Re: Memory leak with CALL to Procedure with COMMIT.

[Jonathan S. Katz]

> On Jul 23, 2018, at 3:06 AM, Michael Paquier <mich...@paquier.xyz> wrote:
> 
> On Mon, Jul 23, 2018 at 12:19:12PM +0530, Prabhat Sahu wrote:
>> While testing with PG procedure, I found a memory leak on HEAD, with below
>> steps:
>> 
>> postgres=# CREATE OR REPLACE PROCEDURE proc1(v1 INOUT INT)
>> AS $$
>> BEGIN
>> commit;
>> END; $$ LANGUAGE plpgsql;
>> CREATE PROCEDURE
>> 
>> postgres=# call proc1(10);
>> WARNING:  Snapshot reference leak: Snapshot 0x23678e8 still referenced
>> v1
>> ----
>> 10
>> (1 row)
> 
> I can reproduce this issue on HEAD and v11, so an open item is added.
> Peter, could you look at it?

I tested and was able to reproduce this on head. I also tried a few other other
and was able to reproduce it when the procedure contained a few read-only
statements prior to commit, where the argument passed in was designated "INOUT."

Scenarios 1 & 2 show the leak whereas 3 & 4 do not.

    /** Scenario 1: Original scenario */
    CREATE OR REPLACE PROCEDURE proc1(v1 INOUT INT)
    AS $$
    BEGIN
     commit;
    END; $$ LANGUAGE plpgsql;

    CALL proc1(10);

    WARNING:  Snapshot reference leak: Snapshot 0x7f9519826d18 still referenced
    CONTEXT:  PL/pgSQL function proc1(integer) line 3 at COMMIT
     v1
    ----
     10
    (1 row)

    /** Scenario 2: call "perform" prior to the commit */
    CREATE OR REPLACE PROCEDURE proc2(v1 INOUT INT)
    AS $$
    BEGIN
        PERFORM v1;
        COMMIT;
    END; $$ LANGUAGE plpgsql;

    CALL proc2(10);
    WARNING:  Snapshot reference leak: Snapshot 0x7f9519826d18 still referenced
    CONTEXT:  PL/pgSQL function proc2(integer) line 4 at COMMIT
     v1
    ----
     10
    (1 row)


    /** Scenario 3: argument is only IN */
    CREATE OR REPLACE PROCEDURE proc3(v1 IN INT)
    AS $$
    BEGIN
        PERFORM v1;
        COMMIT;
    END; $$ LANGUAGE plpgsql;

    CALL proc3(10);
    CALL

    /** Scenario 4: Same as #2 but with a ROLLBACK  */
    CREATE OR REPLACE PROCEDURE proc4(v1 INOUT INT)
    AS $$
    BEGIN
        PERFORM v1;
        ROLLBACK;
    END; $$ LANGUAGE plpgsql;

    CALL proc4(10);
    CALL

Jonathan

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