Re: Extensions, this time with a patch

Excerpts from Dimitri Fontaine's message of dom oct 17 16:30:47 -0300 2010:

> The bulk of it is now short enough to be inlined in the mail, and if you
> have more comments I guess they'll be directed at this portion of the
> patch, so let's make it easy:
>
> /*
> * We abuse some internal knowledge from spi.h here. As we don't know
> * which queries are going to get executed, we don't know what to expect
> * as an OK return code from SPI_execute(). We assume that
> * SPI_OK_CONNECT, SPI_OK_FINISH and SPI_OK_FETCH are quite improbable,
> * though, and the errors are negatives. So a valid return code is
> * considered to be SPI_OK_UTILITY or anything from there.
> */
> SPI_connect();
> if (SPI_execute(query_string, false, 0) < SPI_OK_UTILITY)
> ereport(ERROR,
> (errcode(ERRCODE_DATA_EXCEPTION),
> errmsg("File '%s' contains invalid query", filename)));
> SPI_finish();

SPI_OK_FETCH is indeed improbable -- it's not used anywhere in the SPI
routines, and hasn't been for ages. SPI_OK_CONNECT and SPI_OK_FINNISH
are only issued by SPI_connect and SPI_finish, so presumably they can't
be returned by a script.

The error message wording needs some work; maybe
errmsg("file \"%s\" could not be executed", filename)

SPI_execute sets the query as errcontext, which is good; but apparently
there is no error position, which is bad. I'm not sure how feasible is
to fix this. (Not this patch's responsibility anyway.)

I happened to notice that there are several pieces of code that are
calling SPI_connect and SPI_finish without checking the return value,
notably the FTS code and xml.c.

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Álvaro Herrera <alvherre(at)commandprompt(dot)com>
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