Re: [HACKERS] SPI_prepare() doesn't work well ?

Hiroshi Inoue wrote:

>
> Hello all,
>
> It seems that SPI_prepare() doesn't work well in some cases.
>
> Pawel Pierscionek [pawel@astercity.net] reported about the
> following case 1([SQL] drop table in pgsql).
> Michael Contzen [mcontzen@dohle.com] reported about the
> following case 2(PL/PGSQL bug using aggregates).
> You can find it from pgsql-hackers archive.
>
> 1. PL/pgSQL can't execute UTILITY commands.
>    SPI_prepare() doesn't copy(save) the utilityStmt member of
>    Query type nodes,because copyObject() is not implemented
>    for nodes of (Create/Destroy etc)Stmt type.

    Thank's  for  that.  I  wondered  why PL/pgSQL wasn't able to
    execute utility statements. Unfortunately I  wasn't  able  to
    track  it  down  the last days, because I had trouble with my
    shared libraries (glibc6 and libstdc++ aren't  easy-going  on
    Linux :-).

    Knowing  where the problem is located saves me a lot of time.

>
> 2. Aggregates in PL/pgSQL cause wrong results.
>
>    Is it proper to use set_agg_tlist_references() function to
>    reconstruct aggs member node for Agg type nodes ?

    Don't know. It is important, that the copy of  the  tree  has
    absolutely  NO  references  to  anything outside itself.  The
    parser/rewrite/planner combo creates all plans in the  actual
    transactions  memory  context.  So they will get destroyed at
    transaction end.

    SPI_saveplan() simply copies it into another  memory  context
    that  lives  until  the  backend  dies. It uses the node copy
    function for this, so the result of that should be a  totally
    independed, self referencing tree that can stand alone.

    I  think  that  copyObject() should produce an ERROR if there
    are nodes  it  cannot  handle  correctly  (like  queries  for
    utilities).  This  would  prevent  the  backend  crashes from
    trying to invoke utilities inside procedural languages.


Jan

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