database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-09-03 15:22:11 +03:00
Code Activity

The previous fix in CVS HEAD and 8.4 for handling the case where a cursor

Browse Source 
being used in a PL/pgSQL FOR loop is closed was inadequate, as Tom Lane
pointed out. The bug affects FOR statement variants too, because you can
close an implicitly created cursor too by guessing the "<unnamed portal X>"
name created for it.

To fix that, "pin" the portal to prevent it from being dropped while it's
being used in a PL/pgSQL FOR loop. Backpatch all the way to 7.4 which is
the oldest supported version.
This commit is contained in:
Heikki Linnakangas
2010-07-05 09:27:24 +00:00
parent bf53e7938d
commit 0f0b236b03
3 changed files with 64 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
src/pl/plpgsql/src/pl_exec.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.244.2.5 2010/06/21 09:49:58 heikki Exp $
* $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.244.2.6 2010/07/05 09:27:24 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1869,7 +1869,6 @@ 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;
@@ -1952,7 +1951,6 @@ 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
@@ -1967,20 +1965,11 @@ exec_stmt_forc(PLpgSQL_execstate *estate, PLpgSQL_stmt_forc *stmt)
rc = exec_for_query(estate, (PLpgSQL_stmt_forq *) stmt, portal, false);
/* ----------
* 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.
* Close portal, and restore cursor variable if it was initially NULL.
* ----------
*/
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);
@@ -4200,13 +4189,6 @@ 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,
@@ -4218,10 +4200,6 @@ 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
@@ -4233,6 +4211,12 @@ exec_for_query(PLpgSQL_execstate *estate, PLpgSQL_stmt_forq *stmt,
else
elog(ERROR, "unsupported target");
/*
* Make sure the portal doesn't get closed by the user statements
* we execute.
*/
PinPortal(portal);
/*
* Fetch the initial tuple(s). If prefetching is allowed then we grab a
* few more rows to avoid multiple trips through executor startup
@@ -4330,22 +4314,8 @@ 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.
*/
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);
}
SPI_cursor_fetch(portal, true, prefetch_ok ? 50 : 1);
tuptab = SPI_tuptable;
n = SPI_processed;
}
@@ -4357,6 +4327,8 @@ loop_exit:
*/
SPI_freetuptable(tuptab);
UnpinPortal(portal);
/*
* Set the FOUND variable to indicate the result of executing the loop
* (namely, whether we looped one or more times). This must be set last so