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Fix "SELECT simple_expression INTO" for expression becoming non-simple.

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Commit ce8d5fe0e failed to think hard enough about the case where
we're forced to replan the expression and it becomes no longer simple.
The code produced the right expression result, but its handling of
FOUND and ROW_COUNT was too simplistic since we might have obtained
zero rows.  To fix, don't use exec_eval_expr, but go directly to
exec_eval_simple_expr, and if that reports failure then fall through
to the full SPI code path.

Another thinko in ce8d5fe0e is that it added

                 if (expr->plan == NULL)
                     exec_prepare_plan(estate, expr, 0);

which is quite useless since we cannot reach here without having
planned the expression at least once.  (If the call were reachable
it'd likely be wrong, since it's not passing the same flags as
either the preceding call or the one inside exec_eval_expr.)

Author: shihao zhong <zhong950419@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAGRkXqQB_aqWU9OeVPGvATBVZ7c9EYrNXJyHG0jKXW0FGAy2-g@mail.gmail.com
Backpatch-through: 19
This commit is contained in:
Tom Lane
2026-10-05 18:33:18 -04:00
parent e7ef2cf256
commit e3199f3149
1 changed files with 26 additions and 19 deletions
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45
src/pl/plpgsql/src/pl_exec.c
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@@ -4307,11 +4307,13 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
if (row->nfields == 1)
{
/* OK, there is a single target variable */
ErrorContextCallback plerrcontext;
Datum value;
bool isnull;
Oid valtype;
int32 valtypmod;
bool simple;
/*
* Setup error traceback support for ereport(). This is so
@@ -4323,13 +4325,15 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
plerrcontext.previous = error_context_stack;
error_context_stack = &plerrcontext;
/* If first time through, create a plan for this expression */
if (expr->plan == NULL)
exec_prepare_plan(estate, expr, 0);
/* And evaluate the expression */
value = exec_eval_expr(estate, expr,
&isnull, &valtype, &valtypmod);
/*
* Evaluate the already-planned expression. This fails if the
* expression is busy, or if replanning occurs and we find it
* is no longer simple. In such cases, fall through to the
* SPI code below.
*/
simple = exec_eval_simple_expr(estate, expr,
&value, &isnull,
&valtype, &valtypmod);
/*
* Pop the error context stack: the code below would not use
@@ -4337,20 +4341,23 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
*/
error_context_stack = plerrcontext.previous;
/* Assign the result to the INTO target */
exec_assign_value(estate, estate->datums[row->varnos[0]],
value, isnull, valtype, valtypmod);
exec_eval_cleanup(estate);
if (simple)
{
/* Success; assign the result to the INTO target */
exec_assign_value(estate, estate->datums[row->varnos[0]],
value, isnull, valtype, valtypmod);
exec_eval_cleanup(estate);
/*
* We must duplicate the other effects of the code below, as
* well. We know that exactly one row was returned, so it
* doesn't matter whether the INTO was STRICT or not.
*/
exec_set_found(estate, true);
estate->eval_processed = 1;
/*
* We must duplicate the other effects of the code below,
* as well. We know that exactly one row was returned, so
* it doesn't matter whether the INTO was STRICT or not.
*/
exec_set_found(estate, true);
estate->eval_processed = 1;
return PLPGSQL_RC_OK;
return PLPGSQL_RC_OK;
}
}
}
}