Spark SQL DataFrame 1.5.0 is extremely slow for take(1) or head() or first()

[Jerry Lam]

Hi Spark Developers,

I just ran some very simple operations on a dataset. I was surprise by the
execution plan of take(1), head() or first().

For your reference, this is what I did in pyspark 1.5:
df=sqlContext.read.parquet("someparquetfiles")
df.head()

The above lines take over 15 minutes. I was frustrated because I can do
better without using spark :) Since I like spark, so I tried to figure out
why. It seems the dataframe requires 3 stages to give me the first row. It
reads all data (which is about 1 billion rows) and run Limit twice.

Instead of head(), show(1) runs much faster. Not to mention that if I do:

df.rdd.take(1) //runs much faster.

Is this expected? Why head/first/take is so slow for dataframe? Is it a bug
in the optimizer? or I did something wrong?

Best Regards,

Jerry

Re: Spark SQL DataFrame 1.5.0 is extremely slow for take(1) or head() or first()

[Jerry Lam]

I just noticed you found 1.4 has the same issue. I added that as well in
the ticket.

On Mon, Sep 21, 2015 at 1:43 PM, Jerry Lam  wrote:

> Hi Yin,
>
> You are right! I just tried the scala version with the above lines, it
> works as expected.
> I'm not sure if it happens also in 1.4 for pyspark but I thought the
> pyspark code just calls the scala code via py4j. I didn't expect that this
> bug is pyspark specific. That surprises me actually a bit. I created a
> ticket for this (SPARK-10731
> ).
>
> Best Regards,
>
> Jerry
>
>
> On Mon, Sep 21, 2015 at 1:01 PM, Yin Huai  wrote:
>
>> btw, does 1.4 has the same problem?
>>
>> On Mon, Sep 21, 2015 at 10:01 AM, Yin Huai  wrote:
>>
>>> Hi Jerry,
>>>
>>> Looks like it is a Python-specific issue. Can you create a JIRA?
>>>
>>> Thanks,
>>>
>>> Yin
>>>
>>> On Mon, Sep 21, 2015 at 8:56 AM, Jerry Lam  wrote:
>>>
 Hi Spark Developers,

 I just ran some very simple operations on a dataset. I was surprise by
 the execution plan of take(1), head() or first().

 For your reference, this is what I did in pyspark 1.5:
 df=sqlContext.read.parquet("someparquetfiles")
 df.head()

 The above lines take over 15 minutes. I was frustrated because I can do
 better without using spark :) Since I like spark, so I tried to figure out
 why. It seems the dataframe requires 3 stages to give me the first row. It
 reads all data (which is about 1 billion rows) and run Limit twice.

 Instead of head(), show(1) runs much faster. Not to mention that if I
 do:

 df.rdd.take(1) //runs much faster.

 Is this expected? Why head/first/take is so slow for dataframe? Is it a
 bug in the optimizer? or I did something wrong?

 Best Regards,

 Jerry

>>>
>>>
>>
>

Re: Spark SQL DataFrame 1.5.0 is extremely slow for take(1) or head() or first()

[Jerry Lam]

Hi Yin,

You are right! I just tried the scala version with the above lines, it
works as expected.
I'm not sure if it happens also in 1.4 for pyspark but I thought the
pyspark code just calls the scala code via py4j. I didn't expect that this
bug is pyspark specific. That surprises me actually a bit. I created a
ticket for this (SPARK-10731
).

Best Regards,

Jerry


On Mon, Sep 21, 2015 at 1:01 PM, Yin Huai  wrote:

> btw, does 1.4 has the same problem?
>
> On Mon, Sep 21, 2015 at 10:01 AM, Yin Huai  wrote:
>
>> Hi Jerry,
>>
>> Looks like it is a Python-specific issue. Can you create a JIRA?
>>
>> Thanks,
>>
>> Yin
>>
>> On Mon, Sep 21, 2015 at 8:56 AM, Jerry Lam  wrote:
>>
>>> Hi Spark Developers,
>>>
>>> I just ran some very simple operations on a dataset. I was surprise by
>>> the execution plan of take(1), head() or first().
>>>
>>> For your reference, this is what I did in pyspark 1.5:
>>> df=sqlContext.read.parquet("someparquetfiles")
>>> df.head()
>>>
>>> The above lines take over 15 minutes. I was frustrated because I can do
>>> better without using spark :) Since I like spark, so I tried to figure out
>>> why. It seems the dataframe requires 3 stages to give me the first row. It
>>> reads all data (which is about 1 billion rows) and run Limit twice.
>>>
>>> Instead of head(), show(1) runs much faster. Not to mention that if I do:
>>>
>>> df.rdd.take(1) //runs much faster.
>>>
>>> Is this expected? Why head/first/take is so slow for dataframe? Is it a
>>> bug in the optimizer? or I did something wrong?
>>>
>>> Best Regards,
>>>
>>> Jerry
>>>
>>
>>
>

Re: Spark SQL DataFrame 1.5.0 is extremely slow for take(1) or head() or first()

[Yin Huai]

Looks like the problem is df.rdd does not work very well with limit. In
scala, df.limit(1).rdd will also trigger the issue you observed. I will add
this in the jira.

On Mon, Sep 21, 2015 at 10:44 AM, Jerry Lam  wrote:

> I just noticed you found 1.4 has the same issue. I added that as well in
> the ticket.
>
> On Mon, Sep 21, 2015 at 1:43 PM, Jerry Lam  wrote:
>
>> Hi Yin,
>>
>> You are right! I just tried the scala version with the above lines, it
>> works as expected.
>> I'm not sure if it happens also in 1.4 for pyspark but I thought the
>> pyspark code just calls the scala code via py4j. I didn't expect that this
>> bug is pyspark specific. That surprises me actually a bit. I created a
>> ticket for this (SPARK-10731
>> ).
>>
>> Best Regards,
>>
>> Jerry
>>
>>
>> On Mon, Sep 21, 2015 at 1:01 PM, Yin Huai  wrote:
>>
>>> btw, does 1.4 has the same problem?
>>>
>>> On Mon, Sep 21, 2015 at 10:01 AM, Yin Huai  wrote:
>>>
 Hi Jerry,

 Looks like it is a Python-specific issue. Can you create a JIRA?

