There are some thoughts about strict field order:
1. Index (A, B) is not equivalent to index (B, A). Some queries may have
different performance on such indexes, and users have to specify the right
index. What if both indexes exist?
2. We should avoid cases when a user uses in query only field B for index
(A, B). We have to force the user to specify range for (A) too, or
explicitly set it (null, null). Otherwise it looks like a mistake.
On Thu, Aug 26, 2021 at 4:39 PM Ivan Daschinsky <ivanda...@gmail.com> wrote:
> 1. I suppose, that the next step is to implement the api for manually
> creating index. I think that user wants to create index that will speed up
> his criteria base queries, so he or she will use the same criteria to
> define the index. So no problem at all
> 2. We should print warning or throws exception if there is not any index
> that match specific criteria.
>
> BTW, Mongo DB doesn't make user to write index name in query. It just
> works.
>
> чт, 26 авг. 2021 г., 15:52 Taras Ledkov <tled...@gridgain.com>:
>
> > Hi,
> >
> > > It is an usability nightmare to make user write index name in all
> cases.
> > I don't see any difference between specifying the index name and
> > specifying the index fields in the right order.
> > Do you see?
> >
> > Let's there is the index:
> > idx_A_B ON TBL (A, B)
> >
> > Is it OK that the query like below doesn't math the index 'idx_A_B'?
> > new IndexQuery<>(..)
> > .setCriteria(lt("b", 1), lt("a", 2));
> >
> > On 26.08.2021 15:23, Ivan Daschinsky wrote:
> > > I am against to make user write index name. It is quite simple and
> > > straightforward algorithm to match index to field names, so it is
> strange
> > > to compare it to sql engine optimizer.
> > >
> > > It is an usability nightmare to make user write index name in all
> cases.
> > >
> > > чт, 26 авг. 2021 г., 14:42 Maksim Timonin <timonin.ma...@gmail.com>:
> > >
> > >> Hi, Igniters!
> > >>
> > >> There is a discussion about how to specify an index to query with an
> > >> IndexQuery [1]. Currently my PR provides 2 ways to specify index:
> > >> 1. With a table and index name;
> > >> 2. With a table and list of index fields (without index name). In this
> > case
> > >> IndexQueryProcessor tries to find an index that matches table and
> index
> > >> fields in strict order (order of fields in criteria has to match the
> > order
> > >> of fields in index).
> > >>
> > >> Discussion is whether is the second approach valid?
> > >>
> > >> Pros:
> > >> 1. Currently index name is an optional field for QueryIndex and
> > >> QuerySqlField. Then users can create an index with a table and list of
> > >> fields. Then, we should provide an opportunity to define an index for
> > >> querying the same way as we do for creating.
> > >> 2. It's required to know the index name to query it (in case the index
> > was
> > >> created without an explicit name). Users can find it and then use it
> as
> > a
> > >> constant in code, but I see some troubles there:
> > >> 2.1. Get index name by querying the system view INDEXES. Note, that
> > system
> > >> views are marked as an experimental feature [2].
> > >> 2.2. There is a workaround to know an index name with EXPLAIN clause
> for
> > >> sql query that uses the required index (but it depends on SQL
> > optimizer).
> > >> 2.3. Users can use the index name builder, but it is in the
> > >> internal package
> > >> (org.apache.ignite.internal.processors.query.QueryUtils#indexName).
> > Then it
> > >> can be changed from version to version without warning, and then the
> > user
> > >> can't rely on it in code.
> > >> 3. Name of the Primary Key index (_key_PK) is predefined and hardcoded
> > in
> > >> Ignite. Users can't set it while creating it, and the name of PK index
> > is
> > >> hardcoded in the internal package too (QueryUtils.PRIMARY_KEY_INDEX).
> > >>
> > >> Cons:
> > >> 1. It's declared that IndexQuery avoids some SQL steps (like planning,
> > >> optimizer) in favor of speed. It looks like that looking for an index
> by
> > >> list of fields is the work of an optimizer.
> > >> 2. It can be not obvious that the order of fields in a query has to
> > match
> > >> the order of fields in the related index. We should have it in mind
> when
> > >> building a query - there should be a check for order of fields before
> > >> querying.
> > >>
> > >> From my side, I think that arguments for enforcing usage of an index
> > name
> > >> for queries are strong enough. But for me it's strange that it's
> > possible
> > >> to create an index without a name, but it's required to use name to
> > query
> > >> it. Also taking in consideration that there is no guaranteed way to
> get
> > an
> > >> index name (or I don't know it).
