There are "local" histograms that are allocated by one thread for
one TABLE object, and "global" that are allocated for TABLE_SHARE.

- Don't use 'res' uninitialized
- multiply it by col_non_nulls before set_if_bigger(...) call.

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

* Also merges tests relating to JSON statistics into one file
Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

* 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>

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.

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

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.

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

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>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>

Signed-off-by: Michael Okoko <okokomichaels@outlook.com>