1c455078b0
Although selfuncs.c will never call a target operator with null inputs, some functions might return null anyway. The existing coding will fail if that happens (since FunctionCall2Coll will punt), which seems undesirable given that matchingsel() has such a broad range of potential applicability --- in fact, we already have a problem because we apply it to jsonb_path_exists_opr, which can return null. Hence, rejigger the underlying functions mcv_selectivity and histogram_selectivity to cope, treating a null result as false. While we are at it, we can move the InitFunctionCallInfoData overhead out of the inner loops, which isn't a huge number of cycles but might save something considering we are likely calling functions as cheap as int4eq(). Plus, the number of loop cycles to be expected is much more than it was when this code was written, since typical settings of default_statistics_target are higher. In view of that consideration, let's apply the same change to var_eq_const, eqjoinsel_inner, and eqjoinsel_semi. We do not expect equality functions to ever return null for non-null inputs (and certainly that code has been that way a long time without complaints), but the cycle savings seem attractive, especially in the eqjoinsel loops where there's potentially an O(N^2) savings. Similar code exists in ineq_histogram_selectivity and get_variable_range, but I forebore from changing those for now. The performance argument for changing ineq_histogram_selectivity is really weak anyway, since that will only iterate log2(N) times. Nikita Glukhov and Tom Lane Discussion: https://postgr.es/m/9d3b0959-95d6-c37e-2c0b-287bcfe5c705@postgrespro.ru
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