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Implement point selectivity for JSON histograms

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* Also merges tests relating to JSON statistics into one file

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
This commit is contained in:
Michael Okoko
2021-08-21 09:17:23 +01:00
committed by Sergei Petrunia
parent 547f805311
commit bff65a813e
8 changed files with 254 additions and 501 deletions
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43
sql/sql_statistics.cc
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@@ -1452,10 +1452,37 @@ double pos_in_interval_through_strxfrm(Field *field,
}
double Histogram_json::point_selectivity(Field *field, key_range *min_endp,
key_range *max_endp, double avg_sel)
double Histogram_json::point_selectivity(Field *field, key_range *endpoint, double avg_sel)
{
return 0.5;
double sel;
store_key_image_to_rec(field, (uchar *) endpoint->key,
field->key_length());
const uchar *min_key = endpoint->key;
if (field->real_maybe_null())
min_key++;
uint min_idx= find_bucket(field, min_key);
uint max_idx= min_idx;
// find how many buckets this value occupies
while ((max_idx + 1 < get_width() ) &&
(field->key_cmp((uchar *)histogram_bounds[max_idx + 1].data(), min_key) == 0)) {
max_idx++;
}
//todo: do we need to account for zero value-length similarly to binary histograms.
if (max_idx > min_idx)
{
// value spans multiple buckets
double bucket_sel= 1.0/(get_width() + 1);
sel= bucket_sel * (max_idx - min_idx + 1);
} else
{
// the value fits within a single bucket
sel = MIN(avg_sel, get_width());
}
return sel;
}
/*
@param field The table field histogram is for. We don't care about the
@@ -1572,11 +1599,8 @@ int Histogram_json::find_bucket(Field *field, const uchar *endpoint)
if (res < 0) {
low = mid + 1;
min_bucket_index = mid;
} else if (res > 0) {
} else if (res >= 0) {
high = mid - 1;
} else {
//todo: endpoint is on a bucket boundary
break;
}
}
@@ -4326,7 +4350,7 @@ double get_column_range_cardinality(Field *field,
if (hist && hist->is_usable(thd))
{
res= col_non_nulls *
hist->point_selectivity(field, min_endp, max_endp,
hist->point_selectivity(field, min_endp,
avg_frequency / col_non_nulls);
}
}
@@ -4390,8 +4414,7 @@ double get_column_range_cardinality(Field *field,
value.
*/
double Histogram_binary::point_selectivity(Field *field, key_range *min_endp,
key_range *max_endp, double avg_sel)
double Histogram_binary::point_selectivity(Field *field, key_range *min_endp, double avg_sel)
{
double sel;
Column_statistics *col_stats= field->read_stats;