Request for conditional index feature in boost multi-index
Hi,
First of all thanks for the great library, which had reduced our
development time by a lot.
In boost multi-index, we currently have almost all the indexing concepts
integrated. Hence i am requesting for a new feature called conditional
indexes, where in an index/view inside multi-index will only index a portion
of the entries inside the entire multi-index(Say something that satisfies a
functor). This is in resemblance to the partial indexes in Postgresql.
I feel that would provide elegant solutions to lot of issues without
forming round about solutions. For example i have a requirement where in
there are two sets of data with the same search criteria, but different
eviction criteria
Say i have two sets of data with same search condition, but one set needs a
MRU(Most Recently Used) list of 100 and the other set requires a MRU of 200.
Say the entry is like this
class Student
{
int student_no;
char sex;
std::string address;
};
The search criteria is student_no, but for sex='m', we need MRU of 200 and
for sex='f', we need a MRU of 100. Now i have a solution where in i
introduce a new ordered index to maintain ordering.
For example the IndexSpecifierList will be something like this
typedef multi_index_container<
Student,
indexed_by<
ordered_unique< member
student_set
Here i have to introduce a new counter called sex_specific_student_counter, and during the eviction time, i need a logn search. Insertion also involves a extra logn complexity. Now instead if i have two sequenced indexes (like mentioned in the MRU example) in the place of second ordered index, but both with a condition on indexing only a few items, this would have looked more elegant and with better performance. Thanks in advance, Gokul.
Gokulakannan Somasundaram escribió:
Hi, First of all thanks for the great library, which had reduced our development time by a lot. In boost multi-index, we currently have almost all the indexing concepts integrated. Hence i am requesting for a new feature called conditional indexes, where in an index/view inside multi-index will only index a portion of the entries inside the entire multi-index(Say something that satisfies a functor). This is in resemblance to the partial indexes in Postgresql. I feel that would provide elegant solutions to lot of issues without forming round about solutions. For example i have a requirement where in there are two sets of data with the same search criteria, but different eviction criteria
Say i have two sets of data with same search condition, but one set needs a MRU(Most Recently Used) list of 100 and the other set requires a MRU of 200. Say the entry is like this [...]
The general request (composing partial indices to cover the whole
sequence) is
interesting and a considered it some years ago, though I never found the
time
to implement it (and I'm suspicious it might be a little too "smart" for
the general
public).
In any case, I think you can solve your particular problem without that
feature
in a convenient manner. Please see the attached example and report whether
it satisfies your needs.
Best regards,
Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo
#include <algorithm>
#include
student_list;
public:
typedef student_list::iterator iterator;
student_mru_list(std::size_t max_male,std::size_t max_female):
max_male(max_male),max_female(max_female),
size_male(0),size_female(0){}
void insert(const student& s)
{
bool is_male=(s.sex=='m');
std::size_t& size =is_male? size_male :size_female;
std::size_t max_size=is_male? max_male :max_female;
iterator it =is_male? male_begin():female_begin();
std::pair
Hi,
Thanks for the reply. But there is a mention in random_access<> like this
"This added flexibility comes at a price: insertions and deletions at
positions other than the end of the index have linear complexity"
So isn't this a O(n) operation? But i quite gives me a hint that the
random_access<> is more like std::deque than std::vector. Can you throw me
little bit light on this? But the approach even suggests me to keep a
iterator of sequenced<> cached and use it for male insertions.
Thanks,
Gokul.
On Wed, Dec 22, 2010 at 3:59 PM,
Gokulakannan Somasundaram escribió:
Hi, First of all thanks for the great library, which had reduced our development time by a lot. In boost multi-index, we currently have almost all the indexing concepts integrated. Hence i am requesting for a new feature called conditional indexes, where in an index/view inside multi-index will only index a portion of the entries inside the entire multi-index(Say something that satisfies a functor). This is in resemblance to the partial indexes in Postgresql. I feel that would provide elegant solutions to lot of issues without forming round about solutions. For example i have a requirement where in there are two sets of data with the same search criteria, but different eviction criteria
Say i have two sets of data with same search condition, but one set needs a MRU(Most Recently Used) list of 100 and the other set requires a MRU of 200. Say the entry is like this [...]
The general request (composing partial indices to cover the whole sequence) is interesting and a considered it some years ago, though I never found the time to implement it (and I'm suspicious it might be a little too "smart" for the general public).
In any case, I think you can solve your particular problem without that feature in a convenient manner. Please see the attached example and report whether it satisfies your needs.
Best regards,
Joaquín M López Muñoz Telefónica, Investigación y Desarrollo
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
On Wed, Dec 22, 2010 at 8:59 AM,
The general request (composing partial indices to cover the whole sequence) is interesting and a considered it some years ago, though I never found the time to implement it (and I'm suspicious it might be a little too "smart" for the general public).
Sorry to wake up an old thread, but I've just encountered a problem where partial indices would be the perfect solution. I'm working on a problem where I have several unique identifiers for each object, but I'm not guaranteed that I have all of them at the same time. I can get updates from two sources, which don't necessarily don't use the same ID, yet they will sooner or later be linked. Using postgresql a simplified version could look like this: CREATE TABLE test( a text, b text, data text); CREATE UNIQUE INDEX test_a_par_uidx ON test(a) WHERE a IS NOT NULL; CREATE UNIQUE INDEX test_b_par_uidx ON test(b) WHERE a IS NOT NULL; Are we thinking of the same sort of partial indices? ... and is this something that is feasible to implement in multi_index_container? -- Eld på åren og sol på eng gjer mannen fegen og fjåg. [Jøtul] <demo> 2011 Tore Halvorsen || +052 0553034554
participants (3)
-
Gokulakannan Somasundaram -
joaquin＠tid.es -
Tore Halvorsen