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In a PL/pgSQL "FOR cursor" statement, the statements executed in the loop

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might close the cursor,  rendering the Portal pointer to it invalid.
Closing the cursor in the middle of the loop is not a very sensible thing
to do, but we must handle it gracefully and throw an error instead of
crashing.
This commit is contained in:
Heikki Linnakangas 2010-06-21 09:49:58 +00:00
parent c4ac2ff765
commit 855d440a2f
1 changed files with 39 additions and 3 deletions
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42
src/pl/plpgsql/src/pl_exec.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.244.2.4 2010/04/14 23:52:16 tgl Exp $
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.244.2.5 2010/06/21 09:49:58 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@ -1869,6 +1869,7 @@ exec_stmt_forc(PLpgSQL_execstate *estate, PLpgSQL_stmt_forc *stmt)
{
PLpgSQL_var *curvar;
char *curname = NULL;
const char *portalname;
PLpgSQL_expr *query;
Portal portal;
int rc;
@ -1951,6 +1952,7 @@ exec_stmt_forc(PLpgSQL_execstate *estate, PLpgSQL_stmt_forc *stmt)
if (portal == NULL)
elog(ERROR, "could not open cursor: %s",
SPI_result_code_string(SPI_result));
portalname = portal->name;
/*
* If cursor variable was NULL, store the generated portal name in it
@ -1965,11 +1967,20 @@ exec_stmt_forc(PLpgSQL_execstate *estate, PLpgSQL_stmt_forc *stmt)
rc = exec_for_query(estate, (PLpgSQL_stmt_forq *) stmt, portal, false);
/* ----------
* Close portal, and restore cursor variable if it was initially NULL.
* Close portal. The statements executed in the loop might've closed the
* cursor already, rendering our portal pointer invalid, so we mustn't
* trust the pointer.
* ----------
*/
portal = SPI_cursor_find(portalname);
if (portal == NULL)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_CURSOR),
errmsg("cursor \"%s\" closed unexpectedly",
portalname)));
SPI_cursor_close(portal);
/* Restore cursor variable if it was initially NULL. */
if (curname == NULL)
{
free_var(curvar);
@ -4189,6 +4200,13 @@ exec_run_select(PLpgSQL_execstate *estate,
* exec_for_query --- execute body of FOR loop for each row from a portal
*
* Used by exec_stmt_fors, exec_stmt_forc and exec_stmt_dynfors
*
* If the portal is for a cursor that's visible to user code, the statements
* we execute might move or close the cursor. You must pass prefetch_ok=false
* in that case to disable optimizations that rely on the portal staying
* unchanged over execution of the user statements.
* NB: With prefetch_ok=false, the portal pointer might point to garbage
* after the call. Caller beware!
*/
static int
exec_for_query(PLpgSQL_execstate *estate, PLpgSQL_stmt_forq *stmt,
@ -4200,6 +4218,10 @@ exec_for_query(PLpgSQL_execstate *estate, PLpgSQL_stmt_forq *stmt,
bool found = false;
int rc = PLPGSQL_RC_OK;
int n;
const char *portalname;
/* Remember portal name so that we can re-find it */
portalname = portal->name;
/*
* Determine if we assign to a record or a row
@ -4308,8 +4330,22 @@ exec_for_query(PLpgSQL_execstate *estate, PLpgSQL_stmt_forq *stmt,
/*
* Fetch more tuples. If prefetching is allowed, grab 50 at a time.
* Otherwise the statements executed in the loop might've moved or
* even closed the cursor, so check that the cursor is still open,
* and fetch only one row at a time.
*/
SPI_cursor_fetch(portal, true, prefetch_ok ? 50 : 1);
if (prefetch_ok)
SPI_cursor_fetch(portal, true, 50);
else
{
portal = SPI_cursor_find(portalname);
if (portal == NULL)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_CURSOR),
errmsg("cursor \"%s\" closed unexpectedly",
portalname)));
SPI_cursor_fetch(portal, true, 1);
}
tuptab = SPI_tuptable;
n = SPI_processed;
}