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From Miles Spielberg <>
Subject Re: Runtime DDL supported?
Date Tue, 27 Feb 2018 23:39:46 GMT
As we discussed, indexes across views are stored in a single HBase table
associated with the original table (_IDX_<tablename>). That's grand for
limiting the number of HBase tables created, but I just realized that the
actual index data within is differentiated by the 16-bit "viewIndexId",
which limits us to 64K indexes across all views for a given table. That's
concerning for our use case, especially if its a cumulative autoincrement
across all CREATE INDEX and DROP INDEX operations over the lifetime of the
base table.

Is there any workaround for this? A quick grep across the source indicates
that the length of viewIndexId is currently hard-coded.

At least, this limitation should probably be added to the list of caveats
and warnings at

Miles Spielberg
Staff Software Engineer

O. 650.485.1102
900 Jefferson Ave
Redwood City, CA 94063

On Thu, Feb 22, 2018 at 7:42 AM, James Taylor <>

> Another option would be to use dynamic columns[1] when querying across
> views. You’d have to disable column encoding [2] in this case.
> [1]
> [2]
> On Wed, Feb 21, 2018 at 11:57 PM Miles Spielberg <> wrote:
>> I believe each query in a UNION needs to have the same result tuple
>> format, which would work in this toy example, but in the general case each
>> view would have a different schema. We could make the result tuples conform
>> with each other by selecting NULL literals for every column except those in
>> a view. It would get quite verbose though. Assuming f1,f2,f3 all have
>> incompatible types, were you suggesting something like this?
>> Select f1, null, null from v1 where PK=?
>> Union all
>> Select null, f2, null from v2 where PK=?
>> Union all
>> Select null, null, f3 from v3 where PK=?
>> We might just run separate parallel queries against each view and merge
>> the results client side. I would guess this should perform well since the
>> block cache can be leveraged for queries after the first.
>> We could also use the HBase API to run a point row get. We'd have to
>> reimplement decoding for Phoenix's column values, which is not ideal but
>> quite doable.
>> Sent from my iPhone
>> On Feb 21, 2018, at 9:09 PM, James Taylor <> wrote:
>> Have you tried a UNION ALL query on (f1, f2, f3) instead? It seems
>> you’re on a good track with multiple views over a single (or handful) of
>> physical table(s).
>> On Wed, Feb 21, 2018 at 6:45 PM Miles Spielberg <> wrote:
>>> I've done some experimentation with views, with a schema resembling this:
>>> create table t1(
>>>>     pk bigint not null primary key
>>>> );
>>>>> create view v1(
>>>>     f1 varchar
>>>> ) AS SELECT * FROM t1;
>>>> create INDEX v1_f1 ON v1(f1);
>>>>> create view v2(
>>>>     f2 varchar
>>>> ) AS SELECT * FROM t1;
>>>> create INDEX v2_f2 ON v2(f2);
>>>>> create view v3(
>>>>     f3 varchar
>>>> ) AS SELECT * FROM t1;
>>>> create INDEX v3_f3 ON v3(f3);
>>> Most of the time we'll be accessing data via the indexed views, but we'd
>>> also like to be able to query all columns (f1, f2, f3) for a given pk. At
>>> the HBase level, this should be doable as a point get on t1. The SQL-y
>>> way to express this would probably be with JOINs, but the EXPLAIN plan is
>>> not encouraging.
>>> > explain SELECT * from t1 left join v1 on left join v2 on
>>>> left  join v3 on where;
>>> This is pushing me back towards a design of having a single table,
>>> except for the issue of proliferating physical HBase tables for the
>>> indexes. Would you advise having a single table + a single view on it
>>> containing all columns, to coerce Phoenix to consolidate the indexes into a
>>> single physical table? Are there other alternatives we should be
>>> considering?
>>> Miles Spielberg
>>> Staff Software Engineer
>>> O. 650.485.1102 <(650)%20485-1102>
>>> 900 Jefferson Ave
>>> <,+CA+94063&entry=gmail&source=g>
>>> Redwood City
>>> <,+CA+94063&entry=gmail&source=g>,
>>> CA 94063
>>> <,+CA+94063&entry=gmail&source=g>
>>> On Fri, Feb 16, 2018 at 3:27 PM, James Taylor <>
>>> wrote:
>>>> All indexes on views are stored in a single physical table, so you'll
>>>> be ok in that regard.
>>>> If you could file bugs for any local index issues, we'd really
>>>> appreciate it. We've been steadily improving local indexes
>>>> (see PHOENIX-3941 for some recent perf improvements - applicable for
