diff options
Diffstat (limited to 'src/backend/utils/adt/selfuncs.c')
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index b659013bdec..d5a60256d12 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -15,7 +15,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.256 2008/10/21 20:42:53 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.257 2008/10/23 00:24:50 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -2143,10 +2143,22 @@ eqjoinsel_inner(Oid operator, * XXX Can we be smarter if we have an MCV list for just one side? It * seems that if we assume equal distribution for the other side, we * end up with the same answer anyway. + * + * An additional hack we use here is to clamp the nd1 and nd2 values + * to not more than what we are estimating the input relation sizes + * to be, providing a crude correction for the selectivity of + * restriction clauses on those relations. (We don't do that in the + * other path since there we are comparing the nd values to stats for + * the whole relations.) */ double nullfrac1 = stats1 ? stats1->stanullfrac : 0.0; double nullfrac2 = stats2 ? stats2->stanullfrac : 0.0; + if (vardata1->rel) + nd1 = Min(nd1, vardata1->rel->rows); + if (vardata2->rel) + nd2 = Min(nd2, vardata2->rel->rows); + selec = (1.0 - nullfrac1) * (1.0 - nullfrac2); if (nd1 > nd2) selec /= nd1; @@ -2305,6 +2317,11 @@ eqjoinsel_semi(Oid operator, */ double nullfrac1 = stats1 ? stats1->stanullfrac : 0.0; + if (vardata1->rel) + nd1 = Min(nd1, vardata1->rel->rows); + if (vardata2->rel) + nd2 = Min(nd2, vardata2->rel->rows); + if (nd1 <= nd2 || nd2 <= 0) selec = 1.0 - nullfrac1; else |