JSON functions were implemented violating an assumption of their
pureness, as they should not have any state. This concrete patch
fixes implementation of JSON_VALUE function.
MCOL-271 introduced a bug in JSON_VALUE that was discovered during
implementation of ASAN builds. The changes here restore normal
functionality.
In short, changes in MCOL-271 introduced a local variable instead of
reference to a string in ConstantColumn's fResult.strVal. The handling
of ConstantColumn is different because ConstantColumn's value is used
to initialize JSON path once. JSON path value holds pointer to data it
does not own and if there are two or more rows the data can be corrupted
and/or be out of stack bounds.
The changes here introduce reference to a NullString that is held in the
ConstantColumn's fResult.strVal and uses appropriate functions to obtain
data from the NullString. CC's fResult is held by CC and strVal is also
neither changing nor moving during operation, which allow JSON path to
hold correct pointers during multi-row operation.
This patch improves handling of NULLs in textual fields in ColumnStore.
Previously empty strings were considered NULLs and it could be a problem
if data scheme allows for empty strings. It was also one of major
reasons of behavior difference between ColumnStore and other engines in
MariaDB family.
Also, this patch fixes some other bugs and incorrect behavior, for
example, incorrect comparison for "column <= ''" which evaluates to
constant True for all purposes before this patch.
The following functions are created:
Create function JSON_VALID and test cases
Create function JSON_DEPTH and test cases
Create function JSON_LENGTH and test cases
Create function JSON_EQUALS and test cases
Create function JSON_NORMALIZE and test cases
Create function JSON_TYPE and test cases
Create function JSON_OBJECT and test cases
Create function JSON_ARRAY and test cases
Create function JSON_KEYS and test cases
Create function JSON_EXISTS and test cases
Create function JSON_QUOTE/JSON_UNQUOTE and test cases
Create function JSON_COMPACT/DETAILED/LOOSE and test cases
Create function JSON_MERGE and test cases
Create function JSON_MERGE_PATCH and test cases
Create function JSON_VALUE and test cases
Create function JSON_QUERY and test cases
Create function JSON_CONTAINS and test cases
Create function JSON_ARRAY_APPEND and test cases
Create function JSON_ARRAY_INSERT and test cases
Create function JSON_INSERT/REPLACE/SET and test cases
Create function JSON_REMOVE and test cases
Create function JSON_CONTAINS_PATH and test cases
Create function JSON_OVERLAPS and test cases
Create function JSON_EXTRACT and test cases
Create function JSON_SEARCH and test cases
Note:
Some functions output differs from MDB because session variables that affects functions output,e.g JSON_QUOTE/JSON_UNQUOTE
This depends on MCOL-5212
