oid)
{
if (erm)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" has multiple FOR UPDATE/SHARE references to table \"%s\"",
cursor_name, table_name)));
erm = thiserm;
}
}
if (erm == NULL)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" does not have a FOR UPDATE/SHARE reference to table \"%s\"",
cursor_name, table_name)));
/*
* The cursor must have a current result row: per the SQL spec, it's
* an error if not.
*/
if (portal->atStart || portal->atEnd)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" is not positioned on a row",
cursor_name)));
/* Return the currently scanned TID, if there is one */
if (ItemPointerIsValid(&(erm->curCtid)))
{
*current_tid = erm->curCtid;
return true;
}
/*
* This table didn't produce the cursor's current row; some other
* inheritance child of the same parent must have. Signal caller to
* do nothing on this table.
*/
return false;
}
else
{
/*
* Without FOR UPDATE, we dig through the cursor's plan to find the
* scan node. Fail if it's not there or buried underneath
* aggregation.
*/
ScanState *scanstate;
bool pending_rescan = false;
scanstate = search_plan_tree(queryDesc->planstate, table_oid,
&pending_rescan);
if (!scanstate)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" is not a simply updatable scan of table \"%s\"",
cursor_name, table_name)));
/*
* The cursor must have a current result row: per the SQL spec, it's
* an error if not. We test this at the top level, rather than at the
* scan node level, because in inheritance cases any one table scan
* could easily not be on a row. We want to return false, not raise
* error, if the passed-in table OID is for one of the inactive scans.
*/
if (portal->atStart || portal->atEnd)
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" is not positioned on a row",
cursor_name)));
/*
* Now OK to return false if we found an inactive scan. It is
* inactive either if it's not positioned on a row, or there's a
* rescan pending for it.
*/
if (TupIsNull(scanstate->ss_ScanTupleSlot) || pending_rescan)
return false;
/*
* Extract TID of the scan's current row. The mechanism for this is
* in principle scan-type-dependent, but for most scan types, we can
* just dig the TID out of the physical scan tuple.
*/
if (IsA(scanstate, IndexOnlyScanState))
{
/*
* For IndexOnlyScan, the tuple stored in ss_ScanTupleSlot may be
* a virtual tuple that does not have the ctid column, so we have
* to get the TID from xs_ctup.t_self.
*/
IndexScanDesc scan = ((IndexOnlyScanState *) scanstate)->ioss_ScanDesc;
*current_tid = scan->xs_ctup.t_self;
}
else
{
/*
* Default case: try to fetch TID from the scan node's current
* tuple. As an extra cross-check, verify tableoid in the current
* tuple. If the scan hasn't provided a physical tuple, we have
* to fail.
*/
Datum ldatum;
bool lisnull;
ItemPointer tuple_tid;
#ifdef USE_ASSERT_CHECKING
if (!slot_getsysattr(scanstate->ss_ScanTupleSlot,
TableOidAttributeNumber,
&ldatum,
&lisnull))
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" is not a simply updatable scan of table \"%s\"",
cursor_name, table_name)));
Assert(!lisnull);
Assert(DatumGetObjectId(ldatum) == table_oid);
#endif
if (!slot_getsysattr(scanstate->ss_ScanTupleSlot,
SelfItemPointerAttributeNumber,
&ldatum,
&lisnull))
ereport(ERROR,
(errcode(ERRCODE_INVALID_CURSOR_STATE),
errmsg("cursor \"%s\" is not a simply updatable scan of table \"%s\"",
cursor_name, table_name)));
Assert(!lisnull);
tuple_tid = (ItemPointer) DatumGetPointer(ldatum);
*current_tid = *tuple_tid;
}
Assert(ItemPointerIsValid(current_tid));
return true;
}
}
static PyObject *
PLy_cursor_fetch(PyObject *self, PyObject *args)
{
PLyCursorObject *cursor;
int count;
PLyResultObject *ret;
volatile MemoryContext oldcontext;
volatile ResourceOwner oldowner;
Portal portal;
if (!PyArg_ParseTuple(args, "i", &count))
return NULL;
cursor = (PLyCursorObject *) self;
if (cursor->closed)
{
PLy_exception_set(PyExc_ValueError, "fetch from a closed cursor");
return NULL;
}
portal = GetPortalByName(cursor->portalname);
if (!PortalIsValid(portal))
{
PLy_exception_set(PyExc_ValueError,
"iterating a cursor in an aborted subtransaction");
return NULL;
}
ret = (PLyResultObject *) PLy_result_new();
if (ret == NULL)
return NULL;
oldcontext = CurrentMemoryContext;
oldowner = CurrentResourceOwner;
PLy_spi_subtransaction_begin(oldcontext, oldowner);
PG_TRY();
{
SPI_cursor_fetch(portal, true, count);
if (cursor->result.is_rowtype != 1)
PLy_input_tuple_funcs(&cursor->result, SPI_tuptable->tupdesc);
Py_DECREF(ret->status);
ret->status = PyInt_FromLong(SPI_OK_FETCH);
Py_DECREF(ret->nrows);
ret->nrows = PyInt_FromLong(SPI_processed);
if (SPI_processed != 0)
{
int i;
Py_DECREF(ret->rows);
ret->rows = PyList_New(SPI_processed);
for (i = 0; i < SPI_processed; i++)
{
PyObject *row = PLyDict_FromTuple(&cursor->result,
SPI_tuptable->vals[i],
SPI_tuptable->tupdesc);
PyList_SetItem(ret->rows, i, row);
}
}
SPI_freetuptable(SPI_tuptable);
PLy_spi_subtransaction_commit(oldcontext, oldowner);
}
PG_CATCH();
{
PLy_spi_subtransaction_abort(oldcontext, oldowner);
return NULL;
}
PG_END_TRY();
return (PyObject *) ret;
}
