Re: B-Tree support function number 3 (strxfrm() optimization)

On Tue, Sep 2, 2014 at 12:22 PM, Robert Haas  wrote:
> Most places that use a SortSupportData initialize ssup.position
> explicitly, but tuplesort_begin_datum() doesn't.  That's an
> inconsistency that should be fixed, but I'm not sure which direction
> is best.

I'm not sure what you mean. tuplesort_begin_datum() only
uses/initializes the Tuplesortstate.onlyKey field, and in fact that
did have its ssup.position initialized to zero in the last revision.
This indicates that we should not apply the optimization, because:

/** Conversion to abbreviated representation infeasible in the Datum case.* It must be possible to subsequently fetch original datum values within* tuplesort_getdatum(), which would require special-case preservation of* original values that we prefer to avoid.*/
state->onlyKey->position = sortKeyOther;

-- 
Peter Geoghegan