when calculating GROUP_CONCAT all blob fields are transformed
to varchar when making the temp table.
However a varchar has at max 2 bytes for length.
This fix makes the conversion only for blobs whose max length
is below that limit.
Otherwise blob field is created by make_string_field() call.
used
In a simple queries a result of the GROUP_CONCAT() function was always of
varchar type.
But if length of GROUP_CONCAT() result is greater than 512 chars and temporary
table is used during select then the result is converted to blob, due to
policy to not to store fields longer than 512 chars in tmp table as varchar
fields.
In order to provide consistent behaviour, result of GROUP_CONCAT() now
will always be converted to blob if it is longer than 512 chars.
Item_func_group_concat::field_type() is modified accordingly.
The GROUP_CONCAT uses its own temporary table. When ROLLUP is present
it creates the second copy of Item_func_group_concat. This copy receives the
same list of arguments that original group_concat does. When the copy is
set up the result_fields of functions from the argument list are reset to the
temporary table of this copy.
As a result of this action data from functions flow directly to the ROLLUP copy
and the original group_concat functions shows wrong result.
Since queries with COUNT(DISTINCT ...) use temporary tables to store
the results the COUNT function they are also affected by this bug.
The idea of the fix is to copy content of the result_field for the function
under GROUP_CONCAT/COUNT from the first temporary table to the second one,
rather than setting result_field to point to the second temporary table.
To achieve this goal force_copy_fields flag is added to Item_func_group_concat
and Item_sum_count_distinct classes. This flag is initialized to 0 and set to 1
into the make_unique() member function of both classes.
To the TMP_TABLE_PARAM structure is modified to include the similar flag as
well.
The create_tmp_table() function passes that flag to create_tmp_field().
When the flag is set the create_tmp_field() function will set result_field
as a source field and will not reset that result field to newly created
field for Item_func_result_field and its descendants. Due to this there
will be created copy func to copy data from old result_field to newly
created field.
Added test cases for bug #12863.
item_sum.cc, item_sum.h:
Fixed bug #12863.
Added a flag to Item_func_group_concat set to FALSE after
concatenation of the first element of a group.
Item_func_group_concat::fix_fields() set maybe_null flag to 0, and set it to
1 only if some of it's arguments may be null. When used in subquery in tmp
table created field which can't be null. When no data retireved result field
have to be set to null and error mentioned in bug report occurs. Also this
bug can occur if selecting from not null field in empty table.
Function group_concat now marked maybe_null from the very beginning not only
if some of it's argument may be null.
Cannot convert the charset of a GROUP_CONCAT result:
item_sum.cc:
"result" character set was not set into proper value.
func_gconcat.result, func_gconcat.test:
Fixing tests accordingly.
Added a test case for bug #12095.
sql_class.h:
Fixed bug #12095: a join query with GROUP_CONCAT over a single row table.
Added a flag to the TMP_TABLE_PARAM class forcing to put constant
items generated after elimination of a single row table into temp table
in some cases (e.g. when GROUP_CONCAT is calculated over a single row
table).
bk ci sql/item_sum.cc
Fixed bug #12095: a join query with GROUP_CONCAT over a single row table.
If GROUP_CONCAT is calculated we always put its argument into a temp
table, even when the argument is a constant item.
sql_select.cc:
Fixed bug #12095: a join query with GROUP_CONCAT over one row table.
If temp table is used to calculate GROUP_CONCAT the argument should
be always put into this table, even when it is a constant item.
Adding test
item_sum.cc:
Adding a call for collation/charset aggregation,
to collect attributes from the arguments. The actual bug fix.
item_func.h, item_func.cc, item.h, item.cc:
- Removing collation aggrgation functions from Item_func class
in item.cc, and adding it as non-class functions in item.cc
to be able to reuse this code for group_concat.
- Adding replacement for these functions into Item_func class
as wrappers for moved functions, to minizize patch size,
Ensure that 'null_value' is not accessed before val() is called in FIELD() functions
Fixed initialization of key maps. This fixes some problems with keys when you have more than 64 keys
Fixed that ROLLUP don't always create a temporary table. This fix ensures that func_gconcat.test results are now predictable
Added a test case for bug #7769.
item_sum.h:
Fixed bug #7769: a crash for queries with group_concat and
having when the query table was empty.
The bug was due an unsafe dereferencing.
(Bug #4315: GROUP_CONCAT with ORDER BY returns strange results for TEXT fields
Bug #5564: Strange behaviour with group_concat and distinct
Bug #5970: group_concat doesn't print warnings)
