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Re: Elasticsearch Adapter. Removal of Mapping Types (by vendor). Index == Table


Let's assume we have the following indexes  / types in ES (same cluster)

(Index with two types. Legacy format. Not supported in ES8+)
- index1: t1 + t2

(Index with single type. Default and most used format)
- index2: t1

(Index with two types having same name as index1)
- index3: t1 + t2

Technically these are 5 separate tables in relational world (as of ES2-6).
User might want to query all of them within same calcite schema.

There are a couple of (not ideal) options:
1) Not support this scenario.
2) Force user to have unique (type?) names.
3) Somehow merge index and type into unique calcite table name.
4) Force user to have different schemas





On Fri, Jun 29, 2018 at 2:28 PM Christian Beikov <christian.beikov@xxxxxxxxx>
wrote:

> I'm not sure what the benefit of allowing users to specify this scheme
> would be. We'd have to parse it, interpret it, make sure the expressions
> don't result conflicting names etc.
>
> IMO a simple mode configuration would be way easier to implement and
> probably cover 99% of the use cases.
>
>
> Mit freundlichen Grüßen,
> ------------------------------------------------------------------------
> *Christian Beikov*
> Am 29.06.2018 um 20:19 schrieb Julian Hyde:
> > Andrei,
> >
> > I'm not an ES user so I don't fully understand this issue, but my two
> > cents anyway...
> >
> > Can you show how those examples affect SQL against the ES adapter
> > and/or how they affect JSON models?
> >
> > You seem to be using '_' as a separator character. Are we sure that
> > people will never use it in index or type name? Separator characters
> > often cause problems.
> >
> > Julian
> >
> >
> >
> >
> > On Fri, Jun 29, 2018 at 10:58 AM, Andrei Sereda <andrei@xxxxxxxxx>
> wrote:
> >> I agree there should be a configuration option. How about the following
> >> approach.
> >>
> >> Expose both variables ${index} and ${type} in configuration (JSON) and
> user
> >> will use them to generate table name in calcite schema.
> >>
> >> Example
> >> "table_name": "${type}" // current
> >> "table_name": "${index}" // new (default?)
> >> "table_name": "${index}_${type}" // most generic. supports multiple
> types
> >> per index
> >>
> >>
> >>
> >>
> >>
> >> On Fri, Jun 29, 2018 at 9:26 AM Michael Mior <mmior@xxxxxxxxxx> wrote:
> >>
> >>> I think it sounds like you and Andrei are in a good position to tackle
> this
> >>> one so I'm happy to have you both work on whatever solution you think
> is
> >>> best.
> >>>
> >>> --
> >>> Michael Mior
> >>> mmior@xxxxxxxxxx
> >>>
> >>>
> >>>
> >>> Le ven. 29 juin 2018 à 04:19, Christian Beikov <
> christian.beikov@xxxxxxxxx
> >>> a écrit :
> >>>
> >>>> IMO the best solution would be to make it configurable by introducing
> a
> >>>> "table_mapping" config with values
> >>>>
> >>>>    * type - every type in the known indices is mapped as table
> >>>>    * index - every known index is mapped as table
> >>>>
> >>>> We'd probably also need a "type_field" configuration for defining
> which
> >>>> field to use for the type determination as one of the possible future
> >>>> ways to do things is to introduce a custom field:
> >>>>
> >>>>
> >>>
> https://www.elastic.co/guide/en/elasticsearch/reference/master/removal-of-types.html#_custom_type_field_2
> >>>> We already detect the ES version, so we can set a smart default for
> this
> >>>> setting. Let's make the index config param optional.
> >>>>
> >>>>    * When no index is given, we discover indexes, the default for
> >>>>      "table_mapping" then is "index"
> >>>>    * When index is given, the we only discover types according to the
> >>>>      "type_field" configuration and the default for "table_mapping" is
