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From Alexey Goncharuk <alexey.goncha...@gmail.com>
Subject Re: IGNITE-2294 implementation details
Date Thu, 21 Jul 2016 11:14:45 GMT
For me the main question here is how we define Key and Value for a cache
when using SQL interface. Unless we are going to re-architect the whole
Ignite, it will still be a key-value storage in the first place, so
whenever we do an INSERT, we must generate Key and Value. Given that values
in INSERT are supposed to be fields of either Key or Value, this confuses
me a lot.

Maybe we should come up with DDL first?

2016-07-21 14:06 GMT+03:00 Sergi Vladykin <sergi.vladykin@gmail.com>:

> No, this does not make sense.
>
> There is no upsert mode in databases. There are operations: INSERT, UPDATE,
> DELETE, MERGE.
>
> I want to have clear understanding of how they have to behave in SQL
> databases and how they will actually behave in Ignite in different
> scenarios. Also I want to have clear understanding of performance
> implications of each decision here.
>
> Anything wrong with that?
>
> Sergi
>
> On Thu, Jul 21, 2016 at 1:04 PM, Dmitriy Setrakyan <dsetrakyan@apache.org>
> wrote:
>
> > Serj, are you asking what will happen as of today? Then the answer to all
> > your questions is that duplicate keys are not an issue, and Ignite always
> > operates in **upsert** mode (which is essentially a *“put(…)” *method).
> >
> > However, the *“insert”* that is suggested by Alex would delegate to
> > *“putIfAbsent(…)”*, which in database world makes more sense. However, in
> > this case, the *“update”* syntax should delegate to *“replace(…)”*, as
> > update should fail in case if a key is absent.
> >
> > Considering the above, a notion of “*upsert”* or “*merge” *operation is
> > very much needed, as it will give a user an option to perform
> > “insert-or-update” in 1 call.
> >
> > Does this make sense?
> >
> > D.
> >
> > On Wed, Jul 20, 2016 at 9:39 PM, Sergi Vladykin <
> sergi.vladykin@gmail.com>
> > wrote:
> >
> > > I'd prefer to do MERGE operation last because in H2 it is not standard
> > ANSI
> > > SQL MERGE. Or may be not implement it at all, or may be contribute ANSI
> > > correct version to H2, then implement it on Ignite. Need to investigate
> > the
> > > semantics deeper before making any decisions here.
> > >
> > > Lets start with simple scenarios for INSERT and go through all the
> > possible
> > > cases and answer the questions:
> > > - What will happen on key conflict in TX cache?
> > > - What will happen on key conflict in Atomic cache?
> > > - What will happen with the previous two if we use DataLoader?
> > > - How to make these operations efficient (it will be simple enough to
> > > implement them with separate put/putIfAbsent operations but probably we
> > > will need some batching like putAllIfAbsent for efficiency)?
> > >
> > > As for API, we still will need to have a single entry point for all SQL
> > > queries/commands to allow any console work with it transparently. It
> > would
> > > be great if we will be able to come up with something consistent with
> > this
> > > idea on public API.
> > >
> > > Sergi
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > On Wed, Jul 20, 2016 at 2:23 PM, Dmitriy Setrakyan <
> > > dsetrakyan@gridgain.com>
> > > wrote:
> > >
> > > > Like the idea of merge and insert. I need more time to think about
> the
> > > API
> > > > changes.
> > > >
> > > > Sergi, what do you think?
> > > >
> > > > Dmitriy
> > > >
> > > >
> > > >
> > > > On Jul 20, 2016, at 12:36 PM, Alexander Paschenko <
> > > > alexander.a.paschenko@gmail.com> wrote:
> > > >
> > > > >> Thus, I suggest that we implement MERGE as a separate operation
> > backed
> > > > by putIfAbsent operation, while INSERT will be implemented via put.
> > > > >
> > > > > Sorry, of course I meant that MERGE has to be put-based, while
> INSERT
> > > > > has to be putIfAbsent-based.
> > > > >
> > > > > 2016-07-20 12:30 GMT+03:00 Alexander Paschenko
> > > > > <alexander.a.paschenko@gmail.com>:
> > > > >> Hell Igniters,
> > > > >>
> > > > >> In this thread I would like to share and discuss some thoughts
on
> > DML
> > > > >> operations' implementation, so let's start and keep it here.
> > Everyone
> > > > >> is of course welcome to share their suggestions.
> > > > >>
> > > > >> For starters, I was thinking about semantics of INSERT. In
> > traditional
> > > > >> RDBMSs, INSERT works only for records whose primary keys don't
> > > > >> conflict with those of records that are already persistent -
you
> > can't
> > > > >> try to insert the same key more than once because you'll get
an
> > error.
> > > > >> However, semantics of cache put is obviously different - it does
> not
> > > > >> have anything about duplicate keys, it just quietly updates values
> > in
> > > > >> case of keys' duplication. Still, cache has putIfAbsent operation
> > that
> > > > >> is closer to traditional notion of INSERT, and H2's SQL dialect
> has
> > > > >> MERGE operation which corresponds to semantics of cache put.
> Thus, I
> > > > >> suggest that we implement MERGE as a separate operation backed
by
> > > > >> putIfAbsent operation, while INSERT will be implemented via put.
> > > > >>
> > > > >> And one more, probably more important thing: I suggest that we
> > create
> > > > >> separate class Update and corresponding operation update() in
> > > > >> IgniteCache. The reasons are as follows:
> > > > >>
> > > > >> - Query bears some flags that are clearly redundant for Update
> (page
> > > > >> size, locality)
> > > > >> - query() method in IgniteCache (one that accepts Query) and
> query()
> > > > >> methods in GridQueryIndexing return iterators. So, if we strive
to
> > > > >> leave interfaces unchanged, we still will introduce some design
> > > > >> ugliness like query methods returning empty iterators for certain
> > > > >> queries, and/or query flags that indicate whether it's an update
> > query
> > > > >> or not, etc.
> > > > >> - If some Queries are update queries, then continuous queries
> can't
> > be
> > > > >> based on them - more design-wise ugly checks and stuff like that.
> > > > >> - I'm pretty sure there's more I don't know about.
> > > > >>
> > > > >> Comments and suggestions are welcome. Sergi Vladykin, Dmitry
> > > > >> Setrakyan, your opinions are of particular interest, please
> advise.
> > > > >>
> > > > >> Regards,
> > > > >> Alex
> > > >
> > >
> >
>

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