Re: freeing bms explicitly

Zhihong Yu <zyu@yugabyte.com> writes:

I was looking at calls to bms_free() in PG code.
e.g. src/backend/commands/publicationcmds.c line 362
bms_free(bms);
The above is just an example, there're other calls to bms_free().
Since the bms is allocated from some execution context, I wonder why this
call is needed.

When the underlying execution context wraps up, isn't the bms freed ?

Yeah, that's kind of pointless --- and the pfree(rfnode) after it is even
more pointless, since it'll free only the top node of that expression
tree. Not to mention the string returned by TextDatumGetCString, and
whatever might be leaked during the underlying catalog accesses.

If we were actually worried about transient space consumption of this
function, it'd be necessary to do a lot more than this. It doesn't
look to me like it's worth worrying about though -- it doesn't seem
like it could be hit more than once per query in normal cases.

regards, tom lane

On Mon, Mar 21, 2022 at 3:05 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Zhihong Yu <zyu@yugabyte.com> writes:

I was looking at calls to bms_free() in PG code.
e.g. src/backend/commands/publicationcmds.c line 362
bms_free(bms);
The above is just an example, there're other calls to bms_free().
Since the bms is allocated from some execution context, I wonder why

this

call is needed.

When the underlying execution context wraps up, isn't the bms freed ?

Yeah, that's kind of pointless --- and the pfree(rfnode) after it is even
more pointless, since it'll free only the top node of that expression
tree. Not to mention the string returned by TextDatumGetCString, and
whatever might be leaked during the underlying catalog accesses.

If we were actually worried about transient space consumption of this
function, it'd be necessary to do a lot more than this. It doesn't
look to me like it's worth worrying about though -- it doesn't seem
like it could be hit more than once per query in normal cases.

regards, tom lane

Thanks Tom for replying.

What do you think of the following patch ?

Cheers

On Tue, Mar 22, 2022 at 3:39 AM Zhihong Yu <zyu@yugabyte.com> wrote:

On Mon, Mar 21, 2022 at 3:05 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Zhihong Yu <zyu@yugabyte.com> writes:

I was looking at calls to bms_free() in PG code.
e.g. src/backend/commands/publicationcmds.c line 362
bms_free(bms);
The above is just an example, there're other calls to bms_free().
Since the bms is allocated from some execution context, I wonder why this
call is needed.

When the underlying execution context wraps up, isn't the bms freed ?

Yeah, that's kind of pointless --- and the pfree(rfnode) after it is even
more pointless, since it'll free only the top node of that expression
tree. Not to mention the string returned by TextDatumGetCString, and
whatever might be leaked during the underlying catalog accesses.

If we were actually worried about transient space consumption of this
function, it'd be necessary to do a lot more than this. It doesn't
look to me like it's worth worrying about though -- it doesn't seem
like it could be hit more than once per query in normal cases.

regards, tom lane

Thanks Tom for replying.

What do you think of the following patch ?

Your patch looks good to me. I have found one more similar instance in
the same file and changed that as well accordingly. Let me know what
you think of the attached?

--
With Regards,
Amit Kapila.

On Tue, Mar 22, 2022 at 8:45 PM Amit Kapila <amit.kapila16@gmail.com> wrote:

On Tue, Mar 22, 2022 at 3:39 AM Zhihong Yu <zyu@yugabyte.com> wrote:

On Mon, Mar 21, 2022 at 3:05 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Zhihong Yu <zyu@yugabyte.com> writes:

I was looking at calls to bms_free() in PG code.
e.g. src/backend/commands/publicationcmds.c line 362
bms_free(bms);
The above is just an example, there're other calls to bms_free().
Since the bms is allocated from some execution context, I wonder why

this

call is needed.

When the underlying execution context wraps up, isn't the bms freed ?

Yeah, that's kind of pointless --- and the pfree(rfnode) after it is

even

more pointless, since it'll free only the top node of that expression
tree. Not to mention the string returned by TextDatumGetCString, and
whatever might be leaked during the underlying catalog accesses.

If we were actually worried about transient space consumption of this
function, it'd be necessary to do a lot more than this. It doesn't
look to me like it's worth worrying about though -- it doesn't seem
like it could be hit more than once per query in normal cases.

regards, tom lane

Thanks Tom for replying.

What do you think of the following patch ?

Your patch looks good to me. I have found one more similar instance in
the same file and changed that as well accordingly. Let me know what
you think of the attached?

--
With Regards,
Amit Kapila.

Hi, Amit:
The patch looks good to me.

Cheers

On Tue, Mar 22, 2022 at 9:04 PM Zhihong Yu <zyu@yugabyte.com> wrote:

On Tue, Mar 22, 2022 at 8:45 PM Amit Kapila <amit.kapila16@gmail.com>
wrote:

On Tue, Mar 22, 2022 at 3:39 AM Zhihong Yu <zyu@yugabyte.com> wrote:

On Mon, Mar 21, 2022 at 3:05 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Zhihong Yu <zyu@yugabyte.com> writes:

I was looking at calls to bms_free() in PG code.
e.g. src/backend/commands/publicationcmds.c line 362
bms_free(bms);
The above is just an example, there're other calls to bms_free().
Since the bms is allocated from some execution context, I wonder

why this

call is needed.

When the underlying execution context wraps up, isn't the bms freed

?

Yeah, that's kind of pointless --- and the pfree(rfnode) after it is

even

more pointless, since it'll free only the top node of that expression
tree. Not to mention the string returned by TextDatumGetCString, and
whatever might be leaked during the underlying catalog accesses.

If we were actually worried about transient space consumption of this
function, it'd be necessary to do a lot more than this. It doesn't
look to me like it's worth worrying about though -- it doesn't seem
like it could be hit more than once per query in normal cases.

regards, tom lane

Thanks Tom for replying.

What do you think of the following patch ?

Your patch looks good to me. I have found one more similar instance in
the same file and changed that as well accordingly. Let me know what
you think of the attached?

--
With Regards,
Amit Kapila.

Hi, Amit:
The patch looks good to me.

Cheers

Tom:
Do you mind taking a look at the latest patch ?

Thanks

On Wed, Mar 23, 2022 at 9:30 AM Zhihong Yu <zyu@yugabyte.com> wrote:

On Tue, Mar 22, 2022 at 8:45 PM Amit Kapila <amit.kapila16@gmail.com> wrote:

On Tue, Mar 22, 2022 at 3:39 AM Zhihong Yu <zyu@yugabyte.com> wrote:

Your patch looks good to me. I have found one more similar instance in
the same file and changed that as well accordingly. Let me know what
you think of the attached?

Hi, Amit:
The patch looks good to me.

Thanks. I'll push this tomorrow unless Tom or someone else wants to
look at it or would like to commit.

--
With Regards,
Amit Kapila.

On Thu, Mar 24, 2022 at 7:43 AM Amit Kapila <amit.kapila16@gmail.com> wrote:

On Wed, Mar 23, 2022 at 9:30 AM Zhihong Yu <zyu@yugabyte.com> wrote:

On Tue, Mar 22, 2022 at 8:45 PM Amit Kapila <amit.kapila16@gmail.com> wrote:

On Tue, Mar 22, 2022 at 3:39 AM Zhihong Yu <zyu@yugabyte.com> wrote:

Your patch looks good to me. I have found one more similar instance in
the same file and changed that as well accordingly. Let me know what
you think of the attached?

Hi, Amit:
The patch looks good to me.

Thanks. I'll push this tomorrow unless Tom or someone else wants to
look at it or would like to commit.

Pushed.

--
With Regards,
Amit Kapila.