diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index cc24c8aeb56..5c382a2013e 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -3404,7 +3404,7 @@ estimate_num_groups(PlannerInfo *root, List *groupExprs, double input_rows, RelOptInfo *rel = varinfo1->rel; double reldistinct = 1; double relmaxndistinct = reldistinct; - int relvarcount = 1; + int relvarcount = 0; List *newvarinfos = NIL; List *relvarinfos = NIL; @@ -3436,6 +3436,10 @@ estimate_num_groups(PlannerInfo *root, List *groupExprs, double input_rows, * we multiply them together. Any remaining relvarinfos after * no more multivariate matches are found are assumed independent too, * so their individual ndistinct estimates are multiplied also. + * + * While iterating, count how many separate numdistinct values we + * apply. We apply a fudge factor below, but only if we multiplied + * more than one such values. */ while (relvarinfos) { @@ -3447,7 +3451,7 @@ estimate_num_groups(PlannerInfo *root, List *groupExprs, double input_rows, reldistinct *= mvndistinct; if (relmaxndistinct < mvndistinct) relmaxndistinct = mvndistinct; - relvarcount++; /* inaccurate, but doesn't matter */ + relvarcount++; } else { |