From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Dmitry Chichkov <dchichkov(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: How to get value of 'Param' of the WHERE clause in the FDW? |
Date: | 2015-09-25 18:44:26 |
Message-ID: | 17172.1443206666@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Dmitry Chichkov <dchichkov(at)gmail(dot)com> writes:
> It seems like during fdwPlan(..., RelOptInfo *baserel) stage I'm getting
> baserel->baserestrictinfo, in which I see a Node *x of IsA(x, Param).
> But it looks like the value 'abc123' is not yet available in the planning
> stage, right? And I don't see how can I get baserestrictinfo in the
> execution stage or if the 'abc123' value would be there...
If you are trying to get an estimated value for some subexpression at plan
time, estimate_expression_value() is what to use; see for example the uses
of that function in selfuncs.c. Keep in mind that it *is* an estimate and
cannot be guaranteed to still be correct at execution time, since the plan
might be re-used with another parameter value.
regards, tom lane
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