BUG #19073: there are meaningless code in _SPI_execute_plan() when canSetTag is true

there is patch.
I have remove the meaningless code.

------------------ 原始邮件 ------------------
发件人: "webbohan" <noreply@postgresql.org&gt;;
发送时间:&nbsp;2025年10月5日(星期天) 上午10:29
收件人:&nbsp;"pgsql-bugs"<pgsql-bugs@lists.postgresql.org&gt;;
抄送:&nbsp;"webbohan"<webbohan@qq.com&gt;;
主题:&nbsp;BUG #19073: there are meaningless code in _SPI_execute_plan() when canSetTag is true

The following bug has been logged on the website:

Bug reference:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 19073
Logged by:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Webbo Han
Email address:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; webbohan@qq.com
PostgreSQL version: 18.0
Operating system:&nbsp;&nbsp; all
Description:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

In function _SPI_execute_plan(), `my_tuptable` is local variable and
initialized as NULL.
If plan is canSetTag subqueries, `SPI_freetuptable(my_tuptable)` is
meaningless, because `my_tuptable` is NULL.
We'd better remove this code.

On Sat, Oct 4, 2025, at 11:29 PM, PG Bug reporting form wrote:

In function _SPI_execute_plan(), `my_tuptable` is local variable and
initialized as NULL.
If plan is canSetTag subqueries, `SPI_freetuptable(my_tuptable)` is
meaningless, because `my_tuptable` is NULL.
We'd better remove this code.

There could be multiple statements. The first case will call SPI_freetuptable()
and it is a noop. The code path you are referring to is inside a foreach loop
and a previous statement might set my_tuptable and needs to be freed before
reusing it. That's exactly what the comment says.

/*
* The last canSetTag query sets the status values returned to the
* caller. Be careful to free any tuptables not returned, to
* avoid intra-transaction memory leak.
*/
if (canSetTag)
{
my_processed = _SPI_current->processed;
SPI_freetuptable(my_tuptable);
my_tuptable = _SPI_current->tuptable;
my_res = res;
}

--
Euler Taveira
EDB https://www.enterprisedb.com/

"Euler Taveira" <euler@eulerto.com> writes:

On Sat, Oct 4, 2025, at 11:29 PM, PG Bug reporting form wrote:

If plan is canSetTag subqueries, `SPI_freetuptable(my_tuptable)` is
meaningless, because `my_tuptable` is NULL.

There could be multiple statements. The first case will call SPI_freetuptable()
and it is a noop. The code path you are referring to is inside a foreach loop
and a previous statement might set my_tuptable and needs to be freed before
reusing it. That's exactly what the comment says.

Yeah. You'd only reach this case if there were multiple SQL
statements in the string given to SPI_execute() or similar,
but that's perfectly legal.

regards, tom lane