> > >>
> > >> Igniters, what do you think?
> > >> [1] https://github.com/apache/ignite/pull/9118#discussion_r642557531
> > >> [2]
> > https://ignite.apache.org/docs/latest/monitoring-metrics/system-views
> > >>
> > >>
> > >> On Fri, Aug 6, 2021 at 4:04 PM Maksim Timonin <
> timonin.ma...@gmail.com>
> > >> wrote:
> > >>
> > >>> Hi, all!
> > >>>
> > >>> It's a gentle reminder. There is a PR for the new Index API [1]. It
> was
> > >>> approved by Alex Plekhanov. Does anybody want to review this API too?
> > If
> > >>> there won't be objections we're going to merge it Monday, 16th of
> > August.
> > >>>
> > >>> Thanks!
> > >>>
> > >>> [1] https://github.com/apache/ignite/pull/9118
> > >>>
> > >>> On Fri, May 21, 2021 at 10:43 PM Maksim Timonin <
> > timonin.ma...@gmail.com
> > >>>
> > >>> wrote:
> > >>>
> > >>>> Andrey, hi!
> > >>>>
> > >>>> Some updates, there.
> > >>>>
> > >>>> I've submitted a PR for IndexQuery [1]. There is an issue about lazy
> > >> page
> > >>>> loading, that is also related to Text query ticket IGNITE-12291.
> > >>>>
> > >>>> CacheQueries already have pending pages functionality, it's done
> with
> > >>>> multiple sending GridCacheQueryRequest. There was an issue with
> > >> TextQuery
> > >>>> and limit, after exceeding a limit we still send requests, so I
> > >> submitted a
> > >>>> patch to fix this [2].
> > >>>>
> > >>>> But currently, TextQuery, as SqlFieldsQuery also does, prepares
> whole
> > >>>> data on query request, holds it, and provides a cursor over this
> > >>>> collection.
> > >>>>
> > >>>> As I understand you correctly, you propose to run TextQuery over
> index
> > >>>> with every poll page request. We can do this with Lucene
> > >>>> IndexSearcher.searchAfter. So from one side, it will save resources.
> > But
> > >>>> from the other side, no queries (no TextQuery, no SqlFieldsQuery)
> lock
> > >>>> index for querying. So there can be data inconsistency, as there can
> > be
> > >>>> concurrent operations on an index while a user iterates over the
> > >> cursor. It
> > >>>> also could be for queries now, due to no index lock being there, but
> > the
> > >>>> window of time of such inconsistency is much shorter.
> > >>>>
> > >>>> The same dilemma I have for IndexQuery. In my patch [1] I provide
> lazy
> > >>>> iteration over BPlusTree. There is no lock on an index too while
> > >> querying.
> > >>>> And I want to discuss the right way. I have in mind the next things:
> > >>>> 1. Indexes currently doesn't support transactions, also SQL queries
> > >> don't
> > >>>> lock index for queries, so Ignite don't guarantee data consistency;
> > >>>> 2. As I understand preparing whole data for SQL queries is required
> > due
> > >>>> to relations between tables. The more complex query and relations we
> > >> have,
> > >>>> the much consistency issues we have in result in case of parallel
> > >>>> operations;
> > >>>> 3. Querying a single index only (by TextQuery or IndexQuery) doesn't
> > >>>> affect any relations, so we can allow concurrent updates, as it
> could
> > >>>> affect a query result but it doesn't hurt.
> > >>>>
> > >>>> And following these thoughts, it's right to implement lazy
> iterations
> > >>>> over indexes. What do you think?
> > >>>>
> > >>>> Also, there is a second topic to discuss. BPlusTree indexes support
> > >> query
> > >>>> parallelism. But CacheQueries don't. There needs to be a change to
> > >>>> infrastructure to support query parallelism, so on this patch [1] I
> > >> handle
> > >>>> multiple segments in a single thread. And this works OK, as in the
> > case
> > >> of
> > >>>> lazy querying it's very fast to initialize a cursor, so there is not
> > >> much
> > >>>> overhead on multiple segments. I ran performance tests and found
> that
> > in
> > >>>> some cases, IndexQuery beats SqlFieldsQuery even with enabled
> > >>>> queryParallelism (it helps a SqlFieldsQuery much). So the need for
> > >>>> supporting queryParallelism for IndexQuery is required to be tested
> > >> well.
> > >>>> As IndexQuery already can help users to speed up some queries I
> > propose
> > >> to
> > >>>> check queryParallelism a little bit later. WDYT?
