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From Muhammad Gelbana <m.gelb...@gmail.com>
Subject Re: FindHardDistributionScans throws a NPE while visiting a TableScan
Date Wed, 21 Jun 2017 10:41:41 GMT
This has been bugging me for sometime, and I've only solved it after
starting this thread !

I solved this by overriding the
*org.apache.calcite.rel.AbstractRelNode.accept(RelShuttle)* method for the
relational node(s) containing *JdbcTableScan* to avoid this.

@Override
>     public RelNode accept(RelShuttle shuttle) {
>
> if(shuttle.getClass().getName().equals("org.apache.drill.exec.planner.sql.handlers.FindHardDistributionScans")){
>         return this;
>     }
>     return super.accept(shuttle);
> }


If someone finds this introducing another bug, please tell me about it.


*---------------------*
*Muhammad Gelbana*
http://www.linkedin.com/in/mgelbana

On Tue, Jun 20, 2017 at 2:13 AM, Jinfeng Ni <jni@apache.org> wrote:

> unwrap() essentially is doing a cast.  If it returns null for
> unwrap(DrillTranslatableTable.class) or unwrap(DrillTable.class), it means
> the table associate with this TableScan does not implement either
> interface. My suspicion is  JDBC storage plugin returns JdbcTable [1],
> unlikely other storage plugin which returns an instance implementing
> DrillTable.
>
> This seems to indicate FindHardDistributionScans could not be used to
> non-DrillTable. I'm not sure if that's the intention of that code, though.
>
> 1.
> https://github.com/apache/calcite/blob/master/core/src/
> main/java/org/apache/calcite/adapter/jdbc/JdbcSchema.java#L233-L234
>
> On Mon, Jun 19, 2017 at 2:19 PM, Muhammad Gelbana <m.gelbana@gmail.com>
> wrote:
>
> > Everyone,
> >
> > I made a copy of the Jdbc plugin and made modifications to it by adding a
> > few rules. None of the modification I made or the rules I wrote should
> have
> > anything extra to do with handling the following SQL query
> >
> > SELECT * FROM incorta.SALES.SALES SALES WHERE 1 = 2 LIMIT 1
> >
> >
> > I know the query is useless, but I need to to know how to fix the
> following
> > error thrown while handling this query. This is the final query plan:
> >
> > DEBUG o.a.d.e.p.s.h.DefaultSqlHandler - HEP_BOTTOM_UP:Convert SUM to
> $SUM0
> > > (0ms):
> > > DrillLimitRel(*fetch=[1]*): rowcount = 1.0, cumulative cost = {201.0
> > > rows, 205.0 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 2653
> > >   DrillLimitRel(*offset=[0], fetch=[0]*): rowcount = 1.0, cumulative
> cost
> > > = {200.0 rows, 201.0 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 2651
> > >     GelbanaJdbcDrel: rowcount = 100.0, cumulative cost = {200.0 rows,
> > > 201.0 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 2649
> > >       JdbcTableScan(table=[[gelbana, SALES, SALES]]): rowcount = 100.0,
> > > cumulative cost = {100.0 rows, 101.0 cpu, 0.0 io, 0.0 network, 0.0
> > memory},
> > > id = 2572
> >
> >
> > This is the throw error stacktrace
> >
> > [Error Id: 83ea094a-db24-4d6d-bf0d-271db26db933 on 640fb7ebbd1a:31010]
> > at
> > org.apache.drill.common.exceptions.UserException$
> > Builder.build(UserException.java:543)
> > ~[drill-common-1.9.0.jar:1.9.0]
> > at
> > org.apache.drill.exec.work.foreman.Foreman$ForemanResult.
> > close(Foreman.java:825)
> > [drill-java-exec-1.9.0.jar:1.9.0]
> > at org.apache.drill.exec.work.foreman.Foreman.moveToState(
> > Foreman.java:935)
> > [drill-java-exec-1.9.0.jar:1.9.0]
> > at org.apache.drill.exec.work.foreman.Foreman.run(Foreman.java:281)
> > [drill-java-exec-1.9.0.jar:1.9.0]
> > at
> > java.util.concurrent.ThreadPoolExecutor.runWorker(
> > ThreadPoolExecutor.java:1142)
> > [na:1.8.0_131]
> > at
> > java.util.concurrent.ThreadPoolExecutor$Worker.run(
