hive-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Dmitry Goldenberg <dgoldenb...@hexastax.com>
Subject Re: Is it possible to use LOAD DATA INPATH with a PARTITIONED, STORED AS PARQUET table?
Date Thu, 06 Apr 2017 12:48:10 GMT
Thanks, Ryan.

I was actually more curious about scenario B. If we represent our data as
delimited files, why don't we just use LOAD DATA INPATH and load it right
into the final, parquet, partitioned table in one step, bypassing dealing
with the temp table?

Are there any advantages to having a temp table besides the validation? One
advantage could possibly be making it a transactional table and being able
to run direct INSERT's into the temp table, avoiding having to deal with
delimited files and LOAD DATA INPATH.

If we go with route B, LOAD DATA INPATH directly into the parquet,
partitioned table, would we have to:

1) represent the input files as Parquet? - it looks like the data is still
delimited, and Hive represents it as Parquet internally
2) do anything specific in the input files / with the input files in order
to make partitioning work, or does Hive just take the data and take full
care of partitioning it?



On Tue, Apr 4, 2017 at 6:14 PM, Ryan Harris <Ryan.Harris@zionsbancorp.com>
wrote:

> For A) I’d recommend mapping an EXTERNAL table to the raw/original source
> files…then you can just run a SELECT query from the EXTERNAL source and
> INSERT into your destination.
>
>
>
> LOAD DATA can be very useful when you are trying to move data between two
> tables that share the same schema but 1 table is partitioned and the other
> table is NOT partitioned…once the files have been inserted into the
> unpartitioned table the source files from the hive warehouse can be added
> to the partitioned table using LOAD DATA.  Another place I’ve frequently
> used LOAD DATA is when synchronizing hive table data between two clusters,
> the hive warehouse data files can be copied from one cluster to the other
> with distcp and then loading the data flies to the duplicate cluster using
> LOAD DATA to ensure the metadata is recorded in hive metastore.
>
>
>
> *From:* Dmitry Goldenberg [mailto:dgoldenberg@hexastax.com]
> *Sent:* Tuesday, April 04, 2017 3:31 PM
> *To:* user@hive.apache.org
> *Subject:* Re: Is it possible to use LOAD DATA INPATH with a PARTITIONED,
> STORED AS PARQUET table?
>
>
>
> [External Email]
> ------------------------------
>
> Right, that makes sense, Dudu.
>
>
>
> So basically, if we have our data in "some form", and a goal of loading it
> into a parquet, partitioned table in Hive, we have two choices:
>
>
>
> A. Load this data into a temporary table first. Presumably, for this we
> should be able to do a LOAD INPATH, from delimited data files. Perhaps we
> could designate the temp table as transactional and then simply do direct
> INSERT's into this temp table - ? Then, as the second step, we'd do an
> INSERT... SELECT, to move the data into the destination table, and then
> DROP the temp table.
>
>
>
> B. Represent the data as a delimited format and do a LOAD INPATH directly
> into the destination table. Understandably, we lose the 'data verification'
> this way. If we go this route, must the data in the input files be in the
> PARQUET format or in a delimited format?  I would guess, the former.  And,
> how does partitioning play into it?  How would the input data need to be
> organized and inserted so as to adhere to the partitions (the 'date' and
> 'content-type' columns, in my example)?
>
>
>
>
>
>
>
> On Tue, Apr 4, 2017 at 2:22 PM, Markovitz, Dudu <dmarkovitz@paypal.com>
> wrote:
>
> “LOAD” is very misleading here. it is all in done the metadata level.
>
> The data is not being touched. The data in not being verified. The
> “system” does not have any clue if the flies format match the table
> definition and they can be actually used.
>
> The data files are being “moved” (again,  a metadata operation) from their
> current HDFS location to the location defined for the table.
>
> Later on when you  query the table the files will be scanned. If there are
> in the right format you’ll get results. If not, then no.
>
>
>
> *From:* Dmitry Goldenberg [mailto:dgoldenberg@hexastax.com]
> *Sent:* Tuesday, April 04, 2017 8:54 PM
> *To:* user@hive.apache.org
> *Subject:* Re: Is it possible to use LOAD DATA INPATH with a PARTITIONED,
> STORED AS PARQUET table?
>
>
>
> Thanks, Dudu. I think there's a disconnect here. We're using LOAD INPATH
> on a few tables to achieve the effect of actual insertion of records. Is it
> not the case that the LOAD causes the data to get inserted into Hive?
>
> Based on that I'd like to understand whether we can get away with using
> LOAD INPATH instead of INSERT/SELECT FROM.
>
>
> On Apr 4, 2017, at 1:43 PM, Markovitz, Dudu <dmarkovitz@paypal.com> wrote:
>
> I just want to verify that you understand the following:
>
>
>
> ·         LOAD DATA INPATH is just a HDFS file movement operation.
>
> You can achieve the same results by using *hdfs dfs -mv …*
>
>
>
> ·         LOAD DATA LOCAL  INPATH is just a file copying operation from
> the shell to the HDFS.
>
