Revert "fix JSON_ARRAYAGG not to over-quote json in joins"
This removes 8711adb786 but keeps the test case.
A different fix is coming up.
Because args can be Item_field's that are later
replaced by Item_direct_view_ref to the actual field.
While Item_field preserved in orig_args will stay unfixed
with item->field==NULL and no metadata
use metadata (in particular is_json() property) of the original
argument item, even if the actual argument was later replaced
with an Item_temptable_field
Quick grouping is not supported for JSON_OBJECTAGG. The same for GROUP_CONCAT too
so make sure that Item::quick_group is set to FALSE. We need to make sure that in
the case of JSON_OBJECTAGG we don't create an index over grouping fields of
the temp table and update the result after each iteration.
Instead we should first sort the result in accordance to the
GROUP BY fields and then perform the grouping and
write the result to the temp table.
The problem here is similar to the case with DISTINCT, the tree used for ORDER BY
needs to also hold the null bytes of the record. This was not done for GROUP_CONCAT
as NULLS are rejected by GROUP_CONCAT.
Also introduced a comparator function for the order by tree to handle null
values with JSON_ARRAYAGG.
For DISTINCT to be handled with JSON_ARRAYAGG, we need to make sure
that the Unique tree also holds the NULL bytes of a table record
inside the node of the tree. This behaviour for JSON_ARRAYAGG is
different from GROUP_CONCAT because in GROUP_CONCAT we just reject
NULL values for columns.
Also introduced a comparator function for the unique tree to handle null
values for distinct inside JSON_ARRAYAGG.
We have to include NULL in the result which the GOUP_CONCAT doesn't
always do. Also converting should be done into another String instance
as these can be same.
The JSON_ARRAYAGG function extends the GROUP_CONCAT function and provides
a method of aggregating JSON results. The current implementation supports
DISTINCT and LIMIT but not ORDER BY (Oracle supports GROUP BY).
Adding GROUP BY support is possible but it requires some extra work as the
grouping appears to be done inside a temporary table that complicates
matters.
Added test cases that covert aggregation of all JSON types and JSON
validation for the generated results.
Now the boolean data type is preserved in hybrid functions and MIN/MAX,
so COALESCE(bool_expr,bool_expr) and MAX(bool_expr) are correctly
detected by JSON_OBJECT() as being boolean rather than numeric expressions.