 Thanks,

 Yin

 On Mon, Sep 21, 2015 at 8:56 AM, Jerry Lam 
 wrote:

> Hi Spark Developers,
>
> I just ran some very simple operations on a dataset. I was surprise by
> the execution plan of take(1), head() or first().
>
> For your reference, this is what I did in pyspark 1.5:
> df=sqlContext.read.parquet("someparquetfiles")
> df.head()
>
> The above lines take over 15 minutes. I was frustrated because I can
> do better without using spark :) Since I like spark, so I tried to figure
> out why. It seems the dataframe requires 3 stages to give me the first 
> row.
> It reads all data (which is about 1 billion rows) and run Limit twice.
>
> Instead of head(), show(1) runs much faster. Not to mention that if I
> do:
>
> df.rdd.take(1) //runs much faster.
>
> Is this expected? Why head/first/take is so slow for dataframe? Is it
> a bug in the optimizer? or I did something wrong?
>
> Best Regards,
>
> Jerry
>


>>>
>>
>

Re: Spark SQL DataFrame 1.5.0 is extremely slow for take(1) or head() or first()

[Yin Huai]

Seems 1.4 has the same issue.

On Mon, Sep 21, 2015 at 10:01 AM, Yin Huai  wrote:

> btw, does 1.4 has the same problem?
>
> On Mon, Sep 21, 2015 at 10:01 AM, Yin Huai  wrote:
>
>> Hi Jerry,
>>
>> Looks like it is a Python-specific issue. Can you create a JIRA?
>>
>> Thanks,
>>
>> Yin
>>
>> On Mon, Sep 21, 2015 at 8:56 AM, Jerry Lam  wrote:
>>
>>> Hi Spark Developers,
>>>
>>> I just ran some very simple operations on a dataset. I was surprise by
>>> the execution plan of take(1), head() or first().
>>>
>>> For your reference, this is what I did in pyspark 1.5:
>>> df=sqlContext.read.parquet("someparquetfiles")
>>> df.head()
>>>
>>> The above lines take over 15 minutes. I was frustrated because I can do
>>> better without using spark :) Since I like spark, so I tried to figure out
>>> why. It seems the dataframe requires 3 stages to give me the first row. It
>>> reads all data (which is about 1 billion rows) and run Limit twice.
>>>
>>> Instead of head(), show(1) runs much faster. Not to mention that if I do:
>>>
>>> df.rdd.take(1) //runs much faster.
>>>
>>> Is this expected? Why head/first/take is so slow for dataframe? Is it a
>>> bug in the optimizer? or I did something wrong?
>>>
>>> Best Regards,
>>>
>>> Jerry
>>>
>>
>>
>

Re: Spark SQL DataFrame 1.5.0 is extremely slow for take(1) or head() or first()

[Yin Huai]

btw, does 1.4 has the same problem?

On Mon, Sep 21, 2015 at 10:01 AM, Yin Huai  wrote:

> Hi Jerry,
>
> Looks like it is a Python-specific issue. Can you create a JIRA?
>
> Thanks,
>
> Yin
>
> On Mon, Sep 21, 2015 at 8:56 AM, Jerry Lam  wrote:
>
>> Hi Spark Developers,
>>
>> I just ran some very simple operations on a dataset. I was surprise by
>> the execution plan of take(1), head() or first().
>>
>> For your reference, this is what I did in pyspark 1.5:
>> df=sqlContext.read.parquet("someparquetfiles")
>> df.head()
>>
>> The above lines take over 15 minutes. I was frustrated because I can do
>> better without using spark :) Since I like spark, so I tried to figure out
>> why. It seems the dataframe requires 3 stages to give me the first row. It
>> reads all data (which is about 1 billion rows) and run Limit twice.
>>
>> Instead of head(), show(1) runs much faster. Not to mention that if I do:
>>
>> df.rdd.take(1) //runs much faster.
>>
>> Is this expected? Why head/first/take is so slow for dataframe? Is it a
>> bug in the optimizer? or I did something wrong?
>>
>> Best Regards,
>>
>> Jerry
>>
>
>

Re: Spark SQL DataFrame 1.5.0 is extremely slow for take(1) or head() or first()

[Yin Huai]

Hi Jerry,

Looks like it is a Python-specific issue. Can you create a JIRA?

Thanks,

Yin

On Mon, Sep 21, 2015 at 8:56 AM, Jerry Lam  wrote:

> Hi Spark Developers,
>
> I just ran some very simple operations on a dataset. I was surprise by the
> execution plan of take(1), head() or first().
>
> For your reference, this is what I did in pyspark 1.5:
> df=sqlContext.read.parquet("someparquetfiles")
> df.head()
>
> The above lines take over 15 minutes. I was frustrated because I can do
> better without using spark :) Since I like spark, so I tried to figure out
> why. It seems the dataframe requires 3 stages to give me the first row. It
> reads all data (which is about 1 billion rows) and run Limit twice.
>
> Instead of head(), show(1) runs much faster. Not to mention that if I do:
>
> df.rdd.take(1) //runs much faster.
>
> Is this expected? Why head/first/take is so slow for dataframe? Is it a
> bug in the optimizer? or I did something wrong?
>
> Best Regards,
>
> Jerry
>