Re: Access to dynamic SQL in PL/pgSQL

Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> It's not currently possible to access the SQL used in a dynamic PL/pgSQL
> statement using a PL/pgSQL plugin.

> In src/pl/plpgsql/src/pl_exec.c's exec_stmt() we call each dynamic
> statement type, evaluate the SQL and free memory again before the plugin
> gains control again.

> It seems simple to attach querystr to PLpgSQL_execstate and free it
> after the plugin has seen it. The difference in lifetime of the memory
> allocation is very small.

That seems like a complete crock --- you're talking about leaving a
dangling pointer to transient data in a permanent data structure.
In most contexts it would be difficult to be sure if the pointer was
valid or not.

If we need this it would be better to provide another plugin hook call
during the execution of a statement that uses a dynamic query.

> Would a patch to make this simple change be acceptable? It would need to
> be backpatched to 8.1 also?

As for the first, I vote "not like that", and as for backpatching,
you're out of your mind. This would be an incompatible ABI change,
and we don't lightly make those in stable branches. Even if we were
willing to take the risk, how would a plugin know if it were dealing
with a version of plpgsql that had this field?

regards, tom lane