On 27.06.2016 13:07, Sergei Golubchik wrote:
Hi, Sanja!
On May 04, Olaksandr Byslkin wrote:
still haven't fixed the typo? :)
revision-id: eb9fab76fb4322a7821e6502e6303ed381624429 (mariadb-10.1.13-18-geb9fab7) parent(s): 732adec0a4c75d99389230feeb0deca0ad668de7 committer: Oleksandr Byelkin timestamp: 2016-05-04 19:15:31 +0200 message:
MDEV-9531: GROUP_CONCAT with ORDER BY inside takes a lot of memory while it's executed
Limitation added to Red-Black tree.
diff --git a/include/my_tree.h b/include/my_tree.h index f8be55f..f1916b9 100644 --- a/include/my_tree.h +++ b/include/my_tree.h @@ -57,11 +57,14 @@ typedef struct st_tree_element { } TREE_ELEMENT;
#define ELEMENT_CHILD(element, offs) (*(TREE_ELEMENT**)((char*)element + offs)) +#define R_ELEMENT_CHILD(element, offs) ((TREE_ELEMENT**)((char*)element + offs)) what does "R_ELEMENT_CHILD" mean? What's "R"? reference
typedef struct st_tree { TREE_ELEMENT *root,null_element; TREE_ELEMENT **parents[MAX_TREE_HEIGHT]; + TREE_ELEMENT *free_element;
why do you need a free_element pointer?
We can free element not when tree grows enough but only when we are going to insert new element, but then we will need to go back and make path jet another time tho the place of insertion (because of possible rebalancing). Instead we check in the beginning if tree is too big to insert and delete element, then probably we will use it to insert new, but if when we went down to the element and see that we do not need to insert, the element will be left as free for the next time.
uint offset_to_key,elements_in_tree,size_of_element; + uint elements_limit, del_direction;
why do you need to support different directions here?
to make the routine more general.
size_t memory_limit, allocated; qsort_cmp2 compare; void *custom_arg; diff --git a/mysql-test/r/mysqld--help.result b/mysql-test/r/mysqld--help.result index bef0390..3699b18 100644 --- a/mysql-test/r/mysqld--help.result +++ b/mysql-test/r/mysqld--help.result @@ -240,6 +240,9 @@ The following options may be given as the first argument: --group-concat-max-len=# The maximum length of the result of function GROUP_CONCAT() + --group-concat-max-mem=# + The maximum memory used to calculate result of function + GROUP_CONCAT()
No, please. There is group_concat_max_len already, it's all that user needs. There is no reason why one might need to configure a second limit on for the GROUP_CONCAT.
OK, the problem is that even by key length we can not predict string output of the values, the only what we can say is that it will be at least one character (coma) because empty lines possible. Do you have ideas how predict minimal possible string size by value?
--gtid-domain-id=# Used with global transaction ID to identify logically independent replication streams. When events can propagate through multiple parallel paths (for example Regards, Sergei Chief Architect MariaDB and security@mariadb.org
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