Re: [HACKERS] PATCH: multivariate histograms and MCV lists

> On Nov 18, 2017, at 12:28 PM, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)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>

Hello Tomas,

In 0002-multivariate-histograms.patch, src/include/nodes/relation.h,
struct StatisticExtInfo, you change:

- char kind; /* statistic kind of this entry */
+ int kinds; /* statistic kinds of this entry */

to have 'kinds' apparently be a bitmask, based on reading how you use
this in the code. The #defines just below the struct give the four bits
to be used,

#define STATS_EXT_INFO_NDISTINCT 1
#define STATS_EXT_INFO_DEPENDENCIES 2
#define STATS_EXT_INFO_MCV 4
#define STATS_EXT_INFO_HISTOGRAM 8

except that nothing in the file indicates that this is so. Perhaps a comment
could be added here mentioning that 'kinds' is a bitmask, and that these
#defines are related?

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