Re: [PATCHES] Re: Recursion and SPI - Mailing list pgsql-hackers

Applied.  Thanks.

> "Mikheev, Vadim" <vmikheev@SECTORBASE.COM> writes:
>
> > > Does the SPI interface support recursion?  That is, can a function
> > > use SPI to make a query which involves calling another function which
> > > uses SPI?
> >
> > >From http://www.postgresql.org/docs/programmer/spi.htm :
> >
> > "SPI procedures are always called by some (upper) Executor and the SPI
> > manager
> > uses the Executor to run your queries. Other procedures may be called by the
> >                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > Executor running queries from your procedure."
> >
> > > The documentation suggests not, saying that if a function which uses
> > > SPI calls another function which uses SPI, it won't work, and calling
> > > that ``bad practice.''
> >
> > >From http://www.postgresql.org/docs/programmer/spi-spiconnect.htm :
> >
> > "You may get SPI_ERROR_CONNECT error if SPI_connect is called from an
> > already
> > connected procedure - e.g. if you *directly call* one procedure from another
> >                                   ^^^^^^^^^^^^^^^
> > connected one. Actually, while the child procedure will be able to use SPI,
> > your parent procedure will not be able to continue to use SPI after the
> > child
> > returns (if SPI_finish is called by the child). It's bad practice."
> >
> > But you are able to run queries which call SPI functions.
>
> Thanks for the clarification.
>
> Approaching the current documentation from a position of ignorance, I
> find it ambiguous.  I propose something along the lines of the
> following patch to clarify it.  Thanks.
>
> (Alternatively, perhaps the code could maintain a count of nested
> calls to SPI_connect/SPI_finish.  But I didn't try to write that
> patch.)
>
> Ian
>
> Index: spi.sgml
> ===================================================================
> RCS file: /home/projects/pgsql/cvsroot/pgsql/doc/src/sgml/spi.sgml,v
> retrieving revision 1.8
> diff -u -r1.8 spi.sgml
> --- spi.sgml    2000/12/22 18:57:50    1.8
> +++ spi.sgml    2001/01/05 22:10:13
> @@ -34,10 +34,11 @@
>  </Para>
>
>  <Para>
> -<Acronym>SPI</Acronym> procedures are always called by some (upper)
> -Executor and the <Acronym>SPI</Acronym>
> -manager uses the Executor to run your queries. Other procedures may be
> -called by the Executor running queries from your procedure.
> +Procedures which use <Acronym>SPI</Acronym> are called by the
> +Executor.  The <Acronym>SPI</Acronym> calls recursively invoke the
> +Executor in turn to run queries.  When the Executor is invoked
> +recursively, it may itself call procedures which may make
> +<Acronym>SPI</Acronym> calls.
>  </Para>
>
>  <Para>
> @@ -146,12 +147,17 @@
>     utility SPI functions may be called from un-connected procedures.
>  </PARA>
>  <PARA>
> -   You may get <ReturnValue>SPI_ERROR_CONNECT</ReturnValue> error if <Function>SPI_connect</Function> is
> -   called from an already connected procedure - e.g. if you directly call one
> -   procedure from another connected one.  Actually, while the child procedure
> -   will be able to use SPI, your parent procedure will not be able to continue
> -   to use SPI after the child returns (if <Function>SPI_finish</Function> is called by the child).
> -   It's bad practice.
> +   If your procedure is already connected,
> +   <Function>SPI_connect</Function> will return an
> +   <ReturnValue>SPI_ERROR_CONNECT</ReturnValue> error.  Note that this
> +   may happen if a procedure which has called
> +   <Function>SPI_connect</Function> directly calls another procedure
> +   which itself calls <Function>SPI_connect</Function>.  While
> +   recursive calls to the <Acronym>SPI</Acronym> manager are permitted
> +   when an <Acronym>SPI</Acronym> query invokes another function which
> +   uses <Acronym>SPI</Acronym>, directly nested calls to
> +   <Function>SPI_connect</Function> and
> +   <Function>SPI_finish</Function> are forbidden.
>  </PARA>
>  </REFSECT1>
>  <REFSECT1 ID="R1-SPI-SPICONNECT-2">
>


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