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From Jacques Nadeau <jacq...@apache.org>
Subject Re: Assertion check in RelOptTableImpl.create()
Date Mon, 11 Jan 2016 03:47:16 GMT
It seems better to remove the assertion. If those are marker interfaces
that have more meaning, I think we should avoid forcing people to implement
one of those interfaces and then not support the implied functionality.
Hadoop had a similiar problem when they added ByteBuffer read apis marker
interface and then added some implementations that had the marker interface
but fail to implement the appropriate functionality. This means people can
no longer rely on the marker interface to ensure that functionality is
available. For those that are interested, this is the kind of hoops the
Parquet library had to jump through because of this problem [1].

[1]
https://github.com/apache/parquet-mr/blob/master/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/util/CompatibilityUtil.java#L79


On Sun, Jan 10, 2016 at 5:58 PM, Julian Hyde <jhyde@apache.org> wrote:

> I don’t think it would do any harm if DrillTable implements
> ScannableTable. The method could throw UnsupportedOperationException if you
> don’t intend to use it.
>
> > On Jan 8, 2016, at 9:58 PM, Jinfeng Ni <jinfengni99@gmail.com> wrote:
> >
> > Thanks for the explanation, Julian.
> >
> > The places where I want to create an instance of RelOptTable is not in
> > SqlValidator or SqlToRelConverter. Rather, it's in a RelOptRule, where
> > CalciteSchema or Path is not available, which makes it not possible to
> > call the other create() methods. In that sense, such table is "free
> > floating" table.
> >
> > The RelOptRule, which essentially is trying to pushing partition
> > filter into scan, has to create a new instance of RelOptTable, after
> > certain transformation. In that sense, it's quite similar to
> > DeltaTableScanRule in Calcite code base [1].  The difference is
> > DeltaTableScanRule has a ScannableTable, while in Drill, DrillTable
> > does not implement ScannableTable [2].
> >
> > Do you think it makes sense to make DrillTable implement ScannableTable?
> >
> > Thanks!
> >
> > [1]
> https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/stream/StreamRules.java#L192-L195
> > [2]
> https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillTable.java#L34
> >
> > On Fri, Jan 8, 2016 at 5:24 PM, Julian Hyde <jhyde@apache.org> wrote:
> >> Tables created using “create(RelOptSchema, RelDataType, Table)” have
> their names field set to the empty list. That is, they don’t know their
> location within the schema hierarchy and in fact may not be in the schema
> hierarchy. Usually a table implements itself by generating code like
> >>
> >>  rootSchema.getSubSchema(“FOODMART”).getTable(“CUSTOMERS”)
> >>
> >> But such “free floating” tables cannot implement themselves in that
> way. Therefore this method is only for kinds of tables that know how to get
> to their own data: TranslatableTable, ModifiableTable, ScannableTable.
> >>
> >> Julian
> >>
> >>
> >>> On Jan 7, 2016, at 5:40 PM, Jinfeng Ni <jni@apache.org> wrote:
> >>>
> >>> Does anyone know why one of the static create() methods in
> >>> RelOptTableImpl has the following assertion check (to check table is
> >>> instance of TranslatableTable, or ScannableTable, or ModifiableTable)
> >>> [1], while the rest of create() methods do not do such check? [2]
> >>>
> >>> Looks like RelOptTableImpl.toRel() actually expects table instance
> >>> other than the above three class[3].
> >>>
> >>> Does it makes sense to remove the assertion check in [1]?
> >>>
> >>> Best Regards,
> >>>
> >>> Jinfeng
> >>>
> >>>
> >>> [1].
> https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/prepare/RelOptTableImpl.java#L167-L169
> >>>
> >>> [2]
> https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/prepare/RelOptTableImpl.java#L118
> >>>
> >>> [3]
> https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/prepare/RelOptTableImpl.java#L225
> >>
>
>

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