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 [email protected]
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