2017-04-05 23:22 GMT+02:00 Tom Lane <t...@sss.pgh.pa.us>:

> Andres Freund <and...@anarazel.de> writes:
> > I'd like some input from other committers whether we want this.  I'm
> > somewhat doubtful, but don't have particularly strong feelings.
> I don't really want to expose the workings of the plancache at user level.
> The heuristics it uses certainly need work, but it'll get hard to change
> those once there are SQL features depending on it.

I am very sceptical about enhancing heuristics - but I am open to any

The advanced users disable a plan cache with dynamic SQL. But this
workaround has strong disadvantages:

1. it is vulnerable to SQL injection
2. it is less readable

> Also, as you note, there are debatable design decisions in this particular
> patch.  There are already a couple of ways in which control knobs can be
> attached to plgsql functions (i.e. custom GUCs and the comp_option stuff),
> so why is this patch wanting to invent yet another fundamental mechanism?
> And I'm not very happy about it imposing a new reserved keyword, either.


custom GUC has not local scope - so it doesn't allow precious settings.
With PRAGMA I have perfect control what will be impacted.

#option has function scope

2. I'll not introduce a PRAGMA keyword just for this feature. We would to
implement autonomous transactions. There was not any objection against this
feature. The PRAGMA allows to share PL/SQL syntax and functionality.

> A bigger-picture question is why we'd only provide such functionality
> in plpgsql, and not for other uses of prepared plans.

It is out of scope of this patch.

> Lastly, it doesn't look to me like the test cases prove anything at all
> about whether the feature does what it's claimed to.

I can enhance regress tests - currently there are not direct access to
these attributes - so the tests can be indirect only :(



>                         regards, tom lane

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