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From Robert Hou <r...@maprtech.com>
Subject Re: Drill where clause vs Hive on non-partition column
Date Tue, 15 Nov 2016 08:32:00 GMT
I have used Hive 1.2 and I have found that the stats in parquet files are
populated for some data types.  Integer, bigint, float, double, date work.
String does not seem to work.

You can then use Drill to query the Hive table and get predicate pushdown
for simple compare filters.  This has the form "where col = value".  Other
standard operators are !=, <, <=, >, >=.  Compound filters can use "and/or"
logic.  This will be supported in Drill 1.9.

In the future, we will add expressions and functions.

Thanks.

--Robert


On Mon, Nov 14, 2016 at 3:53 PM, Sonny Heer <sonnyheer@gmail.com> wrote:

> Is there a way to do that during the creation of the parquet table?  Might
> be a hive question but all we do is 'STORED AS parquet' and then during
> insert set the parquet.* properties.  I'm just trying to see if #2 is an
> option for us to utilize filter pushdown via dfs
>
> On Mon, Nov 14, 2016 at 3:43 PM, rahul challapalli <
> challapallirahul@gmail.com> wrote:
>
> > I do not know of any plans to support filter pushdown when using the hive
> > plugin.
> > If you run analyze stats then hive computes the table stats and stores
> them
> > in the hive metastore for the relevant table. I believe drill uses some
> of
> > these stats. However running analyze stats command does not alter(or add)
> > the metadata in the parquet files themselves. The parquet level metadata
> > should be written when the parquet file itself is created in the first
> > place.
> >
> > - Rahul
> >
> > On Mon, Nov 14, 2016 at 3:32 PM, Sonny Heer <sonnyheer@gmail.com> wrote:
> >
> > > Rahul,
> > >
> > > Thanks for the details.  Is there any plans to support filter pushdown
> > for
> > > #1?  Do you know if we run analyze stats through hive on a parquet file
> > if
> > > that will have enough info to do the pushdown?
> > >
> > > Thanks again.
> > >
> > > On Mon, Nov 14, 2016 at 9:50 AM, rahul challapalli <
> > > challapallirahul@gmail.com> wrote:
> > >
> > > > Sonny,
> > > >
> > > > If the underlying data in the hive table is in parquet format, there
> > are
> > > 3
> > > > ways to query from drill :
> > > >
> > > > 1. Using the hive plugin : This does not support filter pushdown for
> > any
> > > > formats (ORC, Parquet, Text...etc)
> > > > 2. Directly Querying the folder in maprfs/hdfs which contains the
> > parquet
> > > > files using DFS plugin: With DRILL-1950, we can now do a filter
> > pushdown
> > > > into the parquet files. In order to take advantage of this feature,
> the
> > > > underlying parquet files should have the relevant stats. This feature
> > > will
> > > > only be available with the 1.9.0 release
> > > > 3. Using the drill's native parquet reader in conjunction with the
> hive
> > > > plugin (See store.hive.optimize_scan_with_native_readers) : This
> > allows
> > > > drill to fetch all the metadata about the hive table from the
> metastore
> > > and
> > > > then drill uses its own parquet reader for actually reading the
> files.
> > > This
> > > > approach currently does not support parquet filter pushdown but this
> > > might
> > > > be added in the next release after 1.9.0.
> > > >
> > > > - Rahul
> > > >
> > > > On Sun, Nov 13, 2016 at 11:06 AM, Sonny Heer <sonnyheer@gmail.com>
> > > wrote:
> > > >
> > > > > I'm running a drill query with a where clause on a non-partitioned
> > > column
> > > > > via hive storage plugin.  This query inspects all partitions (kind
> of
> > > > > expected), but when i run the same query in Hive I can see a
> > predicate
> > > > > passed down to the query plan.  This particular query is much
> faster
> > in
> > > > > Hive vs Drill.  BTW these are parquet files.
> > > > >
> > > > > Hive:
> > > > >
> > > > > Stage-0
> > > > >
> > > > > Fetch Operator
> > > > >
> > > > > limit:-1
> > > > >
> > > > > Select Operator [SEL_2]
> > > > >
> > > > > outputColumnNames:["_col0"]
> > > > >
> > > > > Filter Operator [FIL_4]
> > > > >
> > > > > predicate:(my_column = 123) (type: boolean)
> > > > >
> > > > > TableScan [TS_0]
> > > > >
> > > > > alias:my_table
> > > > >
> > > > >
> > > > > Any idea on why this is?  My guess is Hive is storing hive specific
> > > info
> > > > in
> > > > > the parquet file since it was created through Hive.  Although it
> > seems
> > > > > drill-hive plugin should honor this to.  Not sure, but willing to
> > look
> > > > > through code if someone can point me in the right direction.
> Thanks!
> > > > >
> > > > > --
> > > > >
> > > >
> > >
> > >
> > >
> > > --
> > >
> > >
> > > Pushpinder S. Heer
> > > Senior Software Engineer
> > > m: 360-434-4354 h: 509-884-2574
> > >
> >
>
>
>
> --
>
>
> Pushpinder S. Heer
> Senior Software Engineer
> m: 360-434-4354 h: 509-884-2574
>

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