diff options
Diffstat (limited to 'src/include/catalog/pg_statistic.h')
| -rw-r--r-- | src/include/catalog/pg_statistic.h | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/src/include/catalog/pg_statistic.h b/src/include/catalog/pg_statistic.h index 3b46dc7091d..55a20b81c5a 100644 --- a/src/include/catalog/pg_statistic.h +++ b/src/include/catalog/pg_statistic.h @@ -269,11 +269,15 @@ typedef FormData_pg_statistic *Form_pg_statistic; #define STATISTIC_KIND_DECHIST 5 /* - * An "empty frac" slot describes the fraction of empty ranges in a range-type - * column. stavalues is not used and should be NULL. stanumbers contains a - * single entry, the fraction of empty ranges (0.0 to 1.0). + * A "length histogram" slot describes the distribution of range lengths in + * rows of a range-type column. stanumbers contains a single entry, the + * fraction of empty ranges. stavalues is a histogram of non-empty lengths, in + * a format similar to STATISTIC_KIND_HISTOGRAM: it contains M (>=2) range + * values that divide the column data values into M-1 bins of approximately + * equal population. The lengths are stores as float8s, as measured by the + * range type's subdiff function. Only non-null rows are considered. */ -#define STATISTIC_KIND_RANGE_EMPTY_FRAC 6 +#define STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM 6 /* * A "bounds histogram" slot is similar to STATISTIC_KIND_HISTOGRAM, but for |