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| author | Alvaro Herrera <alvherre@alvh.no-ip.org> | 2017-07-26 11:40:39 -0400 |
|---|---|---|
| committer | Alvaro Herrera <alvherre@alvh.no-ip.org> | 2017-07-26 11:40:39 -0400 |
| commit | c28e4f4dc6aeb75cf35f1339cbe3387263e0e69b (patch) | |
| tree | 207736e3f5c484d430c9722ce823c9694e16ab73 | |
| parent | 54dacc746628799a3a09ebb78876b0a8d2742d23 (diff) | |
| download | postgresql-c28e4f4dc6aeb75cf35f1339cbe3387263e0e69b.tar.gz postgresql-c28e4f4dc6aeb75cf35f1339cbe3387263e0e69b.zip | |
Remove obsolete comments about functional dependencies
Initial submitted versions of the functional dependencies patch ignored
row groups that were smaller than a configured size. However, that
consideration was removed in late stages of the patch just before
commit, but some comments referring to it remained. Remove them to
avoid confusion.
Author: Atsushi Torikoshi
Discussion: https://postgr.es/m/7cfb23fc-4493-9c02-5da9-e505fd0115d2@lab.ntt.co.jp
| -rw-r--r-- | src/backend/statistics/README.dependencies | 4 | ||||
| -rw-r--r-- | src/backend/statistics/dependencies.c | 8 |
2 files changed, 0 insertions, 12 deletions
diff --git a/src/backend/statistics/README.dependencies b/src/backend/statistics/README.dependencies index 702d34e3f80..6c446bde274 100644 --- a/src/backend/statistics/README.dependencies +++ b/src/backend/statistics/README.dependencies @@ -71,10 +71,6 @@ To count the rows consistent with the dependency (a => b): (c) If there's a single distinct value in 'b', the rows are consistent with the functional dependency, otherwise they contradict it. -The algorithm also requires a minimum size of the group to consider it -consistent (currently 3 rows in the sample). Small groups make it less likely -to break the consistency. - Clause reduction (planner/optimizer) ------------------------------------ diff --git a/src/backend/statistics/dependencies.c b/src/backend/statistics/dependencies.c index 89dece33504..2e7c0ad6ba6 100644 --- a/src/backend/statistics/dependencies.c +++ b/src/backend/statistics/dependencies.c @@ -286,14 +286,6 @@ dependency_degree(int numrows, HeapTuple *rows, int k, AttrNumber *dependency, * first (k-1) columns. If there's a single value in the last column, we * count the group as 'supporting' the functional dependency. Otherwise we * count it as contradicting. - * - * We also require a group to have a minimum number of rows to be - * considered useful for supporting the dependency. Contradicting groups - * may be of any size, though. - * - * XXX The minimum size requirement makes it impossible to identify case - * when both columns are unique (or nearly unique), and therefore - * trivially functionally dependent. */ /* start with the first row forming a group */ |