* it also adds an "explain select" statement to the test so that the fprintf calls
can print the computed intervals to mysqld.1.err
Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
This fixes the wrong calculation for avg_frequency in json histograms
by replacing the specific histogram objects with the generic Histogram_base class.
It also restores get/set size functions as they were useful in calculating fields
for binary histogram.
Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
A demo of how to use in-memory data structure for histogram.
The patch shows how to
* convert string form of data to binary form
* compare two values in binary form
* compute a fraction for val in [X, Y] range.
grep for GSOC-TODO for notes.
Preparation for handling different kinds of histograms:
- In Column_statistics, change "Histogram histogram" into
"Histogram *histogram_". This allows for different kinds
of Histogram classes with virtual functions.
- [Almost] remove the usage of Histogram->set_values and
Histogram->set_size. The code outside the histogram should
not make any assumptions about what/how is stored in the Histogram.
- Introduce drafts of methods to read/save histograms to/from disk.
This fixes the memory allocation for json histogram builder and add more column types for testing.
Some challenges at the moment include:
* Garbage value at the end of JSON array still persists.
* Garbage value also gets appended to bucket values if the column is a primary key.
* There's a memory leak resulting in a "Warning: Memory not freed" message at the end of tests.
Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
This patch changes the main name of 3 byte character set from utf8 to
utf8mb3. New old_mode UTF8_IS_UTF8MB3 is added and set TRUE by default,
so that utf8 would mean utf8mb3. If not set, utf8 would mean utf8mb4.
only collect persistent stats for columns explicitly listed
by the user in the ANALYZE TABLE PERSISTENT FOR COLUMNS (...)
clause. The engine can extend table->read_set as much as
it wants, it should not affect the collected statistics.
Test case from the 3b94309a6c applies - it used to crash,
because ha_partition extended table->read_set after the loop that
initialized some objects based on bits in the read_set but before the
loop that used these objects based on bits in the read_set.
This reverts the commit 3b94309a6c but keeps the test
Because the fix is a hack that isn't supposed to do anything,
and relies on a side-effect of rnd_init inside ha_partition.
A different fix is coming up.
The issue here was histogram statistics were being used even when
the level of optimizer_use_condition_selectivity doesn't allow
usage of statistics from histogram.
The histogram statistics are read for a table only when
optimizer_use_condition_selectivity > 3. But the TABLE structure can be
stored in the internal table cache and be reused for the next query.
So in this case the histogram statistics will be available for the next query.
The fix would be to make sure to use the histogram statistics only when
optimizer_use_condition_selectivity > 3.