> > ThreadPoolExecutor.java:617)
> > [na:1.8.0_131]
> > at java.lang.Thread.run(Thread.java:748) [na:1.8.0_131]
> > Caused by: org.apache.drill.exec.work.foreman.ForemanException:
> Unexpected
> > exception during fragment initialization: null
> > ... 4 common frames omitted
> > *Caused by: java.lang.NullPointerException: null*
> > at
> > org.apache.drill.exec.planner.sql.handlers.FindHardDistributionScans.
> > visit(FindHardDistributionScans.java:55)
> > ~[drill-java-exec-1.9.0.jar:1.9.0]
> > at org.apache.calcite.rel.core.TableScan.accept(TableScan.java:166)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.RelShuttleImpl.visitChild(
> > RelShuttleImpl.java:53)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at
> > org.apache.calcite.rel.RelShuttleImpl.visitChildren(
> > RelShuttleImpl.java:68)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.RelShuttleImpl.visit(RelShuttleImpl.java:126)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.AbstractRelNode.accept(
> AbstractRelNode.java:256)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.RelShuttleImpl.visitChild(
> > RelShuttleImpl.java:53)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at
> > org.apache.calcite.rel.RelShuttleImpl.visitChildren(
> > RelShuttleImpl.java:68)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.RelShuttleImpl.visit(RelShuttleImpl.java:126)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.AbstractRelNode.accept(
> AbstractRelNode.java:256)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.RelShuttleImpl.visitChild(
> > RelShuttleImpl.java:53)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at
> > org.apache.calcite.rel.RelShuttleImpl.visitChildren(
> > RelShuttleImpl.java:68)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.RelShuttleImpl.visit(RelShuttleImpl.java:126)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at org.apache.calcite.rel.AbstractRelNode.accept(
> AbstractRelNode.java:256)
> > ~[calcite-core-1.4.0-drill-r19.jar:1.4.0-drill-r19]
> > at
> > org.apache.drill.exec.planner.sql.handlers.FindHardDistributionScans.
> > canForceSingleMode(FindHardDistributionScans.java:45)
> > ~[drill-java-exec-1.9.0.jar:1.9.0]
> > at
> > org.apache.drill.exec.planner.sql.handlers.DefaultSqlHandler.
> > convertToDrel(DefaultSqlHandler.java:262)
> > ~[drill-java-exec-1.9.0.jar:1.9.0]
> > at
> > org.apache.drill.exec.planner.sql.handlers.DefaultSqlHandler.
> > convertToDrel(DefaultSqlHandler.java:290)
> > ~[drill-java-exec-1.9.0.jar:1.9.0]
> > at
> > org.apache.drill.exec.planner.sql.handlers.DefaultSqlHandler.getPlan(
> > DefaultSqlHandler.java:168)
> > ~[drill-java-exec-1.9.0.jar:1.9.0]
> > at
> > org.apache.drill.exec.planner.sql.DrillSqlWorker.getPhysicalPlan(
> > DrillSqlWorker.java:123)
> > ~[drill-java-exec-1.9.0.jar:1.9.0]
> > at
> > org.apache.drill.exec.planner.sql.DrillSqlWorker.getPlan(
> > DrillSqlWorker.java:97)
> > ~[drill-java-exec-1.9.0.jar:1.9.0]
> > at org.apache.drill.exec.work.foreman.Foreman.runSQL(Foreman.java:1008)
> > [drill-java-exec-1.9.0.jar:1.9.0]
> > at org.apache.drill.exec.work.foreman.Foreman.run(Foreman.java:264)
> > [drill-java-exec-1.9.0.jar:1.9.0]
> > ... 3 common frames omitted
> >
> > Whic is because this statement
> >
> > unwrap =
> > > scan.getTable().unwrap(DrillTranslatableTable.class).getDrillTable();
> >
> >
> > In *FindHardDistributionScans.java:55* evaluates
> > *scan.getTable().unwrap(DrillTranslatableTable.class)* to null
> >
> > Would someone please explain to me what is Drill trying to do and what
> did
> > I do wrong ?
> >
> > *---------------------*
> > *Muhammad Gelbana*
> > http://www.linkedin.com/in/mgelbana
> >
>

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