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Fix SPI_cursor_open() and SPI_is_cursor_plan() to push the SPI stack before

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doing anything interesting, such as calling RevalidateCachedPlan().  The
necessity of this is demonstrated by an example from Willem Buitendyk:
during a replan, the planner might try to evaluate SPI-using functions,
and so we'd better be in a clean SPI context.

A small downside of this fix is that these two functions will now fail
outright if called when not inside a SPI-using procedure (ie, a
SPI_connect/SPI_finish pair).  The documentation never promised or suggested
that that would work, though; and they are normally used in concert with
other functions, mainly SPI_prepare, that always have failed in such a case.
So the odds of breaking something seem pretty low.

In passing, make SPI_is_cursor_plan's error handling convention clearer,
and fix documentation's erroneous claim that SPI_cursor_open would
return NULL on error.

Before 8.3 these functions could not invoke replanning, so there is probably
no need for back-patching.
This commit is contained in:
Tom Lane 2008-02-12 04:09:44 +00:00
parent 953c2c9b71
commit 745e6edaae
2 changed files with 28 additions and 7 deletions
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15
doc/src/sgml/spi.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/spi.sgml,v 1.59 2007/09/14 04:18:27 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/spi.sgml,v 1.60 2008/02/12 04:09:44 tgl Exp $ -->
<chapter id="spi">
<title>Server Programming Interface</title>
@ -1077,9 +1077,12 @@ bool SPI_is_cursor_plan(SPIPlanPtr <parameter>plan</parameter>)
<title>Return Value</title>
<para>
<symbol>true</symbol> or <symbol>false</symbol> to indicate if the
<parameter>plan</parameter> can produce a cursor or not.
If the <parameter>plan</parameter> is <symbol>NULL</symbol> or invalid,
<varname>SPI_result</varname> is set to <symbol>SPI_ERROR_ARGUMENT</symbol>
<parameter>plan</parameter> can produce a cursor or not, with
<varname>SPI_result</varname> set to zero.
If it is not possible to determine the answer (for example,
if the <parameter>plan</parameter> is <symbol>NULL</symbol> or invalid,
or if called when not connected to SPI), then
<varname>SPI_result</varname> is set to a suitable error code
and <symbol>false</symbol> is returned.
</para>
</refsect1>
@ -1442,8 +1445,8 @@ Portal SPI_cursor_open(const char * <parameter>name</parameter>, SPIPlanPtr <par
<title>Return Value</title>
<para>
pointer to portal containing the cursor, or <symbol>NULL</symbol>
on error
Pointer to portal containing the cursor. Note there is no error
return convention; any error will be reported via <function>elog</>.
</para>
</refsect1>
</refentry>

20
src/backend/executor/spi.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.187 2008/01/01 19:45:49 momjian Exp $
* $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.188 2008/02/12 04:09:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -886,6 +886,10 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
Assert(list_length(plan->plancache_list) == 1);
plansource = (CachedPlanSource *) linitial(plan->plancache_list);
/* Push the SPI stack */
if (_SPI_begin_call(false) < 0)
elog(ERROR, "SPI_cursor_open called while not connected");
/* Reset SPI result (note we deliberately don't touch lastoid) */
SPI_processed = 0;
SPI_tuptable = NULL;
@ -1041,6 +1045,9 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
Assert(portal->strategy != PORTAL_MULTI_QUERY);
/* Pop the SPI stack */
_SPI_end_call(false);
/* Return the created portal */
return portal;
}
@ -1180,9 +1187,17 @@ SPI_is_cursor_plan(SPIPlanPtr plan)
}
if (list_length(plan->plancache_list) != 1)
{
SPI_result = 0;
return false; /* not exactly 1 pre-rewrite command */
}
plansource = (CachedPlanSource *) linitial(plan->plancache_list);
/* Need _SPI_begin_call in case replanning invokes SPI-using functions */
SPI_result = _SPI_begin_call(false);
if (SPI_result < 0)
return false;
if (plan->saved)
{
/* Make sure the plan is up to date */
@ -1190,6 +1205,9 @@ SPI_is_cursor_plan(SPIPlanPtr plan)
ReleaseCachedPlan(cplan, true);
}
_SPI_end_call(false);
SPI_result = 0;
/* Does it return tuples? */
if (plansource->resultDesc)
return true;