> > >>>>
> > >>>> So, those 2 things affect the Apache Ignite release that IndexQuery
> > will
> > >>>> be delivered with. So, please let me know your thoughts.
> > >>>>
> > >>>> Any thoughts from the community are welcome too.
> > >>>>
> > >>>>
> > >>>> [1] https://github.com/apache/ignite/pull/9118
> > >>>> [2] https://github.com/apache/ignite/pull/9086
> > >>>>
> > >>>> On Mon, Apr 12, 2021 at 1:52 PM Maksim Timonin <
> > timonin.ma...@gmail.com
> > >>>> wrote:
> > >>>>
> > >>>>> Andrey,
> > >>>>>
> > >>>>> Thanks! I picked it.
> > >>>>>
> > >>>>> On Mon, Apr 12, 2021 at 1:51 PM Maksim Timonin <
> > >> timonin.ma...@gmail.com>
> > >>>>> wrote:
> > >>>>>
> > >>>>>> Stephen,
> > >>>>>>
> > >>>>>> I don't see a reason to replace or deprecate IndexingSpi. I'm not
> > >>>>>> sure how smbd uses it, but it works now.
> > >>>>>>
> > >>>>>> On Mon, Apr 12, 2021 at 1:42 PM Stephen Darlington <
> > >>>>>> stephen.darling...@gridgain.com> wrote:
> > >>>>>>
> > >>>>>>> Is this a replacement for IndexingSpi? Put bluntly, do we
> deprecate
> > >>>>>>> (and remove) it?
> > >>>>>>>
> > >>>>>>> Or do you see them as complimentary?
> > >>>>>>>
> > >>>>>>>> On 12 Apr 2021, at 11:29, Maksim Timonin <
> timonin.ma...@gmail.com
> > >
> > >>>>>>> wrote:
> > >>>>>>>> Hi Stephen!
> > >>>>>>>>
> > >>>>>>>> Please have a look at the QueryProcessing paragraph [1]. I've
> > >>>>>>> described
> > >>>>>>>> why IndexingSpi doesn't fit us well.
> > >>>>>>>>
> > >>>>>>>> [1]
> > >>>>>>>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/IGNITE/IEP-71+Public+API+for+secondary+index+search#IEP71PublicAPIforsecondaryindexsearch-2)QueryProcessing
> > >>>>>>>> On Mon, Apr 12, 2021 at 1:24 PM Stephen Darlington <
> > >>>>>>>> stephen.darling...@gridgain.com> wrote:
> > >>>>>>>>
> > >>>>>>>>> How does this fit with the current IndexingSpi? Superficially
> > they
> > >>>>>>> appear
> > >>>>>>>>> to do very similar things?
> > >>>>>>>>>
> > >>>>>>>>> Regards,
> > >>>>>>>>> Stephen
> > >>>>>>>>>
> > >>>>>>>>>> On 6 Apr 2021, at 14:13, Maksim Timonin <
> > timonin.ma...@gmail.com
> > >>>>>>> wrote:
> > >>>>>>>>>> Hi, Igniters!
> > >>>>>>>>>>
> > >>>>>>>>>> I'd like to propose a new feature - opportunity to query and
> > >> create
> > >>>>>>>>> indexes
> > >>>>>>>>>> from public API.
> > >>>>>>>>>>
> > >>>>>>>>>> It will help in some cases, where:
> > >>>>>>>>>> 1. SQL is not applicable by design of user application;
> > >>>>>>>>>> 2. Where IndexScan is preferable than ScanQuery for
> performance
> > >>>>>>> reasons;
> > >>>>>>>>>> 3. Functional indexes are required.
> > >>>>>>>>>>
> > >>>>>>>>>> Also it'll be great to have a transactional support for such
> > >>>>>>> queries,
> > >>>>>>>>> like
> > >>>>>>>>>> the "select for update" query provides. But I don't dig there
> > >>>>>>> much. It
> > >>>>>>>>> will
> > >>>>>>>>>> be a next step if this API will be implemented.
> > >>>>>>>>>>
> > >>>>>>>>>> I've prepared an IEP-71 for that [1] with more details. Please
> > >>>>>>> share your
> > >>>>>>>>>> thoughts.
> > >>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>> [1]
> > >>>>>>>>>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/IGNITE/IEP-71+Public+API+for+secondary+index+search
> > >>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>
> > >>>>>>>
> > --
> > Taras Ledkov
> > Mail-To: tled...@gridgain.com
> >
> >
>
