I wrote:
> Yeah, I don't like that either. What we need to do instead is fix
> exec_assign_value so that it can cope with the case of the caller having
> an open expression evaluation. We can easily have it save/restore
> eval_tuptable. Not resetting eval_econtext is a bit harder, but maybe
> we could have a use-count variable ... or even easier, just decree that
> the caller has to do exec_eval_cleanup after calling exec_assign_value,
> whether or not it had an open expression eval.
After a bit of experimentation, I propose the attached patch. I don't
think any additional resets of eval_econtext are necessary. There are
some callers of exec_assign_value that don't immediately do an
exec_eval_cleanup afterwards, but one will happen soon enough.
regards, tom lane
Index: pl_exec.c
===================================================================
RCS file: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v
retrieving revision 1.262
diff -c -r1.262 pl_exec.c
*** pl_exec.c 9 Aug 2010 02:25:05 -0000 1.262
--- pl_exec.c 9 Aug 2010 16:27:56 -0000
***************
*** 2701,2706 ****
--- 2701,2709 ----
*
* NB: the result of the evaluation is no longer valid after this is done,
* unless it is a pass-by-value datatype.
+ *
+ * NB: if you change this code, see also the hacks in exec_assign_value's
+ * PLPGSQL_DTYPE_ARRAYELEM case.
* ----------
*/
static void
***************
*** 3464,3469 ****
--- 3467,3476 ----
/* ----------
* exec_assign_value Put a value into a target field
+ *
+ * Note: in some code paths, this may leak memory in the eval_econtext;
+ * we assume that will be cleaned up later by exec_eval_cleanup. We cannot
+ * call exec_eval_cleanup here for fear of destroying the input Datum value.
* ----------
*/
static void
***************
*** 3714,3719 ****
--- 3721,3729 ----
case PLPGSQL_DTYPE_ARRAYELEM:
{
+ /*
+ * Target is an element of an array
+ */
int nsubscripts;
int i;
PLpgSQL_expr *subscripts[MAXDIM];
***************
*** 3729,3738 ****
coerced_value;
ArrayType *oldarrayval;
ArrayType *newarrayval;
/*
- * Target is an element of an array
- *
* To handle constructs like x[1][2] := something, we have to
* be prepared to deal with a chain of arrayelem datums. Chase
* back to find the base array datum, and save the subscript
--- 3739,3757 ----
coerced_value;
ArrayType *oldarrayval;
ArrayType *newarrayval;
+ SPITupleTable *save_eval_tuptable;
+
+ /*
+ * We need to do subscript evaluation, which might require
+ * evaluating general expressions; and the caller might have
+ * done that too in order to prepare the input Datum. We
+ * have to save and restore the caller's SPI_execute result,
+ * if any.
+ */
+ save_eval_tuptable = estate->eval_tuptable;
+ estate->eval_tuptable = NULL;
/*
* To handle constructs like x[1][2] := something, we have to
* be prepared to deal with a chain of arrayelem datums. Chase
* back to find the base array datum, and save the subscript
***************
*** 3786,3793 ****
--- 3805,3827 ----
ereport(ERROR,
(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
errmsg("array subscript in assignment must not be null")));
+
+ /*
+ * Clean up in case the subscript expression wasn't simple.
+ * We can't do exec_eval_cleanup, but we can do this much
+ * (which is safe because the integer subscript value is
+ * surely pass-by-value), and we must do it in case the
+ * next subscript expression isn't simple either.
+ */
+ if (estate->eval_tuptable != NULL)
+ SPI_freetuptable(estate->eval_tuptable);
+ estate->eval_tuptable = NULL;
}
+ /* Now we can restore caller's SPI_execute result if any. */
+ Assert(estate->eval_tuptable == NULL);
+ estate->eval_tuptable = save_eval_tuptable;
+
/* Coerce source value to match array element type. */
coerced_value = exec_simple_cast_value(value,
valtype,
--
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