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Diffstat (limited to 'src/backend/optimizer/path/costsize.c')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index ffb066283f..c292e24ac3 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -3324,6 +3324,34 @@ set_cte_size_estimates(PlannerInfo *root, RelOptInfo *rel, Plan *cteplan) set_baserel_size_estimates(root, rel); } +/* + * set_foreign_size_estimates + * Set the size estimates for a base relation that is a foreign table. + * + * There is not a whole lot that we can do here; the foreign-data wrapper + * is responsible for producing useful estimates. We can do a decent job + * of estimating baserestrictcost, so we set that, and we also set up width + * using what will be purely datatype-driven estimates from the targetlist. + * There is no way to do anything sane with the rows value, so we just put + * a default estimate and hope that the wrapper can improve on it. The + * wrapper's PlanForeignScan function will be called momentarily. + * + * The rel's targetlist and restrictinfo list must have been constructed + * already. + */ +void +set_foreign_size_estimates(PlannerInfo *root, RelOptInfo *rel) +{ + /* Should only be applied to base relations */ + Assert(rel->relid > 0); + + rel->rows = 1000; /* entirely bogus default estimate */ + + cost_qual_eval(&rel->baserestrictcost, rel->baserestrictinfo, root); + + set_rel_width(root, rel); +} + /* * set_rel_width |