Hi,
On 11/25/2017 05:15 PM, Mark Dilger wrote:
>
>> On Nov 18, 2017, at 12:28 PM, Tomas Vondra <tomas.von...@2ndquadrant.com>
>> wrote:
>>
>> Hi,
>>
>> Attached is an updated version of the patch, adopting the psql describe
>> changes introduced by 471d55859c11b.
>>
>> regards
>>
>> --
>> Tomas Vondra http://www.2ndQuadrant.com
>> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>> <0001-multivariate-MCV-lists.patch.gz><0002-multivariate-histograms.patch.gz>
>
> Thanks, Tomas, again for your work on this feature.
>
> Applying just the 0001-multivariate-MCV-lists.patch to the current master, and
> then extending the stats_ext.sql test as follows, I am able to trigger an
> error,
> "ERROR: operator 4294934272 is not a valid ordering operator".
>
Ah, that's a silly bug ...
The code assumes that VacAttrStats->extra_data is always StdAnalyzeData,
and attempts to extract the ltopr from that. But for arrays that's of
course not true (array_typanalyze uses ArrayAnalyzeExtraData instead).
The reason why this only fails after the second INSERT is that we need
at least two occurrences of a value before considering it eligible for
MCV list. So after the first INSERT we don't even call the serialize.
Attached is a fix that should resolve this in MCV lists by looking up
the operator using lookup_type_cache() when serializing the MCV.
FWIW histograms have the same issue, but on more places (not just in
serialize, but also when building the histogram).
I'll send a properly updated patch series shortly, with tests checking
correct behavior with arrays.
Thanks for the report.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>From 1d546eb3d27507ee51824d5a8c348b86187d1754 Mon Sep 17 00:00:00 2001
From: Tomas Vondra <to...@2ndquadrant.com>
Date: Sat, 25 Nov 2017 18:44:14 +0100
Subject: [PATCH] MCV fix
---
src/backend/statistics/mcv.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c
index 0586054..af4d894 100644
--- a/src/backend/statistics/mcv.c
+++ b/src/backend/statistics/mcv.c
@@ -515,7 +515,13 @@ statext_mcv_serialize(MCVList *mcvlist, VacAttrStats **stats)
for (dim = 0; dim < ndims; dim++)
{
int ndistinct;
- StdAnalyzeData *tmp = (StdAnalyzeData *) stats[dim]->extra_data;
+ TypeCacheEntry *typentry;
+
+ /*
+ * Lookup the LT operator (can't get it from stats extra_data, as
+ * we don't know how to interpret that - scalar vs. array etc.).
+ */
+ typentry = lookup_type_cache(stats[dim]->attrtypid, TYPECACHE_LT_OPR);
/* copy important info about the data type (length, by-value) */
info[dim].typlen = stats[dim]->attrtype->typlen;
@@ -543,7 +549,7 @@ statext_mcv_serialize(MCVList *mcvlist, VacAttrStats **stats)
ssup[dim].ssup_collation = DEFAULT_COLLATION_OID;
ssup[dim].ssup_nulls_first = false;
- PrepareSortSupportFromOrderingOp(tmp->ltopr, &ssup[dim]);
+ PrepareSortSupportFromOrderingOp(typentry->lt_opr, &ssup[dim]);
qsort_arg(values[dim], counts[dim], sizeof(Datum),
compare_scalars_simple, &ssup[dim]);
--
2.9.5
