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connectors experimental galera main
MDEV-25830 optimizer_use_condition_selectivity=4 sometimes produces worse plan than optimizer_use_condition_selectivity=1

The issue was that calc_cond_selectivity_for_table prefered ranges with
many parts and when deciding on which selectivity to use.

Fixed by going through ranges according to the number of rows in the range.

This ensures that selectivity from ranges with few rows will be prefered
over ranges with many rows for indexes that uses the same columns.
Sergei Petrunia
Switch the default histogram_type to still be DOUBLE_PREC_HB

MTR still uses JSON_HB as the default.
Sergei Petrunia
MDEV-26886: Estimation for filtered rows less precise with JSON histogram

- Make Histogram_json_hb::range_selectivity handle singleton buckets
  specially when computing selectivity of the max. endpoint bound.
  (for min. endpoint, we already do that).

- Also, fixed comments for Histogram_json_hb::find_bucket
Sergei Petrunia
MDEV-27229: Estimation for filtered rows less precise ... #5

Followup: remove this line from get_column_range_cardinality()

      set_if_bigger(res, col_stats->get_avg_frequency());

and make sure it is only used with the binary histograms.
For JSON histograms, it makes the estimates unnecessarily imprecise.
Sergei Petrunia
MDEV-26901: Estimation for filtered rows less precise ... #4

In Histogram_json_hb::point_selectivity(), do return selectivity of 0.0
when the histogram says so.

The logic of "Do not return 0.0 estimate as it causes a multiply-by-zero
meltdown in cost and cardinality calculations" is moved into
records_in_column_ranges() where it is one *once* per column pair (as
opposed to doing once per range, which can cause the error to add-up
to large number when there are many ranges)
Sergei Petrunia
Merge MDEV-26519: JSON_HB histograms into 10.8
Sergei Petrunia
MDEV-26764: JSON_HB Histograms: handle BINARY and unassigned characters

Encode such characters in hex.
Sergei Petrunia
MDEV-27243: Estimation for filtered rows less precise ... #7

Added a testcase
Sergei Petrunia
Code cleanup
Sergei Petrunia
MDEV-26519: Improved histograms

Save extra information in the histogram:

    "target_histogram_size": nnn,
    "collected_at": "(date and time)",
    "collected_by": "(server version)",
DBUG_ASSERT(flags != Gtid_log_event::FL_START_ALTER_E1...) in THD::set_binlog_flags_for_alter

is fixed to reset binlog_cache_mngr::gtid_flags3 in the error return
from write_bin_log() of write_bin_log_start_alter().
In other error cases gtid_flags3 has been reset correctly for any flag
Sergei Petrunia
MDEV-27062: Make histogram_type=JSON_HB the new default
Sergei Petrunia