> >>>> "type"
> >>>>
> >>>> This would also allow to discover indexes but still use "type" as
> >>>> "table_mapping".
> >>>>
> >>>> What do you think?
> >>>>
> >>>> Mit freundlichen Grüßen,
> >>>>
> ------------------------------------------------------------------------
> >>>> *Christian Beikov*
> >>>> Am 29.06.2018 um 02:41 schrieb Andrei Sereda:
> >>>>> Yes. There is an API to list all indexes / types in elastic. They can
> >>> be
> >>>>> automatically imported into a schema.
> >>>>>
> >>>>> What needs to be agreed upon is how to expose those elements in
> calcite
> >>>>> schema (naming / behaviour).
> >>>>>
> >>>>> 1) Many (most?) of setups are single type per index. Natural way to
> >>> name
> >>>>> would be  "elastic.$index" (elastic being schema name). Multiple
> >>> indexes
> >>>>> would be under same schema "elastic.index1" "elastic.index2" etc.
> >>>>>
> >>>>> 2) What if index has several types should they exported as calcite
> >>>> tables:
> >>>>> "elastic.$index_type1" "elastic.$index_type2" ?  Or (current
> behaviour)
> >>>> as
> >>>>> "elastic.type1" and "elastic.type2". Or as subschema
> >>>>> "elastic.$index.type1" ?
> >>>>>
> >>>>> Now what if one has combination of (1) and (2) ?
> >>>>> Setup (2) is already deprecated (and will be unsupported in next
> >>> version)
> >>>>>
> >>>>> On Thu, Jun 28, 2018 at 7:31 PM Christian Beikov <
> >>>> christian.beikov@xxxxxxxxx>
> >>>>> wrote:
> >>>>>
> >>>>>> Is there an API to discover indexes? If there is, I'd suggest we
> >>> allow a
> >>>>>> config option that to make the adapter discover the possible
> indexes.
> >>>>>> We'd still have to adapt the code a bit, but internally, the schema
> >>>>>> could just keep a cache of type name to index name map and be able
> to
> >>>>>> support both scenarios.
> >>>>>>
> >>>>>>
> >>>>>> Mit freundlichen Grüßen,
> >>>>>>
> >>>
> ------------------------------------------------------------------------
> >>>>>> *Christian Beikov*
> >>>>>> Am 29.06.2018 um 00:12 schrieb Andrei Sereda:
> >>>>>>>> 1) What's the time horizon for the current adapter no longer
> working
> >>>>>> with these
> >>>>>>> changes to ES ?
> >>>>>>> Current adapter will be working for a while with existing setup.
> The
> >>>>>>> problem is nomenclature and ease of use.
> >>>>>>>
> >>>>>>> Their new SQL concepts mapping
> >>>>>>> <
> >>>
> https://www.elastic.co/guide/en/elasticsearch/reference/current/_mapping_concepts_across_sql_and_elasticsearch.html
> >>>>>>> drops
> >>>>>>> the notion of ES type (which before was equivalent of RDBMS table)
> >>> and
> >>>>>> uses
> >>>>>>> ES index as new table equivalent (before ES index was equal to
> >>>> database).
> >>>>>>> Most users use elastic this way (one type , one index) index ==
> >>> table.
> >>>>>>> Currently calcite requires schema per index. In RDBMS parlance
> >>> database
> >>>>>> per
> >>>>>>> table (I'd like to change that).
> >>>>>>>
> >>>>>>>> 2) Any guess how complicated it would be to maintain code paths
> for
> >>>> both
> >>>>>>>> behaviours? I know this is probably really challenging to
> estimate,
> >>>> but
> >>>>>> I
> >>>>>>>> really have no idea of the scope of these changes. Would it mean
> two
> >>>>>>>> different ES adapters?
> >>>>>>> One can have just a separate calcite schema implementations (same
> >>>>>> adapter /
> >>>>>>> module) :
> >>>>>>> 1)  LegacySchema (old). Schema can have only one index (but
> multiple
> >>>>>>> types). Type == table in this case.
> >>>>>>> 2)  NewSchema (new). Single schema can have multiple indexes (type
> is
> >>>>>>> dropped). Index == table in this case
> >>>>>>>
> >>>>>>>> 3) Do we really need compatibility with the current version of the
> >>>>>>> adapter?