> You can achieve the same results by using *hdfs dfs -put …*
>
>
>
>
>
> *From:* Dmitry Goldenberg [mailto:dgoldenberg@hexastax.com
> <dgoldenberg@hexastax.com>]
> *Sent:* Tuesday, April 04, 2017 7:48 PM
> *To:* user@hive.apache.org
> *Subject:* Re: Is it possible to use LOAD DATA INPATH with a PARTITIONED,
> STORED AS PARQUET table?
>
>
>
> Dudu,
>
>
>
> This is still in design stages, so we have a way to get the data from its
> source. The data is *not* in the Parquet format.  It's up to us to format
> it the best and most efficient way.  We can roll with CSV or Parquet;
> ultimately the data must make it into a pre-defined PARQUET, PARTITIONED
> table in Hive.
>
>
>
> Thanks,
>
> - Dmitry
>
>
>
> On Tue, Apr 4, 2017 at 12:20 PM, Markovitz, Dudu <dmarkovitz@paypal.com>
> wrote:
>
> Are your files already in Parquet format?
>
>
>
> *From:* Dmitry Goldenberg [mailto:dgoldenberg@hexastax.com]
> *Sent:* Tuesday, April 04, 2017 7:03 PM
> *To:* user@hive.apache.org
> *Subject:* Re: Is it possible to use LOAD DATA INPATH with a PARTITIONED,
> STORED AS PARQUET table?
>
>
>
> Thanks, Dudu.
>
>
>
> Just to re-iterate; the way I'm reading your response is that yes, we can
> use LOAD INPATH for a PARQUET, PARTITIONED table, provided that the data in
> the delimited file is properly formatted.  Then we can LOAD it into the
> table (mytable in my example) directly and avoid the creation of the temp
> table (origtable in my example).  Correct so far?
>
>
>
> I did not quite follow the latter part of your response:
>
> >> You should only create an external table which is an interface to read
> the files and use it in an INSERT operation.
>
>
>
> My assumption was that we would LOAD INPATH and not have to use INSERT
> altogether.  Am I missing something in groking this latter part of your
> response?
>
>
>
> Thanks,
>
> - Dmitry
>
>
>
> On Tue, Apr 4, 2017 at 11:26 AM, Markovitz, Dudu <dmarkovitz@paypal.com>
> wrote:
>
> Since LOAD DATA INPATH  only moves files the answer is very simple.
>
> If you’re files are already in a format that matches the destination table
> (storage type, number and types of columns etc.) then – yes and if not,
> then – no.
>
>
>
> But –
>
> You don’t need to load the files into intermediary table.
>
> You should only create an external table which is an interface to read the
> files and use it in an INSERT operation.
>
>
>
> Dudu
>
>
>
> *From:* Dmitry Goldenberg [mailto:dgoldenberg@hexastax.com]
> *Sent:* Tuesday, April 04, 2017 4:52 PM
> *To:* user@hive.apache.org
> *Subject:* Is it possible to use LOAD DATA INPATH with a PARTITIONED,
> STORED AS PARQUET table?
>
>
>
> We have a table such as the following defined:
>
> CREATE TABLE IF NOT EXISTS db.mytable (
>   `item_id` string,
>   `timestamp` string,
>   `item_comments` string)
> PARTITIONED BY (`date`, `content_type`)
> STORED AS PARQUET;
>
> Currently we insert data into this PARQUET, PARTITIONED table as follows,
> using an intermediary table:
>
> INSERT INTO TABLE db.mytable PARTITION(date, content_type)
> SELECT itemid as item_id, itemts as timestamp, date, content_type
> FROM db.origtable
> WHERE date = “${SELECTED_DATE}”
> GROUP BY item_id, date, content_type;
>
> Our question is, would it be possible to use the LOAD DATA INPATH.. INTO
> TABLE syntax to load the data from delimited data files into 'mytable'
> rather than populating mytable from the intermediary table?
>
>
>
> I see in the Hive documentation that:
>
> * Load operations are currently pure copy/move operations that move
> datafiles into locations corresponding to Hive tables.
>
> * If the table is partitioned, then one must specify a specific partition
> of the table by specifying values for all of the partitioning columns.
>
>
>
> This seems to indicate that using LOAD is possible; however looking at
> this discussion: http://grokbase.com/t/hive/user/114frbfg0y/
> can-i-use-hive-dynamic-partition-while-loading-data-into-tables
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__grokbase.com_t_hive_user_114frbfg0y_can-2Di-2Duse-2Dhive-2Ddynamic-2Dpartition-2Dwhile-2Dloading-2Ddata-2Dinto-2Dtables&d=DwMFaQ&c=9WYoWBgz3TbmQlstBqb6LDRA8PY_DPmoAS0YWoTLU-g&r=_W3sXrqd7teXL8R6ey10dgFH1GT5KbehFX_EaUG41XM&m=w2-Xt3zXd67KWRPyy83l4Kn5EWquC767DmMpcE5RpgI&s=01kme5ZDH2EBjzLWRz6kJ5jQ9vxr-IzFeNepynsQ7-M&e=>,
> perhaps not?
>
>
>
> We'd like to understand if using LOAD in the case of PARQUET, PARTITIONED
> tables is possible and if so, then how does one go about using LOAD in that
> case?
>
>
>
> Thanks,
>
> - Dmitry
>
>
>
>
>
>
>
>
> ------------------------------
> THIS ELECTRONIC MESSAGE, INCLUDING ANY ACCOMPANYING DOCUMENTS, IS
> CONFIDENTIAL and may contain information that is privileged and exempt from
> disclosure under applicable law. If you are neither the intended recipient
> nor responsible for delivering the message to the intended recipient,
> please note that any dissemination, distribution, copying or the taking of
> any action in reliance upon the message is strictly prohibited. If you have
> received this communication in error, please notify the sender immediately.
> Thank you.
>

Mime
View raw message