>>>> multi-tenant tables in particular - these will appear in our 4.14 release).
>>>> Handling non covered columns is pretty isolated, so we should be able to
>>>> fix bugs you find. Plus, there's a workaround - you can cover your indexes
>>>> until any issues are fixed.
>>>> Global, mutable indexes have had many improvements over the last
>>>> several releases too, but there's more operational overhead if/when a data
>>>> table gets out of sync with it's index table (plus some amount of
>>>> configurable eventual consistency or index disablement). With local indexes
>>>> (and HBase 1.3), this isn't possible.
>>>> Thanks,
>>>> James
>>>> On Fri, Feb 16, 2018 at 3:10 PM, Miles Spielberg <> wrote:
>>>>> Hi James,
>>>>> Thanks for the tips around reducing the number of physical tables
>>>>> while still maintaining the appearance of multiple tables via view
>>>>> definitions. In our use case we don't anticipate having much if any
>>>>> immutable data, so unfortunately I don't expect to be able to take
>>>>> advantage of Phoenix's optimizations there.
>>>>> We're expecting many indexes, mostly likely with several per logical
>>>>> per-tenant table. Given that global indexes are implemented as physical
>>>>> HBase tables, will the view-oriented optimizations help very much? We've
>>>>> done some experiments with local indexes on 4.13.2 and found bugs,
>>>>> particularly with the rewrite optimization to read non-covered columns
>>>>> the main table, so we're not confident in using local indexes to optimize
>>>>> queries. (I've looked through the 5.0-alpha release notes and couldn't
>>>>> anything related to this issue, so if desired I'll collect info for a
>>>>> separate bug report.)
>>>>> Miles Spielberg
>>>>> Staff Software Engineer
>>>>> O. 650.485.1102 <(650)%20485-1102>
>>>>> 900 Jefferson Ave
>>>>> <,+CA+94063&entry=gmail&source=g>
>>>>> Redwood City
>>>>> <,+CA+94063+%3C,%2BCA%2B94063%26entry%3Dgmail%26source%3Dg%3E&entry=gmail&source=g>,
>>>>> CA 94063
>>>>> <,+CA+94063&entry=gmail&source=g>
>>>>> On Fri, Feb 16, 2018 at 2:49 PM, James Taylor <>
>>>>> wrote:
>>>>>> Hi Miles,
>>>>>> You'll be fine if you use views [1] and multi-tenancy [2] to limit
>>>>>> the number of physical HBase tables. Make sure you read about the
>>>>>> limitations of views too [3].
>>>>>> Here's the way I've seen this modeled successfully:
>>>>>> - create one schema per use case. This will let you leverage some
>>>>>> nice features in HBase for quotas and throttling. If you'll have
a single
>>>>>> use case, you don't have to worry about it. Read about namespaces
here [4]
>>>>>> and make sure to enable them before you start creating tables.
>>>>>> - define an immutable, multi-tenant base table that has TENANT_ID
>>>>>> TYPE_ID primary key. There are optimizations Phoenix does over immutable
>>>>>> tables that you'll want to leverage (assuming you have use cases
that fit
>>>>>> into this category). This Phoenix table will be backed by a physical
>>>>>> HBase table, but you won't execute Phoenix DML against it. Think
of it as a
>>>>>> kind of "abstract" type. Instead, you'll create updatable views over
>>>>>> - define a regular/mutable, multi-tenant base table that has
>>>>>> TENANT_ID + TYPE_ID primary key. Same deal as above, but this would
be the
>>>>>> base table for any tables in which the rows change in place.
>>>>>> - define global views per "logical" table (against either your
>>>>>> immutable base table or mutable base table depending on the functionality
>>>>>> needed) with each view having a WHERE TYPE_ID='your type identifier'
>>>>>> which adds specific columns to the primary key. This view will be
>>>>>> (i.e. you can execute DML against it). The columns you add to your
PK will
>>>>>> depend on your most common query patterns.
>>>>>> - optionally define indexes on these global views.
>>>>>> - each tenant can further extend or just use the global views.
>>>>>> FYI, lots of good performance/tuning tips can be found here[5].
>>>>>> Thanks,
>>>>>> James
>>>>>> [1]
>>>>>> [2]
>>>>>> [3]
>>>>>> [4]
>>>>>> [5]
>>>>>> On Fri, Feb 16, 2018 at 11:47 AM, Miles Spielberg <>
>>>>>> wrote:
>>>>>>> We're looking at employing Phoenix in a multi-tenant use case
>>>>>>> tenants can create their own tables and indexes, running into
totals of
>>>>>>> tens-of-thousands of each. Is this a supported scenario, or are
we headed
>>>>>>> for trouble?

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