From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 6 Jan 2009 23:46:06 +0000 (+0000)
Subject: Clarify a confusing comment about MCVs vs histogram entries.
X-Git-Tag: recoveryinfrav9~107
X-Git-Url: http://waps.l3s.uni-hannover.de/gitweb/?a=commitdiff_plain;h=01e050fd2bcbef383911f1ead4c0f3be275e2d08;p=users%2Fsimon%2Fpostgres.git

Clarify a confusing comment about MCVs vs histogram entries.
Per Nathan Boley.
---

diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 7fa8cee2e1..311397b360 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -2149,7 +2149,9 @@ compute_scalar_stats(VacAttrStatsP stats,
 		 * least 2 instances in the sample.  Also, we won't suppress values
 		 * that have a frequency of at least 1/K where K is the intended
 		 * number of histogram bins; such values might otherwise cause us to
-		 * emit duplicate histogram bin boundaries.
+		 * emit duplicate histogram bin boundaries.  (We might end up with
+		 * duplicate histogram entries anyway, if the distribution is skewed;
+		 * but we prefer to treat such values as MCVs if at all possible.)
 		 */
 		if (track_cnt == ndistinct && toowide_cnt == 0 &&
 			stats->stadistinct > 0 &&