arthernan wrote:
> OidFunctionCall7 is called from costsize.c, in function void cost_index. From
> the comments, I understand that there is an indirection mechanism here to
> allow for different index access methods. Looking at fmgr.h where it is
> declared is not clear to me where I would ultimately find the code.
>
> Any pointers will be greatly appreciated
The code you're really looking for is the amcostestimate function of the
AM that the index uses. So if it's a btree you want btcostestimate, for
instance. You can see the AM definitions in the pg_am system catalog
and src/include/catalog/pg_am.h.
> /*
> * Call index-access-method-specific code to estimate the processing cost
> * for scanning the index, as well as the selectivity of the index (ie,
> * the fraction of main-table tuples we will have to retrieve) and its
> * correlation to the main-table tuple order.
> */
> OidFunctionCall7(index->amcostestimate,
> PointerGetDatum(root),
> PointerGetDatum(path),
> Float8GetDatum(loop_count),
> PointerGetDatum(&indexStartupCost),
> PointerGetDatum(&indexTotalCost),
> PointerGetDatum(&indexSelectivity),
> PointerGetDatum(&indexCorrelation));
--
Álvaro Herrera http://www.2ndQuadrant.com/
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