In the Batch API only a single operator can be chained to another operator.
So we're starting with this code:
input = ...
input.filter(conditionA).output(formatA)
input.filter(conditonB).output(formatB)
In the Batch API this would create a CHAIN(filterA -> formatA) and a
CHAIN(filterB -> formatB), both having "input" as their input.
Since the filtering is not done as part of "input" the entire input
DataSet must be sent to both tasks.
This means that both chains have to deserialize the entire DataSet to
apply the filter; the serialization should only be done once though.
In contrast the solution you wrote creates a single CHAIN(input,
format), with no serialization in between at all.
The Streaming API doesn't have this limitation and would get by without
any serialization as well. Probably.
On 02.05.2017 15:23, Newport, Billy wrote:
Why doesn’t this work with batch though. We did
input = ...
input.filter(conditionA).output(formatA)
input.filter(conditonB).output(formatB)
And it was pretty slow compared with a custom outputformat with an
integrated filter.
*From:*Chesnay Schepler [mailto:ches...@apache.org]
*Sent:* Monday, May 01, 2017 12:56 PM
*To:* Newport, Billy [Tech]; 'user@flink.apache.org'
*Subject:* Re: Collector.collect
Oh you have multiple different output formats, missed that.
For the Batch API you are i believe correct, using a custom
output-format is the best solution.
In the Streaming API the code below should be equally fast, if the
filtered sets don't overlap.
input = ...
input.filter(conditionA).output(formatA)
input.filter(conditonB).output(formatB)
That is because all filters would be chained; hell all sources might
be as well (not to sure on this one).
On 01.05.2017 17:05, Newport, Billy wrote:
There is likely a bug then, the ENUM,Record stream to a filter to
a set of outputformats per filter was slower than the
BITMASK,Record to single OutputFormat which demux’s the data to
each file internally
Are you saying do a custom writer inside a map rather than either
of the 2 above approaches?
*From:*Chesnay Schepler [mailto:ches...@apache.org]
*Sent:* Monday, May 01, 2017 10:41 AM
*To:* user@flink.apache.org <mailto:user@flink.apache.org>
*Subject:* Re: Collector.collect
Hello,
@Billy, what prevented you from duplicating/splitting the record,
based on the bitmask, in a map function before the sink?
This shouldn't incur any serialization overhead if the sink is
chained to the map. The emitted Tuple could also share the
GenericRecord; meaning you don't even have to copy it.
On 01.05.2017 14:52, Newport, Billy wrote:
We’ve done that but it’s very expensive from a serialization
point of view when writing the same record multiple times,
each in a different tuple.
For example, we started with this:
.collect(new Tuple<Short, GenericRecord)).
The record would be written with short = 0 and again with
short = 1. This results in the GenericRecord being serialized
twice. You also prolly need filters on the output dataset
which is expensive also.
We switched instead to a bitmask. Now, we write the record
once and set bits in the short for each file the record needs
to be written to. Our next step is to write records to a file
based on the short. We wrote a new outputrecordformat which
checks the bits in the short and writes the GenericRecord to
each file for the corresponding bit. This means no filter to
split the records for each file and this is much faster.
We’re finding a need to do this kind of optimization pretty
frequently with flink.
*From:*Gaurav Khandelwal [mailto:gaurav671...@gmail.com]
*Sent:* Saturday, April 29, 2017 4:32 AM
*To:* user@flink.apache.org <mailto:user@flink.apache.org>
*Subject:* Collector.collect
Hello
I am working on RichProcessFunction and I want to emit
multiple records at a time. To achieve this, I am currently
doing :
while(condition)
{
Collector.collect(new Tuple<>...);
}
I was wondering, is this the correct way or there is any other
alternative.