> >>>>>>>> IMO this depends on what versions of ES we would lose support for
> >>> and
> >>>>>> how
> >>>>>>>> complex it would be for users of the current ES adapter to make
> >>>> updates
> >>>>>>> for
> >>>>>>>> any Calcite API changes.
> >>>>>>> The issue is not in adapter but how calcite schema exposes tables.
> >>>>>> Should
> >>>>>>> it expose index as individual table (new), or ES type (old) ?
> >>>>>>>
> >>>>>>> Andrei.
> >>>>>>>
> >>>>>>> On Thu, Jun 28, 2018 at 5:23 PM Michael Mior <mmior@xxxxxxxxxx>
> >>> wrote:
> >>>>>>>> Unfortunately I know very little about ES so I'm not in a great
> >>>>>> position to
> >>>>>>>> asses the impact of these changes. I will say that that legacy
> >>>>>>>> compatibility is great, but maintaining two sets of logic is
> always
> >>> a
> >>>>>>>> challenge. A few follow up questions:
> >>>>>>>>
> >>>>>>>> 1) What's the time horizon for the current adapter no longer
> working
> >>>>>> with
> >>>>>>>> these changes to ES?
> >>>>>>>>
> >>>>>>>> 2) Any guess how complicated it would be to maintain code paths
> for
> >>>> both
> >>>>>>>> behaviours? I know this is probably really challenging to
> estimate,
> >>>> but
> >>>>>> I
> >>>>>>>> really have no idea of the scope of these changes. Would it mean
> two
> >>>>>>>> different ES adapters?
> >>>>>>>>
> >>>>>>>> 3) Do we really need compatibility with the current version of the
> >>>>>> adapter?
> >>>>>>>> IMO this depends on what versions of ES we would lose support for
> >>> and
> >>>>>> how
> >>>>>>>> complex it would be for users of the current ES adapter to make
> >>>> updates
> >>>>>> for
> >>>>>>>> any Calcite API changes.
> >>>>>>>>
> >>>>>>>> Thanks for your continued work on the ES adapter Andrei!
> >>>>>>>>
> >>>>>>>> --
> >>>>>>>> Michael Mior
> >>>>>>>> mmior@xxxxxxxxxx
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Le jeu. 28 juin 2018 à 12:57, Andrei Sereda <andrei@xxxxxxxxx> a
> >>>> écrit
> >>>>>> :
> >>>>>>>>> Hello,
> >>>>>>>>>
> >>>>>>>>> Elastic announced
> >>>>>>>>> <
> >>>>>>>>>
> >>>
> https://www.elastic.co/guide/en/elasticsearch/reference/master/removal-of-types.html
> >>>>>>>>> that they will be deprecating mapping types in ES6 and indexes
> will
> >>>> be
> >>>>>>>>> single-typed only.
> >>>>>>>>>
> >>>>>>>>> Historical analogy <https://www.elastic.co/blog/index-vs-type>
> >>>> between
> >>>>>>>>> RDBMS and elastic was that index is equivalent to a database and
> >>> type
> >>>>>>>>> corresponds to table in that database. In a couple of releases
> >>>> (ES6-8)
> >>>>>>>> this
> >>>>>>>>> shall not longer be true.
> >>>>>>>>>
> >>>>>>>>> Recent SQL addition
> >>>>>>>>> <https://www.elastic.co/blog/elasticsearch-6-3-0-released> to
> >>>> elastic
> >>>>>>>>> confirms
> >>>>>>>>> this trend
> >>>>>>>>> <
> >>>>>>>>>
> >>>
> https://www.elastic.co/guide/en/elasticsearch/reference/current/_mapping_concepts_across_sql_and_elasticsearch.html
> >>>>>>>>>> .
> >>>>>>>>> Index is equivalent to a table and there are no more ES types.
> >>>>>>>>>
> >>>>>>>>> I would like to propose to include this logic in Calcite ES
> >>> adapter.
> >>>>>> IE,
> >>>>>>>>> expose each ES single-typed index as a separate table inside
> >>> calcite
> >>>>>>>>> schema. This is in contrast to  current integration where schema
> >>> can
> >>>>>> only
> >>>>>>>>> have a single index. Current approach forces you to create
> multiple
> >>>>>>>> schemas
> >>>>>>>>> to query single-typed indexes (on the same ES cluster).
> >>>>>>>>>
> >>>>>>>>> Legacy compatibility can always be controlled with configuration
> >>>>>>>>> parameters.
> >>>>>>>>>
> >>>>>>>>> Do you agree with such changes ? If yes, would you consider a PR
> ?
> >>>>>>>>>
> >>>>>>>>> Regards,
> >>>>>>>>> Andrei.
> >>>>>>>>>
> >>>>
>
>


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